| Summary: | 碩士 === 國立成功大學 === 資源工程學系 === 102 === Mullite synthesized by thermal treatment of kaolinite and alumina powders has the advantage of adopting ready obtainable raw materials and thus it lowers the production thermal cost. However, its process requires higher temperature at 1500 to 1700°C. In the study, mixtures of identical raw materials, kaolin (particle size 3μm) and alumina powder (size 0.3μm) were mixed with mullite powders (used as the seed) of 0.23, 0.4, 2, and 7.5μm in diameters were used as the starting materials to fabricating mullite. The DTA profiles revealed that finer-sized mullite seeds would significantly reduce the peak height occurred at 980oC, indicating that the seed addition eventually weaken the exothermal peak of Al-Si spinel formation. And the effect increases with finer seed addition. There are four reaction routes to synthesize mullite, (a) primary mullite which is affected by mullite seed, (b) primary mullite which is not affected by mullite seed, (c) secondary mullite which is affected by mullite seed, (d)secaondary mullite which is not affected by mullite seed. When the particle size of seed is 0.4μm, the complete reaction temperature is lowered to 1400oC.
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