Mechanical and Interfacial Bonding Properties of TRISO Coatings in Ceramic-Based Dispersed Matrix Fuel

Ceramic-based dispersed matrix fuel (CDM) takes advantage of the excellent thermal conductivity and irradiation resistance of SiC materials, which can further enhance the operational safety of TRISO (Tristructural-isotropic) pellets and meet the requirements of higher temperatures and fuel consumption in reactors. In this work, the mechanical properties of the TRISO pellets coating and its interfacial bonding properties with the SiC matrix in CDM with zirconia simulated core were studied. The Young's modulus and Vickers’ hardness of each coating, as well as the fracture toughness of the SiC coating and the SiC substrate, were tested by the micrometer indentation method. Furthermore, the bonding force of the relevant interfaces was evaluated by using the push-out method and the indentation method, and the crack propagation behavior at each coating and interface was investigated with microstructure characterization. The results show that considering the bonding force of each interface of the CDM sample and the strength of each coating area itself, the relatively loose Buffer layer and the core/Buffer interface with weak bonding are prone to damage and failure. The study has proposed feasible testing methods and analytical approaches for the characterization of the mechanical properties and interfacial bonding of fuel microsphere-coated coatings, providing an important reference for the improvement of the sample processing technology of TRISO and CDM.