Improving specific stiffness of silicon carbide ceramics by adding boron carbide

A strategy for improving the specific stiffness of silicon carbide (SiC) ceramics by adding B4C was developed. The addition of B4C is effective because (1) the mass density of B4C is lower than that of SiC, (2) its Young's modulus is higher than that of SiC, and (3) B4C is an effective additive for sintering SiC ceramics. Specifically, the specific stiffness of SiC ceramics increased from-142 x 106 m2 center dot s- 2 to-153 x 106 m2 center dot s- 2 when the B4C content was increased from 0.7 wt% to 25 wt%. The strength of the SiC ceramics was maximal with the incorporation of 10 wt % B4C (755 MPa), and the thermal conductivity decreased linearly from-183 to-81 W center dot m- 1 center dot K- 1 when the B4C content was increased from 0.7 to 30 wt%. The flexural strength and thermal conductivity of the developed SiC ceramic containing 25 wt% B4C were-690 MPa and-95 W center dot m- 1 center dot K-1, respectively.