Formation of silicon nitride whiskers from rice hulls.

The formation of Si3N4 whiskers from rice hulls was studied. Si3N4 whiskers were synthesized by nitridation of SiO2-C system in N2-gas flows at 1400°C and 1450°C. The shape and microstructure of the whiskers were inspected by means of SEM and TEM. The whiskers of a cylindrical shape grew along the <1011> direction whithout any deffects. The phase of the whiskers was α-type and their diameter and length were 0.1 to 0.5μm and 300 to 1800μm, respectively. The droplet of Fe-Si system was found at the tip of the whiskers. It is suggested that the VLS mechanism controls the growth of whisker.