Accelerated polymorphous transformations of alumina induced by copper ions impede spinel formation

Abstract

Slower copper spinel formation on alumina type supports relative to zinc and magnesium spinel formation has been investigated. Spinel formation occurs at high temperatures and is usually accompanied by polymorphous transformations of alumina support and sintering. In samples containing zinc and magnesium ions, decelerated polymorphous transformations of alumina occur relative to the transformation of pure aluminum sample. The impeded phase transformation of alumina coincides with decreased degree of sintering. In contrast, copper ions accelerate polymorphous transformations of alumina, and consequently the corresponding copper-alumina spinel formation is slower. Accelerated sintering may be explained by accelerated phase transformation of alumina, which itself is caused by copper ions slowing down spinel formation.