Scientific Papers in SCI
2022
2022
Materiales Ópticos Multifuncionales
Nanoantennas Patterned by Colloidal Lithography for Enhanced Nanophosphor Light Emission
Viana, JM; Romero, M; Lozano, G; Míguez, HACS Applied Nano Materials, 5(11) (2022) 16242-16249
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Transparent coatings made of rare-earth doped nanocrystals, also known as nanophosphors, feature efficient photoluminescence and excellent thermal and optical stabi l i t y . Herein, we demonstrate that the optical antennas prepared by colloidal lithography render thin nanophosphor films with a brighter emission. In particular, we fabricate gold nanostructures in the proximity of GdVO4:Eu3+ nanophosphors by metal evaporation using a mask made of a monolayer of polymer beads arranged in a triangular lattice. Optical modes supported by the antennas can be controlled by tuning the diameter of the polymer spheres in the colloidal mask, which determines the shape of the gold nanostructure, as confirmed by numerical simulations. Confocal microscopy reveals that metallic antennas induce brighter photoluminescence at specific spatial regions of the nanophosphor film at targeted frequencies as a result of the coupling between gold nanostructures and nanophosphors. Patterning of nanophosphor thin layers with arrays of metallic antennas offers an inexpensive nanophotonic solution to develop bright emitting coatings of interest for color conversion, labeling , or anti-counterfeiting.
November, 2022 | DOI: 10.1021/acsanm.2c03258
Reactividad de Sólidos
Reactive flash sintering of SrFe12O19 ceramic permanent magnets
Manchon-Gordon, AF; Sanchez-Jimenez, PE; Blazquez, JS; Perejon, A; Perez-Maqueda, LAJournal of Alloys and Compounds, 922 (2022) 166203
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Reactive flash-sintering technique has been used in order to obtain strontium ferrite magnets from a mixture of SrCO3 and Fe2O3 commercial powders. This technique allows preparing sintered SrFe12O19 at a furnace temperature of just 973 K during just 2 min by applying a modest field of 40 V cm(-1), instead of the conventional sintering process employed in ferrite magnet manufacturing that demands high temperature and long dwell times. Analysis of structural and magnetic properties were performed as a function of time in which the flash event was held. Mossbauer spectra show the existence of five different kinds of local environments, confirming the formation of strontium hexaferrite. The resulting samples exhibit comparable magnetic properties to the state-of-the-art ferrite magnets. In particular, produced samples reach a coercivity of 0.4 T and a specific saturation magnetization of 70 Am-2 kg(-1).
November, 2022 | DOI: 10.1016/j.jallcom.2022.166203
Materiales de Diseño para la Energía y Medioambiente
Exploring the local environment of the engineered nanoclay Mica-4 under hydrothermal conditions using Eu(3+)as a luminescent probe
Martin-Rodriguez, R; Aguado, F; Alba, MD; Valiente, R; Pavon, E; Perdigon, ACJournal of Alloys and Compounds, 921 (2022) 166086
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High charge mica Na4Al4Si4Mg6O20F4 , Mica-4, is a promising candidate as a filling material to immobilize high-level radioactive waste in deep geological repositories due to its extraordinary adsorption capacity. In contrast to traditional clay materials, the structural composition of this mica, with a high content of alu-minum in the tetrahedral sheet, enhances its chemical reactivity, favoring the formation of new crystalline phases under mild hydrothermal conditions, and thus providing a definitive isolation of the radionuclides in the engineered barrier. Moreover, this synthetic clay has some features that allow its use as an optical sensor by doping with luminescent rare earth cations such as Eu3+. In this paper we discuss the local structure of the nanoclay Mica-4 using Eu3+ as a local probe to track the physical and chemical modifica-tions under hydrothermal conditions. For that purpose, a set of hydrothermal experiments has been carried out heating Mica-4 and an aqueous Eu(NO3)(3) solution in a stainless steel reactor at different temperatures and times. Optical properties of the as-treated samples were characterized by spectroscopic measurements. The fine peak structure of emission and the relative intensity of different Eu3+ transitions as well as the luminescence lifetime have been correlated with the structure and composition of this nanoclay, and the interaction mechanisms between the lanthanide ions and the clay mineral at different temperatures and times. Special attention has been paid to understanding the role of the aluminum content, which may act as either an aggregating or dispersing agent, in the optical features and reactivity of the system.
November, 2022 | DOI: 10.1016/j.jallcom.2022.166086
Materiales de Diseño para la Energía y Medioambiente
Insights into the Impact of Activators on the 'Catalytic' Graphitization to Design Anode Materials for Lithium Ion Batteries
Hanhart, V; Frankenstein, L; Ramirez-Rico, J; Diozios, V; Winter, M; Gomez-Martin, A; Placke, TChemelectrochem, 9 (2022) e202200819
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In this work, we systematically investigate the 'catalytic' graphitization of a biomass precursor (coffee ground) using 10-60 wt.% of the activator iron (III) chloride hexahydrate in a temperature range of 1000 degrees C-2400 degrees C. Special focus is put on the correlation of synthesis conditions, e.g., heat treatment temperature and mass fraction of iron chloride, with the electrochemical performance in carbon vertical bar vertical bar Li metal cells. The structural investigations of the materials reveal a positive impact of an increasing heat treatment temperature and/or mass fraction of inserted activator on the degree of graphitization and the delithiation capacity. However, a saturation point regarding the maximum degree of graphitization at 2000 degrees C and reversible capacity by the 'catalytic' graphitization approach using iron (III) chloride has been found. A maximum degree of graphitization of approximate to 69% could be reached by applying 2000 degrees C and 40 wt.% FeCl3 center dot 6H(2)O, resulting in a reversible capacity of 235 mAh g(-1).
November, 2022 | DOI: 10.1002/celc.202200819
Reactividad de Sólidos
Improvement in cyclic CO2 capture performance and fluidization behavior of eggshell-derived CaCO3 particles modified with acetic acid used in calcium looping process
Imani, M; Tahmasebpoor, M; Sanchez-Jimenez, PE; Valverde, JM; Moreno, VJournal of CO2 Utilization, 65 (2022) 102207
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Although calcium-based materials are the most promising adsorbents used in calcium looping process for carbon dioxide removing, their CO2 capture capacity decaying besides poor fluidization, still are the important challenges. In the present investigation, eggshell as a cheap, easily available and unpolluted source of calcium carbonate was used for CO2 capturing in calcium looping process. Eggshell particles were treated with various volume concentrations of acetic acid to improve its sorption capacity. According to the TGA results after 20 carbonation/calcination cycles, the effective carbonation conversion of modified eggshell with 5%, 20%, 30% and 40%. v/v acetic acid was 21.33%, 24.26%, 25.97% and 28.97%, respectively, which is considerable compared to 20.54% for untreated eggshell. The effect of initial eggshell particle size on the adsorption behavior of final adsorbent was also investigated by using two different sizes including dp < 45 mu m and dp > 320 mu m. The results showed that the effective conversion of the adsorbent containing 40%. v/v acetic acid derived from small particle size eggshells was 9.32% higher than that from larger particle size eggshells. In terms of fluidization behavior, surprisingly the addition of acetic acid to the eggshell particles also increased the bed expansion ratio as 8% and 36.2% at gas velocities of 0.27 and 6.67 cm/s, respectively. Further improvement in the fluidity of eggshell modified with 40% acid was performed by manually mixing of SiO2 nanoparticles at different weight percentages. According to the results, adding 7.5 wt% SiO2 leaded to the homogeneous and agglomerate particulate fluidization.
November, 2022 | DOI: 10.1016/j.jcou.2022.102207
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