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.