Production of SiC and Si3N4 whiskers in C+SiO2 solid mixtures

The production of silicon carbide and silicon nitride whiskers in silica/ca rbon solid mixtures under nitrogen-containing atmospheres was investigated. The morphology of the products was analysed by scanning electron microscop y and its composition was determined by elemental analysis. The effect of h ydrogen in the atmosphere was studied, and it was concluded that the presen ce of this gas lowers the temperature necessary for SiC formation and incre ases the SiO2/C reaction yields. The introduction of transition metals in t he solid mixtures allowed SiC and Si3N4 whisker formation by a vapour-liqui d-solid mechanism, and the morphological characteristics of the materials p roduced can be controlled by the use of other additives, like alkaline and alkaline-earth metals and rare earths. (C) 2001 Elsevier Science B.V. All r ights reserved.