Pressureless sintering of SiC ceramics with improved specific stiffness

The effects of B4C content on the specific stiffness and mechanical and thermal properties of pressureless-sintered SiC ceramics were investigated. SiC ceramics containing 2.5 wt% C and 0.7–20 wt% B4C as sintering aids could be sintered to ≥ 99.4% of the theoretical density at 2150 °C for 1 h in Ar. The specific stiffness of SiC ceramics increased from 136.1 × 106 to 144.4 × 106 m2‧s−2 when the B4C content was increased from 0.7 to 20 wt%. The flexural strength and fracture toughness of the SiC ceramics were maximal with the incorporation of 10 wt% B4C (558 MPa and 3.69 MPa‧m1/2, respectively), while the thermal conductivity decreased from ∼154 to ∼83 W‧m−1‧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 20 wt% B4C were ∼346 MPa and ∼105 W‧m−1‧K−1, respectively.