Light-weight refractory has many advantages, such as low heat conductivity, high refractoriness and acid resistance,1"3 which can be wildly used as the lining of the high-temperature furnace and heating furnace. But it is well-known that its poor construction strength limits its application greatly. Fiber reinforcement is one of the feasible ways to relieve this problem.4"6 The fibre used to enforce refractory should posses high refractoriness. Sillimanite powders are hence desirable candidate materials. A fibrous powder is usually prepared by both chemical and physical methods. The chemical method mainly includes chemical precipitation,, sol-gel and microemulsion methods. Yin and Fujishiro7 synthesized fibrous titania from hydrothermal reactions. Wang8 produced fibrous nano-SrTi03 powders with a length/diameter (L/D) ratio of 20 with hydrothermal processes. High purity, small particle size and high L/D ratio are the characteristics of the powders prepared using the chemical methods. But they have poor yield with high costs. As an alternative, the physical method has a relatively high yield, and it is simple and inexpensive. For instance, Hashimoto9 produced aramid fiber powders using a vibrating ball mill. The preparation of rod-shape sillimanite powders has not been reported yet. In this paper, rod-shape sillimanite powders were prepared using a laboratory scale spiral jet mill and the processing parameters were optimized. In addition, the fragmentation mechanism of sillimanite crystals was discussed in detail.
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