电纺双相前驱体制备纳米莫来石纤维及其微结构和机械性能研究

The research of electrospinning mullite nanofibers was carried out in order to meet the demand of the fabrication of mullite nanofibrous aerogel. Due to the low polymerization degree of the mullite diphasic precursor, the polymethylsilicone-alumina sol diphasic precursor with a long molecular chain was designed to facilitate the fabrication of mullite fibers by electrospinning the diphasic precursor. The molecular structure and the electrospinnability of the diphasic precursor were investigated, and the pyrolysis process and phase transformation of the polymethylsilicone and alumina sol were discussed. Based on the characterization of the microstructure and physical properties of the mullite nanofibers, the fracture mechanism of mullite nanofibers were discussed and the effect of the mullite crystal morphology and the existed defects on the fiber’s mechanical properties were explained in order to show the advantage of using diphasic precursor for the fabrication of mullite fibers. This research would promote the development of the mullite nanofibrous aerogel. In addition, the diphasic precursor designed in this work could also be used to produce mullite microfibers and other mullite ceramics with complicated shape.

项目针对纳米莫来石纤维气凝胶对高性能纳米莫来石纤维的迫切需求，开展静电纺丝工艺制备纳米莫来石纤维的相关问题研究。鉴于莫来石双相前驱体分子链聚合程度低，纺丝性能差的不足，项目提出具有长分子链的聚甲基硅氧烷-铝溶胶的设计思路，从而实现莫来石静电纺丝前驱体的双相化。分析双相前驱体在纺丝溶液中的键链结构及纺丝特性，明确前驱体纤维在高温烧结过程中聚甲基硅氧烷和铝溶胶的分解及相转变过程。对莫来石纤维的显微结构与机械性能进行表征，分析纤维的断裂机制，阐明晶粒形貌及结构缺陷对纤维机械性能的影响规律，进而明确双相前驱体在制备机械性能优良的莫来石纤维上的优势。此项的目完成可推动纳米莫来石气凝胶的发展，同时项目所设计的双相前驱体也为溶胶凝胶甩丝法制备微米级莫来石纤维或其他方法制备复杂形状莫来石提供了一种新型的双相前驱体。

莫来石纤维因其具有良好的热稳定性、化学稳定性和高温强度，常被用作高温隔热材料、高温结构材料以及纤维增强体。项目针对目前纳米莫来石纤维析晶温度低、高温热稳定性差的缺点，提出了聚甲基硅氧烷（MK硅树脂）-仲丁醇铝和聚甲基氢硅氧烷（PHMS硅油）-仲丁醇铝两种双相莫来石前驱体的设计思路，通过静电纺丝工艺成功制备出耐高温纳米莫来石纤维，并对纺丝前驱体的价键结构、助纺剂含量对纺丝性能的影响以及纤维的莫来石化过程进行了探讨。红外分析表明，项目所设计的两种莫来石前驱体仅含有Si-O-Si结构和Al-O-Al结构，而无Si-O-Al结构，这表明两种前驱体均为双相莫来石前驱体。XRD分析表明两种双相莫来石前驱体的莫来石化温度均为1200℃。本项目所制的莫来石纤维在1500℃烧结后仍能保持较好的形貌以及高致密化结构，且晶粒尺寸仅为100nm，这保证了所制备出的纤维具有优良的机械性能。