The polymer-converted SiC fiber with high mechanical strength at high temperatures is attracting attention as reinforcing materials for ceramic matrix composites (CMCs) in the aerospace and defense fields. Japan’s Nippon carbon and Ube industries, which were the first to successfully commercialize products based on Professor Yajima’s research, have established a continuous fiber product line-up classified as the three generations. First-generation Si-C-O (Nicalon) fibers and Si-Ti-C-O (Tyranno Lox M) fibers contain more than 12 wt% oxygen due to oxygen introduced during the curing process, and their strength deteriorates rapidly above 1,300°C. The second-generation SiC fibers and Si-Zr-C-O fibers have relatively low oxygen contents of 1-8 wt% by applying electron beam curing process or controlling thermodynamic decomposition. The second-generation SiC fibers exhibited a strength retention temperature of up to 1,500°C due to their low oxygen impurity content. However, their high-temperature tensile strength and creep resistance (Max. 1,150°C) were still insufficient owing to the excess carbon induced from the precursor polymer. The third-generation fibers are stoichiometric SiC fibers with a C/Si ratio controlled to nearly 1:1 (Hi-Nicalon Type S, Tyranno SA, and Sylramic fiber). In other words, these third-generation fibers have strength retention temperatures of up to 1700°C and creep resistance of 1400°C, making them suitable for use in CMCs for high-temperature structural applications such as gas turbine blades, flaps and shrouds. However, polymer-derived SiC fibers are difficult to widely use because they are very expensive and their application fields are not developed.
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