Effect of Pyrolysis on Strength of Nicalon

Abstract

The deterioration of Nicalon by high-temperature heat-treatment was investigated. Early in the pyrolysis, the violent evolution of pyrolytic gases (SiO and CO) caused surface imperfections and great loss of strength of Nicalon. During the subsequent pyrolysis, the strength remained practically unchanged. At the last stage of the pyrolysis, although the evolution of gases became gradual, the strength was drastically reduced because of the coarsening of β-SiC crystals. The strength of the low-oxygen SiC fiber, which was prepared by the electron-irradiation curing method, was dependent solely on the crystal size of SiC, because of the mild generation of pyrolytic gases.