2024-03-28T20:25:09Zhttp://uvadoc.uva.es/oai/requestoai:uvadoc.uva.es:10324/217522021-06-23T10:16:51Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Fully porous GaN p-n junction diodes fabricated by chemical vapor deposition
Bilousov, O. V.
Carvajal, Joan Josep
Geaney, H.
Zubialevich, V.
Parbrook, Peter
Martínez Sacristán, Óscar
Jiménez López, Juan Ignacio
Díaz, Francesc
Aguiló, Magdalena
O'Dwyer, C.
Chemical vapor deposition
Modern society is experiencing an ever-increasing demand for energy to power a vast array of electrical and mechanical devices. A significant amount of the energy consumed is used for lighting purposes. For instance, this demand is ~17% of the total energy consumed in the USA in 2011 [1]. Thus, any approach that can reduce energy consumption is important. In this context, the development of light emitting diodes (LEDs) incorporating at least one porous component, with improved light extraction efficiency, is being explored intensively [2]. However, up to now, only partially porous p-n junctions have been analyzed for this purpose.
2016-12-15T09:21:43Z
2016-12-15T09:21:43Z
2016-12-15T09:21:43Z
2014
info:eu-repo/semantics/article
ACS Applied Materials & Interfaces 6, p. 17954-17964 (2014)
1944-8244
http://uvadoc.uva.es/handle/10324/21752
https://doi.org/10.1021/am504786b
eng
http://pubs.acs.org/journal/aamick
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
American Chemical Society
oai:uvadoc.uva.es:10324/217542021-06-23T10:16:43Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Fully porous GaN p-n junctions fabricated by Chemical Vapor Deposition: a green technology towards more efficient LEDs
Carvajal, Joan Josep
Mena Rodríguez, José Manuel
Bilousov, O. V.
Martínez Sacristán, Óscar
Jiménez López, Juan Ignacio
Zubialevich, V.
Parbrook, Peter
Geaney, H.
O’Dwyer, C.
Díaz, Francesc
Aguiló, Magdalena
LEDs
Porous GaN based LEDs produced by corrosion etching techniques
demonstrated enhanced light extraction efficiency in the past.
However, these fabrication techniques require further postgrown
processing steps, which increase the price of the final system. In
this paper, we review the process followed towards the fabrication
of fully porous GaN p-n junctions directly during the growth step,
using a sequential chemical vapor deposition (CVD) process to
produce the different layers that form the p-n junction.
2016-12-15T09:36:21Z
2016-12-15T09:36:21Z
2016-12-15T09:36:21Z
2015
info:eu-repo/semantics/article
ECS Transactions, 2015, vol. 66, 163
1938-5862
http://uvadoc.uva.es/handle/10324/21754
eng
http://ecst.ecsdl.org/
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Electrochemical Society
oai:uvadoc.uva.es:10324/217572021-11-04T13:10:28Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
About the physical meaning of the critical temperature for catastrophic optical damage in high power quantum well laser diodes
Souto Bartolomé, Jorge Manuel
Pura Ruiz, José Luis
Jiménez López, Juan Ignacio
Catastrophic optical damage
It is usually assumed that the catastrophic optical damage of high power laser diodes is launched when a critical local temperature (Tc) is reached; temperatures ranging from 120ºC to 200ºC were experimentally reported. However, the physical meaning of Tc in the degradation process is still unclear. In this work we show that, in the presence of a local heat source in the active region, the temperature of the laser structure, calculated using finite element methods, is very inhomogeneously distributed among the different layers forming the device. This is due to the impact that the low dimensionality and the thermal boundary resistances have on the thermal transport across the laser structure. When these key factors are explicitly considered, the quantum well (QW) temperature can be several hundred degrees higher than the temperature of the guides and cladding layers. Due to the size of the experimental probes, the measured critical temperature is a weighted average over the QW, guides and claddings. We show the existence of a great difference between the calculated average temperature, equivalent to the experimentally measured temperature, and the peak temperature localized in the QW. A parallel study on double heterostructure lasers is also included for comparison.
2016-12-15T09:45:12Z
2016-12-15T09:45:12Z
2016-12-15T09:45:12Z
2016
info:eu-repo/semantics/article
Laser Physics Letters 2016, 13, 025005
1612-2011
http://uvadoc.uva.es/handle/10324/21757
eng
http://www.wiley-vch.de/en/shop/journals/
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
IOP Publishing
oai:uvadoc.uva.es:10324/217582021-10-04T07:32:43Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Defect formation during chlorine-based dry etching and their effects on the electronic and structural properties of InP/InAsP quantum wells
Landesman, Jean-Pierre
Jiménez López, Juan Ignacio
Levallois, Christophe
Pommereau, Frédéric
Frigeri, Cesare
Torres, Alfredo
Le Ger, Yoan
Beck, Alexandre
Rhallabi, Ahmed
Quantum wells
The general objective is the investigation of the defects formed by dry etching tools such as those involved in the fabrication of photonic devices with III–V semiconductors. Emphasis is put on plasma exposures with chlorine-based chemistries. In addition to identifying these defects and describing their effects on the electro-optic and structural properties, the long-term target would be to predict the impact on the parameters of importance for photonic devices, and possibly include these predictions in their design. The work is first centered on explaining the experimental methodology. This methodology starts with the design and growth of a quantum well structure on indium phosphide, including ternary indium arsenide/phosphide quantum wells with graded arsenic/phosphor composition. These samples have then been characterized by luminescence methods (photo- and cathodoluminescence), high-resolution transmission electron microscopy, and secondary ion mass spectrometry. As one of the parameters of importance in this study, the authors have also included the doping level. The samples have been exposed to the etching plasmas for “short” durations that do not remove completely the quantum wells, but change their optical signature. No masking layer with lithographic features was involved as this work is purely oriented to study the interaction between the plasma and the samples. A significant difference in the luminescence spectra of the as-grown undoped and doped samples is observed. A mechanism describing the effect of the built-in electric field appearing as a consequence of the doping profile is proposed. This mechanism involves quantum confined Stark effect and electric-field induced carrier escape from the quantum wells. In the following part, the effects of exposure to various chlorine-based plasmas were explored. Differences are again observed between the undoped and doped samples, especially for chemistries containing silicon tetrachloride. Secondary ion mass spectrometry indicates penetration of chlorine in the structures. Transmission electron microscopy is used to characterize the quantum well structure before and after plasma bombardment. By examining carefully the luminescence spectral properties, the authors could demonstrate the influence of the etching plasmas on the built-in electric field (in the case of doped samples), and relate it to some ionic species penetrating the structures. Etching plasmas involving both chlorine and nitrogen have also been studied. The etching rate for these chemistries is much slower than for some of the silicon tetrachloride based chemistries. Their effects on the samples are also very different, showing much reduced effect on the built-in electric field (for the doped samples), but significant blue-shifts of the luminescence peaks that the authors attributed to the penetration of nitrogen in the structures. Nitrogen, in interstitial locations, induces mechanical compressive stress that accounts for the blue-shifts. Finally, from the comparison between secondary ion mass spectrometry and luminescence spectra, the authors suggest some elements for a general mechanism involved in the etching by chloride-chemistries, in which a competition takes place between the species at the surface, active for the etching mechanism, and the species that penetrate the structure, lost for the etching process, but relevant in terms of impact on the electro-optic and structural features of the exposed materials.
2016-12-15T10:05:48Z
2016-12-15T10:05:48Z
2016-12-15T10:05:48Z
2016
info:eu-repo/semantics/article
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films , 2016, Volume 34, Issue 4
0734-2101
http://uvadoc.uva.es/handle/10324/21758
10.1116/1.4950445
eng
http://avspublications.org/jvsta/
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
AIP Publishing
oai:uvadoc.uva.es:10324/217592021-06-23T10:16:47Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Local electric field enhancement at the heterojunction of Si/SiGe axially heterostructured nanowires under laser illumination
Pura Ruiz, José Luis
Anaya, Julián
Souto Bartolomé, Jorge Manuel
Carmelo Prieto, Ángel
Rodríguez, Andrés
Rodríguez, Tomás
Jiménez López, Juan Ignacio
Laser illumination
We present a phenomenon concerning the electric eld enhancement at the
heterojunction region of axially heterostructured Si/SiGe nanowires when the nanowire
is illuminated by a focused laser beam. The electric eld is sensed by micro Raman
spectroscopy, which permits to reveal the enhancement of the Raman signal arising
from the heterojunction region; the Raman signal per unit volume increases at least
10 times with respect to the homogeneous Si, and SiGe nanowire segments. In order
to explore the physical meaning of this phenomenon, a 3-dimensional solution of the
Maxwell equations of the interaction between the focused laser beam and the nanowire
was carried out by nite element methods. A local enhancement of the electric eld
at the heterojunction was deduced; however, the magnitude of the electromagnetic
eld enhancement only approaches the experimental one when the free carriers are
considered, showing enhanced absorption at the carrier depleted heterojunction region.
The existence of this e ect promises a way to improve the photon harvesting using
axially heterostructured semiconductor NWs.
2016-12-15T10:12:44Z
2016-12-15T10:12:44Z
2016-12-15T10:12:44Z
2016
info:eu-repo/semantics/article
Nanotechnology, Volume 27, Number 45
0957-4484
http://uvadoc.uva.es/handle/10324/21759
https://doi.org/10.1088/0957-4484/27/45/455709
eng
http://iopscience.iop.org/journal/0957-4484
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
IOP
oai:uvadoc.uva.es:10324/217602021-06-23T10:16:53Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Spectrally and spatially resolved cathodoluminescence of undoped/Mg-doped GaN core-shell nanowires: a local probe into activation of Mg acceptors in non-polar and semi-polar crystal faces
Hortelano Santos, Vanesa
Martínez Sacristán, Óscar
Artús, L.
Cuscó, R.
Jiménez López, Juan Ignacio
Cathodoluminescence
Spectrally and spatially resolved cathodoluminescence (CL) measurements were carried out at 80 K on undoped/Mg-doped GaN core-shell nanowires grown by selective area growth metalorganic vapor phase epitaxy in order to investigate locally the optical activity of the Mg dopants. A study of the luminescence emission distribution over the different regions of the nanowires is presented. We have investigated the CL fingerprints of the Mg incorporation into the non-polar lateral prismatic facets and the semi-polar facets of the pyramidal tips. The amount of Mg incorporation/activation was varied by using several Mg/Ga flow ratios and post-growth annealing treatments. For lower Mg/Ga flow ratios, the annealed nanowires clearly display a donor-acceptor pair band emission peaking at 3.26-3.27 eV and up to 4 LO phonon replicas, which can be considered as a reliable indicator of effective p-type Mg doping in the nanowire shell. For higher Mg/Ga flow ratios, a substantial enhancement of the yellow luminescence emission as well as several emission subbands are observed, which suggests an increase of disorder and the presence of defects as a consequence of the excess Mg doping,
2016-12-15T10:23:58Z
2016-12-15T10:23:58Z
2016-12-15T10:23:58Z
2016
info:eu-repo/semantics/article
Nanotechnology, 2016, 27(9), p. 095706
0957-4484
http://uvadoc.uva.es/handle/10324/21760
eng
http://iopscience.iop.org/journal/0957-4484
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
IOP Publishing
oai:uvadoc.uva.es:10324/217702021-06-23T10:16:54Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Catastrophic optical damage of high power InGaAs/AlGaAs laser diodes
Souto Bartolomé, Jorge Manuel
Pura Ruiz, José Luis
Torres, Alfredo
Jiménez López, Juan Ignacio
Bettiati, Mauro
Laruelle, Francois
Cathodoluminescence
The defects generated by the catastrophic optical degradation (COD) of high power laser diodes have been examined using cathodoluminescence (CL). Discontinuous dark lines that correspond to different levels of damage have been observed along the ridge. Finite element methods have been applied to solve a physical model for the degradation of the diodes that explicitly considers the thermal and mechanical properties of the laser structure. According to this model, the COD is triggered by a local temperature enhancement that gives rise to thermal stresses leading to the generation of dislocations. Damage is initially localized in the QW, and when it propagates to the waveguide layers the laser ends its life.
2016-12-15T12:35:28Z
2016-12-15T12:35:28Z
2016-12-15T12:35:28Z
2016
info:eu-repo/semantics/article
Microelectron. Reliability 64, 627 (1916)
0026-2714
http://uvadoc.uva.es/handle/10324/21770
10.1016/j.microrel.2016.07.038
eng
http://www.journals.elsevier.com/microelectronics-reliability/
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Elsevier
oai:uvadoc.uva.es:10324/217862021-06-23T10:16:39Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Mechanisms driving the catastrophic optical damage in high power laser diodes
Souto Bartolomé, Jorge Manuel
Pura Ruiz, José Luis
Rodríguez, M.
Anaya, Julián
Torres, Alfredo
Jiménez López, Juan Ignacio
Laser diodes,
The catastrophic optical damage (COD) of laser diodes consists of the sudden drop off of the optical power. COD is
generally associated with a thermal runaway mechanism in which the active zone of the laser is molten in a positive
feedback process. The full sequence of the degradation follows different phases: in the first phase, a weak zone of the laser
is incubated and the temperature is locally increased there; when a critical temperature is reached the thermal runaway
process takes place. Usually, the positive feedback leading to COD is circumscribed to the sequential enhancement of the
optical absorption in a process driven by the increase of the temperature. However, the meaning of the critical temperature
has not been unambiguously established. Herein, we will discuss about the critical temperature, and the physical
mechanisms involved in this process. The influence of the progressive deterioration of the thermal conductivity of the laser
structure as a result of the degradation during the laser operation will be addressed.
2016-12-16T07:53:09Z
2016-12-16T07:53:09Z
2016-12-16T07:53:09Z
2015
info:eu-repo/semantics/article
SPIE Proceedings, 2015, Vol. 9348, P. 9348O-1-7 Mark S. Zediker, Editor(s)
0277-786X
http://uvadoc.uva.es/handle/10324/21786
10.1117/12.2079464
eng
http://spie.org/publications/conference-proceedings?WT.svl=mddp2
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Society of Photo-optical Instrumentation Engineers (SPIE)
oai:uvadoc.uva.es:10324/217952023-03-20T16:10:52Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Thermal conductivity of rough and smooth Silicon naanowires: a predictive approach
Anaya, Julián
Rodríguez, Tomás
Jiménez López, Juan Ignacio
Thermal conductivity
Predictive Model for the Thermal Conductivity of Rough and Smooth Silicon Nanowires.
2016-12-16T09:34:53Z
2016-12-16T09:34:53Z
2016-12-16T09:34:53Z
2014
info:eu-repo/semantics/article
Science of Advanced Materials. Vol. 6, pp. 1–11, 2014
1947-2935
http://uvadoc.uva.es/handle/10324/21795
eng
http://www.aspbs.com/sam/
American Scientific Publishers
oai:uvadoc.uva.es:10324/217972021-06-23T10:16:40Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Raman Spectroscopy in Group IV Nanowires and Nanowire Axial Heterostructures
Anaya, Julián
Torres, Alfredo
Jiménez López, Juan Ignacio
Rodríguez, Andrés
Rodríguez, Tomás
Ballesteros, Carmen
Raman Spectroscopy
The control of the SiGe NW composition is fundamental for the fabrication of high
quality heterostructures. Raman spectroscopy has been used to analyse the composition
of SiGe alloys. We present a study of the Raman spectrum of SiGe nanowires and
SiGe/Si heterostructures. The inhomogeneity of the Ge composition deduced from the
Raman spectrum is explained by the existence of a Ge-rich outer shell and by the
interaction of the NW with the electromagnetic field associated with the laser beam.
2016-12-16T10:03:44Z
2016-12-16T10:03:44Z
2016-12-16T10:03:44Z
2014
info:eu-repo/semantics/article
MRS Proceedings, 2014, Volume 1659, p. 143-148
http://uvadoc.uva.es/handle/10324/21797
10.1557/opl.2014.197
eng
https://www.cambridge.org/
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Cambridge University Press
oai:uvadoc.uva.es:10324/217992021-06-23T10:16:44Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Electromagnetic interaction between a laser beam and semiconductor nanowires deposited on different substrates: Raman enhancement in Si Nanowires
Anaya, Julián
Jiménez López, Juan Ignacio
Rodríguez, Andrés
Rodríguez, Tomás
Electromagnetic interaction
Raman scattering of Si nanowires (NWs) presents antenna effects. The
electromagnetic resonance depends on the electromagnetic coupling of the system
laser/NW/substrate. The antenna effect of the Raman signal was measured in individual
NWs deposited on different substrates, and also free standing NWs in air. The one
phonon Raman band in NWs can reach high intensities depending on the system
configuration; values of Raman intensity per unit volume more than a few hundred
times with respect to bulk substrate can be obtained.
2016-12-16T10:12:34Z
2016-12-16T10:12:34Z
2016-12-16T10:12:34Z
2014
info:eu-repo/semantics/article
MRS Online Proceedings Library 2014, vol. 1627, L09-38
http://uvadoc.uva.es/handle/10324/21799
10.1557/opl.2014.250
eng
https://www.cambridge.org/
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Cambridge University Press
oai:uvadoc.uva.es:10324/218012021-06-23T10:16:41Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Enhanced Signal Micro-Raman Study of SiGe Nanowires and SiGe/Si Nanowire Axial Heterojuntions Grown Using Au and Ga-Au Catalysts
Anaya, Julián
Torres, Alfredo
Jiménez López, Juan Ignacio
Prieto Colorado, Ángel Carmelo
Rodríguez, Andrés
Rodríguez, Tomás
Ballesteros, Carmen
Enhanced Signal Micro-Raman
MicroRaman spectroscopy was used for the characterization of heterostructured
SiGe/Si nanowires. The NWs were grown with alloyed AuGa catalysts droplets with
different Ga compositions aiming to make more abrupt heterojunctions. The
heterojunctions were first characterized by TEM; then the NWs were scanned by the
laser beam in order to probe the heterojunction. The capability of the MicroRaman
spectroscopy for studying the heterojunction is discussed. The results show that the use
of catalysts with lower Ge and Si solubility (AuGa alloys) permits to achieve more
abrupt junctions.
2016-12-16T10:24:57Z
2016-12-16T10:24:57Z
2016-12-16T10:24:57Z
2015
info:eu-repo/semantics/article
MRS Proceedings, 2015, vol. 1751
http://uvadoc.uva.es/handle/10324/21801
10.1557/opl.2015.88
eng
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Materials Reseracrh Society
oai:uvadoc.uva.es:10324/229982021-06-23T10:17:01Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
In situ Raman characterization of minerals and degradation processes in a variety of cultural and geological heritage sites
Gázquez, Fernando
Rull Pérez, Fernando
Sanz Arranz, Aurelio
Medina García, Jesús
Calaforra, José María
Heras, C. de las
Lasheras, J.A.
Wetest the capabilities of in situ Raman spectroscopy for non-destructive analysis of degradation processes in invaluable
masterpieces, as well as for the characterization of minerals and prehistoric rock-art in caves. To this
end, we have studied the mechanism of decay suffered by the 15th-century limestone sculptures that decorate
the retro-choir of Burgos Cathedral (N Spain). In situ Raman probe detected hydrated sulfate and nitrateminerals
on the sculptures, which are responsible for the decay of the original limestone. In addition, in situ Raman analyses
were performed on unique speleothems in El Soplao Cave (Cantabria, N Spain) and in the Gruta de las
Maravillas (Aracena, SWSpain). Unusual cavemineralswere detected in El Soplao Cave, such as hydromagnesite
(Mg5(CO3)4(OH)2·4H2O), as well as ferromanganese oxides in the black biogenic speleothems recently discovered
in this cavern. In the Gruta de las Maravillas, gypsum (CaSO4·2H2O) was identified for the first time, as
part of the oldest cave materials, so providing additional evidence of hypogenic mechanisms that occurred in
this cave during earlier stages of its formation. Finally, we present preliminary analyses of several cave paintings
in the renowned “Polychrome Hall” of Altamira Cave (Cantabria, N. Spain). Hematite (Fe2O3) is the most abundant
mineral phase, which provides the characteristic ochre-reddish color to the Altamira bison and deer paintings.
Thus, portable Raman spectroscopy is demonstrated to be an analytical technique compatible with
preserving our cultural and natural heritage, since the analysis does not require physical contact between the
Raman head and the analyzed items.
2017-04-05T11:28:38Z
2017-04-05T11:28:38Z
2017-04-05T11:28:38Z
2016
info:eu-repo/semantics/article
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
http://uvadoc.uva.es/handle/10324/22998
eng
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/229992022-01-17T12:15:39Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Estudio de basaltos mediante espectroscopía de plasma inducido por láser (LIBS) para la fabricación de bloques de lapilli
Viuda Pérez, Ismael de la
Navarro Azor, Rafael
Lalla, Emmanuel Alexis
Rodríguez Losada, Jose Antonio
Aquilano, Roberto
Medina García, Jesús
Rull Pérez, Fernando
Se analizaron mediante espectroscopía de plasma inducido por láser (LIBS), espectroscopía Raman y difracción de rayos x (XRD) muestras seleccionadas de diversas zonas de Tenerife, con el objetivo de identificar su composición química elemental y mineralógica. Los resultados mostraron los elementos mayoritarios siguientes: O, F, Na, K, Mg, Al, Si, Ca, Ti y Fe. La identificación de las muestras, mediante espectroscopía Raman y XRD, mostró una mineralogía de tipo basáltica coincidente con los resultados de composición elemental LIBS. Los resultados de los análisis con instrumentación portátil demuestran la aplicabilidad de la espectroscopía LIBS y, en especial, en combinación con la espectroscopía Raman, para su utilización en la detección mineralógica-química en las zonas de extracción de basaltos y picón para la construcción en Tenerife.
2017-04-05T11:33:25Z
2017-04-05T11:33:25Z
2017-04-05T11:33:25Z
2016
info:eu-repo/semantics/article
Minería y Geología / v.32
1993 8012
http://uvadoc.uva.es/handle/10324/22999
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/230002021-06-23T10:17:06Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Survival of Moss Reproductive Structures under Simulated Martian Environmental Conditions and Extreme Thermal Stress: Vibrational Spectroscopic Study and Astrobiological Implications
Gómez Gómez, José María
Estébanez, Belén
Sanz Arranz, Aurelio
Mateo Martí, Eva
Medina García, Jesús
Rull Pérez, Fernando
The principal goal of astrobiology is the search for extraterrestrial life forms. A key aspect is the study of the
ability of different kinds of terrestrial organisms to support simulated extraterrestrial environmental conditions.
Mosses are multicellular green plants, poorly studied from an astrobiological perspective. In this paper, we report
experimental results obtained using two species of moss, which demonstrate that both the spores of the moss
Funaria hygrometrica as well as the desiccated vegetative gametophyte shoots of the moss Tortella squarrosa
(=Pleurochaete squarrosa) were capable of resisting Simulated Martian Environmental Conditions (SMEC): Mars
simulated atmospheric composition 99.9% CO2, and 0.6% H2O with a pressure of 7 mbars, -73 ºC and UV irradiation
of 30 mW cm-2 in a wavelength range of 200-400 nm under a limited short time of exposition of 2 hours. After being
exposed to SMEC and then transferred to an appropriate growth medium, the F. hygrometrica spores germinated,
producing typical gametophyte protonemal cells and leafy shoots. Likewise, detached leaves from SMEC-exposed
gametophyte shoots of T. squarrosa retained the ability to produce new protonemata and shoots under suitable
growth conditions. Furthermore, we studied the tolerance of these moss structures to a thermal stress of 100 °C for 1
h; in both cases the spores and shoots were capable of resisting this heat treatment. Our study using FT-Raman and
FT-IR vibrational spectroscopy demonstrated that neither spores nor shoots apparently suffered significant damage
in their biomolecular makeup after being subject to these stress treatments. The implications of these findings for the
search of life on Mars are discussed.
2017-04-05T11:37:30Z
2017-04-05T11:37:30Z
2017-04-05T11:37:30Z
2016
info:eu-repo/semantics/article
Gómez et al., Astrobiol Outreach 2016, 4:2
http://uvadoc.uva.es/handle/10324/23000
eng
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/230012021-06-23T10:17:07Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
A Rich Morphological Diversity of Biosaline Drying Patterns Is Generated by Different Bacterial Species, Different Salts and Concentrations: Astrobiological Implications
Gómez Gómez, José María
Medina García, Jesús
Rull Pérez, Fernando
Biosaline formations (BSFs) are complex self-organized biomineral patterns formed by ‘‘hibernating’’ bacteria
as the biofilm that contains them dries out. They were initially described in drying biofilms of Escherichia coli
cells + NaCl. Due to their intricate 3-D morphology and anhydrobiosis, these biomineralogical structures are of
great interest in astrobiology. Here we report experimental data obtained with various alkali halide salts (NaF,
NaCl, NaBr, LiCl, KCl, CsCl) on BSF formation with E. coli and Bacillus subtilis bacteria at two saline
concentrations: 9 and 18 mg/mL. Our results indicate that, except for LiCl, which is inactive, all the salts
assayed are active during BSF formation and capable of promoting the generation of distinctive drying patterns
at each salt concentration. Remarkably, the BSFs produced by these two bacterial species produce characteristic
architectural hallmarks as the BSF dries. The potential biogenicity of these biosaline drying patterns is studied,
and the astrobiological implications of these findings are discussed
2017-04-05T11:40:26Z
2017-04-05T11:40:26Z
2017-04-05T11:40:26Z
2016
info:eu-repo/semantics/article
ASTROBIOLOGY Volume 16, Number 7, 2016
http://uvadoc.uva.es/handle/10324/23001
eng
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/230022021-06-23T10:17:08Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Nd3+-doped TeO2–PbF2–AlF3 glasses for laser applications
Lalla, Emmanuel Alexis
Rodríguez Mendoza, U. R.
Lozano Gorrín, A.D.
Sanz Arranz, Aurelio
Rull Pérez, Fernando
Lavín, V.
A study of the optical properties of Nd3+ ion in TeO2–PbF2–AlF3 glasses has been carried out for different
Nd3+ concentrations. Based on the Judd–Ofelt theory, intensity parameters and radiative properties were
determined from the absorption spectra. Focusing on the suitability of this host for laser applications, the
spectroscopic quality factor v was obtained with a value of 1.07, a value of the order of other
compositions proposed as laser hosts. For the most intense emission corresponding with the
4F3/2?4I11/2 transition (1.06 lm), the absorption and emission and have been calculated with values
of 1.20 10 20 cm2, 2.08 10 20 cm2. A positive value for the gain cross-sections has been found for a
population inversion factor c of 0.4 in the spectral range from 1060 to 1110 nm. All these results suggest
the potentially use of this system as a laser host.
2017-04-05T11:44:03Z
2017-04-05T11:44:03Z
2017-04-05T11:44:03Z
2016
info:eu-repo/semantics/article
Optical Materials 51 (2016) 35–41
http://uvadoc.uva.es/handle/10324/23002
eng
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/230032022-01-21T12:34:09Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Raman-IR vibrational and XRD characterization of ancient and modern mineralogy from volcanic eruption in Tenerife Island: Implication for Mars
Lalla, Emmanuel Alexis
López Reyes, Guillermo Eduardo
Sansano Caramazana, Antonio
Sanz Arranz, Aurelio
Martínez Frías, Jesús
Medina García, Jesús
Rull Pérez, Fernando
A detailed vibrational Raman-IR spectroscopic and diffractional analyses have been performed on basalts
from two locations from Tenerife Island: (1) the Arenas Negras volcano which belongs to the historical
eruption not showing visible alteration and (2) Pillow Lavas zone from Anaga Massif which shows a
clearly fluid-rock interaction caused by submarine alteration. These places have been extensively studied
due to its similarity with the surface of Mars. The analysis is based on the mineral detection of selected
samples by a Micro-Raman study of the materials. The complementary techniques have confirmed the
mineralogy detected by the Raman measurement. The results show a volcanic environment behavior
with primary phases like olivine, pyroxene, and feldspar/plagioclase. Moreover, the presence of accessory
minerals or secondary mineralization like phosphate, iron oxides, zeolite or carbonates shows the
alteration processes on each outcrop. The variation in the crystallinity and amorphous phases is related
to fluid-rock interaction caused by hydrothermal episodes and external weathering processes, which
shows several analogies with the ancient volcanic activity from Mars.
2017-04-05T11:48:02Z
2017-04-05T11:48:02Z
2017-04-05T11:48:02Z
2016
info:eu-repo/semantics/article
Geoscience Frontiers 7 (2016) 673-681
http://uvadoc.uva.es/handle/10324/23003
eng
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/230042022-01-21T12:34:23Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Raman–Mo¨ssbauer–XRD studies of selected samples from ‘‘Los Azulejos” outcrop: A possible analogue for assessing the alteration processes on Mars
Lalla, Emmanuel Alexis
Sanz Arranz, Aurelio
López Reyes, Guillermo Eduardo
Sansano Caramazana, Antonio
Medina García, Jesús
Schmanke, D.
Klingelhöefer, G.
Rodríguez Losada, Jose Antonio
Martínez Frías, Jesús
Rull Pérez, Fernando
The outcrop of ‘‘Los Azulejos” is visible at the interior of the Can˜adas Caldera in Tenerife Island (Spain). It exhibits a great variety of
alteration processes that could be considered as terrestrial analogue for several geological processes on Mars. This outcrop is particularly
interesting due to the content of clays, zeolite, iron oxides, and sulfates corresponding to a hydrothermal alteration catalogued as ‘‘Azulejos”
type alteration. A detailed analysis by portable and laboratory Raman systems as well as other different techniques such as X-ray
diffraction (XRD) and Mo¨ssbauer spectroscopy has been carried out (using twin-instruments from Martian lander missions: Mo¨ssbauer
spectrometer MIMOS-II from the NASA-MER mission of 2001 and the XRD diffractometer from the NASA-MSL Curiosity mission of
2012). The mineral identification presents the following mineral species: magnetite, goethite, hematite, anatase, rutile, quartz, gregoryite,
sulfate (thenardite and hexahydrite), diopside, feldspar, analcime, kaolinite and muscovite. Moreover, the in-situ Raman and Micro-
Raman measurements have been performed in order to compare the capabilities of the portable system specially focused for the next
ESA Exo-Mars mission. The mineral detection confirms the sub-aerial alteration on the surface and the hydrothermal processes by
the volcanic fluid circulations in the fresh part. Therefore, the secondary more abundant mineralization acts as the color agent of the
rocks. Thus, the zeolite–illite group is the responsible for the bluish coloration, as well as the feldspars and carbonates for the whitish
and the iron oxide for the redish parts. The XRD system was capable to detect a minor proportion of pyroxene, which is not visible by
Raman and Mo¨ssbauer spectroscopy due to the ‘‘Azulejos” alteration of the parent material on the outcrop. On the other hand, Mo¨ ssbauer
spectroscopy was capable of detecting different types of iron-oxides (Fe3+/2+-oxide phases). These analyses emphasize the strength
of the different techniques and the working synergy of the three different techniques together for planetary space missions.
2017-04-05T11:52:49Z
2017-04-05T11:52:49Z
2017-04-05T11:52:49Z
2016
info:eu-repo/semantics/article
Advances in Space Research 57 (2016) 2385–2395
http://uvadoc.uva.es/handle/10324/23004
eng
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/230052022-01-21T12:35:14Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Testing the ability of the ExoMars 2018 payload to document geological context and potential habitability on Mars
Bost, N.
Ramboz, C.
LeBreton, N.
Foucher, F.
López Reyes, Guillermo Eduardo
Angelis, S. de
Josset, M.
Josset, J.L.
Souchon, A.
Ammannito, E.
Sanctis, M.C. de
Di Iorio, T.
Carli, C.
Westall, F.
Vago, Jorge L.
Sanz Arranz, Aurelio
Venegas, Gloria
Rull Pérez, Fernando
Medina García, Jesús
The future ExoMars rover mission (ESA/Roscosmos), to be launched in 2018, will investigate the habitability of the Martian surface and near subsurface, and search for traces of past life in the form of textural biosignatures and organic molecules. In support of this mission, a selection of relevant Mars analogue materials has been characterised and stored in the International Space Analogue Rockstore (ISAR), hosted in Orléans, France. Two ISAR samples were analysed by prototypes of the ExoMars rover instruments used for petrographic study. The objective was to determine whether a full interpretation of the rocks could be achieved on the basis of the data obtained by the ExoMars visible-IR imager and spectrometer (MicrOmega), the close-up imager (CLUPI), the drill infrared spectrometer (Ma_Miss) and the Raman spectrometer (RLS), first separately then in their entirety. In order to not influence the initial instrumental interpretation, the samples were sent to the different teams without any additional
2017-04-05T12:17:05Z
2017-04-05T12:17:05Z
2017-04-05T12:17:05Z
2015
info:eu-repo/semantics/article
Planetary and Space Science 108 (2015) 87–97
http://uvadoc.uva.es/handle/10324/23005
eng
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/230062022-01-19T10:11:28Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Estudio espectroscópico y DRX de afloramientos terrestres volcánicos en la isla de Tenerife como posibles análogos de la geología marciana
Lalla, Emmanuel Alexis
López Reyes, Guillermo Eduardo
Sansano Caramazana, Antonio
Sanz Arranz, Aurelio
Schmanke, D.
Klingelhöefer, G.
Medina García, Jesús
Martínez Frías, Jesús
Rull Pérez, Fernando
Se ha llevado a cabo una selección de varios afloramientos volcánicos en la Isla de Tenerife (La Caldera de las Cañadas, vulcanismo histórico y la zona del Malpaís de Güimar) como posibles análogos terrestres de Marte, considerando los procesos volcánicos ocurridos durante algunas de las etapas geológicas del planeta rojo. En la selección de las áreas de estudio se han tenido en cuenta la diversidad de procesos de alteración, que incluyen
fenómenos como meteorización y alteración hidrotermal. Estos procesos terrestres podrían servir como modelo de la actividad volcánica primitiva en Marte.
Los materiales seleccionados se han analizado mediante espectroscopia micro-Raman, difracción de rayos X (DRX) y espectroscopia Mössbauer. Los resultados revelan que la mineralogía de los afloramientos está constituida por una matriz de olivinos, piroxenos y feldespatos. Además, se ha detectado una gran variedad de especies minerales correspondientes a procesos de alteración como óxidos, arcillas y carbonatos.
Los resultados obtenidos han demostrado ser un punto de partida para desarrollar investigaciones en estos entornos volcánicos especialmente enfocados al desarrollo de la ciencia de instrumentación para exploración planetaria. La instrumentación utilizada en la investigación ha sido a través de prototipos gemelos empleados en la exploración espacial, como DRX (actualmente en la misión NASA-MSL-Curiosity), espectroscopia Mössbauer
(a bordo de la misión NASA-MER) y el futuro instrumento Raman de la misión ESA-ExoMars. Además, la mineralogía detectada coincide con los resultados reportados en Marte.
Los métodos de análisis Raman, tanto de caracterización e identificación, mediante el estudio de patrones espectrales se han aplicado exitosamente, donde el análisis de los perfiles Raman son de extrema utilidad para aclarar el origen de las especies minerales. La espectroscopia Mössbauer y la difracción de rayos X han confirmado los resultados Raman.
2017-04-05T12:23:11Z
2017-04-05T12:23:11Z
2017-04-05T12:23:11Z
2015
info:eu-repo/semantics/article
Estudios Geológicos julio-diciembre 2015, 71(2), e035
http://uvadoc.uva.es/handle/10324/23006
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/253732021-07-06T08:33:29Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
About the impact of the materials properties in the catastrophic degradation of high power GaAs based laser
Souto Bartolomé, Jorge Manuel
Pura Ruiz, José Luis
Torres, Alfredo
Jiménez López, Juan Ignacio
The catastrophic degradation of high power lasers depends on both external factors, associated with the technological processes followed to fabricate the laser, and also on intrinsic aspects related to the materials forming the laser structure, more specifically the active zone composed by the QW, guide layers and claddings.
The materials properties: optical, thermal and mechanical, play a paramount role in the degradation of the laser. We analyse here how these properties have an impact on the mechanisms responsible for the catastrophic degradation.
2017-09-04T16:35:07Z
2017-09-04T16:35:07Z
2017-09-04T16:35:07Z
2017
info:eu-repo/semantics/article
Proceedings of SPIE, 2017, Vol. 10086: High-Power Diode Laser Technology XV
0277786X
http://uvadoc.uva.es/handle/10324/25373
https://doi.org/10.1117/12.2251890
100860P-1
100860P-6
High Power Diode Laser Technology XV
10086
eng
http://spie.org/Publications/Proceedings/Paper/10.1117/12.2251890
info:eu-repo/semantics/restrictedAccess
SPIE Digital Library
Society of Photo-optical Instrumentation Engineers (SPIE)
oai:uvadoc.uva.es:10324/253742021-06-23T10:17:14Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Nanoscale effects on the thermal and mechanical properties of AlGaAs/GaAs quantum well laser diodes: influence on the catastrophic optical damage
Souto Bartolomé, Jorge Manuel
Pura Ruiz, José Luis
Jiménez López, Juan Ignacio
In this work we study the catastrophic optical damage (COD) of graded-index separate
confinement heterostructure quantum well (QW) laser diodes based on AlGaAs/GaAs.
The emphasis is placed on the impact that the nanoscale physical properties have on the
operation and degradation of the active layers of these devices. When these laser diodes run
in continuous-wave mode with high internal optical power densities, the QW and guide layers
can experiment very intense local heating phenomena that lead to device failure. A thermomechanical model has been set up to study the mechanism of degradation. This model has been solved by applying finite element methods. A variety of physical factors related to the materials properties, which play a paramount role in the laser degradation process, have been considered. Among these, the reduced thicknesses of the QW and the guides lead to thermal conductivities smaller than the bulk figures, which are further reduced as extended defects develop in these layers. This results in a progressively deteriorating thermal management in the device. To the best of our knowledge, this model for laser diodes is the first one to have taken into account low scale mechanical effects that result in enhanced strengths in the structural layers. Moreover, the consequences of these conflicting size-dependent properties on the thermo-mechanical behaviour on the route to COD are examined. Subsequently, this approach opens the possibility of taking advantage of these properties in order to design robust diode lasers (or other types of power devices) in a controlled manner.
2017-09-04T16:48:03Z
2017-09-04T16:48:03Z
2017-09-04T16:48:03Z
2017
info:eu-repo/semantics/article
Journal of Physics D: Applied Physics, 2017, Volume 50, Number 23
0022-3727
http://uvadoc.uva.es/handle/10324/25374
https://doi.org/10.1088/1361-6463/aa6fbd
235101-1
235101-12
Nanoscale effects on the thermal and mechanical properties of AlGaAs/GaAs quantum well laser diodes: influence on the catastrophic optical damage
50
eng
https://iopscience.iop.org/article/10.1088/1361-6463/aa6fbd
info:eu-repo/semantics/restrictedAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
IOP Publishing
Attribution-NonCommercial-NoDerivatives 4.0 International
Institute of Physics Publishing
oai:uvadoc.uva.es:10324/258782021-06-30T09:37:48Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
PMMA-sepiolite nanocomposites as new promising materials for the production of nanocellular polymers
Bernardo García, Victoria
Martín de León, Judit
Laguna Gutiérrez, Ester
Rodríguez Pérez, Miguel Ángel
In this work, a new system based on poly(methyl methacrylate) (PMMA) sepiolite nanocomposites
that allow producing nanocellular polymers by using the gas dissolution foaming technique
is described. Nanocomposites with different nanoparticle types and contents have been produced
by extrusion. From these blends, cellular materials have been fabricated using the so-called gas
dissolution foaming method. An extensive study of the effect of the processing parameters (saturation
pressure and foaming temperature) on the cellular materials produced has been performed.
Results showed that among the three sepiolites used, only those modified with a quaternary
ammonium salt are suitable for being used as nucleating agents in PMMA. With these
nanoparticles bimodal cellular polymers, with micro and nanometric cells, have been produced.
Cell sizes in the range of 300–500 nm and cell densities of the order of 1013–1014 nuclei/cm3
have been obtained in the nanocellular region. A foaming temperature of 80 °C and a wide range
of saturation pressures (between 10 and 30 MPa) and low particle contents (between 0.5 and
1.5 wt%) allow obtaining these materials. Furthermore, it has been found that cell size in the
nanometric population can be controlled by means of the particles content; a reduction in the cell size is obtained when the particles content increases. Finally, results indicate that an increase in the foaming temperature leads to cellular nanocomposites with lower relative densities (below 0.21) and larger cell sizes (above 450 nm).
2017-09-24T14:40:59Z
2017-09-24T14:40:59Z
2017-09-24T14:40:59Z
2017
info:eu-repo/semantics/article
European Polymer Journal, 2017, vol. 96. p. 10–26
http://uvadoc.uva.es/handle/10324/25878
10.1016/j.eurpolymj.2017.09.002
eng
https://www.sciencedirect.com/science/article/pii/S0014305717310017?via%3Dihub
info:eu-repo/semantics/restrictedAccess
Elsevier
Elsevier
oai:uvadoc.uva.es:10324/258792021-06-23T10:17:17Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Light transmission in nanocellular polymers: Are semi-transparent cellular polymers possible?
Pérez Tamarit, Saúl
Notario Collado, Belén
Solórzano Quijano, Eusebio
Rodríguez Pérez, Miguel Ángel
This work presents the light transmission through a collection of solid cellular polymers based on poly
(methyl methacrylate) (PMMA) with cells sizes covering the micro and nano-scale. The obtained results
showed that the behavior of light transmission when cell size is in the nano-scale is opposite to the one
shown by microcellular foams or the one predicted by theoretical models of light scattering (LS). In fact,
the expected trend is that a reduction of cell size increases the opacity of the samples. However, for
nanocellular polymers based on amorphous polymers reducing the cell size increases the light transmission.
Therefore, this result indicates that a further reduction of the cell size could result in cellular polymers
optically semi-transparent.
2017-09-24T14:46:45Z
2017-09-24T14:46:45Z
2017-09-24T14:46:45Z
2017
info:eu-repo/semantics/article
Materials Letters 210 (2018) 39–41
http://uvadoc.uva.es/handle/10324/25879
10.1016/j.matlet.2017.08.109
spa
info:eu-repo/semantics/restrictedAccess
elsevier
Elsevier
http://linkinghub.elsevier.com/retrieve/pii/S0167577X17313162
oai:uvadoc.uva.es:10324/258802021-06-24T07:47:46Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Nanoporous PMMA foams with templated pore size obtained by localized in situ synthesis of nanoparticles and CO2 foaming
Pinto Sanz, Javier
Morselli, Davide
Bernardo García, Victoria
Notario Collado, Belén
Fragouli, Despina
Rodríguez Pérez, Miguel Ángel
Athanassiou, Athanassia
Polymer foams with controlled and templated pore size have been obtained for the first time by CO2 gas
dissolution foaming from poly(methyl methacrylate) (PMMA) films. This kind of materials, with a variable
porous structure, mimic some high-performance natural materials and could present significant
interest in many applications. However, up to now their controlled fabrication has not been successfully
achieved. Herein, we present a method to achieve a fine control in the production of such materials.
Thermal in situ synthesis of ZnO nanoparticles from Zn(OAc)2 was proposed to obtain PMMA nanocomposites,
in which the ZnO nanoparticles induce heterogeneous nucleation that leads to formation of
pores with size below the micron, upon CO2 foaming. Starting from templated solid PMMA samples with
well-differentiated regions, presenting or not ZnO nanoparticles, it was possible to obtain PMMA-based
foams with well-defined areas of different pore sizes.
2017-09-24T14:53:38Z
2017-09-24T14:53:38Z
2017-09-24T14:53:38Z
2017
info:eu-repo/semantics/article
Polymer 124 (2017) 176-185
http://uvadoc.uva.es/handle/10324/25880
eng
http://linkinghub.elsevier.com/retrieve/pii/S0032386117307425
info:eu-repo/semantics/restrictedAccess
Elsevier
Elsevier
oai:uvadoc.uva.es:10324/258812021-06-24T07:47:49Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Highly anisotropic crosslinked HDPE foams with a controlled anisotropy ratio: Production and characterization of the cellular structure and mechanical properties
Bernardo García, Victoria
Laguna Gutiérrez, Ester
López Gil, Alberto
Rodríguez Pérez, Miguel Ángel
In this paper a two-step foaming process was used to produce highly anisotropic foams with controlled anisotropy
ratio. Anisotropic cellularmaterials are of great interest due to the enhanced mechanical properties that they show
in the anisotropy direction. Therefore, the production of foams with high and controlled anisotropy ratios is an essential
topic when it comes to designmaterialswith goodmechanical performance. In thiswork, high density polyethylene
(HDPE) foams with anisotropy ratios larger than 3 have been produced. A foaming process consisting of
two consecutive heating steps: pre-foaming and foaming, has been employed. Foaming kinetics at four different
pre-foaming temperatures (145 °C, 155 °C, 170 °C and 180 °C) and at a constant foaming temperature (180 °C)
have been performed. Results showed that the pre-foaming temperature is the key parameter that allows controlling
the anisotropy ratio of the final foam. A relationship between the pre-foaming temperature, the number of cells
and the anisotropy ratio has been established. Low pre-foaming temperatures lead to low numbers of cells, which
eventually results in high anisotropy ratios. Mechanical properties in compression were measured and compared
with the anisotropy of the cellular structure, being that the elastic modulus increases with the anisotropy ratio.
2017-09-24T14:58:16Z
2017-09-24T14:58:16Z
2017-09-24T14:58:16Z
2017
info:eu-repo/semantics/article
Materials and Design 114 (2017) 83–91
http://uvadoc.uva.es/handle/10324/25881
eng
http://linkinghub.elsevier.com/retrieve/pii/S0264127516313491
info:eu-repo/semantics/restrictedAccess
Elsevier
Elsevier
oai:uvadoc.uva.es:10324/258822021-06-24T07:45:46Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Dielectric behavior of porous PMMA: From the micrometer to the nanometer scale
Notario Collado, Belén
Pinto Sanz, Javier
Verdejo, Raquel
Rodríguez Pérez, Miguel Ángel
In recent years, there has been a significant interest of the scientific community on nanocellular polymeric
foams as a possible next generation of materials with a low dielectric constant for microelectronics
applications In this work, the dielectric behavior of microcellular and nanocellular poly (methyl methacrylate)
(PMMA) based foams has been characterized, both as a function of frequency and temperature,
in order to analyze the effect of reducing the cell size to the nanoscale on the dielectric properties.
Experimental results have shown clear differences in the dielectric behavior of the samples with cell
sizes in the nanoscale as well as a sharp reduction of the dielectric constant when the porosity increases.
2017-09-24T15:05:38Z
2017-09-24T15:05:38Z
2017-09-24T15:05:38Z
2017
info:eu-repo/semantics/article
Polymer 107 (2016) 302e305
http://uvadoc.uva.es/handle/10324/25882
eng
http://www.sciencedirect.com/science/article/pii/S0032386116310230?via%3Dihub
info:eu-repo/semantics/restrictedAccess
Elsevier
Elsevier
oai:uvadoc.uva.es:10324/258832021-06-23T10:17:24Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Extensional rheology, cellular structure, mechanical behavior relationships in HMS PP/montmorillonite foams with similar densities
Laguna Gutiérrez, Ester
López Gil, Alberto
Sáiz Arroyo, Cristina
Van Hooghten, Ron
Moldenaers, Paula
Rodríguez Pérez, Miguel Ángel
The main goal of this work is to analyze the relationships
between the extensional rheological behavior of solid
nanocomposites based on high melt strength polypropylene
(HMS PP) and montmorillonites (MMT) and the cellular structure
and mechanical properties of foams produced from these
materials. For this purpose two systems have been analyzed.
The first one incorporates organomodified MMT and a
compatibilizer and the second system contains natural clays
and is produced without the compatibilizer. Results indicate
that the extensional rheological behavior of both materials is
completely different. The strain hardening of the polymer containing
organomodified clays decreases as the clay content
increases. As a consequence, the open cell content of this material
increaseswith the clay content and hence, themechanical
properties get worse. However, in the materials produced with
natural clays this relationship is not so clear. While no changes
are detected in the extensional rheological behavior by adding
these particles, the nano-filled materials show an open cell
structure, opposite to the closed cell structure of the pure polymer,
which is caused by the fact of having particle agglomerates
with a size larger than the thickness of the cell walls and a
poor compatibility between the clays and the polymer.
2017-09-24T15:11:49Z
2017-09-24T15:11:49Z
2017-09-24T15:11:49Z
2016
info:eu-repo/semantics/article
J Polym Res (2016) 23: 251
http://uvadoc.uva.es/handle/10324/25883
eng
https://link.springer.com/article/10.1007/s10965-016-1143-x
info:eu-repo/semantics/restrictedAccess
Springer
Springer
oai:uvadoc.uva.es:10324/258842021-06-24T07:45:48Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Influence of the irradiation dose in the cellular structure of naturalrubber foams cross-linked by electron beam irradiation
Salmazo, Leandra
López Gil, Alberto
Ariff, Z.M
Job, Aldo Eloizo
Rodríguez Pérez, Miguel Ángel
tThis work focused on the production of natural rubber foams by cross-linking the polymer matrix usinghigh energy electron beam at different irradiation doses (from 50 to 150 kGy) and foaming it with achemical blowing agent. The aim was to study how the irradiation dose influenced the cellular structuremorphology of the produced foams. This was accomplished by quantifying the evolution of cellular struc-ture parameters, such as cell size and cell density, with respect to foaming time and irradiation dose. Theresults showed that the foams irradiated at the lowest dose are more prone to suffer cellular structuredegeneration, resulting in the formation of bimodal cellular structures, while foams irradiated with thehighest dose, exhibited more uniform cellular structure. In the latter case, the nucleation density clearlyincreased resulting in the formation of foams with homogeneous cellular structures and smaller cell sizes(≈20 microns).
2017-09-24T15:15:10Z
2017-09-24T15:15:10Z
2017-09-24T15:15:10Z
2016
info:eu-repo/semantics/article
Industrial Crops and Products 89 (2016) 339–349
http://uvadoc.uva.es/handle/10324/25884
eng
http://www.sciencedirect.com/science/article/pii/S0926669016303430?via%3Dihub
info:eu-repo/semantics/restrictedAccess
Elsevier
Elsevier
oai:uvadoc.uva.es:10324/258852021-06-24T07:45:53Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Production and characterization of nanocellular polyphenylsulfone foams
Martín de León, Judit
Bernardo García, Victoria
Rodríguez Pérez, Miguel Ángel
Nanocellular foamshavebeenproducedbymeansofagasdissolutionprocessusingpolyphenylsulfone
(PPSU) asmatrixpolymer.Cellsizesintherange20–30 nmandcellnucleationdensitieshigherthan
1015 cm 3 havebeenachievedformaterialswithrelativedensitiesintherange0.65–0.75. Theinfluence
of bothsaturationpressureandfoamingtemperaturehasbeenstudied.Ontheonehand,ithasbeen
provedthatthereisalargeinfluence oftheamountofgas(CO2) absorbedinthe final cellularstructure,
in factithasbeenfoundacriticalCO2 uptake between9%and9.5%atwhichthecellsizesevolvefromthe
micro tothenanoscale.Ontheotherhand,ithasbeenfoundthatthereisawiderangeoffoaming
parameters(foamingtimeandfoamingtemperature)inwhichnanocellularfoamscanbeproduced.
2017-09-24T15:18:50Z
2017-09-24T15:18:50Z
2017-09-24T15:18:50Z
2016
info:eu-repo/semantics/article
Materials Letters178(2016)155–158
http://uvadoc.uva.es/handle/10324/25885
eng
http://linkinghub.elsevier.com/retrieve/pii/S0167577X16307261
info:eu-repo/semantics/restrictedAccess
Elsevier
oai:uvadoc.uva.es:10324/258862021-06-24T07:45:54Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Rigid polyurethane foams with infused nanoclays: Relationship between cellular structure and thermal conductivity
Estravís Sastre, Sergio
Tirado Mediavilla, Josias
Santiago Calvo, Mercerdes
Ruiz Herrero, José Luis
Villafañe González, Fernando
Rodríguez Pérez, Miguel Ángel
A water blown rigid polyurethane (PU) formulation has been used to manufacture cellular
nanocomposites containing different concentrations of montmorillonite nanoclays. The PU
foams have been produced using a low shear mixing technique for dispersing the nanoclays
and by reactive foaming to generate the cellular structure. A detailed characterization
of the cellular structure has been performed. The effect of the nanoparticles on the
reaction kinetics and the state of intercalation of the nanoparticles in the foams has been
analyzed. The thermal conductivity and extinction coefficient of the different materials has
been measured and the results obtained have been correlated with the materials structure.
A strong reduction of cell size and modifications on cell size distribution, anisotropy ratio
and fraction of material in the struts has been detected when the clays are added. In addition,
a reduction of the thermal conductivity has been observed. Different theoretical models
have been employed to explain thermal conductivity changes in terms of structural
features. It has been found that, in addition to the modifications in the cellular structure,
changes in the extinction coefficient and thermal conductivity of the matrix polymer play
an important role on the final values of the thermal conductivity for these materials.
2017-09-24T15:22:53Z
2017-09-24T15:22:53Z
2017-09-24T15:22:53Z
2016
info:eu-repo/semantics/article
European Polymer Journal 80 (2016) 1–15
http://uvadoc.uva.es/handle/10324/25886
eng
http://linkinghub.elsevier.com/retrieve/pii/S0014305716302968
info:eu-repo/grantAgreement/EC/FP7/214148
info:eu-repo/semantics/restrictedAccess
Elsevier
Elsevier
oai:uvadoc.uva.es:10324/258872021-06-24T07:45:51Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Low density nanocellular polymers based on PMMA produced by gas dissolution foaming: Fabrication and cellular structure characterization
Martín de León, Judit
Bernardo García, Victoria
Rodríguez Pérez, Miguel Ángel
This paper describes the processing conditions needed to produce low density nanocellular
polymers based on polymethylmethacrylate (PMMA) with relative densities between 0.45 and 0.25,
cell sizes between 200 and 250 nm and cell densities higher than 1014 cells/cm3. To produce these
nanocellular polymers, the foaming parameters of the gas dissolution foaming technique using CO2
as blowing agent have been optimized. Taking into account previous works, the amount of CO2
uptake was maintained constant (31% by weight) for all the materials. Foaming parameters were
modified between 40 C and 110 C for the foaming temperature and from 1 to 5 min for the foaming
time. Foaming temperatures in the range of 80 to 100 C and foaming times of 2 min allow for
production of nanocellular polymers with relative densities as low as 0.25. Cellular structure has
been studied in-depth to obtain the processing-cellular structure relationship. In addition, it has
been proved that the glass transition temperature depends on the cellular structure. This effect is
associated with a confinement of the polymer in the cell walls, and is one of the key reasons for the
improved properties of nanocellular polymers.
2017-09-24T15:28:26Z
2017-09-24T15:28:26Z
2017-09-24T15:28:26Z
2016
info:eu-repo/semantics/article
Polymers, 2016, vol. 8, n. 9. 16 p.
2073-4360
http://uvadoc.uva.es/handle/10324/25887
10.3390/polym8070265
eng
https://www.mdpi.com/2073-4360/8/7/265/htm
info:eu-repo/semantics/openAccess
© 2016 MDPI
MDPI
oai:uvadoc.uva.es:10324/258882021-06-24T07:45:56Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Nanoporous polymeric materials: A new class of materials with enhanced properties
Notario Collado, Belén
Pinto Sanz, Javier
Rodríguez Pérez, Miguel Ángel
Nanoporous polymeric materials are porous materials with pore
sizes in the nanometer range (i.e., below 200 nm), processed as
bulk or film materials, and from a wide set of polymers. Over the
last several years, research and development on these novel materials
have progressed significantly, because it is believed that the
reduction of the pore size to the nanometer range could strongly
influence some of the properties of porous polymers, providing
unexpected and improved properties compared to conventional
porous and microporous polymers and non-porous solids.
In this review, the key properties of these nanoporous polymeric
materials (mechanical, thermal, dielectric, optical, filtration, sensing,
etc.) are analyzed. The experimental and theoretical results
obtained up to date related to the structure–property relations
are presented. In several sections, in order to present a more compressive
approach, the trends obtained for nanoporous polymers
are compared to those for metallic and ceramic nanoporous systems.
Moreover, some specific characteristics of these materials,
such as the consequences of the confinement of both gas and solid
phases, are described. Likewise, the main production methods are
briefly described. Finally, some of the potential applications of
these materials are also discussed in this paper.
2017-09-24T15:31:37Z
2017-09-24T15:31:37Z
2017-09-24T15:31:37Z
2016
info:eu-repo/semantics/article
Progress in Materials Science 78-79 (2016) 93–139
http://uvadoc.uva.es/handle/10324/25888
eng
http://www.sciencedirect.com/science/article/pii/S0079642516000165?via%3Dihub
info:eu-repo/semantics/restrictedAccess
Elsevier
Elsevier
oai:uvadoc.uva.es:10324/273792021-06-23T10:17:35Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Control of Molecular weight and polydispersity in polyethylene/needle-like shaped clay nanocomposites obtained by in situ polymerization with metallocene catalysts
Herrero Villar, Manuel
Núñez Carrero, Karina Carla
Gallego Castro, Raúl
Merino Senovilla, Juan Carlos
Pastor Barajas, José María
In an effort to understand the influence of the shape and area of the nanoclay type used in
the in situ polymerization process, two different types of clays (fibrillar and laminar) were
employed to obtain nanocomposites. The preliminary results demonstrated that a needlelike
shaped clay promotes higher molar mass and better mechanical properties compared
with laminar clay. The ultra-high molecular weight of sepiolite/nanocomposites introduces
significant problems with processability. Therefore, a new method of polymerization was
designed to include two significant changes. The first change was related to the use of a
non-isothermal temperature profile and the second to the addition of an additional amount
of non-anchored co-catalyst leading to materials with higher fluidity.
2017-11-27T12:27:57Z
2017-11-27T12:27:57Z
2017-11-27T12:27:57Z
2016
info:eu-repo/semantics/article
European Polymer Journal (2016) 75. p.125-141
http://uvadoc.uva.es/handle/10324/27379
eng
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by/4.0/
Ministerio de Economía y Competitividad
Attribution 4.0 International
Elsevier
oai:uvadoc.uva.es:10324/313172021-06-23T10:17:36Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Growth dynamics of SiGe nanowires by the vapour-liquid-solid method and its impact on SiGe/Si axial heterojunction abruptness
Pura Ruiz, José Luis
Periwal, Priyanka
Baron, Thierry
Jiménez López, Juan Ignacio
The vapour–liquid–solid (VLS) method is by far the most extended procedure for bottom-up
nanowire growth. This method also allows for the manufacture of nanowire axial heterojunctions in a straightforward way. To do this, during the growth process, precursor gases are switched on/off to obtain the desired change in the nanowire composition. Using this technique, axially heterostructured nanowires can be grown, which are crucial for the fabrication of electronic and optoelectronic devices. SiGe/Si nanowires are compatible with complementary metal oxide semiconductor (CMOS) technology, which improves their versatility and the possibility of integration with current electronic technologies. Abrupt heterointerfaces are fundamental for the development and correct operation of electronic and optoelectronic devices. Unfortunately, the VLS growth of SiGe/Si heterojunctions does not provide abrupt transitions because of the high solubility of group IV semiconductors in Au, with the corresponding reservoir effect that precludes the growth of sharp interfaces. In this work, we studied the growth dynamics of SiGe/Si heterojunctions based on already developed models for VLS growth. A composition map of the Si–Ge–Au liquid alloy is proposed to better understand the impact of the growing conditions on the nanowire growth process and the heterojunction formation. The solution of our model provides heterojunction profiles that are in good agreement with the experimental measurements.
Finally, an in-depth study of the composition map provides a practical approach to the drastic
reduction of heterojunction abruptness by reducing the Si and Ge concentrations in the catalyst droplet. This converges with previous approaches, which use catalysts aiming to reduce the solubility of the atomic species. This analysis opens new paths to the reduction of heterojunction abruptness using Au catalysts, but the model can be naturally extended to other catalysts and semiconductors.
2018-08-31T07:07:50Z
2018-08-31T07:07:50Z
2018-08-31T07:07:50Z
2018
info:eu-repo/semantics/article
Nanotechnology, 2018, Volume 29, Number 35, 355602
http://uvadoc.uva.es/handle/10324/31317
https://doi.org/10.1088/1361-6528/aaca74
Nanotechnology
29
eng
http://iopscience.iop.org/article/10.1088/1361-6528/aaca74
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
IOP Publishing
oai:uvadoc.uva.es:10324/313182021-06-23T10:17:42Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Mapping of mechanical strain induced by thin and narrow dielectric stripes on InP surfaces
Landesman, Jean-Pierre
Cassidy, Daniel T.
Fouchier, Marc
Pargon, Erwine
Levallois, Christophe
Mokhtari, Merwan
Jiménez López, Juan Ignacio
Torres, Alfredo
We investigated deformation of InP that was introduced by
thin, narrow, dielectric SiNx stripes on the (100) surface of
InP substrates. Quantitative optical measurements were
performed using two different techniques based on luminescence
from the InP: first, by degree of polarization of
photoluminescence; and second, by cathodoluminescence spectroscopy. The two techniques provide complementary information on deformation of the InP and thus together provide a means to evaluate approaches to simulation of the deformation owing to dielectric stripes. Ultimately, these deformations can be used to estimate changes in refractive index and gain that are a result of the stripes
2018-08-31T07:17:52Z
2018-08-31T07:17:52Z
2018-08-31T07:17:52Z
2018
info:eu-repo/semantics/article
Optics Letters, Vol. 43, No. 15
http://uvadoc.uva.es/handle/10324/31318
https://doi.org/10.1364/OL.43.003505
43
eng
https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-15-3505
info:eu-repo/semantics/openAccess
Optical Society of America
oai:uvadoc.uva.es:10324/313192021-06-23T10:17:43Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
About the interaction between a laser beam and group IV nanowires: a study of the electromagnetic field enhancement in homogeneous and heterostructured nanowires
Pura Ruiz, José Luis
Anaya, Julián
Jiménez López, Juan Ignacio
The optical properties of semiconductor nanowires (NWs) are object of study
because they are the building blocks of the future nanophotonic devices. The
high refractive index and its reduced dimension, make them suitable for
photon engineering. The study of the interaction between NWs and visible
light has revealed resonances of the light absorption/scattering by the NWs.
Micro-Raman spectroscopy is used as a characterization method of semiconductor
NWs. The relation between the Raman intensity and the incident
electromagnetic (EM) field permits to study the light/NW interaction through
the micro-Raman spectra of individual NWs. As compared to either metallic
or dielectric NWs, the semiconductor NWs add additional tools to modify its
interaction with light, for example, the composition, the presence of
heterostructures, both axial and radial, doping, and the surface morphology.
One presents herein a study of the optical response of group IV semiconductor
NWs to visible photons. The study is experimentally carried out through the micro-Raman spectroscopy of different group IV NWs, both homogeneous and heterostructured (SiGe/Si), and the results are analyzed in terms of the EM modeling of the light/NW interaction using finite element methods (FEMs). The heterostructures are seen to produce additional resonances allowing new photonic capacities to the semiconductor NWs.
2018-08-31T07:29:34Z
2018-08-31T07:29:34Z
2018-08-31T07:29:34Z
2018
info:eu-repo/semantics/article
Phys. Status Solidi A 2018, 1800336
http://uvadoc.uva.es/handle/10324/31319
http://dx.doi.org/10.1002/pssa.201800336
Phys. Status Solidi A
eng
https://onlinelibrary.wiley.com/doi/abs/10.1002/pssa.201800336
info:eu-repo/semantics/openAccess
WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
oai:uvadoc.uva.es:10324/313202021-06-23T10:17:44Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Thermomechanical degradation of single and multiple quantum well AlGaAs/GaAs laser diodes
Souto Bartolomé, Jorge Manuel
Pura Ruiz, José Luis
Torres, Alfredo
Jiménez López, Juan Ignacio
The catastrophic degradation of laser diodeswith active zones comprising either single (SQW) or multiple quantum wells (MQW) has been analysed via finite elementmethods. This analysis is based on a physical model that explicitly considers the thermal and mechanical properties of the diode laser structure and the relevant size effects associated with the small thickness of the active layers of the device. The reduced thermal conductivities and the thermal barriers at the interfaces result in a significant local heating process which is accentuated as more quantum wells form the active part of the device. Therefore, in the design of high power devices, the SQW configuration would be more appropriate than the MQW alternative.
2018-08-31T07:39:27Z
2018-08-31T07:39:27Z
2018-08-31T07:39:27Z
2017
info:eu-repo/semantics/article
Microelectronics Reliability 76–77 (2017) 588–591
http://uvadoc.uva.es/handle/10324/31320
https://doi.org/10.1016/j.microrel.2017.07.005
Microelectronics Reliability
eng
https://www.sciencedirect.com/science/article/pii/S0026271417302895
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Elsevier
oai:uvadoc.uva.es:10324/313272021-06-23T10:17:38Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Electromagnetic field enhancement effects in group IV semiconductor nanowires. A Raman spectroscopy approach
Pura Ruiz, José Luis
Anaya, Julián
Souto Bartolomé, Jorge Manuel
Prieto Colorado, Ángel Carmelo
Rodríguez, A.
Rodríguez, Tomás
Periwal, Priyanka
Baron, Thierry
Jiménez López, Juan Ignacio
Semiconductor nanowires (NWs) are the building blocks of future nanoelectronic devices.
Furthermore, their large refractive index and reduced dimension make them suitable for
nanophotonics. The study of the interaction between nanowires and visible light reveals resonances that promise light absorption/scattering engineering for photonic applications. Micro-Raman spectroscopy has been used as a characterization tool for semiconductor nanowires. The light/nanowire interaction can be experimentally assessed through the micro-Raman spectra of individual nanowires. As compared to both metallic and dielectric nanowires, semiconductor nanowires add additional tools for photon engineering. In particular, one can grow heterostructured nanowires, both axial and radial, and also one could modulate the doping level and the surface condition among other factors than can affect the light/NW interaction. We present herein a study of the optical response of group IV semiconductor nanowires to visible photons. The study is experimentally carried out through micro-Raman spectroscopy of different group IV nanowires, both homogeneous and axially heterostructured (SiGe/Si). The results are analyzed in terms of the electromagnetic modelling of the light/nanowire interaction using finite element methods. The presence of axial heterostructures is shown to produce electromagnetic resonances promising new photon engineering capabilities of semiconductor nanowires.
2018-08-31T08:48:43Z
2018-08-31T08:48:43Z
2018-08-31T08:48:43Z
2018
info:eu-repo/semantics/article
Journal of Applied Physics 123, 114302 (2018)
http://uvadoc.uva.es/handle/10324/31327
https://doi.org/10.1063/1.5012987
Journal of Applied Physics
123
eng
https://aip.scitation.org/doi/full/10.1063/1.5012987
info:eu-repo/semantics/openAccess
AIP Publishing.
oai:uvadoc.uva.es:10324/313342021-06-23T10:17:40Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Thermal and mechanical issues of high-power laser diode degradation
Souto Bartolomé, Jorge Manuel
Pura Ruiz, José Luis
Jiménez López, Juan Ignacio
A computational model for the evaluation of the thermomechanical effects that give rise to the catastrophic optical damage of laser diodes has been devised. The model traces the progressive deterioration of the device running in continuous wave conditions. The local heating of the active layer locally leads to the onset of the plastic regime. As a result, dislocations and threads of dislocations grow across the active layers and lead to rapidly growing temperatures in the quantum well. The poor power dissipation under these conditions has been identified as the key factor driving the final degradation of the laser
2018-08-31T09:35:54Z
2018-08-31T09:35:54Z
2018-08-31T09:35:54Z
2018
info:eu-repo/semantics/article
MRS Communications, 2018, Volume 8, Issue 3, pp. 995-999
http://uvadoc.uva.es/handle/10324/31334
https://doi.org/10.1557/mrc.2018.124
eng
https://www.cambridge.org/core/journals/mrs-communications/article/thermal-and-mechanical-issues-of-highpower-laser-diode-degradation/EE79857D7B8AB38AD10EB965076482F0
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Cambridge University Press
oai:uvadoc.uva.es:10324/323782021-06-23T10:17:49Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Raman Study of Multicrystalline Silicon Wafers Produced by the RST Process
Tejero Riosecas, Alejandro
Tupin, E.
González Rebollo, Miguel Ángel
Martínez Sacristán, Óscar
Jiménez López, Juan Ignacio
Belouet, C.
Baillis, C.
In the silicon ribbon on a sacrificial template process silicon is deposited on both sides of a carbon ribbon, thus forming a Si/carbon/Si trilayer. The fast cooling of the ribbon in large temperature gradients generates stresses that are detrimental to both the electrical performance and the mechanical behaviour of the wafers. The assessment of the stresses is crucial for the setting-up of thermal treatments allowing for the stress relaxation of the wafers, prior to the cell fabrication. We present an analysis of the stress in the as-grown trilayer by a simulation of the thermomechanical behaviour of the cooling ribbon. Experimental measurements of the stress in as-grown and annealed trilayers are also presented. The results permit to establish the conditions for optimized growth and annealing.
2018-10-30T08:35:55Z
2018-10-30T08:35:55Z
2018-10-30T08:35:55Z
2014
info:eu-repo/semantics/article
Acta Physica Polonica A 2014; 125, pp. 1006-1009
1898-794X
http://uvadoc.uva.es/handle/10324/32378
https://doi.org/10.12693/APhysPolA.125.1006
eng
http://przyrbwn.icm.edu.pl/APP/SPIS/a125-4.html
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Polish Academy of Sciences Institute of Physics
oai:uvadoc.uva.es:10324/323792021-06-23T10:17:51Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Residual Strain and Electrical Activity of Defects in Multicrystalline Silicon Solar Cells
Martínez Sacristán, Óscar
Mass, Julio
Tejero, A.
Moralejo, B.
Hortelano Santos, Vanesa
González Rebollo, Miguel Ángel
Jiménez López, Juan Ignacio
Parra, V.
The growth process by casting methods of multi-crystalline Si results in a crystalline material with, among other defects, a high density of dislocations and grain boundaries. Impurity incorporation and their gathering around grain boundaries and dislocations seem to be the main factor determining the electrical activity of those defects, which limit the minority carrier lifetime. In this work, we analyze multi-crystalline Si samples by combining etching processes to reveal the defects, Raman spectroscopy for strain measurements, and light beam induced current measurements for the localization of electrically active defects. In particular, we have explored the etching routes capable to reveal the main defects (grain boundaries and dislocation lines), while their electrical activity is studied by the light beam induced current technique. We further analyze the strain levels around these defects by Raman micro-spectroscopy, aiming to obtain a more general picture of the correlation between residual stress and electrical activity of the extended defects. The higher stress levels are observed around intra-grain defects associated with dislocation lines, rather than around the grain boundaries. On the other hand, the intra-grain defects are also observed to give dark light beam induced current contrast associated with a higher electrical activity of these defects as compared to the grain boundaries
2018-10-30T09:00:44Z
2018-10-30T09:00:44Z
2018-10-30T09:00:44Z
2014
info:eu-repo/semantics/article
Acta Physica Polonica A 2014; 125. pp. 1013-1016
1898-794X
http://uvadoc.uva.es/handle/10324/32379
https://doi.org/10.12693/APhysPolA.125.1013
eng
http://przyrbwn.icm.edu.pl/APP/SPIS/a125-4.html
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Polish Academy of Sciences Institute of Physics
oai:uvadoc.uva.es:10324/324282021-06-23T10:17:48Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Influence of metal organic chemical vapour deposition growth conditions on vibrational and luminescent properties of ZnO nanorods
Montenegro, D. N.
Hortelano Santos, Vanesa
Martínez Sacristán, Óscar
Martínez Tomas, M. C
Sallet, V.
Muñoz Sanjosé, V.
Jiménez López, Juan Ignacio
Espectroscopia Raman
Raman Spectroscopy
A detailed optical characterization by means of micro Raman and cathodoluminescence spectroscopy of catalyst-free ZnO nanorods grown by atmospheric-metal organic chemical vapour deposition has been carried out. This characterization has allowed correlating the growth conditions, in particular the precursors partial-pressures and growth time, with the optical properties of nanorods. It has been shown that a high Zn supersaturation can favor the incorporation of nonradiative recombination centers, which can tentatively be associated with ZnI-related defects. Characterization of individual nanorods has evidenced that ZnI-related defects have a tendency to accumulate in the tip part of the nanorods, which present dark cathodoluminescence contrast with respect to the nanorods bottom. The effect of a ZnO buffer layer on the properties of the nanorods has been also investigated, showing that the buffer layer improves the luminescence efficiency of the ZnO nanorods, revealing a significant reduction of the concentration of nonradiative recombination centers.
2018-11-05T11:39:52Z
2018-11-05T11:39:52Z
2018-11-05T11:39:52Z
2013
info:eu-repo/semantics/article
Journal of Applied Physics, 2013, 113, 143513
http://uvadoc.uva.es/handle/10324/32428
https://doi.org/10.1063/1.4801534
eng
https://aip.scitation.org/doi/10.1063/1.4801534
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
AIP Publishing
oai:uvadoc.uva.es:10324/324292021-06-23T10:17:53Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Modification of the optical and structural properties of ZnO nanowires by low-energy Ar+ ion sputtering
Allah, Rabie Fath
Ben, Teresa
González, David
Hortelano Santos, Vanesa
Martínez Sacristán, Óscar
Plaza, Jose Luis
The effects of low-energy (≤2 kV) Ar+ irradiation on the optical and structural properties of zinc oxide (ZnO) nanowires (NWs) grown by a simple and cost-effective low-temperature technique were investigated. Both photoluminescence spectra from ZnO NW-coated films and cathodoluminescence analysis of individual ZnO NWs demonstrated obvious evidences of ultraviolet/visible luminescent enhancement with respect to irradiation fluence. Annihilation of the thinner ZnO NWs after the ion bombardment was appreciated by means of high-resolution scanning electron microscopy and transmission electron microscopy (TEM), which results in an increasing NW mean diameter for increasing irradiation fluences. Corresponding structural analysis by TEM pointed out not only significant changes in the morphology but also in the microstructure of these NWs, revealing certain radiation-sensitive behavior. The possible mechanisms accounting for the decrease of the deep-level emissions in the NWs with the increasing irradiation fluences are discussed according to their structural modifications.
2018-11-05T11:56:07Z
2018-11-05T11:56:07Z
2018-11-05T11:56:07Z
2013
info:eu-repo/semantics/article
Nanoscale Research Letters, 2013, 8:162
1931-7573
http://uvadoc.uva.es/handle/10324/32429
https://doi.org/10.1186/1556-276X-8-162
eng
https://nanoscalereslett.springeropen.com/articles/10.1186/1556-276X-8-162
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Springer
oai:uvadoc.uva.es:10324/349052021-06-23T10:17:59Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Optical and interface properties of direct InP/Si heterojunction formed by corrugated epitaxial lateral overgrowth
Omanakuttan, Giriprasanth
Martínez Sacristán, Óscar
Marcinkevičius, Saulius
Kristijonas Uždavinys, Tomas
Jiménez López, Juan Ignacio
Hasan, Ali
Leifer, Klaus
Lourdudoss, Sebastian
Sun, Yan-Ting
We fabricate and study direct InP/Si heterojunction by corrugated epitaxial lateral overgrowth (CELOG). The crystalline quality and depth-dependent charge carrier dynamics of InP/Si heterojunction are assessed by characterizing the cross-section of grown layer by low-temperature cathodoluminescence, time-resolved photoluminescence and transmission electron microscopy. Compared to the defective seed InP layer on Si, higher intensity band edge emission in cathodoluminescence spectra and enhanced carrier lifetime of InP are observed above the CELOG InP/Si interface despite large lattice mismatch, which are attributed to the reduced threading dislocation density realized by the CELOG method.
2019-03-05T08:34:35Z
2019-03-05T08:34:35Z
2019-03-05T08:34:35Z
2019
info:eu-repo/semantics/article
Optical Materials Express Vol. 9, Issue 3, pp. 1488-1500 (2019)
2159-3930
http://uvadoc.uva.es/handle/10324/34905
https://doi.org/10.1364/OME.9.001488
eng
https://www.osapublishing.org/ome/abstract.cfm?uri=ome-9-3-1488
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Optical Society of America
oai:uvadoc.uva.es:10324/349582021-06-23T10:18:02Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Defect recognition by means of light and electron probe techniques for the characterization of mc-Si wafers and solar cells
Moralejo, B.
Tejero, A.
Hortelano Santos, Vanesa
Martínez Sacristán, Óscar
González Delgado, Manuel Ángel
Jiménez López, Juan Ignacio
Multicristalline Silicon (mc-Si) is the preferred material for current terrestrial photovoltaic applications. However, the high density of defects present in mc-Si deteriorates the material properties, in particular the minority carrier diffusion length. For this reason, a large effort to characterize the mc-Si material is demanded, aiming to visualize the defective areas and to quantify the type of defects, density and its origin. In this work, several complementary light and electron probe techniques are used for the analysis of both mc-Si wafers and solar cells. These techniques comprise both fast and whole-area detection techniques such as Photoluminescence imaging, and highly spatially resolved time consuming techniques, such as light and electron beam induced current techniques and μRaman spectroscopy. These techniques were applied to the characterization of different mc-Si wafers for solar cells, e.g. ribbon wafers, cast mc-Si as well as quasi-monocrystalline material, upgraded metallurgical mc-Si wafers, and finished solar cells.
2019-03-07T09:30:00Z
2019-03-07T09:30:00Z
2019-03-07T09:30:00Z
2016
info:eu-repo/semantics/article
Superlattices and Microstructures, 2016, Volume 99, Pages 45-53
0749-6036
http://uvadoc.uva.es/handle/10324/34958
https://doi.org/10.1016/j.spmi.2016.02.005
eng
https://www.sciencedirect.com/science/article/pii/S0749603616300489
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Elsevier
oai:uvadoc.uva.es:10324/350942021-07-06T08:33:30Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Optical and structural characterisation of epitaxial nanoporous GaN grown by CVD
Mena, Josué
Carvajal, Joan Josep
Martínez Sacristán, Óscar
Jiménez López, Juan Ignacio
Zubialevich, V.
Parbrook, Peter
Díaz, Francesc
Aguiló, Magdalena
In this paper we study the optical properties of nanoporous gallium nitride (GaN) epitaxial layers grown by chemical vapour deposition on non-porous GaN substrates, using photoluminescence, cathodoluminescence, and resonant Raman scattering, and correlate them with the structural characteristic of these films. We pay special attention to the analysis of the residual strain of the layers and the influence of the porosity in the light extraction. The nanoporous GaN epitaxial layers are under tensile strain, although the strain is progressively reduced as the deposition time and the thickness of the porous layer increases, becoming nearly strain free for a thickness of 1.7 μm. The analysis of the experimental data point to the existence of vacancy complexes as the main source of the tensile strain.
2019-03-15T12:00:54Z
2019-03-15T12:00:54Z
2019-03-15T12:00:54Z
2017
info:eu-repo/semantics/article
Nanotechnology, 2017, Volume 28, Number 37, 375701
0957-4484
http://uvadoc.uva.es/handle/10324/35094
https://doi.org/10.1088/1361-6528/aa7e9d
Nanotechnology
eng
https://iopscience.iop.org/article/10.1088/1361-6528/aa7e9d
info:eu-repo/semantics/openAccess
© 2017 IOP Publishing Ltd
IOP Publishing
oai:uvadoc.uva.es:10324/350982021-06-23T10:18:23Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Electromagnetic enhancement effect on the atomically abrupt heterojunction of Si/InAs heterostructured nanowires
Pura Ruiz, José Luis
Magdaleno de Benito, Álvaro Javier
Muñoz Segovia, Daniel
Glasser, M.L.
Lugstein, A.
Jiménez López, Juan Ignacio
Semiconductor nanowires (NWs) present a great number of unique optical properties associated with their reduced dimension and internal structure. NWs are suitable for the fabrication of defect free Si/III-V heterostructures, allowing the combination of the properties of both Si and III-V compounds. We present here a study of the electromagnetic (EM) resonances on the atomically abrupt heterojunction (HJ) of Si/InAs axially heterostructured NWs. We studied the electromagnetic response of Si/InAs heterojunctions sensed by means of micro-Raman spectroscopy. These measurements reveal a high enhancement of the Si Raman signal when the incident laser beam is focused right on the Si/InAs interface. The experimental Raman observations are compared to simulations of finite element methods for the interaction of the focused laser beam with the heterostructured NW. The simulations explain why the enhancement is detected on the Si signal when illuminating the HJ and also provide a physical framework to understand the interaction between the incident EM field and the heterostructured NW. The understanding of this process opens the possibility of controlling the light absorption/scattering on semiconductor NWs with the use of heterostructures while taking advantage of the properties of both Si and III-V semiconductors. This is important not only for current NW based photonic nanodevices, such as light sensors, but also for the design of new optoelectronic devices based on NWs
2019-03-15T12:42:33Z
2019-03-15T12:42:33Z
2019-03-15T12:42:33Z
2019
info:eu-repo/semantics/article
Journal of Applied Physics, 2019, Volume 125, Issue 6, 064303
0021-8979
http://uvadoc.uva.es/handle/10324/35098
https://doi.org/10.1063/1.5058276
eng
https://aip.scitation.org/doi/10.1063/1.5058276
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
AIP Publishing
oai:uvadoc.uva.es:10324/351562021-06-23T10:18:24Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
New strategies invonving upconverting nanoparticles for determining moderate temperatures by luminescence thermometry
Savchuk, Oleksandr A.
Carvajal, Joan Josep
Pujol, María Cinta
Massons, Jaume
Haro González, Patricia
Martínez Sacristán, Óscar
Jiménez López, Juan Ignacio
Aguiló, Magdalena
Díaz, Francesc
Here we analyze alternative luminescence thermometry techniques to FIR, such as intensity ratio luminescence thermometry between the emission arising from two electronic levels that are not necessarily thermally coupled, but that show different evolutions with temperature, and lifetime luminescence nanothermometry in (Ho,Tm,Yb):KLu(WO4)2 and (Er,Yb):NaY2F5O nanoparticles. (Ho,Tm,Yb):KLu(WO4)2 nanoparticles exhibited a maximum relative sensitivity of 0.61% K−1, similar to that achievable in Er-doped systems, which are the upconverting systems presenting the highest sensitivity. From another side, (Er,Yb):NaY2F5O nanocrystals show great potentiality as thermal sensors at the nanoscale for moderate temperatures due to the incorporation of additional non-radiative relaxation mechanisms that shorten the emission lifetime generated by the oxygen present in the structure when compared to (Er,Yb):NaYF4 nanoparticles exhibiting the highest upconversion efficiency. We used those nanoparticles for ex-vivo temperature determination by laser induced heating in chicken breast using lifetime-based thermometry. The results obtained indicate that these techniques might constitute alternatives to FIR with potential applications for the determination of moderate temperatures, with sensitivities comparable to those that can be achieved by FIR or even higher.
2019-03-20T12:30:23Z
2019-03-20T12:30:23Z
2019-03-20T12:30:23Z
2016
info:eu-repo/semantics/article
Journal of Luminescence, 2016, Volume 169, Part B, Pages 711-716
0022-2313
http://uvadoc.uva.es/handle/10324/35156
https://doi.org/10.1016/j.jlumin.2015.05.016
eng
https://www.sciencedirect.com/science/article/pii/S002223131500263X
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Elsevier
oai:uvadoc.uva.es:10324/352032021-06-23T10:18:00Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Polarization-Resolved Near-Field Spectroscopy of Localized States in m-Plane InxGa1−xN/GaN Quantum Wells
Ivanov, Ruslan
Martínez Sacristán, Óscar
Kuritzky, Leah Y.
Myers, Daniel J.
Nakamura, Shuji
Speck, James S.
We present a polarization, spectrally, and spatially resolved near-field photoluminescence (PL) measurement technique and apply it to the study of wide m-plane InxGa1−xN/GaN quantum wells grown on on-axis and miscut GaN substrates. It is found that PL originates from localized states; nevertheless, its degree of linear polarization (DLP) is high with little spatial variation. This allows an unambiguous assignment of the localized states to InxGa1−xN composition-related band potential fluctuations. Spatial PL variations, occurring due to morphology features of the on-axis samples, play a secondary role compared to the variations of the alloy composition. The large PL peak wavelength difference for polarizations parallel and perpendicular to the c axis, the weak correlation between the peak PL wavelength and the DLP, and the temperature dependence of the DLP suggest that effective potential variations and the hole mass in the second valence-band level are considerably smaller than that for the first level. DLP maps for the long wavelength PL tails have revealed well-defined regions with a small DLP, which have been attributed to a partial strain relaxation around dislocations.
2019-03-22T13:59:21Z
2019-03-22T13:59:21Z
2019-03-22T13:59:21Z
2017
info:eu-repo/semantics/article
Physical Review Applied, 2017, vol. 7, n. 6, 064033
2331-7019
http://uvadoc.uva.es/handle/10324/35203
https://doi.org/10.1103/PhysRevApplied.7.064033
eng
https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.7.064033
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
American Physical Society
oai:uvadoc.uva.es:10324/352082021-06-23T10:18:26Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Amorphous zinc borate as a simple standard for baseline correction in Raman spectra
Sanz Arranz, Aurelio
Manrique Martínez, José Antonio
Medina García, Jesús
Rull Pérez, Fernando
In this paper, our research group proposes a simple solution to a usual problem that appears in the Raman analysis of some substances, which is the presence of weak Raman signals, probably in combination with a high‐intensity luminescence background, affected by the presence of distortions in the baseline. Under this condition, the spectroscopist has to face spectra hard to edit and correct and thus hard to study. There are already some standard solutions that allow the correction of spectra from relative intensity to absolute intensity that also solves this problem and also allow quantitative analyses. But these solutions imply expensive standards or devices that could not be a worthy option when not working in absolute intensity or the Raman analyses stay at qualitative level and a quantitative study is not needed. The alternative Do It Yourself solution proposed in this paper is based on the use of amorphous zinc borate, an easy‐to‐find substance, which after a simple processing allows us to correct the baseline of Raman spectra qualitatively, offering a useful and economic reference when an absolute intensity correction is not needed. In order to evaluate the effectiveness of this procedure, some spectra were corrected using amorphous zinc borate and then compared the signal‐to‐noise ratio of some Raman signals before and after this correction. Copyright © 2017 John Wiley & Sons, Ltd.
2019-03-24T16:19:27Z
2019-03-24T16:19:27Z
2019-03-24T16:19:27Z
2017
info:eu-repo/semantics/article
Journal of Raman Spectroscopy, Mayo 2017, vol 48, n. 11. p. 1644-1653.
1097-4555
http://uvadoc.uva.es/handle/10324/35208
https://doi.org/10.1002/jrs.5144
eng
https://onlinelibrary.wiley.com/doi/full/10.1002/jrs.5144
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by/4.0/
© 2017 Wiley
Attribution 4.0 International
Wiley
oai:uvadoc.uva.es:10324/352102022-01-19T10:10:45Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
A method for the automated Raman spectra acquisition.
López Reyes, Guillermo Eduardo
Rull Pérez, Fernando
Raman spectroscopy is a very powerful analytical technique with an increasing acceptance in the scientific community. For theoptimization of the Raman acquisition, two main parameters, the integration time and the number of accumulations, need tobe adjusted to the sample under analysis, as the sample, or even different spots on the same sample, can provide very differentRaman responses one from another. In this paper, we present a suite of algorithms to automate the acquisition parameteradjustment to the sample under analysis, addressing issues such as spectral saturation, fluorescence, cosmic ray detection andremoval, and adjustment of the acquisition parameters to optimize the acquired spectral data. This suite has been developedin the framework of the Raman Laser Spectrometer (RLS) instrument development for the Exomars mission but can be appliedto any Raman spectrometer. This will allow the spectrometer to adapt to the characteristics of the sample that is being analyzed,optimizing the total operative time, while improving the usability and overall efficiency of the system. Copyright © 2017 JohnWiley & Sons, Ltd.
2019-03-25T10:24:31Z
2019-03-25T10:24:31Z
2019-03-25T10:24:31Z
2017
info:eu-repo/semantics/article
Journal of Raman Spectroscopy, Julio 2017, vol. 48, p. 1654–1664
1097-4555
http://uvadoc.uva.es/handle/10324/35210
https://doi.org/10.1002/jrs.5185
eng
https://onlinelibrary.wiley.com/doi/full/10.1002/jrs.5185
info:eu-repo/semantics/openAccess
© 2017 Wiley
Wiley
oai:uvadoc.uva.es:10324/352092021-06-23T10:18:31Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Extremely high diversity of sulfate minerals in caves of the Irazú Volcano (Costa Rica) related to crater lake and fumarolic activity
Ulloa, Andrés
Gázquez, Fernando
Sanz Arranz, Aurelio
Medina García, Jesús
Rull Pérez, Fernando
Calaforra, José María
Alvarado, Guillermo E.
Martínez, María
Avard, Geoffroy
De Moor, J. Maarten
Waele, Jo de
The caves of the Irazú volcano (Costa Rica), became accessible after the partial collapse
of the NW sector of the Irazú volcano in 1994, offering the opportunity to investigate
active minerogenetic processes in volcanic cave environments. We performed a detailed
mineralogical and geochemical study of speleothems in the caves Cueva los Minerales and
Cueva Los Mucolitos, both located in the northwest foothills of the main crater. Mineralogical
analyses included X-ray diffraction (XRD) and Raman spectroscopy, while geochemical
characterization used Energy Dispersive X-ray spectroscopy (EDX) coupled to Scanning
Electron Microscopy (SEM). In addition, measurements of environmental parameters in the
caves, cave drip water and compilation of geochemical analyses of the Irazú volcanic lake
(~150 m above the cave level) and fumarole analyses were conducted between 1991 and
2014. We identified forty-eight different mineral phases, mostly rare hydrated sulfates of the
alunite, halotrichite, copiapite, kieserite and rozenite groups, thirteen of which are described
here as cave minerals for the first time. This includes the first occurrence in cave environments
of aplowite, bieberite, boyleite, dietrichite, ferricopiapite, ferrinatrite, lausenite, lishizhenite,
magnesiocopiapite, marinellite, pentahydrite, szomolnokite, and wupatkiite. The presence
of other new cave minerals such as tolbachite, mercallite, rhomboclase, cyanochroite, and
retgersite, is likely but could not be confirmed by various mineralogical techniques. Uplifting
of sulfurous gases, water seepage from the Irazú volcanic lake and hydrothermal interactions
with the volcanic host rock are responsible for such extreme mineralogical diversity. These
findings make the caves of the Irazú volcano a world-type- reference locality for investigations
on the formation and assemblage of sulfate minerals and the biogeochemical cycle of sulfur,
with potential implications for Astrobiology and Planetary science.
2019-03-24T17:18:23Z
2019-03-24T17:18:23Z
2019-03-24T17:18:23Z
2018
info:eu-repo/semantics/article
International Journal of Speleology, Mayo 2018, vol. 47, n. 2. p. 229-246.
ISSN 0392-6672
http://uvadoc.uva.es/handle/10324/35209
https://doi.org/10.5038/1827-806X.47.2.2198
eng
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by/4.0/
Attribution 4.0 International
oai:uvadoc.uva.es:10324/352352021-07-06T08:33:30Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Overview of the techniques used for the study of non-terrestrial bodies: Proposition of novel non-destructive methodology
Aramendia, Julene
Gómez Nubla, Leticia
Castro, Kepa
Fernández Ortiz de Vallejuelo, Silvia
Arana, Gorka
Maguregui, Maite
García Baonza, Valentín
Medina García, Jesús
Rull Pérez, Fernando
Madariaga Mota, Juan Manuel
Meteorites and impact glasses have been largely analysed using different techniques, but most studies
have been focused on their geologicalemineralogical characterization and isotopic ratios, mainly of a
destructive nature. However, much more information can be gained by applying novel non-destructive
analytical procedures and techniques that have been scarcely used to analyse these materials. This
overview presents some new methodologies to study these materials and compares these new approaches
with the commonly used ones. Techniques such as X-Ray Fluorescence (XRF) and Laser Induced
Breakdown Spectroscopy (LIBS), for elemental characterization, the hyphenated Raman spectroscopy-
SEM/EDS and the combination of them, allow extracting simultaneous information from elemental,
molecular and structural data of the studied sample; furthermore, the spectroscopic image capabilities of
such techniques allow a better understanding of the mineralogical distribution.
© 2017 Elsevier B.V. All rights reserved.
2019-03-26T08:52:37Z
2019-03-26T08:52:37Z
2019-03-26T08:52:37Z
2018
info:eu-repo/semantics/article
Trends in Analytical Chemistry, 2018, vol. 98, p. 36-46
0165-9936
http://uvadoc.uva.es/handle/10324/35235
https://doi.org/10.1016/j.trac.2017.10.018
eng
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/352362022-01-19T10:10:59Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Combined vibrational, structural, elemental and Mössbauer spectroscopic analysis of natural phillipsite (zeolite) from historical eruptions in Tenerife, Canary Islands: Implication for Mars
Lalla, Emmanuel Alexis
López Reyes, Guillermo Eduardo
Lozano Gorrín, A.D.
Rull Pérez, Fernando
The outcrop of “Las Arenas” volcano in Tenerife, Canary Islands (Spain) has been presented as Terrestrial volcanic
analog for ancient Mars, showing a great variety of alteration processes and interesting mineralogy. The
current analysis has been done by means of measurement techniques used or proposed on Martian studies. The
new analysis of the zeolite has been carried out using Raman spectroscopy, Mössbauer spectroscopy, X-ray
diffraction (XRD), Infrared spectroscopy, Laser induced breakdown spectroscopy and Scanning electron microscopy
(SEM-EDX). The zeolite has been carefully analyzed using vibrational spectroscopy and it has been
identified as Ca-phillipsite. The other techniques support and confirm the results. The measurements and results
using the Raman Laser Spectrometer (RLS) simulator system show the capabilities RLS system in the ESA Exo-
Mars mission. The chemometrical methods for the vibrational mineral detection show the advantages of Raman
spectroscopy to understand the possible geological context. Furthermore, the proposed diagenesis and formation
of the zeolites in southern part of Tenerife island have been confirmed by the twin space prototypes used. A new
hypothesis about the origin for the special case of “Las Arenas” volcano Ca-phillipsite has been proposed. Finally,
a multi-complementary comparison among the different techniques used on the current studie has been done
and, also an analogy with the next space mission has been established. These analyses emphasize the strength of
the different techniques and the working synergy of the different techniques together for planetary space missions.
2019-03-26T09:02:06Z
2019-03-26T09:02:06Z
2019-03-26T09:02:06Z
2019
info:eu-repo/semantics/article
Vibrational Spectroscopy, 2019. vol. 101, p. 10–19
0924-2031
http://uvadoc.uva.es/handle/10324/35236
https://doi.org/10.1016/j.vibspec.2018.12.003
eng
info:eu-repo/semantics/openAccess
© 2019 Elsevier
Elsevier
oai:uvadoc.uva.es:10324/352372023-05-30T11:10:44Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
The Raman Laser Spectrometer for the ExoMars Rover Mission to Mars
Rull Pérez, Fernando
Sylvestre, Maurice
Hutchinson, Ian
Moral Inza, Andoni Gaizka
Pérez, Carlos
Díaz, Carlos
Colombo, María
Belenguer Dávila, Tomás
López Reyes, Guillermo Eduardo
Sansano Caramazana, Antonio
Forni, Olivier
Parot, Yann
Striebig, Nicolas
Woodward, Simon
Howe, Chris
Tarcea, Nicolau
Rodríguez, Pablo
Seoane, Laura
Santiago, Amaia
Rodríguez Prieto, Jose Antonio
Medina García, Jesús
Gallego, Paloma
Canchal, Rosario
Santamaría, Pilar
Ramos, Gonzalo
Vago, Jorge L.
The Raman Laser Spectrometer (RLS) on board the ESA/Roscosmos ExoMars 2020 mission will provide
precise identification of the mineral phases and the possibility to detect organics on the Red Planet. The RLS
will work on the powdered samples prepared inside the Pasteur analytical suite and collected on the surface and
subsurface by a drill system. Raman spectroscopy is a well-known analytical technique based on the inelastic
scattering by matter of incident monochromatic light (the Raman effect) that has many applications in laboratory
and industry, yet to be used in space applications. Raman spectrometers will be included in two Mars
rovers scheduled to be launched in 2020. The Raman instrument for ExoMars 2020 consists of three main units:
(1) a transmission spectrograph coupled to a CCD detector; (2) an electronics box, including the excitation laser
that controls the instrument functions; and (3) an optical head with an autofocus mechanism illuminating and
collecting the scattered light from the spot under investigation. The optical head is connected to the excitation
laser and the spectrometer by optical fibers. The instrument also has two targets positioned inside the rover
analytical laboratory for onboard Raman spectral calibration. The aim of this article was to present a detailed
description of the RLS instrument, including its operation on Mars. To verify RLS operation before launch and
to prepare science scenarios for the mission, a simulator of the sample analysis chain has been developed by the
team. The results obtained are also discussed. Finally, the potential of the Raman instrument for use in field
conditions is addressed. By using a ruggedized prototype, also developed by our team, a wide range of
terrestrial analog sites across the world have been studied. These investigations allowed preparing a large
collection of real, in situ spectra of samples from different geological processes and periods of Earth evolution.
On this basis, we are working to develop models for interpreting analog processes on Mars during the mission.
Key Words: Raman spectroscopy—ExoMars mission—Instruments and techniques—Planetary sciences—Mars
mineralogy and geochemistry—Search for life on Mars. Astrobiology 17, 627–654
2019-03-26T09:19:30Z
2019-03-26T09:19:30Z
2019-03-26T09:19:30Z
2017
info:eu-repo/semantics/article
ASTROBIOLOGY, 2017, Vol. 17, n. 6-7, p. 627-654
http://uvadoc.uva.es/handle/10324/35237
https://doi.org/10.1089/ast.2016.1567
eng
https://www.liebertpub.com/doi/10.1089/ast.2016.1567
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
oai:uvadoc.uva.es:10324/352382021-07-06T08:33:30Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover
Vago, Jorge L.
Westall, Frances
Coates, Andrew J
Jaumann, Ralf
Korablev, Oleg
Valérie, Ciarletti
Mitrofanov, Igor
Rull Pérez, Fernando
The second ExoMars mission will be launched in 2020 to target an ancient location interpreted to have strong
potential for past habitability and for preserving physical and chemical biosignatures (as well as abiotic/prebiotic
organics). The mission will deliver a lander with instruments for atmospheric and geophysical investigations and a
rover tasked with searching for signs of extinct life. The ExoMars rover will be equipped with a drill to collect
material from outcrops and at depth down to 2 m. This subsurface sampling capability will provide the best chance
yet to gain access to chemical biosignatures. Using the powerful Pasteur payload instruments, the ExoMars
science team will conduct a holistic search for traces of life and seek corroborating geological context information.
Key Words: Biosignatures—ExoMars—Landing sites—Mars rover—Search for life. Astrobiology 17, 471–510.
2019-03-26T09:33:27Z
2019-03-26T09:33:27Z
2019-03-26T09:33:27Z
2017
info:eu-repo/semantics/article
ASTROBIOLOGY, 2017, vol. 17, n. 6-7, p. 471-510
http://uvadoc.uva.es/handle/10324/35238
https://doi.org/10.1089/ast.2016.1533
eng
https://www.liebertpub.com/doi/full/10.1089/ast.2016.1533
info:eu-repo/semantics/openAccess
Mary Ann Liebert
oai:uvadoc.uva.es:10324/352542021-07-06T08:33:30Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Multispectroscopic methodology to study Libyan desert glass and its formation conditions
Gómez Nubla, Leticia
Aramendia, Julene
Fernández Ortiz de Vallejuelo, Silvia
Alonso Olazabal, Ainhoa
Castro, Kepa
Zuluaga, María Cruz
Ortega, Luis Ángel
Murelaga, Xabier
Madariaga Mota, Juan Manuel
Libyan desert glass (LDG) is a melt product whose
origin is still a matter of controversy. With the purpose of
adding new information about this enigma, the present paper
analyzes the inner part of LDG specimens and compares them
with the results of LDG surfaces. An integrated analytical
methodology was used combining different techniques such
as Raman spectroscopy, in point-by-point and imaging modes,
scanning electron microscopy with X-ray microanalysis
(SEM-EDS), energy-dispersive micro X-ray fluorescence
spectrometry (μ-EDXRF), electron probe micro analyzer
(EPMA), and optical cathodoluminescence (Optical-CL).
According to our results, flow structures of the melt and the
amorphous nature of the matrix could be discerned. Moreover,
the observed displacement of Raman bands, such as in the
cases of quartz and zircon, and the identification of certain
compounds such as coesite (the most clarifying phase of high
pressures), α-cristobalite, gypsum, anhydrite, corundum, rutile,
amorphous calcite, aragonite, and calcite allowed us to
know that LDGs could be subjected to shock pressures between
6 and more than 30 GPa, and temperatures between 300
and 1470 °C. The differences of temperature and pressure
would be provoked by different cooling processes during the
impact. Besides, in most cases the minerals corresponding to
high pressure and temperatures were located in the inner part
of the LDGs, with some exceptions that could be explained
because they were trapped subsequently to the impact; there
was more than one impact or heterogeneous cooling.
Furthermore, nitrogen and oxygen gases were identified
inside bubbles, which could have been introduced from the
terrestrial atmosphere during the meteorite impact.
These data helped us to clarify some clues about the origin
of these enigmatic samples.
2019-03-26T17:13:41Z
2019-03-26T17:13:41Z
2019-03-26T17:13:41Z
2017
info:eu-repo/semantics/article
Analytical and Bioanalytical Chemistry 2017, vol. 409, n. 14. p.3597-3610.
http://uvadoc.uva.es/handle/10324/35254
https://doi.org/10.1007/s00216-017-0299-5
eng
https://link.springer.com/article/10.1007/s00216-017-0299-5
info:eu-repo/semantics/openAccess
© 2017 Springer
oai:uvadoc.uva.es:10324/352552021-07-06T08:33:30Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Geochemical study of the Northwest Africa 6148 Martian meteorite and its terrestrial weathering processes
Torre Fernández, Imanol
Aramendia, Julene
Gómez Nubla, Leticia
Castro, Kepa
Madariaga Mota, Juan Manuel
The number of studies of Mars geology through the geochemical analysis of Martian meteorites has been increasing in the last
years because of the amount of information that can be obtained about the planet. In this study, a Martian meteorite, the
Northwest Africa 6148 nakhlite, has been analysed and characterised, as there were few studies about it. After analysing it by
Raman spectroscopy and Scanning Electron Microscope–Energy Dispersive X-ray Spectroscopy coupled to the Structural and
Chemical Analyser interface, augite and olivine were identified as the main mineral phases of the sample. Moreover, using the
Raman bands position, both minerals’ metal proportions were estimated. This methodology used in meteorite studies provides
good semi-quantitative results and can offer some advantages to other techniques. In addition, calcite was found, being
associated with Earth weathering processes. Surprisingly, Co3O4 was detected in the matrix of the meteorite. This is the first time
that this oxide is observed in ameteorite. Itwas not possible to determine if it is an original compound fromMars or a product of a
weathering process on Earth. However, whichever the case may be, solely the presence of this cobalt oxide represents a relevant
finding, as it could provide a deeper knowledge of theMartian geochemistry or the Earth weathering processes. Copyright © 2017
John Wiley & Sons, Ltd.
2019-03-26T17:20:34Z
2019-03-26T17:20:34Z
2019-03-26T17:20:34Z
2017
info:eu-repo/semantics/article
Journal of Raman Spectroscopy, 2017, vol 48, p. 1536–1543.
http://uvadoc.uva.es/handle/10324/35255
https://doi.org/10.1002/jrs.5148
eng
https://onlinelibrary.wiley.com/doi/full/10.1002/jrs.5148
info:eu-repo/semantics/openAccess
Wiley
oai:uvadoc.uva.es:10324/352562021-07-06T08:33:30Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Detection of organic compounds in impact glasses formed by the collision of an extraterrestrial material with the Libyan Desert (Africa) and Tasmania (Australia)
Gómez Nubla, Leticia
Aramendia, Julene
Fernández Ortiz de Vallejuelo, Silvia
Castro, Kepa
Madariaga Mota, Juan Manuel
Impact glasses are rich silica melted formed at high temperature and pressure by the impact of an extraterrestrial body on Earth.
Here, Libyan Desert glasses (LDGs) and Darwin glasses (DGs) were studied. Two non-destructive analytical techniques were
used to detect and characterize organic compounds present in their inclusions: Raman spectroscopy and scanning electron
microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDS). Phytoliths, humboldtine, palmitic acid, myristic acid,
oleic acid, 4-methyl phthalic acid, and S-H stretching vibrations of amino acids were identified. The presence of these particular
organic compounds in such materials has not been reported so far, providing information about (a) the ancient matter of the area
where the impact glasses were formed, (b) organic matter belonging to the extraterrestrial body which impacted on the Earth, or
(c) even to current plant or bacterial life, which could indicate an active interaction of the LDG and DG with the surrounding
environment. Moreover, the identification of fullerene allowed us to know a pressure (15 GPa) and temperatures (670 K or 1800–
1900 K) at which samples could be subjected.
2019-03-26T17:26:07Z
2019-03-26T17:26:07Z
2019-03-26T17:26:07Z
2018
info:eu-repo/semantics/article
Analytical and Bioanalytical Chemistry, Julio 2018, vol. 410. p. 6609–6617
http://uvadoc.uva.es/handle/10324/35256
https://doi.org/10.1007/s00216-018-1266-5
eng
info:eu-repo/semantics/openAccess
© 2018 Springer
oai:uvadoc.uva.es:10324/352572021-07-06T08:33:30Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Non-destructive characterisation of the Elephant Moraine 83227 meteorite using confocal Raman, micro-energy-dispersive X-ray fluorescence and Raman-scanning electron microscope-energy-dispersive X-ray microscopies
Torre Fernández, Imanol
Aramendia, Julene
Gómez Nubla, Leticia
Castro, Kepa
Maguregui, Maite
Fernández Ortiz de Vallejuelo, Silvia
Arana, Gorka
Madariaga Mota, Juan Manuel
The application of a non-destructive analytical procedure to characterise the mineral phases in meteorites is a key issue in order to
preserve this type of scarce materials. In the present work, the Elephant Moraine 83227 meteorite, found in Antarctica in 1983
and originated from 4 Vesta asteroid, was analysed by micro-Raman spectroscopy, micro-energy-dispersive X-ray fluorescence
and the structural and chemical analyser (Raman spectroscopy coupled with scanning electron microscopy-energy-dispersive
spectroscopy) working in both point-by-point and image modes. The combination of all these techniques allows the extraction of,
at the same time, elemental, molecular and structural data of the studied microscopic area of the meteorite. The most relevant
results of the Elephant Moraine 83227 were the finding of tridymite for the first time in a 4 Vesta meteorite, along with quartz,
which means that the meteorite suffered high temperatures at a certain point. Moreover, both feldspar and pyroxenewere found as
the main mineral phases in the sample. Ilmenite, apatite, chromite and elemental sulphur were also detected as secondary
minerals. Finally, calcite was found as a weathering product, which was probably formed in terrestrial weathering processes of
the pyroxene present in the sample. Besides, Raman spectroscopy provided information about the conditions that the meteorite
experienced; the displacements in some feldspar Raman bands were used to estimate the temperature and pressure conditions to
which the Elephant Moraine 83227 was subjected, because we obtained both low and high formation temperature feldspar.
2019-03-26T17:33:59Z
2019-03-26T17:33:59Z
2019-03-26T17:33:59Z
2018
info:eu-repo/semantics/article
Analytical and Bioanalytical Chemistry, Septiembre 2018, vol. 410. p. 7477–7488
http://uvadoc.uva.es/handle/10324/35257
https://doi.org/10.1007/s00216-018-1363-5
eng
https://link.springer.com/article/10.1007%2Fs00216-018-1363-5
info:eu-repo/semantics/openAccess
© 2018 Springer
Springer
oai:uvadoc.uva.es:10324/352582021-07-06T08:33:30Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Analytical methodology to elemental quantification of weathered terrestrial analogues to meteorites using a portable Laser-Induced Breakdown Spectroscopy (LIBS) instrument and Partial Least Squares (PLS) as multivariate calibration technique
Gómez Nubla, Leticia
Aramendia, Julene
Fernández Ortiz de Vallejuelo, Silvia
Madariaga Mota, Juan Manuel
The present work is focused on the in situ quantitative analysis of Si, Al,Mg, Ca, Ba, Na, and Fe, present in weathered
terrestrial analogues to meteorites (black steel slag and impact glasses), using a portable Laser Induced
Breakdown Spectroscopy (LIBS) instrument. For that purpose, several standards pellets of known elemental concentrations
were manufactured. The elemental and molecular homogeneity of the pellets was studied by means
of Scanning Electron Microscopy coupled to Energy Dispersive X-ray spectroscopy (SEM-EDS) and Raman spectroscopy.
This checkwas always made before the LIBS analysis. Univariate andmultivariate (Partial Least Squares
(PLS) regression) calibration approaches on LIBS spectra were selected as initial calibration models. After a comparison
between both approaches, the former was discarded due to the poor linearity of the calibration curves,
and PLS regressionwas chosen to treat the LIBS spectra as themultivariate calibration approach (in the ultraviolet
(UV) and infrared (IR) spectral ranges). Predictive capabilities of each calibration model were evaluated by calculating
regression coefficient (r), number of PLS factors (rank), relative errors of cross validation (RMSECV), residual
predictive deviation (RPD) and the Bias value. At the end, the simultaneous use of both ranges of
wavelengths was demonstrated to be more fruitful rather than using the individual ones, probably due to the
higher number of emission lines, number of spectral variables and the PLS latent variables for each element.
Moreover, a Reference Material was used as external validation, obtaining satisfactory results in the determination
of elements. The predictive ability of the PLSmodelswas evaluated on samples of Darwin Glasses (Australia),
Libyan Desert Glasses (Western Desert of Egypt) and black steel slag residues (steelworks of Basque Country).
The obtained results were in concordance with the range of composition measured also by X-ray Fluorescence
Spectrometer (ED-XRF). Our methodology is a good, rapid, simple and cost-effective alternative for in situ analysis
of these terrestrial analogues over other techniques.
2019-03-26T17:42:49Z
2019-03-26T17:42:49Z
2019-03-26T17:42:49Z
2018
info:eu-repo/semantics/article
Microchemical Journal, 2018, vol. 137. p. 392–401
0026-265X
http://uvadoc.uva.es/handle/10324/35258
https://doi.org/10.1016/j.microc.2017.11.019
eng
https://www.sciencedirect.com/science/article/pii/S0026265X17310524?via%3Dihub
info:eu-repo/semantics/openAccess
© 2018 Elsevier
Elsevier
oai:uvadoc.uva.es:10324/352592021-06-23T10:18:12Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
AstRoMap European Astrobiology Roadmap
Gerda, Horneck
Walter, Nicolas
Westall, Frances
Grenfell, John Lee
Martin, William F.
Gómez, Felipe
Leuko, Stefan
Lee, Natuschka
Onofri, Silvano
Tsiganis, Kleomenis
Saladino, Raffaele
Pilat-Lohinger, Elke
Palomba, Ernesto
Harrison, Jesse
Rull Pérez, Fernando
Muller, Christian
Strazzulla, Giovanni
Brucato, John R.
Rettberg, Petra
Capria, Maria Teresa
The European AstRoMap project (supported by the European Commission Seventh Framework Programme)
surveyed the state of the art of astrobiology in Europe and beyond and produced the first European roadmap for
astrobiology research. In the context of this roadmap, astrobiology is understood as the study of the origin,
evolution, and distribution of life in the context of cosmic evolution; this includes habitability in the Solar
System and beyond. The AstRoMap Roadmap identifies five research topics, specifies several key scientific
objectives for each topic, and suggests ways to achieve all the objectives. The five AstRoMap Research Topics are
It is strongly recommended that steps be taken towards the definition and implementation of a European
Astrobiology Platform (or Institute) to streamline and optimize the scientific return by using a coordinated
infrastructure and funding system. Key Words: Astrobiology roadmap—Europe—Origin and evolution of
life—Habitability—Life detection—Life in extreme environments. Astrobiology 16, 201–243.
2019-03-27T00:45:09Z
2019-03-27T00:45:09Z
2019-03-27T00:45:09Z
2016
info:eu-repo/semantics/article
ASTROBIOLOGY, 2016, vol. 16, n. 3, p. 201-243.
http://uvadoc.uva.es/handle/10324/35259
https://doi.org/10.1089/ast.2015.1441
eng
https://www.liebertpub.com/doi/10.1089/ast.2015.1441
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribution-NonCommercial-NoDerivatives 4.0 International
Mary Ann Liebert
oai:uvadoc.uva.es:10324/380342021-06-23T10:18:33Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Thermomechanical issues of high power laser diode catastrophic optical damage
Souto Bartolomé, Jorge Manuel
Pura Ruiz, José Luis
Jiménez López, Juan Ignacio
Catastrophic optical damage (COD) of high power laser diodes is a crucial factor limiting
ultra high power lasers. The understanding of the COD process is essential to improve the
endurance of the high power laser diodes. COD is observed as a process in which the active
part of the laser diode is destroyed, forming characteristic defects, the so called dark line
defects (DLDs). The DLDs are formed by arrays of dislocations generated during the laser
operation. Local heating associated with non-radiative recombination is assumed to be at the
origin of the COD process. A summary of the methods used to assess the COD, both in real
time and post-mortem is presented. The main approaches developed in recent years to model
the heat transport in the laser structures under non homogeneous temperature distribution are
overviewed. Special emphasis is paid to the impact of the low dimensionality of QWs in two
physical properties playing a major role in the COD process, namely, thermal conductivity
and mechanical strength. A discussion about the impact of the nanoscale in both physical
properties is presented. Finally, we summarize the main issues of the thermomechanical
modelling of COD. Within this model the COD is launched when the local thermal stresses
generated around the heat source overcome the yield stress of the active zone of the laser. The
thermal runaway is related to the sharp decrease of the thermal conductivity once the onset of
plasticity has been reached in the active zone of the laser.
2019-09-19T15:32:01Z
2019-09-19T15:32:01Z
2019-09-19T15:32:01Z
2019
info:eu-repo/semantics/article
Journal of Physics D: Applied Physics 52, 343002 (2019)
0022-3727
http://uvadoc.uva.es/handle/10324/38034
10.1088/1361-6463/ab243f
343002
34
Journal of Physics D: Applied Physics
52
1361-6463
eng
https://iopscience.iop.org/article/10.1088/1361-6463/ab243f
info:eu-repo/semantics/openAccess
IOP Science
oai:uvadoc.uva.es:10324/407042021-06-24T07:47:54Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Influence of the viscosity of poly(methyl methacrylate) on the cellular structure of nanocellular materials
Bernardo García, Victoria
Laguna Gutiérrez, Ester
Rodríguez Pérez, Miguel Ángel
Three different grades of poly(methyl methacrylate) (PMMA) with different rheological properties are used for the production of nanocellular materials using gas dissolution foaming. The influences of both the viscosity of the different polymers and the processing parameters on the final cellular structure are studied using a wide range of saturation and foaming conditions. Foaming conditions affect similarly all cellular materials. It is found that an increase of the foaming temperature results in less dense nanocellular materials, with higher cell nucleation densities. In addition, it is demonstrated that a lower viscosity leads to cellular polymers with a lower relative density but larger cell sizes and smaller cell nucleation densities, these differences being more noticeable for the conditions in which low solubilities are reached. It is possible to produce nanocellular materials with relative densities of 0.24 combined with cell sizes of 75 nm and cell nucleation densities of 1015 nuclei cm−3 using the PMMA with the lowest viscosity. In contrast, minimum cell sizes of around 14 nm and maximum cell nucleation densities of 3.5 × 1016 nuclei cm−3 with relative densities of 0.4 are obtained with the most viscous one. © 2019 Society of Chemical Industry
2020-04-06T07:29:46Z
2020-04-06T07:29:46Z
2020-04-06T07:29:46Z
2019
info:eu-repo/semantics/article
Polym Int 2020; 69: 72–83
0959-8103
http://uvadoc.uva.es/handle/10324/40704
10.1002/pi.5920
72
1
83
Polymer International
69
1097-0126
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407052021-06-23T10:18:37Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Nanocellular Polymers with a Gradient Cellular Structure Based on Poly(methyl methacrylate)/Thermoplastic Polyurethane Blends Produced by Gas Dissolution Foaming
Bernardo García, Victoria
Martín de León, Judit
Sánchez Calderón, Ismael
Laguna Gutiérrez, Ester
Rodríguez Pérez, Miguel Ángel
Graded structures and nanocellular polymers are two examples of advanced
cellular morphologies. In this work, a methodology to obtain low-density
graded nanocellular polymers based on poly(methyl methacrylate) (PMMA)/
thermoplastic polyurethane (TPU) blends produced by gas dissolution
foaming is reported. A systematic study of the effect of the processing condition is presented. Results show that the melt-blending results in a solid
nanostructured material formed by nanometric TPU domains. The PMMA/
TPU foamed samples show a gradient cellular structure, with a homogeneous nanocellular core. In the core, the TPU domains act as nucleating
sites, enhancing nucleation compared to pure PMMA and allowing the
change from a microcellular to a nanocellular structure. Nonetheless, the
outer region shows a gradient of cell sizes from nano- to micron-sized cells.
This gradient structure is attributed to a non-constant pressure profile in the
samples due to gas desorption before foaming. The nucleation in the PMMA/
TPU increases as the saturation pressure increases. Regarding the effect of
the foaming conditions, it is proved that it is necessary to have a fine control
to avoid degeneration of the cellular materials. Graded nanocellular polymers
with relative densities of 0.16–0.30 and cell sizes ranging 310–480 nm (in the
nanocellular core) are obtained.
2020-04-06T07:32:23Z
2020-04-06T07:32:23Z
2020-04-06T07:32:23Z
2019
info:eu-repo/semantics/article
Macromol. Mater. Eng. 2020, 305, 1900428
1438-7492
http://uvadoc.uva.es/handle/10324/40705
10.1002/mame.201900428
1900428
1
Macromolecular Materials and Engineering
305
1439-2054
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407062021-06-24T07:47:05Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Highly anisotropic nanocellular polymers based on tri-phasic blends of PMMA with two nucleating agents
Bernardo García, Victoria
Martín de León, Judit
Rodríguez Pérez, Miguel Ángel
One strategy to produce nanocellular polymers is the use of nucleating species to promote nucleation. Whereas two-phase systems are widely studied, tri-phasic blends with two nucleating agents are uncommonly investigated. In this work, nanocellular polymers are obtained using tri-phasic blends of polymethylmethacrylate (PMMA) with two nucleating agents: needle-like sepiolites and a polymethylmethacrylate-polybutylacrylate-polymethylmethacrylate (MAM) block copolymer. Blends of PMMA with different concentrations of MAM and a fixed amount of sepiolites are produced by extrusion. Results show that at low MAM contents (1 wt%), the nucleation is a combination of the action of the two additives, but the addition of sepiolites induces the appearance of anisotropic structures. Meanwhile, at high MAM concentrations (10 wt%), MAM nanostructuration controls the nucleation and sepiolites increase the anisotropy. The alignment of the MAM micelles and the sepiolites in the extrusion direction promotes coalescence in this direction, leading to highly anisotropic nanocellular structures. Mean cell sizes of 100–300 nm and an average anisotropy ratio of 2.77 are obtained thanks to the combined effect of MAM and sepiolites.
2020-04-06T07:35:42Z
2020-04-06T07:35:42Z
2020-04-06T07:35:42Z
2019
info:eu-repo/semantics/article
Material Letters 225 (2019) 126587
0167-577X
http://uvadoc.uva.es/handle/10324/40706
10.1016/j.matlet.2019.126587
126587
Materials Letters
255
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407072021-06-24T07:47:06Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Production of PMMA-based nanocellular polymers using low demanding saturation conditions
Bernardo García, Victoria
Martín de León, Judit
Rodríguez Pérez, Miguel Ángel
Nanocellular polymers are novel materials characterized by nanometric cell sizes with huge potential in many industrial applications. However, their production is challenging and usually requires demanding processing conditions that make difficult the production at industrial scale. In this work, we prove that nanocellular polymers based on PMMA can be obtained, thanks to the addition of nucleating species, using low saturation pressure (6 MPa) and room saturation temperature in a gas dissolution foaming process. Nanoparticles and block copolymers at different concentrations are used to obtain a collection of nanocellular polymers with densities ranging 0.16–0.58 and cell sizes from 120 to 900 nm. Comparison with the literature results shows that the processing parameters used in this work are the less demanding ever used for producing nanocellular PMMA.
2020-04-06T07:41:52Z
2020-04-06T07:41:52Z
2020-04-06T07:41:52Z
2019
info:eu-repo/semantics/article
Material Letters 255 (2019) 126551
0167-577X
http://uvadoc.uva.es/handle/10324/40707
10.1016/j.matlet.2019.126551
126551
Materials Letters
255
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407082021-06-24T07:47:04Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
The influence of cell size on the mechanical properties of nanocellular PMMA
Martín de León, Judit
Van Loock, Frederik
Bernardo García, Victoria
Fleck, Norman A.
Rodríguez Pérez, Miguel Ángel
Solid-state foaming experiments are conducted on three grades of polymethyl methacrylate (PMMA). Nanocellular PMMA foams are manufactured with an average cell size ranging from 20 nm to 84 nm and a relative density between 0.37 and 0.5. For benchmarking purposes, additional microcellular PMMA foams with an average cell size close to 1 μm and relative density close to that of the nanocellular foams are manufactured. Uniaxial compression tests and single edge notch bend tests are conducted on the PMMA foams. The measured Young's modulus and yield strength of the PMMA foams are independent of cell size whereas the fracture toughness of the PMMA foam increases with decreasing average cell size from the micron range to the nanometer range.
2020-04-06T08:19:49Z
2020-04-06T08:19:49Z
2020-04-06T08:19:49Z
2019
info:eu-repo/semantics/article
Polymer Volume 181, 24 October 2019, 121805
0032-3861
http://uvadoc.uva.es/handle/10324/40708
10.1016/j.polymer.2019.121805
121805
Polymer
181
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407092021-06-24T07:47:19Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Mechanical Properties of PMMA‐Sepiolite Nanocellular Materials with a Bimodal Cellular Structure
Bernardo García, Victoria
Loock, Frederik
Martín de León, Judit
Fleck, Norman A.
Rodríguez Pérez, Miguel Ángel
imodal cellular poly(methyl methacrylate) with micro‐ and nano‐sized (300–500 nm) cells with up to 5 wt% of sepiolite nanoparticles and porosity from 50% to 75% are produced by solid‐state foaming. Uniaxial compression tests are performed to measure the effect of sepiolite concentration on the elastic modulus and the yield strength of the solid and cellular nanocomposites. Single edge notch bend tests are conducted to relate the fracture toughness of the solid and cellular nanocomposites to sepiolite concentration. The relative modulus is independent of sepiolite content to within material scatter when considering the complete porosity range. In contrast, a mild enhancement of the relative modulus is observed by the addition of sepiolite particles for the foamed nanocomposites with a porosity close to 50%. The relative compressive strength of the cellular nanocomposites mildly decreases as a function of sepiolite concentration. A strong enhancement of the relative fracture toughness by the addition of sepiolites is observed. The enhancement of the relative fracture toughness and the relative modulus (at 50% porosity) can be attributed to an improved dispersion of the particles due to foaming and the migration of micro‐sized aggregates from the solid phase to the microcellular pores during foaming.
2020-04-06T08:22:51Z
2020-04-06T08:22:51Z
2020-04-06T08:22:51Z
2019
info:eu-repo/semantics/article
Macromolecular Materials and EngineeringVolume 304, Issue 7, 2019
1438-7492
http://uvadoc.uva.es/handle/10324/40709
10.1002/mame.201900041
1900041
7
Macromolecular Materials and Engineering
304
1439-2054
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407102021-06-24T07:47:23Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Anisotropy in nanocellular polymers promoted by the addition of needle‐like sepiolites
Bernardo García, Victoria
Martín de León, Judit
Rodríguez Pérez, Miguel Ángel
This work presents a new strategy for obtaining nanocellular materials with high anisotropy ratios by means of the addition of needle‐like nanoparticles. Nanocellular polymers are of great interest due to their outstanding properties, whereas anisotropic structures allow the realization of improved thermal and mechanical properties in certain directions. Nanocomposites based on poly(methyl methacrylate) (PMMA) with nanometric sepiolites are generated by extrusion. From the extruded filaments, cellular materials are produced using a two‐step gas dissolution foaming method. The effect of adding various types and contents of sepiolites is investigated. As a result of the extrusion process, the needle‐like sepiolites are aligned in the machine direction in the solid nanocomposites. Regarding the cellular materials, the addition of sepiolites allows one to obtain anisotropic nanocellular polymers with cell sizes of 150 to 420 nm and cell nucleation densities of 1013–1014 nuclei cm−3 and presenting anisotropy ratios ranging from 1.38 to 2.15, the extrusion direction being the direction of the anisotropy. To explain the appearance of anisotropy, a mechanism based on cell coalescence is proposed and discussed. In addition, it is shown that it is possible to control the anisotropy ratio of the PMMA/sepiolite nanocellular polymers by changing the amount of well‐dispersed sepiolites in the solid nanocomposites.
2020-04-06T08:25:27Z
2020-04-06T08:25:27Z
2020-04-06T08:25:27Z
2019
info:eu-repo/semantics/article
Polymer InternationalVolume 68, Issue 6, 2019
0959-8103
http://uvadoc.uva.es/handle/10324/40710
10.1002/pi.5813
1204
6
1214
Polymer International
68
1097-0126
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407112021-06-24T07:47:20Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Overcoming the Challenge of Producing Large and Flat Nanocellular Polymers: A Study with PMMA
Martín de León, Judit
Bernardo García, Victoria
Cimavilla Román, Paula
Pérez Tamarit, Saúl
Rodríguez Pérez, Miguel Ángel
Although nanocellular polymers are interesting materials with improved properties in comparison with conventional or microcellular polymers, the production of large and flat parts of those materials is still challenging. Herein, gas dissolution foaming process is used to produce large and flat nanocellular polymethylmethacrylate samples. In order to do that, the foaming step is performed in a hot press. The methodology is optimized to produce flat samples with dimensions of 100 × 100 × 6 mm3, relative densities in the range 0.25–0.55 and cell sizes around 250 nm. Additionally, foaming parameters are modified to study their influence on the final cellular structure, and the materials produced in this paper are compared with samples produced by using a most conventional approach in which foaming step is conducted in a thermal bath. Results obtained show that an increment in the foaming temperature leads to a reduction in relative density and an increase of cell nucleation density. Moreover, differences in the final cellular structure for materials produced by both foaming routes are studied, proving that although there exist some differences, the mechanisms governing the nucleation and growing are the same in both processes, leading to the production of homogeneous materials with very similar cellular structures.
2020-04-06T08:27:14Z
2020-04-06T08:27:14Z
2020-04-06T08:27:14Z
2019
info:eu-repo/semantics/article
Advanced Engineering MaterialsVolume 21, Issue 6, 2019
1438-1656
http://uvadoc.uva.es/handle/10324/40711
10.1002/adem.201900148
1900148
6
Advanced Engineering Materials
21
1527-2648
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407122021-06-24T07:47:24Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Transparent nanocellular PMMA: Characterization and modeling of the optical properties
Martín de León, Judit
Pura Ruiz, José Luis
Bernardo García, Victoria
Rodríguez Pérez, Miguel Ángel
In this work, the optical properties of transparent nanocellular polymethylmethacrylate (PMMA) have been studied, experimental and theoretically. Transmittance measurements of samples presenting different cell sizes (14, 24, 39 and 225 nm) and a constant relative density of around 0.45 have been carried out obtaining values as high as 0.94 for the sample with the smaller cell size and a thickness of 0.05 mm. In addition, the light absorption coefficient has been measured as a function of cell size and wavelength. It has been found that the transmittance has a strong dependence with the wavelength, presenting these transparent materials Rayleigh scattering. On the other hand, the transmission of visible light through these nanocellular materials has been modelled for the first time. The developed model reproduces with good accuracy the trends observed in the experimental results and provides remarkable insights into the physics mechanisms controlling the optical behavior of these materials.
2020-04-06T08:29:44Z
2020-04-06T08:29:44Z
2020-04-06T08:29:44Z
2019
info:eu-repo/semantics/article
Volume 170, 29 April 2019, Pages 16-23, 2019
0032-3861
http://uvadoc.uva.es/handle/10324/40712
10.1016/j.polymer.2019.03.010
16
23
Polymer
170
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407132021-06-24T07:47:30Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Low-density PMMA/MAM nanocellular polymers using low MAM contents: Production and characterization
Bernardo García, Victoria
Martín de León, Judit
Pinto Sanz, Javier
Catelani, Tiziano
Athanassiou, Athanassia
Rodríguez Pérez, Miguel Ángel
Low-density nanocellular polymers are required to take advantage of the full potential of these materials as high efficient thermal insulators. However, their production is still a challenging task. One promising approach is the use of nanostructured polymer blends of poly(methyl methacrylate) (PMMA) and a block copolymer poly(methyl methacrylate)-poly(butyl acrylate)-poly(methyl methacrylate) (MAM), which are useful for promoting nucleation but seem to present a severe drawback, as apparently avoid low relative densities. In this work, new strategies to overcome this limitation and produce low-density nanocellular materials based on these blends are investigated. First, the effect of very low amounts of the MAM copolymer is analysed. It is detected that nanostructuration can be prevented using low copolymer contents, but nucleation is still enhanced as a result of the copolymer molecules with high CO2 affinity dispersed in the matrix, so nanocellular polymers are obtained using very low percentages of the copolymer. Second, the influence of the foaming temperature is studied. Results show that for systems in which there is not a clear nanostructuration, cells can grow more freely and smaller relative densities can be achieved.
For these studies, blends of PMMA with MAM with copolymer contents from 10 wt% and as low as 0.1 wt% are used. For the first time, the production strategies proposed in this work have allowed obtaining low density (relative density 0.23) nanocellular polymers based on PMMA/MAM blends.
Graphical abstract
2020-04-06T08:32:01Z
2020-04-06T08:32:01Z
2020-04-06T08:32:01Z
2019
info:eu-repo/semantics/article
Polymer Volume 163, 1 February 2019, Pages 115-124, 2019
0032-3861
http://uvadoc.uva.es/handle/10324/40713
10.1016/j.polymer.2018.12.057
115
124
Polymer
163
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407142021-06-24T07:47:32Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Modeling the heat transfer by conduction of nanocellular polymers with bimodal cellular structures
Bernardo García, Victoria
Martín de León, Judit
Pinto Sanz, Javier
Verdejo, Raquel
Rodríguez Pérez, Miguel Ángel
Nanocellular polymers are a new generation of materials with the potential of being used as very efficient thermal insulators. It has been proved experimentally that these materials present the Knudsen effect, which strongly reduces the conductivity of the gas phase. There are theoretical equations to predict the thermal conductivity due to this Knudsen effect, but all the models consider an average cell size. In this work, we propose a model to predict the thermal conductivity due to the conduction mechanisms of nanocellular materials with bimodal cellular structures, that is, with two populations of cells, micro and nanocellular. The novelty of our work is to consider not only the average cell size, but the cell size distribution. The predictions of the model are compared with the experimental conductivity of two real bimodal systems based on poly(methyl methacrylate) (PMMA), and it is proved that this new model provides more accurate estimations of the conductivity than the models that do not consider the bimodality. Furthermore, this model could be applied to monomodal nanocellular polymers. In particular, for monomodal materials presenting a wide cell size distribution and at low densities, the model predicts important variations in comparison with the current models in the literature. This result indicates that the cell size distribution must be included in the estimations of the thermal conductivity of nanocellular polymers
2020-04-06T08:34:21Z
2020-04-06T08:34:21Z
2020-04-06T08:34:21Z
2019
info:eu-repo/semantics/article
Polymer Volume 160, 3 January 2019, Pages 126-137, 2019
0032-3861
http://uvadoc.uva.es/handle/10324/40714
10.1016/j.polymer.2018.11.047
126
137
Polymer
160
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407152021-06-24T07:47:26Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Nanocellular polymers: The challenge of creating cells in the nanoscale
Martín de León, Judit
Bernardo García, Victoria
Rodríguez Pérez, Miguel Ángel
he evolution of technology means that increasingly better materials are needed. It is well known that as a result of their interesting properties, nanocellular polymers perform better than microcellular ones. For this reason, the investigation on nanocellular materials is nowadays a very topical issue. In this paper, the different approaches for the production of these materials in our laboratory are explained, and results obtained by using polymethylmethacrylate (PMMA) are shown. Homogeneous nucleation has been studied by using raw PMMA, while two different systems were used for heterogeneous nucleation; adding nanoparticles to the system and using nanostructured polymers as solid precursors for foaming. The effects of the different parameters of the production process (gas dissolution foaming process) have been evaluated for all systems being possible to establish a comparison between the materials produced by different approaches. Moreover, the limitations and future work to optimise the materials produced are also discussed.
2020-04-06T08:36:09Z
2020-04-06T08:36:09Z
2020-04-06T08:36:09Z
2019
info:eu-repo/semantics/article
Materials, 2019, vol. 12, n. 5. 19 p.
http://uvadoc.uva.es/handle/10324/40715
10.3390/ma12050797
797
5
Materials
12
1996-1944
spa
https://www.mdpi.com/1996-1944/12/5/797
info:eu-repo/semantics/openAccess
© 2019 MDPI
oai:uvadoc.uva.es:10324/407162021-06-24T07:47:52Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
The mechanics of solid-state nanofoaming
Van Loock, Frederik
Bernardo García, Victoria
Rodríguez Pérez, Miguel Ángel
Fleck, Norman A.
Solid-state nanofoaming experiments are conducted on two polymethyl methacrylate (PMMA) grades of markedly different molecular weight using CO2 as the blowing agent. The sensitivity of porosity to foaming time and foaming temperature is measured. Also, the microstructure of the PMMA nanofoams is characterized in terms of cell size and cell nucleation density. A one-dimensional numerical model is developed to predict the growth of spherical, gas-filled voids during the solid-state foaming process. Diffusion of CO2 within the PMMA matrix is sufficiently rapid for the concentration of CO2 to remain almost uniform spatially. The foaming model makes use of experimentally calibrated constitutive laws for the uniaxial stress versus strain response of the PMMA grades as a function of strain rate and temperature, and the effect of dissolved CO2 is accounted for by a shift in the glass transition temperature of the PMMA. The maximum achievable porosity is interpreted in terms of cell wall tearing and comparisons are made between the predictions of the model and nanofoaming measurements; it is deduced that the failure strain of the cell walls is sensitive to cell wall thickness
2020-04-06T08:39:18Z
2020-04-06T08:39:18Z
2020-04-06T08:39:18Z
2019
info:eu-repo/semantics/article
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences Volume 475, Issue 2230, 2019
1364-5021
http://uvadoc.uva.es/handle/10324/40716
10.1098/rspa.2019.0339
20190339
2230
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
475
1471-2946
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407172021-06-24T07:47:34Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Nanoclay intercalation during foaming of polymeric nanocomposites studied in-situ by synchrotron X-ray diffraction
Bernardo García, Victoria
Múgica Izaguirre, Mikel
Pérez Tamarit, Saúl
Notario Collado, Belén
Jimenez, Catalina
Rodríguez Pérez, Miguel Ángel
The intercalation degree of nanoclays in polymeric foamed nanocomposites containing clays is a key parameter determining the final properties of the material, but how intercalation occurs is not fully understood. In this work, energy dispersive X-ray diffraction (ED-XRD) of synchrotron radiation was used as an in-situ technique to deepen into the intercalation process of polymer/nanoclay nanocomposites during foaming. Foamable nanocomposites were prepared by the melt blending route using low-density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS) with surface treated nanoclays and azodicarbonamide (ADC) as the blowing agent. Foaming was induced by heating at atmospheric pressure. The time and temperature evolution of the interlamellar distance of the clay platelets in the expanding nanocomposites was followed. Upon foaming, interlamellar distances of the nanocomposites based on LDPE and PP increase by 18% and 16% compared to the bulk foamable nanocomposite. Therefore, the foaming process enhances the nanoclay intercalation degree in these systems. This effect is not strongly affected by the type of nanoclay used in LDPE, but by the type of polymer used. Besides, the addition of nanoclays to PP and PS has a catalytic effect on the decomposition of ADC, i.e., the decomposition temperature is reduced, and the amount of gas released increases. This effect was previously proved for LDPE
2020-04-06T08:41:37Z
2020-04-06T08:41:37Z
2020-04-06T08:41:37Z
2018
info:eu-repo/semantics/article
Materials, 2018, vol. 11, n. 12. 12 p.
http://uvadoc.uva.es/handle/10324/40717
10.3390/ma11122459
2459
12
Materials
11
1996-1944
spa
https://www.mdpi.com/1996-1944/11/12/2459
Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project MAT2015-69234-R)
info:eu-repo/semantics/openAccess
© 2018 MDPI
MDPI
oai:uvadoc.uva.es:10324/407182021-06-24T07:47:36Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Understanding the role of MAM molecular weight in the production of PMMA/MAM nanocellular polymers
Bernardo García, Victoria
Martín de León, Judit
Laguna Gutiérrez, Ester
Catelani, Tiziano
Pinto Sanz, Javier
Athanassiou, Athanassia
Rodríguez Pérez, Miguel Ángel
Nanostructured polymer blends with CO2-philic domains can be used to produce nanocellular materials with controlled nucleation. It is well known that this nanostructuration can be induced by the addition of a block copolymer poly(methyl methacrylate)-poly(butyl acrylate)-poly(methyl methacrylate) (MAM) to a poly(methyl methacrylate) (PMMA) matrix. However, the effect of the block copolymer molecular weight on the production of nanocellular materials is still unknown. In this work, this effect is analysed by using three types of MAM triblock copolymers with different molecular weights, and a fixed blend ratio of 90 wt% PMMA and 10 wt% of MAM. Blends were produced by extrusion. As a result of the extrusion process, a non-equilibrium nanostructuration takes place in the blends, and the micelle density increases as MAM molecular weight increases. Micelle formation is proposed to occur as result of two mechanisms: dispersion, controlled by the extrusion parameters and the relative viscosities of the polymers, and self-assembly of MAM molecules in the dispersed domains. On the other hand, in the nanocellular materials produced with these blends, cell size decreases from 200 to 120 nm as MAM molecular weight increases. Cell growth is suggested to be controlled by the intermicelle distance and limited by the cell wall thickness. Furthermore, a theoretical explanation of the mechanisms underlying the limited expansion of PMMA/MAM systems is proposed and discussed.
2020-04-06T08:44:44Z
2020-04-06T08:44:44Z
2020-04-06T08:44:44Z
2018
info:eu-repo/semantics/article
Polymer, Volume 153, 26 September 2018, Pages 262-270
0032-3861
http://uvadoc.uva.es/handle/10324/40718
10.1016/j.polymer.2018.08.022
262
270
Polymer
153
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407192021-06-23T10:19:05Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Light transmission in nanocellular polymers: Are semi-transparent cellular polymers possible?
Pérez Tamarit, Saúl
Notario, B.
Solórzano Quijano, Eusebio
Rodríguez Pérez, Miguel Ángel
This work presents the light transmission through a collection of solid cellular polymers based on poly (methyl methacrylate) (PMMA) with cells sizes covering the micro and nano-scale. The obtained results showed that the behavior of light transmission when cell size is in the nano-scale is opposite to the one shown by microcellular foams or the one predicted by theoretical models of light scattering (LS). In fact, the expected trend is that a reduction of cell size increases the opacity of the samples. However, for nanocellular polymers based on amorphous polymers reducing the cell size increases the light transmission. Therefore, this result indicates that a further reduction of the cell size could result in cellular polymers optically semi-transparent
2020-04-06T08:49:53Z
2020-04-06T08:49:53Z
2020-04-06T08:49:53Z
2018
info:eu-repo/semantics/article
Materials Letters, Volume 210, 1 January 2018, Pages 39-41
0167-577X
http://uvadoc.uva.es/handle/10324/40719
10.1016/j.matlet.2017.08.109
39
41
Materials Letters
210
spa
info:eu-repo/semantics/openAccess
Elsevier
oai:uvadoc.uva.es:10324/407202021-06-24T07:47:42Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Key Production Parameters to Obtain Transparent Nanocellular PMMA
Martín de León, Judit
Bernardo García, Victoria
Rodríguez Pérez, Miguel Ángel
Transparent nanocellular polymethylmethacrylate (PMMA) with relative density around 0.4 is produced for the first time by using the gas dissolution foaming technique. The processing conditions and the typical characteristics of the cellular structure needed to manufacture this novel material are discovered. It is proved that low saturation temperatures (−32 °C) combined with high saturation pressures (6, 10, 20 MPa) allow increasing the solubility of PMMA up to values not reached before. In particular, the highest CO2 uptake ever reported for PMMA, (i.e., 48 wt%) is found for a saturation pressure of 20 MPa and a saturation temperature of −32 °C. Due to these processing conditions, cell nucleation densities of 1016 nuclei cm−3 and cell sizes clearly below 50 nm are achieved. The nanocellular polymers obtained, with cell sizes ten times smaller than the wavelength of visible light and very homogeneous cellular structures, show a significant transparency.
2020-04-06T08:52:07Z
2020-04-06T08:52:07Z
2020-04-06T08:52:07Z
2017
info:eu-repo/semantics/article
acromolecular Materials and EngineeringVolume 302, Issue 12
1438-7492
http://uvadoc.uva.es/handle/10324/40720
10.1002/mame.201700343
1700343
12
Macromolecular Materials and Engineering
302
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407212021-06-24T07:47:47Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Molecular confinement of solid and gaseous phases of self-standing bulk nanoporous polymers inducing enhanced and unexpected physical properties
Pinto Sanz, Javier
Notario Collado, Belén
Verdejo, Raquel
Dumon, Michel
Costeux, Stephane
Rodríguez Pérez, Miguel Ángel
In this work it is provided the first evidence of the polymer chains confinement within self-standing pore walls of nanoporous materials based on poly (methyl methacrylate) (PMMA). This was made possible by producing a series of porous samples with a wide range of pore sizes between 90 nm and 3 μm using processes combining CO2 sorption, selective block copolymer swelling or homogeneous physical foaming. Mobility restrictions of the PMMA chains in the porous samples with pore size below 200 nm was consistently demonstrated with several experimental techniques, including differential scanning calorimetry, Raman spectroscopy, and broadband dielectric spectroscopy.
In addition, several scale-reduction phenomena related to the constitutive elements of the porous materials, both in the polymeric and gaseous phases, and to the porous architecture are identified. The significance of these phenomena on macroscopic electrical conductivity and permittivity of the nanoporous materials is demonstrated, and the presented observations support previous explanations of improved mechanical properties and thermal insulation of this type of nano-materials.
2020-04-06T08:54:02Z
2020-04-06T08:54:02Z
2020-04-06T08:54:02Z
2017
info:eu-repo/semantics/article
Polymer Volume 113, 24 March 2017, Pages 27-33
0032-3861
http://uvadoc.uva.es/handle/10324/40721
10.1016/j.polymer.2017.02.046
27
33
Polymer
113
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/407222021-09-13T09:25:22Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Nanoporous PMMA: A novel system with different acoustic properties
Notario Collado, Belén
Ballesteros Agudo, Alberto
Pinto Sanz, Javier
Rodríguez Pérez, Miguel Ángel
The acoustic properties of closed cell nanoporous and microporous poly(methyl methacrylate) (PMMA) foams have been well characterized, showing that nanoporous PMMA exhibit a different absorption coefficient and transmission loss behavior in comparison with microporous PMMA. Experimental differences may be explained by the different wave propagation mechanism in the micro and nanoscale, which is determined by the confinement of both the gas (Knudsen regime) and the solid phases. These results place nanoporous materials as a new class of polymeric porous material with potential properties in the field of acoustics, especially in multifunctional systems requiring a certain degree of soundproofing.
2020-04-06T09:01:28Z
2020-04-06T09:01:28Z
2020-04-06T09:01:28Z
2016
info:eu-repo/semantics/article
Materials Letters Volume 168, 1 April 2016, Pages 76-79
0167-577X
http://uvadoc.uva.es/handle/10324/40722
10.1016/j.matlet.2016.01.037
76
79
Materials Letters
168
spa
info:eu-repo/semantics/openAccess
oai:uvadoc.uva.es:10324/409712021-06-24T07:48:05Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Foams with enhanced ductility and impact behavior based on polypropylene composites
Muñoz Pascual, Santiago
Sáiz Arroyo, Cristina
Vuluga, Zina
Corobea, Mihai Cosmin
Rodríguez Pérez, Miguel Ángel
In this work, formulations based on composites of a linear polypropylene (L-PP), a long-chain branched polypropylene (LCB-PP), a polypropylene–graft–maleic anhydride (PP-MA), a styrene-ethylene-butylene-styrene copolymer (SEBS), glass fibers (GF), and halloysite nanotubes (HNT-QM) have been foamed by using the improved compression molding route (ICM), obtaining relative densities of about 0.62. The combination of the inclusion of elastomer and rigid phases with the use of the LCB-PP led to foams with a better cellular structure, an improved ductility, and considerable values of the elastic modulus. Consequently, the produced foams presented simultaneously an excellent impact performance and a high stiffness with respect to their corresponding solid counterparts.
2020-06-01T13:12:07Z
2020-06-01T13:12:07Z
2020-06-01T13:12:07Z
2020
info:eu-repo/semantics/article
Polymers, 2020, vol. 12, n. 4. 19 p.
2073-4360
http://uvadoc.uva.es/handle/10324/40971
10.3390/polym12040943
eng
https://www.mdpi.com/2073-4360/12/4/943
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2020 MDPI
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
MDPI
oai:uvadoc.uva.es:10324/409722021-06-24T07:47:02Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_31662col_10324_1242
Identification and quantification of cell gas evolution in rigid polyurethane foams by novel GCMS methodology
Galakhova, Anastasiia
Santiago Calvo, Mercerdes
Tirado Mediavilla, Josias
Villafañe González, Fernando
Rodríguez Pérez, Miguel Ángel
Riess, Gisbert
This paper presents a new methodology based on gas chromatography-mass spectrometry (GCMS) in order to separate and quantify the gases presented inside the cells of rigid polyurethane (RPU) foams. To demonstrate this novel methodology, the gas composition along more than three years of aging is herein determined for two samples: a reference foam and foam with 1.5 wt% of talc. The GCMS method was applied, on one hand, for the accurate determination of C5H10 and CO2 cell gases used as blowing agents and, on the other hand, for N2 and O2 air gases that diffuse rapidly from the surrounding environment into foam cells. GCMS results showed that CO2 leaves foam after 2.5 month (from 21% to 0.03% for reference foam and from 17% to 0.03% for foam with 1.5% talc). C5H10 deviates during 3.5 months (from 28% up to 39% for reference foam and from 29% up to 36% for foam with talc), then it starts to leave the foam and after 3.5 year its content is 13% for reference and 10% for foam with talc. Air diffuses inside the cells faster for one year (from 51% up to 79% for reference and from 54% up to 81% for foam with talc) and then more slowly for 3.5 years (reaching 86% for reference and 90% for foam with talc). Thus, the fast and simple presented methodology provides valuable information to understand the long-term thermal conductivity of the RPU foams.
2020-06-01T13:29:33Z
2020-06-01T13:29:33Z
2020-06-01T13:29:33Z
2019
info:eu-repo/semantics/article
Polymers, 2019, vol. 11, n. 7. 11 p.
2073-4360
http://uvadoc.uva.es/handle/10324/40972
10.3390/polym11071192
eng
https://www.mdpi.com/2073-4360/11/7/1192
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2019 MDPI
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
MDPI
oai:uvadoc.uva.es:10324/409732021-06-24T07:47:16Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Effect of mold temperature on the impact behavior and morphology of injection molded foams based on polypropylene polyethylene–octene copolymer blends
Muñoz Pascual, Santiago
López González, Eduardo
Sáiz Arroyo, Cristina
Rodríguez Pérez, Miguel Ángel
In this work, an isotactic polypropylene (PP) and a polyethylene–octene copolymer (POE) have been blended and injection-molded, obtaining solids and foamed samples with a relative density of 0.76. Different mold temperature and injection temperature were used. The Izod impact strength was measured. For solids, higher mold temperature increased the impact resistance, whereas in foams, the opposite trend was observed. In order to understand the reasons of this behavior, the morphology of the elastomeric phase, the crystalline morphology and the cellular structure have been studied. The presence of the elastomer near the skin in the case of high mold temperature can explain the improvement produced with a high mold temperature in solids. For foams, aspects as the elastomer coarsening in the core of the sample or the presence of a thicker solid skin are the critical parameters that justify the improved behavior of the materials produced with a lower mold temperature.
2020-06-01T14:57:24Z
2020-06-01T14:57:24Z
2020-06-01T14:57:24Z
2019
info:eu-repo/semantics/article
Polymers, 2019, vol. 11, n. 5. 14 p.
2073-4360
http://uvadoc.uva.es/handle/10324/40973
10.3390/polym11050894
894
5
Polymers
11
2073-4360
eng
https://www.mdpi.com/2073-4360/11/5/894
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2019 MDPI
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
MDPI
oai:uvadoc.uva.es:10324/409762021-06-24T07:47:13Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Transport properties of one-step compression molded epoxy nanocomposite foams
Martín Gallego, Mario
López Hernández, Emil
Pinto Sanz, Javier
Rodríguez Pérez, Miguel Ángel
López Manchado, Miguel Ángel
Verdejo, Raquel
Owing to their high strength and stiffness, thermal and environmental stability, lower shrinkage, and water resistance, epoxy resins have been the preferred matrix for the development of syntactic foams using hollow glass microspheres. Although these foams are exploited in multiple applications, one of their issues is the possibility of breakage of the glass hollow microspheres during processing. Here, we present a straightforward and single-step foaming protocol using expandable polymeric microspheres based on the well-established compression molding process. We demonstrate the viability of the protocol producing two sets of nanocomposite foams filled with carbon-based nanoparticles with improved transport properties.
2020-06-02T11:34:29Z
2020-06-02T11:34:29Z
2020-06-02T11:34:29Z
2019
info:eu-repo/semantics/article
Polymers, 2019, vol. 11, n. 5. 12 p.
2073-4360
http://uvadoc.uva.es/handle/10324/40976
10.3390/polym11050756
eng
https://www.mdpi.com/2073-4360/11/5/756
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2019 MDPI
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
MDPI
oai:uvadoc.uva.es:10324/409772021-06-24T07:47:10Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Influence of the characteristics of expandable graphite on the morphology, thermal properties, fire behaviour and compression performance of a rigid polyurethane foam
Acuña, Pablo
Li, Zhi
Santiago Calvo, Mercerdes
Villafañe González, Fernando
Rodríguez Pérez, Miguel Ángel
Wang, De-YI
Three types of expandable graphite (EG) differing in particle size and expansion volume, are compared as flame retardant additives to rigid polyurethane foams (RPUFs). In this paper we discuss microstructure, thermal stability, fire behavior, and compression performance. We find that ell size distributions were less homogeneous and cell size was reduced. Furthermore, thermal conductivity increased along with EG loading. Thermogravimetric analysis (TGA) showed that EG only increased residue yield differently. The results indicate that a higher expansion of EG increased the limiting oxygen index (LOI) value, whereas a bigger particle size EG improved the rating of the vertical burning test (UL94). Results from the cone calorimeter test showed that a bigger particle size EG effectively reduced peak of heat release rate (pHRR). Furthermore, a higher expansion, led to a decrease in smoke production (TSP). The combination of both characteristics gives extraordinary results. The physical–mechanical characterization of the EG/RPUF foams revealed that their compression performance decreased slightly, mostly due to the effect of a bigger size EG.
2020-06-02T11:48:41Z
2020-06-02T11:48:41Z
2020-06-02T11:48:41Z
2019
info:eu-repo/semantics/article
Polymers, 2019, vol. 11, n. 1. 19 p.
2073-4360
http://uvadoc.uva.es/handle/10324/40977
10.3390/polym11010168
eng
https://www.mdpi.com/2073-4360/11/1/168
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2019 MDPI
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
MDPI
oai:uvadoc.uva.es:10324/409782021-06-24T07:47:08Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Effect of solid phase corrugation on the thermo-mechanical properties of low density flexible cellular polymers
Pérez Tamarit, Saúl
Solórzano Quijano, Eusebio
Hilger, A.
Manke, Ingo
Rodríguez Pérez, Miguel Ángel
This manuscript presents the effect of the solid phase corrugation of low densityflexible cellular polymers onboth their mechanical and thermal properties. First, a detailed quantification of solid phase corrugation hasbeen carried out by means of high resolution synchrotron micro-tomography in a collection of polyethylenefoams. Subsequently, the collapse stress in compression has been analysed both from the theoretical and exper-imental points of view achieving a clear relation between the solid phase corrugation and the ratio of theoreti-cally calculated and experimentally measured collapse stress. Finally, solid phase corrugation has beencorrelated with the thermal expansion coefficient at room temperature.
2020-06-02T12:05:21Z
2020-06-02T12:05:21Z
2020-06-02T12:05:21Z
2019
info:eu-repo/semantics/article
Materials & Design, 2019, vol. 161. p. 106-113
0264-1275
http://uvadoc.uva.es/handle/10324/40978
10.1016/j.matdes.2018.11.020
eng
https://www.sciencedirect.com/science/article/pii/S0264127518308268?via%3Dihub
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2019 Elsevier
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
Elsevier
oai:uvadoc.uva.es:10324/409792021-06-24T07:47:39Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Gas dissolution foaming as a novel approach for the production of lightweight biocomposites of PHB/natural fibre fabrics
Ventura, Heura
Sorrentino, Luigi
Laguna Gutiérrez, Ester
Rodríguez Pérez, Miguel Ángel
Ardanuy, Mònica
The aim of this study is to propose and explore a novel approach for the production of cellular lightweight natural fibre, nonwoven, fabric-reinforced biocomposites by means of gas dissolution foaming from composite precursors of polyhydroxybutyrate-based matrix and flax fabric reinforcement. The main challenge is the development of a regular cellular structure in the polymeric matrix to reach a weight reduction while keeping a good fibre-matrix stress transfer and adhesion. The viability of the process is evaluated through the analysis of the cellular structure and morphology of the composites. The effect of matrix modification, nonwoven treatment, expansion temperature, and expansion pressure on the density and cellular structure of the cellular composites is evaluated. It was found that the nonwoven fabric plays a key role in the formation of a uniform cellular morphology, although limiting the maximum expansion ratio of the composites. Cellular composites with a significant reduction of weight (relative densities in the range 0.4–0.5) were successfully obtained.
2020-06-02T12:53:11Z
2020-06-02T12:53:11Z
2020-06-02T12:53:11Z
2018
info:eu-repo/semantics/article
Polymers, 2018, vol. 10, n. 3. 14 p.
2073-4360
http://uvadoc.uva.es/handle/10324/40979
10.3390/polym10030249
eng
https://www.mdpi.com/2073-4360/10/3/249
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2018 MDPI
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
MDPI
oai:uvadoc.uva.es:10324/410332021-06-23T10:19:39Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Editorial: Metallic foams special section
Rodríguez Pérez, Miguel Ángel
Solórzano Quijano, Eusebio
Porous metals and metallic foams have been, for the last 25 years, the focus of very active research and development activities around the world, both at the academic and industrial levels. These materials are used when the combination of metal properties with the characteristics of a properly designed cellular structure provides advantages over other types of materials. They possess a spectrum of unique properties that can be tailored as a function of the final application, such as high impact energy absorption under mechanical load, high specific stiffness and strength, high fire resistance, air and water permeability, unusual acoustic properties for a metallic component, and low relative thermal conductivity. This special issue of Advanced Engineering Materials mainly contains a selection of the papers presented during MetFoam2015. The conference encompasses papers dealing with basic fundamentals, fabrication, morphological, and microstructural characterization, property profiles, secondary operations, and various applications of porous metals and metallic foams.
2020-06-12T11:12:37Z
2020-06-12T11:12:37Z
2020-06-12T11:12:37Z
2017
info:eu-repo/semantics/article
Advanced Engineering Materials, 2017, vol. 19, n. 11.
1527-2648
http://uvadoc.uva.es/handle/10324/41033
10.1002/adem.201700545
1700545
11
Advanced Engineering Materials
19
eng
https://onlinelibrary.wiley.com/doi/full/10.1002/adem.201700545
info:eu-repo/semantics/openAccess
© 2017 Wiley
Wiley
oai:uvadoc.uva.es:10324/409802021-06-24T07:46:01Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Effects of wet/dry-cycling and plasma treatments on the properties of flax nonwovens intended for composite reinforcing
Ventura, Heura
Claramunt, Josep
Navarro, Antonio
Rodríguez Pérez, Miguel Ángel
Ardanuy, Mònica
This research analyzes the effects of different treatments on flax nonwoven (NW) fabrics which are intended for composite reinforcement. The treatments applied were of two different kinds: a wet/dry cycling which helps to stabilize the cellulosic fibers against humidity changes and plasma treatments with air, argon and ethylene gases considering different conditions and combinations, which produce variation on the chemical surface composition of the NWs. The resulting changes in the chemical surface composition, wetting properties, thermal stability and mechanical properties were determined. Variations in surface morphology could be observed by scanning electron microscopy (SEM). The results of the X-ray photoelectron spectroscopy (XPS) showed significant changes to the surface chemistry for the samples treated with argon or air (with more content on polar groups on the surface) and ethylene plasma (with less content of polar groups). Although only slight differences were found in moisture regain and water retention values (WRV), significant changes were found on the contact angle values, thus revealing hydrophilicity for the air-treated and argon-treated samples and hydrophobicity for the ethylene-treated ones. Moreover, for some of the treatments the mechanical testing revealed an increase of the NW breaking force.
2020-06-02T13:31:58Z
2020-06-02T13:31:58Z
2020-06-02T13:31:58Z
2016
info:eu-repo/semantics/article
Materials, 2016, vol. 9, n. 2. 18 p.
1996-1944
http://uvadoc.uva.es/handle/10324/40980
10.3390/ma9020093
eng
https://www.mdpi.com/1996-1944/9/2/93
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2016 MDPI
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
MDPI
oai:uvadoc.uva.es:10324/409812021-06-24T07:46:04Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Silver nanoparticles embedded in natural rubber films: synthesis, characterization and evaluation of in vitro toxicity
Danna, Caroline Silva
Cavalcante, Dalita Gomes Silva Morais
Gomes, Andressa S.
Ernst Kerche, Leandra
Kerche Silva, Leandra Ernst
Yoshihara, Eidi
Osorio Román, Igor
Salmazo, Leandra
Rodríguez Pérez, Miguel Ángel
Aroca, Ricardo
Job, Aldo Eloizo
Natural rubber (NR) films can reduce silver metal ions forming embedded metal nanoparticles, a process that could be described as green synthesis. The NR films acting as a reactor generate and incorporate silver nanoparticles (AgNPs). Organic acids and amino acids play a crucial role in the formation of AgNPs. The plasmon extinction obtained in the UV-visible spectrum shows the presence of nanoparticles in the film after dipping the NR film into a solution of silver nitrate at 80°C. Electron microscopic analysis confirms the presence of AgNPs in the NR film and characterization by atomic force microscopy shows a change in the roughness of the NR film with AgNPs. In addition, our preliminary results from in vitro toxicity studies (MTT and comet assays) of the NR films and NR films with silver nanoparticles (NR/Ag) show that they are not toxic to cell lineage CHO-K1 (cells from the ovary of a Chinese hamster), an important result for potential medical applications.
2020-06-02T13:49:13Z
2020-06-02T13:49:13Z
2020-06-02T13:49:13Z
2016
info:eu-repo/semantics/article
Journal of Nanomaterials, 2016, vol. 2016. 10 p.
1687-4110
http://uvadoc.uva.es/handle/10324/40981
10.1155/2016/2368630
eng
https://www.hindawi.com/journals/jnm/2016/2368630/
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2016 Hindawi
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
Hindawi
oai:uvadoc.uva.es:10324/409842021-06-23T10:19:34Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Strategies to improve the mechanical properties of starch-based materials: Plasticization and natural fibers reinforcement
López Gil, Alberto
Rodríguez Pérez, Miguel Ángel
Saja Sáez, José Antonio de
Ardanuy, Mònica
Biodegradable polymers are starting to be introduced as raw materials in the food-packaging market. Nevertheless, their price is very high. Starch, a fully biodegradable and bioderived polymer is a very interesting alternative due to its very low price. However, the use of starch as the polymer matrix for the production of rigid food packaging, such as trays, is limited due to its poor mechanical properties, high hidrophilicity and high density. This work presents two strategies to overcome the poor mechanical properties of starch. First, the plasticization of starch with several amounts of glycerol to produce thermoplastic starch (TPS) and second, the production of biocomposites by reinforcing TPS with promising fibers, such as barley straw and grape waste. The mechanical properties obtained are compared with the values predicted by models used in the field of composites; law of mixtures, Kerner-Nielsen and Halpin- Tsai. To evaluate if the materials developed are suitable for the production of foodpackaging trays, the TPS-based materials with better mechanical properties were compared with commercial grades of oil-based polymers, polypropylene (PP) and polyethylene-terphthalate (PET), and a biodegradable polymer, polylactic acid (PLA).
2020-06-03T11:23:42Z
2020-06-03T11:23:42Z
2020-06-03T11:23:42Z
2014
info:eu-repo/semantics/article
Polímeros: Ciência e Tecnologia, 2014, vol. 24, n. especial. p. 36-42
1678-5169
http://uvadoc.uva.es/handle/10324/40984
10.4322/polimeros.2014.054
eng
https://revistapolimeros.org.br/doi/10.4322/polimeros.2014.054
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/4.0/
© 2016 Associação Brasileira de Polímeros
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
Associação Brasileira de Polímeros
oai:uvadoc.uva.es:10324/409852021-06-23T10:19:37Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Green synthesis of gold nanoparticles with self-sustained natural rubber membranes
Cabrera, Flávio C.
Mohan, Haider
dos Santos, Renivaldo J.
Agostini, Deuber L. S.
Aroca, Ricardo
Rodríguez Pérez, Miguel Ángel
Job, Aldo Eloizo
Green chemistry is an innovative way to approach the synthesis of metallic nanostructures employing eco-friendly substances (natural compounds) acting as reducing agents. Usually, slow kinetics are expected due to, use of microbiological materials. In this report we study composites of natural rubber (NR) membranes fabricated using latex from Hevea brasiliensis trees (RRIM 600) that works as reducing agent for the synthesis of gold nanoparticles. A straight and clean method is presented, to produce gold nanoparticles (AuNP) in a flexible substrate or in solution, without the use of chemical reducing reagents, and at the same time providing good size’s homogeneity, reproducibility, and stability of the composites.
2020-06-03T11:38:08Z
2020-06-03T11:38:08Z
2020-06-03T11:38:08Z
2013
info:eu-repo/semantics/article
Journal of Nanomaterials, 2013, vol. 2013. 10 p.
1687-4110
http://uvadoc.uva.es/handle/10324/40985
10.1155/2013/710902
eng
https://www.hindawi.com/journals/jnm/2013/710902/
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/3.0/
© 2013 Hindawi
Attribution-NonCommercial-NoDerivatives 4.0 Internacional
Hindawi
oai:uvadoc.uva.es:10324/409862021-06-23T10:19:38Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
Applicability of solid solution heat treatments to aluminum foams
Lázaro Nebreda, Jaime
Solórzano Quijano, Eusebio
Escudero, Javier
Saja Sáez, José Antonio de
Rodríguez Pérez, Miguel Ángel
Present research work evaluates the influence of both density and size on the treatability of Aluminum-based (6000 series) foam-parts subjected to a typical solid solution heat treatment (water quenching). The results are compared with those obtained for the bulk alloy, evaluating the fulfilment of cooling requirements. Density of the foams was modeled by tomography analysis and the thermal properties calculated, based on validated density-scaled models. With this basis, cooling velocity maps during water quenching were predicted by finite element modeling (FEM) in which boundary conditions were obtained by solving the inverse heat conduction problem. Simulations under such conditions have been validated experimentally. Obtained results address incomplete matrix hardening for foam-parts bigger than 70 mm in diameter with a density below 650 kg/m3. An excellent agreement has been found in between the predicted cooling maps and final measured microhardness profiles.
2020-06-03T11:53:21Z
2020-06-03T11:53:21Z
2020-06-03T11:53:21Z
2012
info:eu-repo/semantics/article
Metals, 2012, vol. 2, n. 4. p. 508-528
2075-4701
http://uvadoc.uva.es/handle/10324/40986
10.3390/met2040508
eng
https://www.mdpi.com/2075-4701/2/4/508
info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-nd/3.0/
© 2012 MDPI
MDPI
oai:uvadoc.uva.es:10324/421012021-06-24T07:48:08Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Non-Invasive Approaches for the Evaluation of the Functionalization of Melamine Foams with In-Situ Synthesized Silver Nanoparticles
Barroso Solares, Suset
Cimavilla Román, Paula
Rodríguez Pérez, Miguel Ángel
Pinto Sanz, Javier
The use of polymeric nanocomposites has arisen as a promising solution to take advantage of the properties of nanoparticles (NPs) in diverse applications (e.g., water treatment, catalysis), while overcoming the drawbacks of free-standing nanoparticles (e.g., aggregation or accidental release). In most of the cases, the amount and size of the NPs will affect the stability of the composite as well as their performance. Therefore, a detailed characterization of the NPs present on the nanocomposites, including their quantification, is of vital importance for the optimization of these systems. However, the determination of the NPs load is often carried out by destructive techniques such as TGA or ICP-OES, the development of non-invasive approaches to that aim being necessary. In this work, the amount of silver NPs synthesized directly on the surface of melamine (ME) foams is studied using two non-invasive approaches: colorimetry and X-ray radiography. The obtained results show that the amount of silver NPs can be successfully determined from the luminosity and global color changes of the surface of the foams, as well as from the X-ray attenuance.
2020-09-03T08:38:32Z
2020-09-03T08:38:32Z
2020-09-03T08:38:32Z
2020
info:eu-repo/semantics/article
Polymers 2020, 12, 996
http://uvadoc.uva.es/handle/10324/42101
10.3390/polym12050996
996
5
Polymers
12
2073-4360
spa
https://www.mdpi.com/2073-4360/12/5/996
info:eu-repo/semantics/openAccess
MDPI
oai:uvadoc.uva.es:10324/421082022-05-01T21:15:46Zcom_10324_31661com_10324_952com_10324_894com_10324_1158com_10324_931col_10324_31662col_10324_1242
Enhanced nitrates-polluted water remediation by polyurethane/sepiolite cellular nanocomposites
Barroso Solares, Suset
Merillas Valero, Beatriz
Cimavilla Román, Paula
Rodríguez Pérez, Miguel Ángel
Pinto Sanz, Javier
Nanocomposite hydrophilic flexible polyurethane foams were prepared by in situ polymerization using an organomodified sepiolite as filler. The sepiolite affinity by nitrates dissolved in water was increased by treating them with quaternary ammonium salts (S-QAS), leading to remarkable nitrates maximum adsorption capacity (qmax = 23.30 mg/g). The Langmuir model well described the adsorption process of the nitrates by the modified sepiolite, and more remarkably, the sepiolite suffers no decrease of their nitrates removal capacity after being imbibed in the flexible polyurethane foam. The proper selection of the polyurethane chemistry allows significant contact between the polluted-water and the sepiolite, even when enclosed inside the cell walls. Accordingly, the as-prepared hydrophilic polyurethane/sepiolite foams provided a facile removal of nitrates-pollution from water, even actual nitrates-polluted water with a competitive adsorption environment, without the need to control or modify the pH and temperature of the polluted water neither to add further filtration steps to collect the active particles from the water.
2020-09-03T10:46:47Z
2020-09-03T10:46:47Z
2020-09-03T10:46:47Z
2020
info:eu-repo/semantics/article
Journal of Cleaner Production, Volume 254, 2020, 120038
0959-6526
http://uvadoc.uva.es/handle/10324/42108
10.1016/j.jclepro.2020.120038
120038
Journal of Cleaner Production
254
eng
https://www.sciencedirect.com/science/article/pii/S0959652620300858#ack0010
info:eu-repo/semantics/openAccess
Elsevier
oai:uvadoc.uva.es:10324/421092021-08-12T21:15:47Zcom_10324_1158com_10324_931com_10324_894col_10324_1242
A new generation of hollow polymeric microfibers produced by gas dissolution foaming
Barroso Solares, Suset
Cuadra Rodríguez, Daniel
Rodríguez Méndez, María Luz
Rodríguez Pérez, Miguel Ángel
Pinto Sanz, Javier
A new and straightforward route to produce polymeric hollow microfibers has been proposed. Polycaprolactone (PCL) hollow fibers are obtained for the first time using an environmentally friendly gas dissolution foaming approach, overcoming its limitations to induce porosity on samples in the micrometric range. Different porous morphologies are achieved from solid PCL microfibers with a well-controlled diameter obtained by conventional electrospinning. The optimization of the foaming parameters provides two sets of well-defined hollow fibers, one showing smooth surfaces and the other presenting an enhanced surface porosity. Accordingly, gas dissolution foaming proves to be not only suitable for the production of hollow polymeric microfibers, but is also capable of providing diverse porous morphologies from the same precursor, solid fibers. Moreover, a preliminary study about the suitability of this new generation of foamed hollow polymeric fibers for drug delivery is carried out, aiming to take advantage of the enhanced surface area and tunable morphology obtained by using the proposed new production method. It is found that the foamed microfibers can be loaded with up to 15 wt% of ibuprofen while preserving the morphology of each kind of fiber. Then, foamed PCL fibers presenting a hollow structure and surface porosity show a remarkable constant release of ibuprofen for almost one and a half days. In contrast, the original solid fibers do not present such behavior, releasing all the ibuprofen in about seven hours.
2020-09-03T10:51:19Z
2020-09-03T10:51:19Z
2020-09-03T10:51:19Z
2020
info:eu-repo/semantics/article
J. Mater. Chem. B, 2020
2050-750X
http://uvadoc.uva.es/handle/10324/42109
10.1039/D0TB01560A
Journal of Materials Chemistry B
2050-7518
eng
https://pubs.rsc.org/en/content/articlelanding/2020/tb/d0tb01560a#!divAbstract
info:eu-repo/semantics/openAccess
RSC
qdc///col_10324_1242/100