Translated Abstract
With the rapid development of science and technology, ceramic based continuous fibers plays an important role in many frontier areas due to its excellent properties. However, beacause of the tecnology blockade and sensitivity of material, the lack of preparation technology with indepenent property rights in China restricts the development of this chain industry. Development of fiber preparation technology with indepenent property rights, as well as realization of its commercial production, are of great theoretical significance and application prospects. The objective of this study is to obtain adapt commercially produced excellent spinnability and improve the properties of the target fiber though the process optimization of sol-gel tecnology applying in the mass process of alumina and silica continuous fibers.
Firstly, the effcts of process parameters on the precursor sol spinnability and fiber diameter is studied, using the similar devices and methods to industrial production. The obtained fiber has a good uniformity of size and microstructure. With the increase in fluid viscosity, the spinnable length of fiber firstly increase and then decrease,at and the best value of 45m is reached at about 30Pa?s.When viscosity is adjusted in the range of 25-38Pa.s, the average fiber length reaches up to 40m. Fiber diameter increases from 7.22um to 8.00um with the increasing of fluid viscosity. With the increase of the winding speed, the spinnability of precursor sol decreases. When the winding speed is 30r?min-1, the length of fiber is 34.67 m and the fiber diameter is 8.21um. When the winding speed is 60r.min-1, they reduced to 15.67m and 7.17?m, respectively. Judged by F ratio, the viscosity of the precursor sol and winding speed have a more significant impact on the continuity of the precursor sol. When viscosity increases, the molecular chain gradually changed from the single to long chain, increasing the degree of polymerization. Gradually the sol is mainly composed of inner linear polymeric and the best spinning point can be obtained. The increasing of winding speed lead to increasing in tensile force, and decreasing in spinnability, finally the fiber diameter become smaller.
When sintering temperature increases from 1100℃to 1250℃, the pore exhaust through the grain boundaries and shrinkage of fiber increases, and porosity decreases from 2.13 to 1.39 percent. The densification is improved while grain diameter increases from 30.51nm to 41.7nm. The main crystal phase substantially transformed from metastable θ-alumina phase to mullite and α-Al2O3 phase with good high temperature stability.
For the sdudy on the preparation of silica fiber by sol-gel method, the impact of the molar ratio of the catalyst of hydrochloric acid and H2O addition and TEOS on the sol and fiber properties is explored. With the increase of the amount of the hydrochloric acid, hydrolysis time is reduced from 90h to 58h, but spinning time is reduced from 8h to 3.5h. Average fiber diameter is distributed around 32um, and shrinkage is about 12 percent. The final sintered fibers are amorphous structure. The reason is that the hydrochloric acid can directly affect the direction and speed of the reaction, but during the sintering process, hydrochloric acid is burned out, and therefore it does not change the structure of the sintered fiber.
The amount of water has a significant effect on the hydrolysis and polycondensation reaction of the sol preparation process, and thus may affect the spinnability of the sol. With the water ratio of 1.25, the hydrolysis is incomplete without spinnability, due to less linear structure; the ratio of 2 is helpful to accelerate gelation process, and drawing time is decreased to only 3.5h; when the water ratio is 1.5, the sol spinnability is more stable with drawing time of up to 5h, and at this time of the sol can be spinned better.
Translated Keyword
[Alumina based fibers, Process optimization, Silica fiber, Sol-gel process]
Corresponding authors email
