Enhanced strength and toughness of SiC/C composite ceramics via SiC@graphene core–shell nanoparticles

Developing high strength and tough silicon carbide (SiC) composite ceramics remains a significant challenge. Here, we report the process of synthesizing fully densified SiC/C composite ceramics using SiC@graphene (SiC@G) core–shell nanoparticles as raw materials through spark plasma sintering (SPS) at 1700°C and 45 MPa. The SiC@G nanoparticles were synthesized by the fluidized bed chemical vapor deposition (FB-CVD) method. During the sintering process, graphene coated, the surface of nanosized SiC particles exhibited high electrical and thermal conductivity, facilitating the uniform distribution of pulse current and heat and promoting the densification of SiC/C composite ceramics. For the prepared SiC/C composite ceramic, the carbon content reaches as high as 14.3 wt%, with carbon uniformly dispersed in a particulate form within the SiC matrix and stable interface bonding. Consequently, the introduction of excessive carbon does not compromise the hardness (28.8 GPa) and flexural strength (517.34 MPa) of the SiC/C composite ceramics. Furthermore, the carbon particles effectively enhance the toughness of the SiC/C composite material through mechanisms such as crack branching, bridging, and deflection, resulting in a fracture toughness of 7.38 MPa m^1/2. The preparation strategy in this study provides a novel route for sintering SiC composites with high-carbon content through nanoscale powder structure design, resulting in the attainment of high-performance lightweight composite materials.