Mechanical properties of nanostructured silicon carbide consolidated by spark plasma sintering

Silicon carbide based materials are foreseen candidates for next generation nuclear applications due to a combination of the following properties: high temperature strength, high thermal conductivity and low nuclear activation. Their main drawback lies in their too low toughness. A promising route to enhance such mechanical properties is to reduce the grain size down to the nanosize range. Enabling a quite low sintering time, the spark plasma sintering technique has been used to process nano size monolithic Silicon carbides with several grain sizes and with or without boron additives. The mechanical properties, including Young modulus, flexural strength and toughness, of these materials have been measured from room temperature to 1300 °C and compared to those of a commercially sintered α-SiC. The results are carefully discussed in correlation with the microstructure. Despite a lower density, the obtained flexural strength and toughness properties of the nano grain silicon carbide are very promising when processed without boron additives. Thus, efforts should be focused on the processing of large size nanograins SiC components by SPS without boron and with high density.