Abstract
Precursor-SiC fibers with high tensile strength are produced by the conversion process of polycarbosilane under an inert atmosphere. The fibers consist of SiCxOy(x=1.2-1.4, y=0.3-0.4), and
are amorphous. The fibers are actively applied as the reinforcements of inorganic composites. The fibers decompose by heat treatment at temperatures above 1573K in N2 or Ar atmosphere, and the evolution of SiO and CO gas occurs. The morphology and crystal structure of the fibers change and the tensile strength rapidly decreases. In order to improve the tensile strength at high temperatures, it is necessary to reduce the oxygen content. The oxygen control in the fibers is studied using radiationchemical reactions, and the tensile strength has been removed. On the other hand, polycarbosilane is converted to silicon nitride by the heat treatment in NH3 gas flow.On the basis of this nitridation process, Si3N4 or Si-N-O fibers are synthesized.
