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Nanosized -SiC powder was prepared by combustion synthesis on a large scale, which was carried out in a N2atmosphere with silicon powder and carbon black as the reactants. Mechanical activation played an important role in enhancing the reactivity of the reactants, and a higher ball/charge weight ratio and a prolonged activation time were favorable for complete reaction. PTFE was added as a reaction promoter, which remarkably reduced the minimum activation time required for successful combustion synthesis. On the basis of experimental results and thermodynamical calculation, it is proposed that combustion synthesis of SiC in N2includes two steps:  (1) Si reacts with N2to form Si3N4, generating a lot of heat energy; (2) at higher temperatures the initially formed Si3N4decomposes, and released Si reacts with carbon to produce SiC.