Combustion co-synthesis of nano SiC and purified Si_(3)N_(4)powders by coupling strong and weak exothermic reactionsOA

Silicon carbide(SiC)powders and silicon nitride(Si_(3)N_(4))powders are critical raw materials for advanced ceramic technology and industry.There are two challenges in their synthesis and production:(i)phase formation of nano SiC powders due to harsh reaction temperature and(ii)preparation of high-purity Si_(3)N_(4)powders due to difficulties in removing trace oxygen impurities.Combustion synthesis is a cheap,scalable method for producing SiC and Si_(3)N_(4)powders.However,there are two additional challenges:(iii)combustion synthesis of SiC requires intense external energy input due to the weak exothermic reaction between Si and C and(iv)combustion synthesis of Si3 N4 requires a diluent to slow down the selfaccelerated reaction and fully convert Si to Si_(3)N_(4)due to the strong exothermic reaction between Si and N_(2).Here,we reported a new combustion co-synthesis of nano SiC and high-purity Si_(3)N_(4)powders in one chamber,which addressed all four challenges mentioned above:(i)the production of nano Si C powders resolved by fast synthesis,(ii)purified pink-grade Si_(3)N_(4)powders using carbon as an efficient hightemperature oxygen getter,(iii)ignited Si–C combustion by a strongly exothermic Si–N_(2)reaction,and(iv)more controllable Si–N_(2)combustion with less diluent usage and less residual Si.We demonstrated nanoβ-SiC powders with~30 nm primary particle size and high-purity pink-coloredβ-Si_(3)N_(4)powders with oxygen impurity content down to 0.46 wt%.This study not only offers practical solutions to the production of high-quality SiC and Si_(3)N_(4)powders but also refreshes the design of combustion synthesis with new possibilities and improved controllability.