In the present study, the effect of silicon additions on the hot pressing of boron carbide was investigated. B4C-based ceramic composites with the addition of silicon powder up to 12 wt.% were prepared by hot pressing at 1850 oC under a vacuum and 60 MPa pressure. The results show that addition of silicon powder affected the sintering behavior of B4C significantly. Silicon powder reacted with free-carbon originating in the B4C phase and formed a solid solution in the B4C structure. For the B4C- 8 wt.%Si specimen, a high fracture toughness of 5.04 MPa·m1/2 and modest flexural strength of 354 MPa were obtained. It seems that the improvement in fracture toughness is attributed to the high relative density and the change of fracture mode by the formation of the SiC phase.

Keywords: Boron carbide, Silicon, Microstructure, Mechanical properties, Hot pressing.