先驱体转化法制备高性能Si-B-N陶瓷纤维

以聚硼硅氮烷为先驱体, 经熔融纺丝、不熔化处理以及在氨气气氛中高温裂解制备了Si-B-N陶瓷纤维. 利用元素分析、FTIR、XRD、SEM和波导法等对纤维的组成结构和性能进行了表征. 结果表明: Si-B-N纤维的组成为Si1.13BN2.47, 室温下纤维的抗拉强度为1.8 GPa, 弹性模量为196 GPa; 纤维具有很好的高温稳定性, 在惰性气氛中可以保持非晶状态至1700 ℃, 加热至1850 ℃结晶, 形成Si3N4和BN等相. 同时, 纤维表现出优良的介电性能, 室温下, 在测试频率为2～18 GHz时, 其平均介电常数和介电损耗角正切值分别为3.68和0.0042. 该纤维有望成为新型耐高温透波复合材料的候选增强材料.

Preparation of High Performance Si-B-N Ceramic Fibers by Polymer Derived Method

Si-B-N ceramic fibers with composition Si_(1.13)BN_(2.47) 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 Si_3N_4 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(s)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.