Preparation of dense B4C ceramics via epoxy system gelcasting and different sintering methods

Abstract

Gelcasting is proven effective for the mass production of large-sized and complex-shaped B₄C ceramics. In this study, the uniform B₄C green body with a relative density of 54.17% and compressive strength of 13.37 MPa was prepared by epoxy gelcasting. The nonlinear drying process of the epoxy system was investigated by real-time monitoring, which guided the preparation route to prevent green bodies defects. Two sintering methods, spark plasma sintering (SPS) and pressureless sintering, were employed to densify the B₄C green bodies. Due to the high quality of green body obtained by gelcasting, B₄C ceramics with a dense and fine-grained microstructure were successfully prepared via SPS at 1700°C. When the B₄C ceramics was pressureless sintered alone at 2250°C, their densification were failed and instead caused abnormal grain growth. By incorporating TiB₂, the pressureless sintering of B₄C at 2100°C basically achieved densification, reaching a relative density of 95.04%. The gelcasting process enabled uniform distribution of TiB₂ grains in the B₄C matrix, which not only inhibited grains growth, but also promoted the sintering ability of B₄C ceramics. These results provide valuable insights into the epoxy gelation of B₄C ceramics, showing potential for large-scale production of complex-shaped B₄C ceramics at relatively low sintering temperatures.