engleski

The Carbothermal Preparation of Silicon Nitride Whiskers

The type of silicon nitride whiskers prepared in this study can be used for reinforcement in plastics, metal or ceramic composites, since silicon nitride has a high strength at high temperatures, high thermal shock resistance, and the whiskers have a tensile strength, close to the theoretical value. Condensed silica fume and graphite was used as the precursors. The precursors must be in the amorphous phase and be particles that are as small as possible. Iron oxides from the precursors have an important role in the carbothermal preparation of silicon nitride whiskers, too. The optimum reaction conditions for preparing the silicon nitride whiskers were found to be: a reaction temperature interval 1380-1400 C, a C/SiO2 molar ratio of 4 and a gas-phase composition of 72% N2 and 28% NH3. The best efficiency rate was 40 mass. % of Si3N4 whiskers.

silicon nitride; whiskers; carbothermal preparation; reaction temperature; molar ratio C/SiO2; gas phase composition

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