The quick increasing of sol viscosity shortens the spinning holding time and is not helpful for the spinning procedure. How to postpone the rapid enhancement of sol viscosity has become an important issue. In this study, mullite fiber was prepared by sol-gel method using low molecular weight acid as modifying agent. The increase of sol viscosity became slow when the low molecular weight acid was mixed in spinning sol. TG/DSC analysis showed no peak corresponding to carboxylic acid group of modifying agents. It was concluded that the carboxylic acid group reacted with hydroxyl group and was absent in spinning sol. Fourier transform infrared analysis revealed that absorption peak concerning ester group was present. It implied that the esterification reaction was carried out between carboxylic group of low molecular weight acid and hydroxylic radical. The measurement of X-ray diffraction indicated that the mullization took place at 1100°C. The mullite fibers with smooth and dense surface were obtained ultimately.

溶胶粘度的快速增加缩短了纺丝保持时间，不利于纺丝过程。如何延缓溶胶粘度的快速增强已成为一个重要问题。本研究以低分子酸为改性剂，采用溶胶-凝胶法制备了莫来石纤维。当低分子量酸混入纺丝溶胶中时，溶胶粘度的增加变得缓慢。TG/DSC分析显示没有对应于改性剂的羧酸基团的峰。结论是羧酸基团与羟基反应并且在纺丝溶胶中不存在。傅里叶变换红外分析表明存在酯基的吸收峰。这表明酯化反应是在低分子量酸的羧基与羟基之间进行的。X射线衍射测量表明，研磨发生在1100℃。最终得到表面光滑致密的莫来石纤维。