37 documents found, page 1 of 4
Photocatalytic removal of benzene over Ti3C2Tx MXene and TiO2–MXene composite m...
Sergiienko, S.A.; Tobaldi, David M.; Lajaunie, Luc; Lopes, Daniela V.; Constantinescu, Gabriel; Shaula, A.L.; Shcherban, Nataliya D.MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separatio...
Redox-promoted tailoring of the high-temperature electrical performance in Ca3C...
Constantinescu, Gabriel; Sarabando, Artur R.; Rasekh, Shahed; Lopes, Diogo; Sergiienko, Sergii; Amirkhizi, Parisa; Frade, Jorge R.This paper reports a novel composite-based processing route for improving the electrical performance of Ca3Co4O9 thermoelectric (TE) ceramics. The approach involves the addition of metallic Co, acting as a pore filler on oxidation, and considers two simple sintering schemes. The (1-x)Ca3Co4O9/xCo composites (x = 0%, 3%, 6% and 9% vol.) have been prepared through a modified Pechini method, followed by one- and t...
Exploring the high-temperature electrical performance of Ca3-xLaxCo4O9 thermoel...
Constantinescu, Gabriel; Rasekh, Shahed; Amirkhizi, Parisa; Lopes, Daniela V.; Vieira, Miguel A.; Kovalevsky, Andrei V.; Diez, Juan C.; Sotelo, AndresAliovalent substitutions in Ca3Co4O9 often result in complex effects on the electrical prop-erties and the solubility, and impact of the substituting cation also depends largely on the prepara-tion and processing method. It is also well-known that the monoclinic symmetry of this material’s composite crystal structure allows for a significant hole transfer from the rock salt-type Ca2CoO3 buffer layers to the hex...
Exploring the high-temperature thermoelectric performance of Al-doped ZnO ceram...
Constantinescu, Gabriel; Mikhalev, Sergey M.; Zakharchuk, Kiryl V.; Kovalevsky, Andrei V.Zinc oxide (ZnO) is a highly versatile and well-known material, widely used for its useful optoelectronic, catalytic, and photochemical properties [1]. In the search for alternative energy sources, ZnO-based ceramics emerge as promising materials for high-temperature thermoelectric (TE) applications [2], capable of direct conversion of (waste) heat to electricity, thanks to the Seebeck effect. Owing to the spec...
Microstructural aspects affecting the performance of thermoelectric oxides: sel...
Kovalevsky, Andrei V.; Arias-Serrano, Blanca I.; Constantinescu, Gabriel; Zakharchuk, Kiryl; Rasekh, Shahed; Ferreira, Nuno M.; Xie, WenjieOxide materials represent certain advantages as compared to traditional thermoelectric materials, including stability at high temperatures and versatility regarding the gas atmosphere composition. Microstructural aspects play a crucial role in the performance of oxides, often dominating even over chemical composition effects. Thus, engineering the microstructure in these materials represents a powerful tool tow...
Specific microstructural effects on the performance of thermoelectric oxides
Kovalevsky, Andrei V.; Arias-Serrano, Blanca I.; Mikhalev, Sergey M.; Constantinescu, Gabriel; Zakharchuk, Kiryl V.; Sergiienko, Sergii A.Oxide materials possess notable high-temperature and chemical stability, thus representing certain advantages over traditional thermoelectrics. The thermoelectric performance of oxides is strongly affected by the microstructure, often even dominating over the chemical composition effects. Thus, engineering the microstructure in these materials represents a powerful tool towards improving their thermoelectric pe...
On the high-temperature degradation mechanism of ZnO-based thermoelectrics
Arias-Serrano, Blanca I.; Mikhalev, Sergey M.; Ferro, Marta C.; Tobaldi, David M.; Frade, Jorge R.; Kovalevsky, Andrei V.The stability and reproducibility of the electric properties in n-type doped ZnO represent known bottlenecks towards potential thermoelectric applications. The degradation is promoted by the vanishing of the electronic defects on oxidation and irreversible exsolution of the phase impurities. This work proposes a microstructural mechanism showing that these processes take place mainly in the pores and highlighti...
Electrical assessment of brownmillerite-type calcium ferrite materials obtained...
Lima, Chrystian G. M.; Araújo, Allan J. M.; Silva, Rinaldo M.; Raimundo, Rafael A.; Grilo, João P. F.; Constantinescu, Gabriel; Kovalevsky, Andrei V.In this work, brownmillerite-type calcium ferrite (Ca2Fe2O5) ceramics were prepared by two distinct routes, namely by a proteic sol-gel synthesis using commercial flavorless gelatin, and by a solid-state reaction method using mollusk shells. XRD analyses revealed single phase brownmillerite-type calcium ferrites in both cases. SEMEDS analysis of sintered Ca2Fe2O5 ceramics revealed larger grain sizes for the sam...
Prospects for electrical performance tuning in Ca3Co4O9 materials by metallic F...
Constantinescu, Gabriel; Mikhalev, Sergey M.; Lisenkov, Aleksey D.; Lopes, Daniela V.; Sarabando, Artur R.; Ferro, Marta C.; Silva, Tiago F. daThis work further explores the possibilities for designing the high-temperature electrical performance of the thermoelectric Ca3Co4O9 phase, by a composite approach involving separate metallic iron and nickel particles additions, and by employing two different sintering schemes, capable to promote the controlled interactions between the components, encouraged by our recent promising results obtained for similar...
Magnetic and structural properties of La1−xGdx CoO3 compounds
Panfilov, Anatoly S.; Grechnev, Gennadiy E.; Lyogenkaya, Anastasiya A.; Pashchenko, Volodymyr A.; Vasylechko, Leonid O.; Hreb, Vasyl M.We present a study of magnetic and structural properties of La1−xGdxCoO3 compounds with x = 0, 0.2, 0.5 and 1. The Gd term in magnetic susceptibility obeys the Curie-Weiss law with antiferromagnetic interaction between the magnetic moments of Gd3+ ions. The value of the paramagnetic Curie temperature Θ is proportional to Gd content and for GdCoO3 it reaches Θ ' −5.5 K. The Co contribution, χCo(T), derived by su...