关键词: 无机纤维, 陶瓷纤维, 氧化铝基纤维, 耐超高温, 晶体结构, 纺丝温度

Abstract:

Objective Ceramic fibrous materials have the advantages of high temperature resistance, high strength, and excellent oxidation resistance, with wide applications in aerospace, new energy vehicles, oil-water separation and other fields. Due to the sudden increase in grain size and defects in Al₂O₃-based fibers materials at ultra-high temperatures, the brittleness of the fibers limited their use in extreme environments. In this research, ZrO₂ is used as an inhibitor of Al₂O₃ crystal growth to slow down the crystal growth rate, aiming at the preparation of ultra-high temperature resistant Al₂O₃-based fibers through centrifugal spinning and calcination, providing new method for the development of ceramic fibers.

Method Al₂O₃ precursor sols were prepared by sol-gel technology and Al₂O₃ precursor gel fibers were prepared by centrifugal spinning, and the viscosity of spinning solution was adjusted by adding polymer. Clear and transparent Al₂O₃ precursor sols were prepared from organic Al salt, Al strong acid salt and solvent water, and then the formation mechanism of Al₂O₃-based fibers were studied. The Al₂O₃ gel fibers were obtained by drawing spinning solution using centrifugal force. The influence of spinning solutions on gel fibers and calcined fibers were analysed, indicating that the higher spinning solution temperature led to the better temperature resistance of the obtained fiber.

Results Al₂O₃-based fibers were fabricated by sol-gel centrifugal spinning and calcination method, First, the formation mechanism of Al precursor sols was studied, with water playing the role of solvent, AIP and AlCl₃·6H₂O as the Al sources, CH₂O₇Zr₂ as the Zr sources, PVP as the polymer to regulate the spinning solution viscosity. AIP was dissolved in aluminum chloride aqueous solution to form a homogeneous system, which avoids the application of organic solvents and reduces the production cost and reduces the pollution to the external environment. Then, the forming mechanism of Al₂O₃-based fibers, influence of spinning solution temperature on gel fibers and Al₂O₃-based fibers were discussed. The spinning fluid of Al₂O₃ precursor was thrown out fast by centrifugal force and rapidly formed in air. Al₂O₃ and ZrO₂ precursor colloidal particles were rapidly hydrolyzed and condensed to form precursor sol fibers. The organic components in precursor gel fibers were removed by calcination to obtain Al₂O₃-based fibers. After calcination, the average diameter of gel fiber was reduced to as low as 1.88 μm. The changes in the crystal structure of Al₂O₃ during the calcination process were monitored using XRD, and the Al₂O₃-based fibers exhibited an amorphous microstructure below 1 000 ℃. The spinning fluid temperature was inversely proportional to the diameter, showing that the higher the temperature the smaller the diameter of gel fiber. The temperature of the spinning solution affected the particle composition of the fibers. It was found that higher temperature of the spinning fluid resulted in smaller particles that formed the fibers.

Conclusion Al₂O₃-based fibers were fabricated by sol-gel method combined with centrifugal spinning and calcination technology, and the spinning fluid temperature and calcination temperature were optimized to prepare Al₂O₃-based fibers materials with smooth surface and fine grain size. The average diameter of the Al₂O₃-based fibers samples prepared was as low as 1.88 μm, indicating that Al₂O₃-based fibers were successfully prepared, and the fiber diameter was adjustable in the range of 1.88-20.40 μm. The Al₂O₃-based fibers exhibited excellent high temperature resistance. When the calcination temperature reached 1 300 ℃, the particles that formed the fibers were very small and could be used as thermal protection materials in aerospace, high-temperature filtration, and other fields.

Key words: inorganic fiber, ceramic fiber, Al₂O₃-based fiber, ultra-high temperature resistance, crystal structure, spinning temperature