Effect of Graphite and Graphene Oxide on Thorium Carbide Microstructural and Thermal Properties

Thorium carbide to be tested as target material for the production of Ac-225 with the ISOL method, was produced via carbothermal reduction of ThO2 nanoparticles by graphite and graphene oxide, respectively. The use of graphene oxide (GO) as carbon source resulted in a reduced reactivity compared to graphite, confirmed by the presence of unreacted ThO2 mainly in the core of the samples. The reacted ThO2 or ThC2-GO showed a faster reactivity in air, mainly observed as ThC2 amorphization. The specific surface area of the ThC2-GO samples was almost doubled compared to ThC2-graphite samples. The effect of these microstructural features was analysed in terms of thermal diffusivity and calculated thermal conductivity that were both reduced in ThC2-GO samples, however the difference with ThC2-graphite samples decreased at increasing temperature. The present study shows that the use of unreduced GO inhibits the solid-state reaction between ThO2 and C; on the other hand, the high reactivity of the ThC2 so produced is expected to be beneficial for the Ac-225 production with the ISOL method, affording a high release efficiency. It is expected that the use of reduced GO could represent a good solution for highly efficient ThC2 targets.