Scientific Papers in SCI
2023
2023
Nanotecnología en Superficies y Plasma - Tribología y Protección de Superficies
Low temperature nucleation of thermochromic VO2 crystal domains in nanocolumnar porous thin films
Alcaide, AM; Regodon, G; Ferrer, FJ; Rico, V; Alvarez, R; Rojas, TC; Gonzalez-Elipe, AR; Palmero, ANanotechnology, 34 (2023) 255702
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The low temperature formation of monoclinic VO2 crystal domains in nanocolumnar vanadium/oxygen thin films prepared by magnetron sputtering at oblique angles is analyzed. The synthesis procedure involved the deposition of amorphous nanocolumnar VO1.9 thin films at room temperature and its subsequent annealing at temperatures between 250 °C and 330 °C in an oxygen atmosphere. The thermochromic transition of these films was found at a temperature of 47 °C when the annealing temperature was 270 °C and 58 °C when the annealing temperature was 280 °C and 290 °C, presenting a clear drop of the optical transmittance in the infrared region of the spectrum. The significant downshift in the temperature window to obtain VO2 in comparison with compact films and other strategies in literature is explained by the particular morphology of the nanocolumnar structures, which contains numerous defects along with open and embedded porosity.
June, 2023 | DOI: 10.1088/1361-6528/acc664
Reactividad de Sólidos
A practical analysis for decelerated growth processes to get physically meaningful kinetic parameters from classical nucleation and growth theory despite of overgrowth
Blazquez, JS; Caballero-Flores, R; Manchon-Gordon, AF; Borrego, JM; Conde, CFJournal of Non-Crystalline Solids, 610 (2023) 122305
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We have analyzed the overgrowth problem arising in decelerated growth processes of spherical crystals in the frame of classical nucleation and growth theory developed by Kolmogorov, Johnson and Mehl, and Avrami (KJMA). To do that, simulations of decelerated growth transformations with a constant nucleation rate have been performed, changing the linear growth rate of spherically shaped nuclei from null (instantaneous growth rate) to constant (characteristic of interface controlled growth processes). We propose the determination of the actual kinetic parameters through the analysis of the inflection point of time evolution of transformed fraction. The correlations found between the effective kinetic parameters from direct KJMA analysis and the actual ones make it possible obtaining physically meaningful parameters. The proposed analysis has been applied to the nano-crystallization of amorphous FINEMET-type compositions.
June, 2023 | DOI: 10.1016/j.jnoncrysol.2023.122305
Materiales Nanoestructurados y Microestructura
Microstructural characterization and thermal stability of He charged amorphous silicon films prepared by magnetron sputtering in helium
Fernández, A; Sauvage, T; Diallo, B; Hufschmidt, D; de Haro, MCJ; Montes, O; Martínez-Blanes, JM; Caballero, J; Godinho, V; Ferrer, FJ; Ibrahim, S; Brault, P; Thomann, ALMaterials Chemistry and Physics, 301 (2023) 127674
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![](https://icms.us-csic.es/sites/icms.us-csic.es/files/1-s2_423.png)
Sputtering of silicon in a Helium magnetron discharge has been reported as a bottom-up procedure to obtain amorphous Si films containing high amounts of gas-filled nanopores. Here we compare the microstructure and composition of Si-He nanocomposite films deposited by magnetron sputtering (MS) with 4He in DC or RF and 3He in RF operation modes. Electron microscopy (SEM and TEM), X-ray diffraction (XRD) and ion beam analysis (IBA) have been used to analyze the films and to investigate the in-situ and ex-situ thermal evolution. Depending on deposition conditions different in depth compositions, nanopore size and shape distributions, porosity and He content could be obtained. The presence of impurities (i.e. oxygen) has shown to promote He diffusivity reducing He accumulation. The start temperature of He-release varied in the range 473-723 K without films crystallization. Films grown in RF mode reached contents of 32 and 29 at% of 4He and 3He and were respectively stable up to 573 and 723 K both in vacuum and under inert gas flow. In-situ p-EBS (proton Elastic Back Scattering) allowed monitoring the He release accompanied by blistering/delamination effects visualized by SEM. These results show the potentiality of annealing to hold nano-porous structures after liberation of trapped gas.
June, 2023 | DOI: 10.1016/j.matchemphys.2023.127674
Reactividad de Sólidos
Reversibility and thermal dependence of the martensitic transformation in a melt-spun Ni55Fe17Ga26Co2 Heusler alloy
Manchon-Gordon, AF; Vidal-Crespo, A; Blazquez, JS; Kowalczyk, M; Ipus, JJ; Kulik, T; Conde, CFJournal of Alloys and Compounds, 946 (2023) 169484
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An almost single phase 14 M modulated martensite is obtained in melt spun ribbon of Ni55Fe17Ga26Co2 Heusler alloy. The effect of thermal treatments on the stability of the reverse martensitic transformation from 14 M modulated martensite to austenite phase in this system has been investigated by both non -isothermal and isothermal treatments. Heating above martensitic transformation promotes a continuous reduction of the martensitic transformation temperature, which stabilizes the austenite phase at room temperature and induces the precipitation of the gamma phase. However, thermal treatments at tem-peratures between the austenite start and finish temperatures induce the decoupling of the austenite formation in a subsequent heating. The two successive reverse martensitic transformations could be as-cribed to the untransformed martensite in the previous interrupted heating and to the new martensite formed during cooling.
June, 2023 | DOI: 10.1016/j.jallcom.2023.169484
Reactividad de Sólidos
Partial oxycombustion-calcium looping hybridisation for CO2 capture in waste-to-energy power plants
Ortiz, C; García-Luna, S; Chacartegui, R; Valverde, JM; Pérez-Maqueda, LJournal of Cleaner Production, 403 (2023) 136776
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Integrating bioenergy and carbon capture and storage (BECCS) presents a great opportunity for power produc-tion with negative global CO2 emissions. This work explores a novel synergetic system that integrates mem-branes, partial biomass oxycombustion and the calcium looping (CaL) process. Polymeric membranes generate oxygen-enriched air (OEA) with an O2 concentration of 39%v/v, which is used for partial oxycombustion of biomass waste. The CO2-enriched flue gas evolves from the waste-to-energy plant to the CaL unit, where CO2 concentration is increased up to 90-95%v/v, ready for purification and sequestration. Compared to only oxy-combustion systems, the proposed concept presents fewer technological challenges in retrofitting boilers to waste-to-energy plants. Moreover, this new approach is highly efficient as integrating membranes to produce OEA instead of cryogenic distillation systems significantly reduces energy consumption. A novel integration concept is modelled to evaluate the whole process efficiency and the effect of key parameters on the system performance, such as the temperature of the reactors, the membrane surface area, and the partial oxy-combustion degree. The results show that the so-called mOxy-CaL system has an energy consumption associ-ated with CO2 capture below 4 MJ/kg CO2 (a 31% lower than that for a conventional CaL process), with a higher CO2 capture efficiency than oxycombustion and the CaL process separately. On the other hand, the economic analysis shows a higher CO2 capture cost for the novel configuration than for the typical CaL configuration due to the additional investment cost of the membrane system. Improvements in membrane performance by increasing its permeance and diminishing the required surface area would significantly reduce the economic cost of this novel integration. Using membranes with permeance over 400 GPU would boost the system's competitiveness.
June, 2023 | DOI: 10.1016/j.jclepro.2023.136776
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