Thermal Shock Resistance of ZrB2-MoSi2-SiC High-Temperature Ceramics Prepared by Spark Plasma Sintering

In this study, ZrB2-MoSi2-based ceramics, namelyZrB(2)-15MoSi(2), were produced by means of spark plasma sintering technology. The effect of the amount of SiC additive on the microstructure of the oxide phase, morphology of the oxidized surface, thermophysical parameters, and thermal shock resistance were investigated with a variety of techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive analysis (EDS), nanoindentation, and thermal expansion coefficient and laser thermal conductivity determinations. The measured thermophysical parameters indicate that SiC improves relative density and thermal conductivity, decreases the thermal expansion coefficient and elastic modulus, which is beneficial for thermal shock resistance. The investigation of the surface microstructure and cross-section of the sample after the thermal shock experiment indicates that although defects like gas pores and microcracks may be generated after the first thermal shock test, the material can self-repair with sufficient and melt-flowing SiO2 phase in the subsequent thermal shock tests. The oxide layer consists of SiO2rich and SiC-depleted layers, and the thickness of the oxide layer depends on the SiC content. The addition of SiC improves the formation of the SiO2 oxide layer, prevents further oxygen penetration, and thus, reduces the thickness of the oxide layer.