Microstructure of SiC-ZrC composite coatings on TRISO particles via fluidized bed chemical vapor deposition

A SiC and ZrC composite coating layer on a tristructural-isotropic (TRISO) coated particle was deposited by fluidized bed chemical vapor deposition method. Methyltrichlorosilane (MTS) and ZrCl4 powder were used as the source materials of the SiC coating and the ZrC coating, respectively. Two kinds of the SiC and ZrC composite coating layers were fabricated with other source gas fraction. The composite coating layer, with a similar ratio of SiC and ZrC, which was observed in the SEM microstructure, was fabricated, and each phase was confirmed by XRD, Raman, and TEM analysis. Only the SiC and ZrC phases were co-deposited; the ZrSi and free carbon phases were not. The composite coating layer with very small ZrC particles embedded in a SiC matrix was fabricated by decreasing the ZrCl4 source gas ratio. Nano-sized ZrC particles in the coating layer were confirmed by high resolution TEM and EDS analysis.