Effects of metal oxides on the synthesis of Si3N4 whiskers from diatomaceous earth

To determine the effects of metal oxides on the whisker shapes and production yield as well as the role of these oxides in the starting material in trace quantities, diatomaceous earth and high-purity SiO₂ were subjected to reduction and nitridation in a flowing mixture of nitrogen and ammonia. The results showed that the growth of outside whiskers was brought about by the vapor-liquid-solid (VLS) mechanism and that Fe is necessary for the growth of the outside whiskers. It was also assumed that manganese and iron oxides present in the diatomaceous earth were reduced to metallic Mn and Fe.