40 documents found, page 1 of 4
Communication - On the possibility of Fe electrowinning from hematite suspensio...
Lopes, Daniela V.; Frade, Jorge R.; Kavaleuski, Andrei V.Iron electrowinning offers a greener path for steel production. While alkaline media has received the most significant attention, the acidic media declined due to low Faradaic efficiency and difficulties imposed by fragile deposits. This study proposes, for the first time, prospects for acidic Fe electrowinning using a mixed-acid electrolyte (H2SO4+C2H2O4), comparing the deposition from hematite suspensions and...
Catalytic O2-steam gasification of biomass over Fe2-xMnxO3 oxides supported on ...
Ruivo, Luis C. M.; Gomes, Helena; Lopes, Daniela V.; Yaremchenko, Aleksey; Vilas-Boas, Catarina; Tarelho, Luís A. C.; Frade, Jorge R.In the present study, catalytic gasification of biomass was investigated by incorporation of a supported Fe2-xMnxO3 catalyst into the freeboard zone of a bubbling fluidized bed gasifier. The material was processed by combining incipient wetness impregnation with microwave-assisted firing methods. These catalysts were characterized by elemental, structural and microstructural analyses, and redox testing by therm...
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...
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...
Mixed ionic-electronic conductivity, redox behavior and thermochemical expansio...
Natoli, Alejandro; Arias-Serrano, Blanca I.; Rodríguez-Castellón, Enrique; Żurawska, Agnieszka; Frade, Jorge R.; Yaremchenko, Aleksey A.Manganese-substituted 5 mol.% yttria-stabilized zirconia (5YSZ) was explored as a prospective material for protective interlayers between electrolyte and oxygen electrodes in reversible solid oxide fuel/electrolysis cells. [(ZrO2)0.95(Y2O3)0.05]1-x[MnOy]x (x = 0.05, 0.10 and 0.15) ceramics with cubic fluorite structure were sintered in air at 1600 °C. The characterization included X-ray diffraction (XRD), scann...
Impact of praseodymia additions and firing conditions on structural and electri...
Natoli, Alejandro; Frade, Jorge R.; Bamburov, Aleksandr; Żurawska, Agnieszka; Yaremchenko, AlekseyCeramics samples with the nominal composition [(ZrO2)0.95(Y2O3)0.05]1-x[PrOy]x and praseodymia contents of x = 0.05–0.15 were prepared by the direct firing of compacted 5YSZ + PrOy mixtures at 1450–1550 C for 1–9 h and characterized for prospective applicability in reversible solid oxide cells. XRD and SEM/EDS analysis revealed that the dissolution of praseodymium oxide in 5YSZ occurs via the formation of pyroc...
Alkaline electrochemical reduction of a magnesium ferrospinel into metallic iro...
Lopes, Daniela V.; Lisenkov, Aleksey D.; Sergiienko, Sergii A.; Constantinescu, Gabriel; Sarabando, Artur; Quina, Margarida J.; Frade, Jorge R.The electrochemical reduction of iron oxides in alkaline media arises as a novel approach for ironmaking and iron-rich waste valorisation. Strong advantages and attractive aspects of alkaline electroreduction include lower electric energy consumption, absence of CO2 emissions, and non-polluting valuable by-products such as H2 and O2. Another potential advantage originates from the compatibility of this concept ...