The formation of thoria by decomposition of the nitrate, oxalate anoxide

The mechanisms of thermal decomposition of thorium hydroxide, nitrate and oxalate have been studied in flowing air and nitrogen and under vacuum conditions. In air, both the hydroxide and nitrate melt before decomposing so that the thoria product, after grinding, consists of angular particles with a wide size distribution. Heating in a vacuum causes all three compounds to decompose below their melting points to crystalline products. Thorium oxalate yields crystalline platelets in all cases. The products from heating in air at 12000C has the appearance of a network of spherical crystallites, joined by necks, while the result of heating to the same temperature in the electron microscope is a relatively dense pseudomorph with well defined grain boundaries. (author)