Synthesis, characterization and sintering of Si-C-N nano-powders via sodium reduction in liquid ammonia

Si-C-N nano-powders with tunable carbon content were synthesized through the reduction of silicon tetrachloride (SiCl4) and trichloromethylsilane (SiCl3CH3) solution by sodium in liquid ammonia. The nano-powders contain two domains of structure, Si-C-N amorphous or continuous random networks (CRNs), and free carbon. The carbon content in Si3+nCnN4 CRNs, is tunable from n = 0 to n = 1. Free carbon will appeared with the increase of the C/Si mole ratio when C/Si is higher than 1/4. The crystallization of amorphous Si-C-N powders occurs at temperatures ranging from 1300 °C to 1500 °C depending on the carbon content. The additive-free dense Si-C-N ceramics with relatively low porosity were fabricated by Spark Plasma Sintering (SPS).