Browsing by Keyword "Raman"
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Item AC Magnetron Sputtering: An Industrial Approach for High-Voltage and High-Performance Thin-Film Cathodes for Li-Ion Batteries(2021-05-21) Rikarte, Jokin; Madinabeitia, Iñaki; Baraldi, Giorgio; Fernández-Carretero, Francisco José; Bellido-González, Víctor; García-Luis, Alberto; Muñoz-Márquez, Miguel Ángel; Fernández‐Carretero, Francisco José; Bellido‐González, Víctor; García‐Luis, Alberto; Muñoz‐Márquez, Miguel Ángel; TECNOLOGÍAS DE HIDRÓGENOIndustrial-oriented mid-frequency alternating current (MF-AC) magnetron sputtering technique is used to fabricate LiNi0.5Mn1.5O4 high-voltage thin-film cathodes. Films are deposited on bare stainless-steel substrate at room temperature and then annealed to induce crystallization in disordered spinel phase. In situ X-ray diffraction is used to follow film structural evolution from room temperature to 900 °C. Scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy are used to study the evolution with temperature of film morphology, surface chemical composition, and crystal structure arrangement, respectively. Film structure evolves almost continuously in the studied temperature range. A pattern corresponding to spinel phase is observed after annealing at 600 °C, while poor crystallization is obtained for lower temperatures, and additional unwanted phase changes are observed for higher temperatures. Cyclic voltammetry, rate capability, and cycling performance of fabricated films are tested. Only the film annealed at 600 °C shows redox peaks corresponding to Ni oxidation from 2+ to 3+ and 3+ to 4+ oxidation states, confirming that this film crystallizes in disordered spinel phase. The thin-film cathode shows good rate performance and outstanding cyclability, despite the impurities formed upon electrolyte decomposition at high voltage.Item Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings(2015) Demnati, Imane; Grossin, David; Marsan, Olivier; Bertrand, Ghislaine; Collonges, Gérard; Combes, Christèle; Parco, Maria; Braceras, I.; Alexis, Joel; Balcaen, Yannick; Rey, Christian; EXTREMAT; INGENIERÍA DE SUPERFICIESChlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.