Processing and properties of unidirectional SiO2f/SiO2 composites

Unidirectional SiO2f/SiO2 composites were processed with pressureless sintering and hot-pressing, respectively. The influences of the sintering temperature, atmosphere and pre-treatment on the properties were studied. It was found that both higher sintering temperature and air atmosphere promoted the crystallization of the silica fiber, which results in degrading the fiber properties and thus restrained the enhancement of mechanical properties of SiO2f/SiO2 composites. Flexural strength of the fibrous composites sintered with hot-pressing was higher than that for pressureless sintering. The promoted mechanical properties were attributed to the pull-out of the fiber. The in situ formed pyrolytic carbon (PyC) layer on the fiber was beneficial to the properties of the fiber, however, detrimental to the dielectric properties.