| In this paper, the importance of the refractory ceramic fibers is brought forward at first, and the present application and development status of the oxide ceramic fibers are expounded, then the present application status and the trend of the mullite fiber are detailedly explained, the preparation methods of the oxide ceramic fibers are summed up, the Sol-Gel method is confirmed finally to prepare the mullite fiber. The continuous mullite fiber is prepared by Al(i-OC3H7)3 (AIP) and A1C13 (AC) as the sources of the Al, (C2H5)4SiO4 (TEOS) as the source of Si. IR, TG-DTA, XRD, XRF and SEM are adopted to investigate the preparation rules and characters of the spinning solution and the spinning processing parameters and the heat-treating parameters of the mullite fiber.The following conclusions are drawn out: AIP:AC=4:1, [H2O]/[A1 + Si] >8 ( mol ratio), pH≤2, HCl and HAc used as compound catalyst, about 0.05% content ( mass percent) PVA used as spinning assistant, the polymerization temperature chosen 80-85℃, the gotten sol has fine spinning ability. The heat-treating of the mullite fibers is divided into two steps, the heating-up speed rate at moderate and low-temperature is lower than 2℃/min, the suitable moderate temperature is 500℃, the heat retaining time is about 20-30min, the heating-up speed rate is faster than 3℃/min. When the gel fibers are sintered, the diffraction peaks of the mullite crystal are found at about 940℃, and other crystals are not detected in the course of heat treating, so the danger of fibers' fracturing because of the inner stress of the crystal transition is avoided, which can increase the ability of fibers. The mullite fibers heat-treated at about 1200℃ have smooth surfaces, the crystal grains are small for about 100-200nm, so the danger of fibers' fragility because of coarse crystals is avoided. Finally, the continuous mullite fibers with little porosity are prepared.
|
PDF Full Text Request