Research On The Preparation Of Continuous Mullite Fiber By Sol-Gel Process

With the development of technology and new process, the research of mechanical materials applied in high-temperature oxidizing environment becomes an important direction. Continuous mullite fiber, a kind of high-performance inorganic fiber, due to its mullite crystal structure, possesses excellent strength, modulus, heat resistance, creep resistance and thermal shock resistance, especially the excellent mechanical property in high-temperature oxidizing environment compared to other inorganic fibers. Thus it is potentially important to be used in composite materials as the reinforcement fiber and heat-resistance fields. So it is of great interest to researchers in the fields of preparing continuous mullite fibers.In this article, the continuous mullite fiber by aqueous sol-gel method with AN-AIP-TEOS-H₂O system was prepared and the mullite precursor sol and gel from sol-gel process was systematically investigated by FT-IR, TEM and particle size analyzer. The existence of the Si-O-Al bond was proved and the mullite was crystallized out under 1000℃ that was also back on the condition there are partly Si-O-Al bonds in the precursor sol. And also we can clearly found the sol was composed ofmany uniform nanoparticles. The effect of parameters such as temperature, spinning aids and viscosity for spinnability of mullite precursor sol were studied. We also investigated the rheological property of mullite precursor sol by HAAKE rheogeniometer which shows shear shinning flow behavior.The thermal behavior was measured by DSC-TG, MS. We clearly analyzed the physical and chemical changes during the heat treatment and figured out the decomposing substances. Based on the above research works, we planed a detail dry way to insure the gel fiber with less drawbacks before heat treatment. The dry of gel fiber was a key phase in the whole process because the gel fiber included lots of water and so on, it was apt to form drawbacks and even be broken directly. At last, the mullite fiber was prepared by controlling the total sinter process carefully. The mullite crystallized before 1000℃ partly and completely formed at about 1260℃ by XRD. But there are some regrets that the mullite fiber has a weak mechanical property. And we hoped to improve its property lately.