Microstructure, mechanical and anti-ablation properties of SiCnw/PyC core-shell networks reinforced C/C-ZrC-SiC composites fabricated by a multistep method of chemical liquid-vapor deposition

C/C-ZrC-SiC composites reinforced by SiC nanowire (SiCnw)/pyrocarbon (PyC) core-shell networks were prepared by a multistep method of chemical liquid-vapor deposition (CLVD). The microstructure, mechanical property and ablation resistance were researched. The investigations presented that the PyC was deposited on the SiC nanowires, and the micro-scale core-shell structures were produced. Moreover, these micro-scale structures not only connected with the fibers and matrices, but also filled the pores in the composites. In contrast with C/C-ZrC-SiC composites, the flexural modulus and strength of SiCnw/PyC-C/C-ZrC-SiC composites increased by 36.91% and 44.53%, and the fracture mode was changed from the brittle to pseudo-plastic fracture. After the oxyacetylene torch ablation at two temperatures for 90s, the composites strengthened by SiCnw/PyC core-shell possessed a better resistant ablation. At ablation temperature of 2300 degrees C, the mass loss rate and linear reduction rate of the composites with core-shell networks decreased by 66.18% and 57.55% in contrast with the non-reinforced composites, and declined by 56.46% and 57.48% at ablation temperature of 3000 degrees C. The obvious decrease of ablation rates was ascribed to the dense microstructure, the small coefficient of thermal expansion (CTE), the good thermal conductivity, and the resistant ablation roles of SiCnw/PyC core-shell systems.