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Mullite has many excellent properties, such as good high temperature creep resistance, high temperature strength, low thermal expansion coefficient, etc., are widely used in many fields. The subject cooperation with Chinese kaolin kaolin as raw material mullite, reduce production costs, improve the added value of kaolin, thereby increasing the economic benefits. The subject using a wet chemical method provides a new way for the preparation of mullite, kaolin, research has better theoretical and practical application value, has been awarded a patent for invention. Experiment to cheap kaolin as the main raw material, instead of the traditional solid-phase method using a wet chemical method, after calcined kaolin hydrochloric acid, aluminum kaolin acid dissolved aluminosilicate kaolin separation. Studied the influence of the molar ratio of the acid-soluble, acid temperature, acid-soluble, and the concentration of hydrochloric acid, and hydrochloric acid and kaolin, aluminum. The acid was dissolved after the reaction, adding a certain amount of aluminum, so that the mixed system silicoaluminophosphate ratio than found mullite theory, and then the aluminum ion precipitate, after filtration, washing, and drying was mullite precursor. Add a different amount of AlF 3 , to study the influence of the the mullite synthesis temperature and morphology. Also a preliminary discussion of the performance of sintered mullite. By using TG-DTA, XRD, SEM, inductively coupled plasma atomic emission spectrometer, and compressive strength test method to characterize the performance of powders and sintered body. By a large number of experiments and analysis show that: (1) Suzhou kaolin calcined at 700 ℃ to form metakaolin is an amorphous material with high activity. (2) of acid-soluble reaction time, select a 20wt% solution of hydrochloric acid, at 100 ° C in a water bath under the conditions, the reaction 3H, hydrochloric acid with the original kaolin alumina molar ratio of 3.5:1, the residual ratio of the kaolin to minimize. (3) in the mullite precursor the AlF 3 can reduce mullite synthesis temperature, 1100 ℃ mullite stone phase began at 1300 ° C, completely synthetic mullite, this ratio did not add AlF 3 when mullitization low temperature of 200 ℃. With the increase in the amount of AlF 3 Add, acicular mullite stone gradually grow 6.0% the AlF 3 accession, needle length of mullite grains 5-8μm, an aspect ratio of 8-12. (4) Add the different amount AlF 3 1500 ℃ sintered samples, after thermal shock strength is diminishing, especially after a thermal shock and loss of strength. Add 6% AlF 3 final sintered samples of the highest strength retention rate.
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