High temperature interfacial reactions of TiC, ZrC, TiN, and ZrN with palladium

SiC as a coating layer of nuclear particle fuels has shown susceptibility to the attack of fission products like palladium. Other high temperature capable ceramics such as TiC, ZrC, TiN, and ZrN, which were identified as candidates for gas-cooled fast reactor systems, can also be examined as potential replacement materials for SiC. The resistance to Pd attack of TiC, ZrC, TiN, and ZrN was examined by diffusion couples annealed at 1400 °C for 10 h. Scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron backscatter diffraction were employed to characterize the interfacial reactions of the diffusion couples. The thickness of the reaction zone of the diffusion couples is dependent upon the microstructure of the ceramics. The results indicate the best resistance to Pd attack of TiN and ZrN, followed by TiC and ZrC in sequence. All the four ceramics showed better resistance to Pd attack than SiC.