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 (225)Ac with the ISOL method, was produced via carbothermal reduction of ThO(2) 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 ThO(2) mainly in the core of the samples. The reacted ThO(2) or ThC(2)–GO showed a faster reactivity in air, mainly observed as ThC(2) amorphization. The specific surface area of the ThC(2)–GO samples was almost doubled compared to ThC(2)–graphite samples. The effect of these microstructural features was analysed in terms of thermal diffusivity and calculated thermal conductivity that were both reduced in ThC(2)–GO samples, however the difference with ThC(2)–graphite samples decreased at increasing temperature. The present study shows that the use of unreduced GO inhibits the solid-state reaction between ThO(2) and C; on the other hand, the high reactivity of the ThC(2) so produced is expected to be beneficial for the (225)Ac 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 ThC(2) targets.