Spark plasma sintering of SiC powders produced by different combustion synthesis routes

In this work silicon carbide (SiC) sub-micron powders were synthesized using four different combustion routes, which include the following reactive systems: Si/C/Teflon (T); Si/C/N2 (N); Si/C mechanically activated composite particles (MA) and reduction SiO2/Mg/C reaction (R). The specific surface area of the as-synthesized SiCT, SiCN, SiCMA and SiCR powders are: 4 ± 0.5; 17 ± 2; 20 ± 2 and 145 ± 5 m2/g respectively. These powders were subjected to spark plasma sintering (SPS) without any additives at 2073 K for 10 min. The densification kinetics for each powder were measured and discussed. The obtained ceramics possess a relative density in the range 80–95% and Vickers micro-hardness (Hv) from 7 to 20 GPa. To illustrate the capability of the method, essentially pore-free ceramics were prepared from SiCMA powder by 1 h SPS without additives at 2273 K, with Hv = 24 GPa and fracture toughness K1C = 3–5 MPa m1/2.