Effect of anionic admixtures on the copper–magnesium mixed oxide reduction

Abstract

The anionic composition, structural parameters, optical properties and reduction behavior of Cu-MgO solid solution in hydrogen dramatically change after exposure to air. The air-exposed Cu-Mg oxide contains a lot of CO 3 2-and OHanions. Its reduction proceeds via two stages: (1) diffusion of Cu 2? to the surface and (2) chemical interaction of Cu 2? with hydrogen. The effective activation energy gradually increases from that of the chemical step (65 kJ/mol) to that of the transport step of Cu 2? diffusion (130 kJ/mol). This behavior follows the ''compensation effect'', which is close to those reported earlier for CuO reduction. On the contrary, reduction of Cu 2? from the Cu-Mg oxide sample, which was not exposed to air after thermal pretreatment in the inert gas, proceeds in one step at 120-160°C with the effective activation energy of 19 kJ/mol, which is manifold less than the reported effective activation energies for various Cu-oxide systems. Water molecules eliminate from the sample slowly along with further heating up to 450°C.

Análise das propriedades de flexão e flamabilidade em compósitos poliméricos com incorporação do resíduo de lama vermelha

“…Esses componentes representam 69,5% da massa total da lama vermelha. Para Khassin et al (2010) e Temuujin et al (2008), o óxido de magnésio é conhecido por ter propriedades retardantes de chama, isso ocorre devido a sua capacidade de liberar água quando aquecido. Ademais, o óxido de alumínio também é capaz de liberar água quando aquecido inibindo, assim, a propagação da chama.…”