Porous TaCx ISOL target materials from mould-casted Ta4AlC3

Mould casting and sacrificial templating techniques, common in bioceramic technology, were employed to process porous TaCx ultra-high temperature ceramics intended as novel target materials for isotope separation on-line (ISOL) facilities, aiming primarily at the production of medical radioisotopes. A feedstock of Ta4AlC3 MAX phase powder, polyamide spheres and wax was used to obtain different porous TaCx grades with bimodal pore size distributions. The ‘green’ bodies underwent de-binding and vacuum annealing to decompose the MAX phase, whereas a reference material was also produced from commercial TaC powders. The thermal stability of the porous TaCx ceramics was assessed at ISOL-relevant conditions by heating in high vacuum up to 2200°C. The MAX phase-derived TaCx porous ceramics evolved from biphasic TaCx/α-Ta2C to single-phase TaCx at higher temperatures, due to carbon incorporation. The porous TaCx microstructure was stable at 2200°C with a specific surface area stabilizing at ~0.25 m2/g and thermal conductivity of 1-4 W/m.K.