Effect of B₄C on the microstructure and properties of B₄C modified three-dimensional needled C/C-SiC composites

The B₄C were introduced into three-dimensional carbon fiber preform by slurry infiltration (SI), then combined with chemical vapor infiltration (CVI) and liquid silicon infiltration (LSI) to get the B₄C modified C/C-SiC composites (C/C-B₄C-SiC). The microstructures, oxidation resistance, mechanical and thermal physical properties of the C/C-B₄C-SiC were investigated. The results indicated that B₄C distributed near the fiber surface and mainly in the region of the needle punched fibers, short-cut fiber web layer, and outside of the fiber bundle in non-woven layer. The C/C-B₄C-SiC possessed good oxidation resistance for B₄C was easy to oxidize into B₂O₃ and the product B₂O₃ could fill in the defects such as pores and cracks to prevent the oxidation. The flexural strength, fracture toughness, and thermal capacity of the C/C-B₄C-SiC were much higher than those of the C/C-SiC. The B₄C both can enhance the interface combination with fibers and act as ceramic particles reinforcement. In addition, B₄C had higher thermal capacity than C, Si or SiC to increase the thermal capacity of the C/C-B₄C-SiC.