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Scientific Papers in SCI



2022


Nanotecnología en Superficies y Plasma

Thin film nanostructuring at oblique angles by substrate patterning

Muñoz-Pina, S; Alcaide, AM; Limones-Ahijon, B; Oliva-Ramirez, M; Rico, V; Alcala, G; Gonzalez, MU; García-Martín, JM; Alvarez, R; Wang, D; Schaaf, P; Gonzalez-Elipe, AR; Palmero, A
Surface & Coatings Technology, 436 (2022) 128293

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It is demonstrated that, besides classical nanocolumnar arrays, the oblique angle geometry induces the growth of singular structures in the nanoscale when using wisely designed patterned substrates. Well-ordered array of crosses, cylindrical nanorods or hole structures arranged in square or hexagonal regular geometries are reported as examples, among others. The fundamental framework connecting substrate topography and film growth at oblique angles is presented, allowing the use of substrate patterning as a feasible thin film nanostructuring technique. A systematic analysis of the growth of TiO2 thin films on 4 different lithographic patterned substrates in 4 different scale lengths is also presented. A first conclusion is the existence of a height-based selective growth in the initial stages of the deposition, by which the film preferentially develops on top of the tallest substrate features. This behavior is maintained until the film reaches a critical thickness, the so-called Oblivion Thickness, above which the film topography becomes gradually independent of the substrate features. A general formula relating the spatial features of the pattern, the coarsening exponent and the Oblivion Thickness has been deduced.


April, 2022 | DOI: 10.1016/j.surfcoat.2022.128293

Reactividad de Sólidos

Ageing-resistant zirconia/graphene-based nanostructures composites for use as biomaterials

Morales-Rodriguez, A; Gonzalez-Orellana, C; Perez-Garcia, AA; Lopez-Pernia, C; Munoz-Ferreiro, C; Poyato, R; Gallardo-Lopez, A
Journal of the European Ceramic Society, 42 (2022) 1784-1795

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This work explores the incorporation of graphene-based two-dimensional nanostructures as moisture barriers to delay hydrothermal ageing of yttria-stabilized zirconia and strengthen its use in biomedical applications. Two sets of highly dense zirconia composites incorporating multilayered graphene with very different lateral dimensions, few layer graphene and exfoliated graphene nanoplatelets, were prepared. The effect of the addition of graphene nanostructures on zirconia ageing was investigated by conducting accelerated hydrothermal degradation experiments in an autoclave. An improved resistance to low-temperature degradation and a high tolerance to damage were achieved in the composites compared to those of monolithic zirconia. The incorporation of 1 vol% multilayered graphene was very effective in restricting the hydrothermal degradation. In particular, the composite incorporating exfoliated graphene nanosheets exhibited outstanding resistance to ageing because of their fine dispersion throughout the matrix, which effectively seemed to restrict grain growth and slow the propagation of the transformation front to the ceramic bulk.


April, 2022 | DOI: 10.1016/j.jeurceramsoc.2021.11.060

Materiales Ópticos Multifuncionales

Transparent Phosphor Thin Films Based on Rare-Earth-Doped Garnets: Building Blocks for Versatile Persistent Luminescence Materials

Castaing, V; Lozano, G; Míguez, H
Advanced Photonics Research, 3 (2022) 2100367

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Afterglow properties of persistent phosphors are attracting a great deal of attention in the fields of bioimaging, sensing, labeling, safety, or security. Complex garnet oxides, especially those doped with Ce3+ and Cr3+, are particularly relevant to this end since their persistent luminescence can be tuned through matrix composition and activated by visible light, in contrast to the vast majority of persistent phosphors that require UV excitation. Most extended preparation routes yield micrometer-sized phosphors that display strong light scattering, which limits their versatility and applicability. Herein, nanostructured garnet oxide-based thin films that are transparent and feature persistent luminescence properties are demonstrated. Following a sol–gel route and after high temperature annealing, few hundred nanometre-thick Y3Al2Ga3O12:Ce3+,Cr3+ transparent films showing efficient green emission and afterglow are attained. Gd3Al2Ga3O12:Ce3+,Cr3+ transparent thin films displaying yellow afterglow with distinct persistent kinetics are demonstrated, to prove the generality of the approach herein proposed. Its versatility is further demonstrated by developing layered phosphors with time-dependent chromaticity due to the unique persistent emission color – upon blue light excitation – and kinetics of each layer forming the stack. The results pave an avenue toward nanodevices and multifunctional coatings in which afterglow offers hitherto unexplored properties.


April, 2022 | DOI: 10.1002/adpr.202100367

Materiales y Procesos Catalíticos de Interés Ambiental y Energético

H2 Photoproduction Efficiency: Implications of the Reaction Mechanism as a Function of the Methanol/Water Mixture

Barba-Nieto, I; Colon, G; Kubacka, A; Fernandez-Garcia, M
Catalysts, 12 (2022) 402

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The influence of the reaction pathway of the sacrificial molecule oxidation to generate hydrogen is here investigated for lean and rich methanol reaction mixtures. Pt-TiO2 powders promoted or not with tin sulfide were used as catalysts. With the help of in situ infrared experiments under reaction conditions, methanol evolution was shown to take place by hole-related oxidation steps, with alkoxy and carbon-centered species as key radical species. The study analyzed quantitatively the fate and chemical use of the photons absorbed by the solids with the help of the quantum efficiency and the useful fraction of photons observables. Within this framework, the role of the sulfide component to promote photoactivity is interpreted, braiding chemical and photonic information.


April, 2022 | DOI: 10.3390/catal12040402

Química de Superficies y Catálisis

3D-printed structured catalysts for CO2 methanation reaction: Advancing of gyroid-based geometries

Gonzalez-Castano, M; Baena-Moreno, F; De Miguel, JCN; Miah, KUM; Arroyo-Torralvo, F; Ossenbrink, R; Odriozola, JA; Benzinger, W; Hensel, A; Wenka, A; Arellano-García, H
Energy Conversion and Management, 258 (2022) 115464

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This work investigates the CO2 methanation rate of structured catalysts by tuning the geometr y of 3D-printed metal Fluid Guiding Elements (FGEs) structures based on periodically variable pseudo-gyroid geometries. The enhanced performance showed by the structured catalytic systems is mostly associated with the capability of the FGEs substrate geometries for efficient heat usages. Thus, variations on the channels diameter resulted in ca. 25% greater CO2 conversions values at intermediate temperature ranges. The highest void fraction evidenced in the best performing catalyst (3D-1) favored the radial heat transfer and resulted in significantly enhanced catalytic activity, achieving close to equilibrium (75%) conversions at 400 ? and 120 mL/min. For the 3D-1 catalyst, a mathematical model based on an experimental design was developed thus enabling the estimation of its behavior as a function of temperature, spatial velocity, hydrogen to carbon dioxide (H-2/CO2) ratio, and inlet CO2 concentration. Its optimal operating conditions were established under 3 different scenarios: 1) no restrictions, 2) minimum H-2:CO2 ratios, and 3) minimum temperatures and H-2/CO2 ratio. For instance, for the lattest scenario, the best CO2 methanation conditions require operating at 431 ?, 200 mL/min, H-2/CO2 = 3 M ratio, and inlet CO2 concentration = 10 %.


April, 2022 | DOI: 10.1016/j.enconman.2022.115464

 

 

 

 

 

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