中文摘要：

以廉价的铝粉、工业盐酸和酸性硅溶胶为主要原料,通过溶胶凝胶法制备了多晶莫来石纤维.采用^27Al NMR测试了聚合氯化铝溶胶中Al^3＋的聚集状态,采用XRD、FT-IR、SEM和TG-DTA等手段表征了不同热处理温度下莫来石纤维的物相组成、纤维形貌以及纤维的热分解特性.^27Al NMR结果表明,Al^3＋主要以Keggin结构的Al13形态存在于聚合氯化铝溶胶中.具有24个活性Al-OH键的Al13聚阳离子易与硅溶胶中的Si-OH发生失水缩聚反应,生成具有长链结构的纺丝溶液.XRD、FT-IR和TG-DTA结果表明,纤维热处理到950℃时开始结晶,到1000℃可获得单一的莫来石晶相,整个过程的纤维失重在48.24％.经1250℃热处理,获得的莫来石纤维的直径为3～5μm,晶粒尺寸约为240 nm,拉伸强度为1.1GPa.

英文摘要：

Polycrystalline mullite fibers were prepared by sol-gel method,using aluminum powders,hydrochloric acid and silica sol as raw materials,water as solvent.The aggregation state of Al^3＋ was measured by ^27Al NMR.The pyrolytic decomposition patterns of mullite fibers were assessed by heating samples to different temperatures and characterizing the products by thermogravimetric analysis （TG）,differential thermal analysis （DTA）,X-ray diffractometry （XRD）,and Fourier transform infrared spectroscopy （FT-IR）.The micrograph of mullite fibers were observed by means of Scanning Electron Microscope （SEM）.The results of ^27Al NMR show that Al^3＋ ions aggregate in the PAC sol in the form of Al13 with Keggin structure.TG/DTA analyses show the exotherm at 970℃ can be attributed to the formation of mullite phase and weight loss of the mullite fibers in the heat treatment reaches 48.24%.XRD and FT-IR analyses show that phasepure mullite can be formed at 1000℃ with no other intermediate.After heat-treated at 1250℃,the mullite crystalline fibers with diameter of 3-5μm,grain size of 240nm and tensile strength of 1.1GPa are obtained.