| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 101 === This study we used talc, kaolinite and four different particle size α-alumina powders to synthesize cordierite by solid-state reaction method. After the raw material powders were mixed, dried, sieved, and pressed into ingot, four samples with different α-alumina particle size were obtained. After heating treatment of samples, the influence between the different particle size α-alumina to synthesis mechanism, and properties of the synthetic cordierite products were observed.
The results indicate that the changing of the particle size of alumina powders affect the reaction temperature. By reacting with protoenstatite (from decomposition of talc), fine particle size of alumina (〈200nm) can yield a large amount of spinel at the temperature lower than 1200℃. After that spinel reacted with silica to synthesize α-cordierite at 1350℃. Coarse alumina (〉 200nm) needs even more higher temperature than 1200℃ in order to react with protoenstatite for yielding β-cordierite. At the temperature higher than 1300℃, β-cordierite will then transfer into α-cordierite. At the temperature higher than 1350℃, the unreacted alumina will become α-cordierite by reacting with protoenstatite and silica.
After heat treatment, four samples with different α-alumina particle size were phase identified and measured their coefficients of thermal expansion (C.T.E). The result indicate that with the same heat treatment conditions, samples mixed with the coarse alumina have higher transition phase content, and their C.T.E was significantly higher than mixed with fine alumina samples. At the end of this experiment, the particle of 100nm alumina powder was used to synthesize high cordierite content sample. The C.T.E is 1.17 × 10-6 m/m℃ from room temperature to 900 ℃.
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