Qionglai-kaolin Synthesis Mullite Whiskers Using Molten Salt Method And The Research Of Whiskers’ Dispersion

Due to rich resources, buried shallowly and a kind of sand, Qionglai kaolin iseasy to mine and purify, which makes it have broad development and utilizationprospect. For it has high temperature resistant, higher temperature strength, oxidationresistance, good thermal shock resistance, smaller thermal expansion coefficient andso on, mullite whisker is a kind of good composite materials reinforce and tougheningagents. Due to rich resources and low price, that using Qionglai kaolin as the basicraw material to produce mullite whisker, have broad commercial development andapplication prospect. That using Qionglai kaolin to prepare mullite whisker on lowtemperature, can make mineral resources advantage into economic advantage andimprove the value of kaolin’s use. Meanwhile it has important academic researchsignificance and application value.In this article, with Qionglai kaolin as basic raw materials, aluminum sulfate asadding raw materials, and sodium sulfate as the molten media, mullite whisker wasprepared by molten salt method. Used XRF, XRD, SEM and other modern testanalysis technology to research the influence of the ratio of raw materials, the size ofpowder grain, reaction temperature and holding time on mullite whisker, andoptimized the preparation process conditions. Got a discussion for the whisker’sdispersion and the influencing factors of dispersion, and preliminary discuss usingQionglai kaolin to industrially prepare mullite whisker. The conclusion is as follows:(1) Using Qionglai kaolin as basic raw materials, aluminum sulfate as addingraw materials, sodium sulfate as the molten medium, the mullite whisker withexcellent performance was prepared on the ultra-low900℃conditions via the moltensalt method.(2) Optimal conditions for the preparation of mullite whisker are as follow. Keepthe size of the powder from60to200mesh, the molar ratio of aluminium oxide andsilica at6:5, and (-2μm kaolin+aluminum sulfate) and sodium sulfate at the massratio1:1.2, holding two hours at900℃. (3) The growth mechanism of mullite whisker via molten salt method abide byliquid-solid(L-S) growth mechanism. The prepared mullite whisker is long strip,which diameter is100nm and length is2μm. The length-diameter ratio is20, and itscontent is more than88%.(4) The studies of mullite whiskers’ dispersion have shown that the concentrationof dispersant and the value of pH have a significant impact on the dispersion. All ofthe dispersants used in the experiment have good dispersion. The best concentrationand the value of pH are as follows: SHP0.2mg/ml, the pH value11.0, SPP0.3mg/ml,the pH value10.0, PEG6.0mg/ml, the pH value6.0, Tween806.0mg/ml, the pHvalue6.0.