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Your search keyword '"Kovalevsky, Andrei V."' showing total 28 results
Start Over Author "Kovalevsky, Andrei V." Publisher elsevier bv
28 results on '"Kovalevsky, Andrei V."'

3. Assessment of the laser floating zone processing of thermoelectric CuFe1–xNixO2 delafossites and their magnetic characterisation

Author

Ferreira, N. M., Grillo, J. G., Ferro, M. C., Dura, Oscar J., Madre, M. A., Kovalevsky, Andrei V., Costa, Florinda M., Sotelo, A., Universidade de Aveiro, Fundação para a Ciência e a Tecnologia (Portugal), Ministério da Ciência, Tecnologia e Ensino Superior (Portugal), European Commission, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), and Gobierno de Aragón

Subjects
Delafossite, Thermal conductivity, Mechanics of Materials, Oxide Thermoelectrics, Mechanical Engineering, ZT, Materials Chemistry, Metals and Alloys, Seebeck coefficient, Laser Floating Zone
Abstract

This work assesses the feasibility of processing CuFe1-xNixO2 (x = 0, 0.02) using the Laser Floating Zone (LFZ) technique to grow fibres with different pulling rates, to tune their thermoelectric performance. Structural analysis showed CuFeO2 as the major phase. Formation of secondary phases is promoted by Ni addition, diminishing with decreasing pulling rate. Grain alignment and crystallite size of the fibres increase with the puling rate and doping. Electrical conductivity is enhanced by decreasing the pulling rate, while Ni-doping decreases the conductivity, and Seebeck coefficient demonstrates quite complex behaviour. Thermal conductivity decreases with temperature and with the pulling rate and Ni-doping. A maximum ZT value of 0.17 was achieved for 10 mm h-1 sample at 1000 K for pure, and 700 K for Ni-doped samples. These ZT values are higher than found in the literature, demonstrating the feasibility of the LFZ method for processing thermoelectric delafossites, indicating a proper optimisation process., This work was developed within the scope of the project i3N (LA/P/0037/2020 & UIDB/50025/2020 & UIDP/50025/2020) and CICECO-Aveiro Institute of Materials (UIDB/50011/2020 & UIDP/50011/2020), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. This work was funded by national funds (OE), through FCT – Fundação para a Ciência e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19. M. A. Madre and A. Sotelo acknowledge the Spanish MINECO-FEDER (Project MAT2017–82183-C3–1-R) and Gobierno de Aragón-FEDER (Research Group T 54–20R) for funding. The support of the project POCI-01–0145-FEDER-031875, financed by COMPETE 2020 Program and National Funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement, is greatly acknowledged.

Published
2022
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7. MXene-containing composite electrodes for hydrogen evolution: Material design aspects and approaches for electrode fabrication

Author

Sergiienko, Sergii A., primary, Lopes, Daniela V., additional, Constantinescu, Gabriel, additional, Ferro, Marta C., additional, Shchaerban, Nataliya D., additional, Tursunov, Obid B., additional, Shkepu, Viacheslav I., additional, Pazniak, Hanna, additional, Tabachkova, Nataliya Yu., additional, Castellón, Enrique Rodríguez, additional, Frade, Jorge R., additional, and Kovalevsky, Andrei V., additional

Published
2021
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28. Flexible design of cellular Al2TiO5 and Al2TiO5-Al2O3 composite monoliths by reactive firing

Author

Carla A.M. Portugal, N. Vitorino, Cristiana Boi, João G. Crespo, Jorge R. Frade, Andrei V. Kovalevsky, Eleonora Lalli, Lalli, Eleonora, Vitorino, Nuno M.D., Portugal, Carla A.M., Crespo, João G., Boi, Cristiana, Frade, Jorge R., Kovalevsky, Andrei V, and Eleonora Lalli, Nuno M. D. Vitorino, Carla A. M. Portugal, João G. Crespo, Cristiana Boi, Jorge R. Frade, Andrei V. Kovalevsky

Subjects
Materials science, Al2TiO5, Liquid paraffin, Composite number, 02 engineering and technology, 01 natural sciences, Cellular ceramics, Designed porosity, Al2TiO5, Taguchi method, Composite monolith, Taguchi methods, Phase (matter), 0103 physical sciences, lcsh:TA401-492, Mechanics of Material, General Materials Science, Ceramic, Composite monolith, Composite material, Porosity, 010302 applied physics, Mechanical Engineering, Cellular ceramic, Designed porosity, 021001 nanoscience & nanotechnology, Surface-area-to-volume ratio, Mechanics of Materials, visual_art, visual_art.visual_art_medium, Taguchi method, lcsh:Materials of engineering and construction. Mechanics of materials, Materials Science (all), 0210 nano-technology, Stoichiometry
Abstract

Cellular Al2TiO5 and Al2TiO5 – Al2O3 composite ceramics were obtained by emulsification of liquid paraffin in aqueous suspensions of mixed TiO2+Al2O3 powders, with subsequent burnout of the organic phase and 2-step reactive firing at high temperatures. The reactants ratio and paraffin to suspension volume ratio were used as primary parameters to control the phase composition and relevant microstructural features, while firing conditions were also adjusted for greater flexibility in designing Al2TiO5-based cellular materials. Taguchi experimental planning was used to assess the relevant impacts of 2-step firing parameters on phase composition and porosity, characterized by detailed XRD/SEM/EDS studies. The results emphasized the positive effects of Al2O3 excess in Al2TiO5 – Al2O3 composite ceramics on stabilization of the Al2TiO5 phase and also for flexible design of cellular materials with controlled porosity and phase distributions. Analysis of correlation matrixes identified the 2-step firing parameters with greatest impact on the porosity and phase composition, and these trends were confirmed by multivariate linear regression. The observed trends indicated significant differences in reactivity and densification mechanisms between compositions with nominal Al2TiO5 stoichiometry and composite materials. These differences were most obvious for samples with significant residual fractions of unreacted titania. Keywords: Cellular ceramics, Designed porosity, Al2TiO5, Taguchi method, Composite monolith

Published
2017
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