Study on formation, morphology, and properties of Si3N4 and SiC fibers

Abstract

AbstractSilicon nitride and silicon carbide fibers were prepared by firing silicon resin mixed with iron under NH3 flow at 1 500°C. The effect of preparation variables, iron content, flow rate of NH3 gas, and time of heating, on the yield and Si3N4/SiC ratio was studied. The yield of reaction increases considerably with increasing the iron content up to 1.7 wt.‐% iron and decreases slightly beyond this value. The Si3N4/SiC ratio in the yield is affected in the same direction. Heating for a longer time at 1 500°C favours the formation of silicon carbide instead of silicon nitride. The conversion reaction remains constant for the gas flow rates greater than 0.5 1/min.The product has grown dominately in the form of smooth and uniform fibers of a mean diameter of less than 0.3 μm. The electrical resistivity and hardness of silicon nitride and carbide composite material were measured and discussed on the basis of its composition.