Continuous silica fiber reinforced silica composites densified by polymer-derived silicon nitride: Mechanical properties and microstructures

Continuous silica glass fiber reinforced silica composites were prepared via silica sol suspension infiltration/sintering method followed by densification treatment by preceramic polymer infiltration/pyrolysis process, and the mechanical properties and microstructures of the composites were investigated. Pyrolyzed at 873 K in ammonia atmosphere, the preceramic polymer polyhydridomethylsilazane resulted in a low-carbon near-stoichiometric ceramic with an empirical formula of Si1.0N1.38C0.01O0.04H0.78. After the densification treatment, the density of the composites increased a little from 1.64 g/cm3 to 1.79 g/cm3, and the flexural strength increased greatly from 69.4 MPa to 95.9 MPa. However, the densified composites exhibited a tendency to brittle failure due to the relatively strong interfacial bonding between the glass fibers and polymer-derived silicon nitride, and also the degradation of glass fibers during post-treatment.