Effect of B3Si on the Structure and Properties of B4C Ceramics

Dense composite ceramics based on B₄C with an addition of 10 to 50 wt % of B₃Si were obtained by hot pressing. An increased amount of boron silicide decreases the hot pressing temperature to obtain a high-density material. We found a hot pressing temperature, optimal for each of the compositions and possess the highest hardness, which is associated with the formation of a fine-grained structure. Densification occurs during reactive hot pressing, which consists in the decomposition of B₃Si into Si and BSi_n (n = 12–23) and further interaction with B₄C to form SiC and B₁₂(Si,B,C)₃. The modification of boron carbide with silicon leads to the stabilization of hardness at ~24–26 GPa in the load range from 2 to 200 N. The highest bending strength of ~500 MPa is observed for samples with up to 20 wt % of B₃Si. The optimal composition, which combines high values of hardness and flexural strength, is B₄C–20 wt % B₃Si.