resumo
Single-phase cerium aluminate was synthesized from mixtures of ceria and metallic aluminum by milling and firing under controlled conditions in reducing (10%H-2 + 90%N-2) or inert atmospheres (N-2 or CO2). Firing in an inert atmosphere (CO2) did not yield conversion to cerium aluminate, and conversion was also low after firing in reducing conditions (10%H-2 + 90%N-2) and only improved slightly on changing from powder mixtures with coarse Al powder (15 mu m) to mixtures with submicron Al (0.77 mu m). High-energy milling promoted reactivity by the combined effects of improved homogeneity, decreasing grain size of the Al precursor, increase in lattice strain and decrease in crystallite size down to 40-50 nm. Extensive oxidation of the metallic Al precursor after long-term milling prevented complete conversion to cerium aluminate even after firing under reducing conditions at temperatures up to 1400 degrees C. Thermodynamic modeling of the Al-Ce-O system provided interpretation for differences between firing in reducing and inert atmospheres. Controlled milling time hinders oxidation of Al to the poorly reactive alpha-Al2O3 polymorph. This was supported by thermogravimetry after controlled milling and yielded phase pure CeAlO3 at T >= 1200 degrees C. The high conversion was achieved even by firing at 1100 degrees C under an inert atmosphere.
palavras-chave
REMARKABLE STABILIZATION; OXIDATION; CEALO3; PEROVSKITE; OXIDE; PARTICLES; AL2O3
categoria
Materials Science
autores
Pinto, RG; Frade, JR; Yaremchenko, AA
nossos autores
Aleksey Yaremchenko
Investigador Principal
Jorge Ribeiro Frade
Professor(a) Jubilado(a)
Rui Gonçalves Pinto
Bolseiro de investigaçãoProjectos
Novos conceitos de catalisadores para oxi-vapor gasificação de biomassa sem alcatrões. (NOTARGAS)
Healing of solid oxide fuel cell materials (HEALING)
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
agradecimentos
FEDER and FCT/MCTES, Grant/Award Numbers: POCI-01-0145-FEDER-030661, POCI-01-0145-FEDER-032036; FCT/MCTES, Grant/Award Numbers: UIDB/50011/2020, UIDP/50011/2020, LA/P/0006/2020; FCT, Grant/Award Number: 2020.04654.BD