Effect of lanthanum, neodymium, thorium, uranium, and plutonium compounds on graphite oxidation

Thermal methods of analysis were used to study graphite oxidation in air in presence of compounds of lanthanum, neodymium, thorium, uranium, and plutonium. Uranyl acetate and thorium acetate decompose at low temperatures, forming U3O8 and ThO2. Both oxides with high surface area were found to be effective catalysts in graphite oxidation, with U3O8 having higher catalytic effect than ThO2. The extent of catalysis by La2O3, Nd2O3, and PuO2 was comparatively less. The two probable mechanisms for catalysis are (1) oxide-providing sites for the dissociative chemisorption of oxygen and (2) reduction-oxidation mechanism. The latter mechanism is not established by our results. La2O3 and Nd2O3 readily pick up moisture forming hydroxides. The hydroxides La(OH)3 and Nd(OH)3 decomposed to LaOOH and NDOOH that were found to react exothermically with graphite and O2 forming oxycarbonates. La2O2CO3 and Nd2O2CO3, respectively. (author)