Development of Continuous Silicon Carbide Fibers Nicalon and Hi-Nicalon for High Temperature Composite Applications

Abstract

In 1975, the SiC fiber was made from polycarbosilane by Prof. Yajima, for the first time. We started to develop the industrial production of the SiC fiber and succeeded in development of manufacturing technology for the multi-filament continuous Si-C-O fiber (Nicalon) in 1978. Nicalon fiber has high tensile strength and modulus, and heat resistance at high temperature in air atmosphere. Nicalon fibers have been used for the reinforcements of composite materials such as Polymer Matrix Composite (PMC), Ceramic Matrix Composite (CMC). In recent years, it has been increasing demand for high performance CMC for high temperature applications. We have improved fiber properties by reducing oxygen content and excess carbon in chemical composition of the SiC fibers. In 1988, low-oxygen-content Si-C fibers (Hi-Nicalon) with 0.5wt% oxygen were prepared from polycarbosilane with electron beam irradiation curing and pyrolysis. The thermal stability of Hi-Nicalon fibers was significantly improved compared to Si-C-O fiber (Nicalon) with 12wt% oxygen. However, creep deformation occurred in the Hi-Nicalon fiber at high temperature, caused by SiC micro crystals and amorphous carbon. Then, stoichiometric and highly crystalline SiC fiber (Hi-Nicalon Type S) was prepared from EB irradiation cured fiber by pyrolysis in a hydrogen gas flow in 1994. Type S fibers had high tensile modulus, excellent thermal stability, and creep resistance at high temperature. Hi-Nicalon and Type S fibers appear to be the best candidates for the reinforcement of ceramic matrix composites. Hi-Nicalon and Type S fiber reinforced SiC composites are being developed as the components of gas turbines for aerospace and power generation.