Si-B-N ceramic fibers with composition Si1.13BN2.47 were prepared by melt-spinning, curing and pyrolysis of a preceramic polyborosilazane. The composition, structure and properties of the fibers were characterized by elemental analysis, FT-IR, X-ray diffraction, SEM and wave-guide methods. The fibers show good room temperature mechanical properties. The average tensile strength (σ) and elastic modulus (E) of Si-B-N fibers is 1.8 and 196 GPa, respectively. They also exhibit excellent high temperature resistance and remain amorphous up to 1700 ℃ in inert atmospheres. A mixture of Si3N4 and BN crystalline phases was observed upon heating to 1850 ℃. In addition, the obtained fibers show good dielectric properties according to the measurement by a wave-guide technique. The average dielectric constant (ε) and loss tangent (tan δ) of the as-obtained fibers are about 3.68 and 0.0042 in 2～18 GHz, respectively. Such performance characteristics make the Si-B-N fiber promising candidate as reinforcement for application to high temperature radar-wave transparent composite materials.

Key words: Si-B-N ceramic fiber, polymer derived method, polyborosilazane, wave-transparent fiber, high temperature resistance