Si-B-N透波纤维的耐超高温性能

Ultra-high temperature resistance properties of Si-B-N wave-transparent fibers

以聚硼硅氮烷（PBSZ）为先驱体,经熔融纺丝、不熔化以及在氨气气氛中高温裂解制备了Si-B-N纤维,然后在高纯氮气保护下加热至超高温。利用元素分析、FTIR、XRD、SEM、力学性能分析和波导法等研究了纤维的耐超高温性能。结果表明：Si-B-N纤维1 500℃退火几乎不失重,在惰性气体中非晶状态可以保持至1 700℃,加热到1 850℃才形成Si3N4和BN等结晶相;Si-B-N纤维的拉伸强度为1.72GPa,弹性模量为196GPa,1 500℃退火Si-B-N纤维的拉伸强度为1.86GPa,弹性模量为205GPa,Si-B-N纤维具有很好的耐超高温性能;此外,采用波导法测量,Si-B-N纤维表现出优良的介电性能,测试频率为8～12GHz,1 400℃退火的Si-B-N纤维平均介电常数和介电损耗角正切值分别为约3.68和0.001 1。

Si-B-N fibers were prepared by melt-spinning,curing and pyrolysis under high temperature of a precursor polyborosilazane（PBSZ）under NH3 atmosphere,then the fibers were heated up to ultra-high temperature under purity N2.The ultra-high temperature resistance property of the fibers was researched by elemental analysis,FTIR,XRD,SEM,mechanical properties analysis and wave-guide methods.The results show that the weight of Si-B-N fibers lose little annealed at 1 500 ℃,the fibers can remain amorphous up to 1 700 ℃ in inert atmospheres,and a mixture of Si3N4 and BN crystalline phases are observed upon heating to 1 850 ℃;average tensile strength and average elastic modulus of Si-B-N fibers are 1.72 GPa and 196 GPa at room temperature respectively,and they are 1.86 GPa and 205 GPa annealed at 1 500℃,respectively.So the fibers exhibit excellent ultra-high temperature resistance property.In addition,the Si-B-N fibers show good dielectric properties according to the measurement by a waveguide method,average dielectric constant and dielectric loss tangent of the Si-B-N fibers annealed at 1 400 ℃ are about 3.68 and 0.001 1in 8-12 GHz,respectively.