Mullite Fiber Prepared by Sol-Gel Method Using Low-Molecular-Weight Acids as Modifying Agents

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. GRAPHICAL ABSTRACT