Preparation of silicon carbide‐silicon nitride fibers by the pyrolysis of polycarbosilazane precursors: A review

The development of silicon carbide‐silicon nitride (SiC‐Si 3 N 4 ) fibers by the pyrolysis of polycarbosilazane precursors that was carried out in this laboratory is reviewed. Precursor resin, which was prepared by heating tris(N‐methylamino)methylsilane or tris(N‐methylamino)phenyl‐silane to about 520°C, was drawn into fibers from the melt and then made unmeltable by humidity conditioning at 100°C and 95 percent relative humidity. The humidity‐treated precursor fibers were pyrolyzed to ceramic fibers with good mechanical properties and electrical resistivity. For example, SiCSi 3 N 4 fibers derived from tris(N‐methyl‐amino)‐methylsilane had a tensile rupture modulus of 29 × 10 6 psi and electrical resistivity of 6.9 × 10 8 Ω‐cm, which is 10 12 times greater than a value obtained for graphite fibers.