Pressureless sintering and ablation behavior of PyC-Csf/ZrB2-SiC-ZrC ceramics doped with B4C

Abstract

B4C has been widely used as a sintering aid for the densification of ZrB2-based ceramics by pressureless sintering. In this study, the effect of B4C on the sintering and ablation mechanism for PyC-Csf/ZrB2-SiC-ZrC ceramics are investigated. The results show that the addition of B4C improves sintering by removing oxide impurities from the grain surface, and inhibiting grain growth by pinning the grain-boundary movement as second phase particles. The structure of PyC-Csf/ZrB2-SiC-ZrC ceramics remained intact after ablation at 2000 °C for 120 s. The mass ablation rate of sample #4 with 14% B4C (−9.17 ×10−4 g/s) is close to 0. A Zr-Si-O layer and ZrO2 layer are formed on the samples’ surface to prevent oxygen diffusion.