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 ²²⁵Ac 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 ²²⁵Ac 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.