Synthesizing silicon nitride whiskers by solvothermal and carbothermal methods

Xerogel was prepared by the sol-gel method using ethyl ester orthosilicate, alcohol, carbamide and glucose with various contents as raw materials. The precursor powders were obtained after xerogel was solvothermally treated at 220 degrees C for 2.5 h. IR analyses showed that the Si-O-Si and Si-O-NH2 bond are obtained in the precursors. XRD analyses indicated that the powders prepared by the solvothermal method are amorphous. Si3N4 powders are produced by heat-treating the precursors at 1400 degrees C in N-2. It was proved that the synthesized powders are alpha-Si3N4 whiskers. With the increase of the glucose contents and the heat-treating temperature, the crystallization of Si3N4 is obviously improved.