Artículos SCI

Doped-PrBaMn2-xTMxO5+delta samples with TM = Co and/or Ni were synthesized by a mechanochemical route from stoichiometric oxide precursor mixtures (Pr6O11, BaO2, MnO, NiO and CoO) using a planetary mill at 600 rpm for 150 min. A disordered ABO(3) pseudocubic perovskite phase was obtained after the milling process that was transformed, as established by XRD, into the double layered AA'B2O5+delta perovskite phase after annealing at 900 degrees C in a reducing atmosphere (10%H-2/Ar). The microstructural characterization by SEM, TEM, and HRTEM ascertained that this reducing treatment induced the exsolution of Ni and Co metallic nanoparticles from the doped samples. Ni-Co alloys were even exsolved when the layered manganite phase was co-doped with both transition metals. It was confirmed that the exsolution process was reversible by switching the working atmosphere from reducing to oxidizing. Polarization resistance values of the doped samples determined in symmetrical cells in air and H-2, as well as the electrochemical performance of electrolyte LSGM-supported planar cells suggested that these samples can be used as symmetrical electrodes in SOFCs.

Plant biomass is an attractive precursor to prepare activated carbons with high surface area for CO2 adsorption due to its low-cost and easy regeneration. Despite this interest, there are still remaining questions regarding the optimal processing conditions and the choice of activating agent. Moreover, since plant biomass shows a highly variable proportion of different biopolymers (cellulose, hemicellulose, lignin), it is important to understand the activation effect on each constituent. In this work, carbons obtained from pyrolysis of cellulose were activated using two potassium salts, using two different activation temperatures. The samples were characterized to elucidate the influence of the activation conditions on their CO2 adsorption capacity. In general, all the carbons activated at higher temperature showed higher adsorption capacity. These results are comparable with other carbons derived from biomass described in the bibliography. Among the activated carbons studied, the carbon activated only with KOH exhibits the highest CO2 adsorption capacity at 1 bar meanwhile the highest adsorption capacity at saturation pressure belongs to the carbon activated with larger ratio of KNO3.

This work shows the synthesis and characterization of the Zn2-xGeO4-GeO2:(x)Mn2+ (x = 0.10, 0.25, and 0.50 at.%) films using the Ultrasonic Spray Pyrolysis (USP) technique. These films were deposited at 500 degrees C and heat treated at 800 degrees C for 13 h. X-ray diffraction (XRD) measurements showed the rhombohedral and hexagonal phases of Zn2-xGeO4 (78.8 %) and GeO2 (21.2 %), respectively. SEM micrographs exhibited the surface morphology of these films. The STEM and HAADF show Ge, Zn, and O atomic layers. In addition, XPS was carried out to observe the oxidation states of Mn2+ (75.4 %) and Mn3+ (24.6 %) for the films doped with Mn ions (0.10 at.%). Incorporating manganese ions into the Zn2-xGeO4-GeO2 host lattice generated an extremely green emission, exciting at 250 nm. The photoluminescence and persistence luminescence properties were studied in accordance with the manganese doping concentration. For photoluminescence, it was found that the optimal doping percentage was 0.25 at.%, and for persistence luminescence, it was 0.10 at.% Mn with lambda(ex) = 250 nm. Quantum efficiency measurements gave a result of 100 %. In addition, preliminary CL measurements were exhibited.

Surface engineering through the deposition of advanced coatings, particularly multilayer coatings has gained significant interest for enhancing the performance of coated parts. The incorporation of Si into TiN coatings has shown promise for improving hardness, oxidation resistance, and thermal stability, while high-power impulse magnetron sputtering (HiPIMS) has emerged as a technique to deposit coatings with exceptional properties. However, TiN/CrN and TiSiN/CrN coatings deposited by HiPIMS remain relatively unexplored. In this study, different TiN/CrN and TiSiN/CrN multilayer coatings with different bilayer periods from 5 to 85 nm were deposited using an industrial-scale HiPIMS reactor, and their microstructure and mechanical properties were investigated using advanced characterization techniques. Results revealed successful deposition of smooth and compact coatings with controlled bilayer periods. X-ray diffraction analysis showed separate crystalline phases for coatings with high bilayer periods, while those with smaller bilayer periods exhibited peak-overlapping and superlattice overtones, especially for the TiN/CrN coatings. Epitaxial grain growth was confirmed by highresolution transmission electron microscopy (HRTEM). HRTEM and electron energy-loss spectroscopy measurements confirmed Si incorporation into the TiN crystal lattice of TiSiN/CrN coatings reducing the crystallinity, especially for coatings with smaller bilayer periods. Nanoindentation tests revealed that coatings with a bilayer period of 15-20 nm displayed the highest hardness values regardless of the composition. The mechanical properties of the TiSiN/CrN coatings showed no improvement over those of the TiN/CrN coatings, attributed to the Si induced amorphization of the Ti(Si)N phase and the absence of SiNx phase segregation within the TiN nanocrystals in these coatings. These findings provide valuable insights into the microstructure and mechanical properties of TiN/CrN and TiSiN/CrN multilayer coatings deposited by HiPIMS in an industrial scale reactor, paving the way for their application in various industrial sectors.