Preparation of SiC coated graphite composite powders by nitriding combustion synthesis

Abstract

Ceramic-coated graphite powders are considered as effective raw materials to fabricate three-dimensional continuous ceramic skeleton-reinforced graphite matrix composites which can overcome their inherent poor densification and improve their mechanical and antioxidation properties. However, the morphology and thickness regulation of ceramic coatings on graphite particles are still a great challenge. Herein, SiC-coated graphite (graphite@SiC) powders were prepared by nitriding combustion synthesis using Si and graphited mesocarbon microbead (MCMB) as raw powders with polytetrafluoroethylene (PTFE) as a promoter. The effects of the PTFE content and the Si/MCMB molar ratio on the phase composition and coating morphology were investigated. The phase transition and microstructure evolution of a combustion synthesis (CS) process were revealed by a gas-released quenching experiment. When the Si/MCMB molar ratio was 1 : 3 and the PTFE content was 10 wt%, the thickness of the SiC coating synthesized under 2 MPa N 2 reached 1.14 μm. The corresponding sintered graphite@SiC composite had relative density of 99.2% and flexural strength of 231 MPa, accompanied by a significant improvement in high-temperature antioxidation properties. The as-synthesized graphite@SiC powders with good sinterability and antioxidation properties show great promise for applications in the nuclear industry and other extreme fields.

SiC skeleton‐reinforced highly oriented graphite with good thermophysical and electromagnetic shielding properties

“…The TC value in the x – y plane first increased from 277 W/m/K for the GF@4SiC composite to 322 W/m/K for the GF@9SiC composite and then decreased to 223 W/m/K for the GF@27SiC composite. Previous studies have shown that the TC of composites is significantly influenced by pores, defects, and interfaces 32–34 . With an increase in the SiC volume fraction, an increase in the number of interfaces leads to a reduction in the TC of the GF@SiC composites.…”

“…and interfaces. [32][33][34] With an increase in the SiC volume fraction, an increase in the number of interfaces leads to a reduction in the TC of the GF@SiC composites. However, our study showed that the density of the GF@SiC composites increased and the porosity decreased as the SiC content increased from 4 to 9 vol.%, resulting in an improvement in the TC of the composites.…”