Study of spark plasma sintering of SiC-B4C nanocomposite synthesized by mechanically activated self-propagating high-temperature synthesis (MASHS)

SiC-B4C nanocomposite with 1:1 molar ratio synthesized in situ by mechanically activated SHS method. Raw materials include Si، B2O3، Mg and graphite. Weighed and milled raw materials pressed by uniaxial cold press to prepare samples. Green compacts samples synthesized in tube furnace with argon gas flow at 900 °C. MgO is one of products of B2O3 reduction by Mg. Synthesized MgO eliminated by hydrochloric acid solution leaching. XRD analysis from synthesized and leached products indicated successful of acid leaching to purify the reaction products. Average crystallite size of leached products calculated less than 15 nm by XRD pattern analysis of leached products. SEM and TEM micrographs indicated the formation of synthesized composite from nanometer grains and crystallites. 91. 5% of synthesized nanocomposite particles were less than 500 nm and 42. 6% were less than 100 nm according to particle size analysis of acid leached products. SiC-B4C nanocomposite powder condensed by spark plasma sintering (SPS) with argon gas atmosphere at 1700 °C. Bulk and apparatus density of obtained part were 73. 26% and 97. 83% respectively compared to the composite powder density. Microhardness and flexural strength of sintered sample، determined 5 GPa and 260 MPa، respectively. Results of microhardness and flexural strength analysis indicated a greater effect of porosities on decrease of the hardness than the flexural strength. XRD pattern of sintered part indicated stability of synthesized SiC-B4C composite at sintering temperature and proper purity.