Microstructure and Properties of Polycarbosilane Transferred Nano SiC Reinforced B_4C Matrix Composites

Nano-sized SiC reinforced B4C matrix composites were fabricated through a pyrolysis route from polycarbosilane(PCS) precursor. The microstructure and properties of the materials, compared with the materials sintered by direct mixed powders, were investigated. It shows that, the composites fabricated via precursor form a kind of complicated intra-intergranular structure: nano SiC within the grains of B4C and Al2O3, sharp angle-layered SiC precipitating in the grain boundaries, and SiC substructures within the grains of B4C. The crack deflection within the crystal grains is caused by intragranular fracture, increasing the fracture toughness significantly. The homogenization, relative density and mechanical properties of the composites fabricated by polycarbosilane precursor are higher than those of the composites made by directly mixed powders.