Fabrication of bulk nano-SiC via in-situ reaction of core–shell structural SiC@C with Si using high pressure high temperature sintering method

• Bulk nano-SiC ceramic was produced via the reaction between SiC@C and Si.
• Slight grain growth happened in the sintering process.
• The produced nano-SiC ceramic had high micro-hardness up to 32 GPa.

Single-phase nano-SiC ceramics are difficult to be prepared due to the low sinterability of SiC and the thermal instability of nanoscale particles which results in a spontaneous grain growth at high temperatures. In this report, we prepared a single-phase nano-SiC ceramic using a high pressure high temperature (HPHT) method via reaction sintering. Firstly, nano-SiC powder was pre-carbonized by acid -etching followed by an annealing treatment to form a core–shell structural SiC@C with graphitic carbon layers covered on SiC surface. Subsequently, the single-phase nano-SiC ceramic was successfully fabricated via the reaction of SiC@C with Si under HPHT sintering condition (1500 °C, 5 GPa, 1 min). The produced nano-SiC ceramic exhibited a high relative density (up to 99.4%) and a high micro-hardness of 32.3 GPa. Despite slight grain growth, the grain size was kept in nanoscale < 100 nm after sintering.