含硅聚硼氮烷裂解转化制备氮化硼陶瓷纤维

以低活性含硅聚硼氮烷为先驱体,经熔融纺丝,BCl₃脱硅不熔化处理以及在氨气气氛中高温裂解制备的氮化硼纤维仍含有硅元素,这主要是含硅聚硼氮烷结构中的B-N(SiMe₃)₂和B-N(SiMe₃)-B由于位阻与BCl₃反应脱除SiMe₃不完全所致.而采用HCl首先与含硅聚硼氮烷反应减少其位阻,再通过BCl₃进一步脱硅不熔化处理制备的氮化硼陶瓷纤维经FT-IR、X射线衍射(XRD)分析表明纤维基本不含硅元素,并且扫描电子显微镜(SEM)表明得到的氮化硼陶瓷纤维直径约为11μm,断面致密无孔,室温下抗拉强度为0.45GPa.

Preparation of Boron Nitride Ceramic Fibers by Pyrolysis of Silicon-containing Polyborazine

ilicon still exists in boron nitride(BN) ceramic fibers which were prepared by melt-spinning,curing with BCl3 and pyrolysis under NH3 of a preceramic silicon-containing polyborazine.That is because B-N(SiMe3)2 and B-N(SiMe3)-B could not react with BCl3 completely for the steric hindrance.So HCl was used to react with silicon-containing polyborazine first to reduce its steric hindrance.Then,BCl3 reacted with silicon-containing polyborazine to remove the residual SiMe3.After pyrolysis under NH3,BN ceramic fibers without silicon were obtained which was proved by FT-IR and X-ray diffraction.The obtained BN ceramic fibers with diameter of about 11 μm were dense which was demonstrated by scanning electron mi-croscopy(SEM) and the fibers showed room temperature mechanical property with average tensile strength of 0.45 GPa.