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Search / Korean Journal of Chemical Engineering
HWAHAK KONGHAK,
Vol.38, No.5, 661-668, 2000
졸-겔법에 의한 구형 mullite 전미분체의 제조 및 mullite화 공정기구의 해석; II. Mullite 단일상 생성을 위한 조성 범위와 발열 반응의 특성
Synthesis of Spherical Pre-mullite Particles by Sol-Gel Method and Mullitization Mechanism of Pre-mullite ; II. Composition Range for Stable Mullite and the Nature of the Exothermic Reaction
황운연, 이승구, 최진훈, 이정운, 박형상, 유승준, 윤호성, 김용렬
본 연구에서는 부분가수분해 및 혼합용매법을 이용하여 세 가지 조성의 mullite 전미분체를 제조하였다. FT-IR 분석 결과 mullite 전미분체는 Siiv-O-Alvi 결합을 형성하고 있음을 알 수 있었다. DTA 결과에 의하면 mullite 전미분체의 알루미나 양이 증가할수록 더 낮은 온도에서 1차 발열반응이 일어났고, mullite 전미분체를 1차 발열 반응이 일어나는 온도까지 하소한 후 HF 용액으로 처리된 시료를 1,600 ℃까지 100 ℃ 간격으로 하소한 시료에 대한 XRD 분석결과에 의하면 Aksay가 제시한 70.5≤Al2O3 wt%≤74의 조성범위에서 mullite 단일상이 생성되었다. 그리고 990 ℃ 부근에서의 1차 발열반응에 의하여 Si-O-Al 결합을 갖고 있는 Al-Si 스피넬상의 생성과 비정질 SiO2의 유리현상이 일어났다. 그리고 mullite 전미분체와 침출공정을 거친 시료에 대한 DTA, XRD 및 FT-IR 분석결과를 종합해 보면 스피넬상의 생성과 함께 유리된 비정질 SiO2가 mullite화 공정에 많은 영향을 미치고 있음을 알 수 있었다.
In this study, spherical pre-mullite powders of three composition were prepared by partial hydrolysis on the TEOS and mixed solvent method. From the FT-IR analysis of pre-mullite powders, the structure could be interpreted that SiO2 tetrahedron and AlO6 octahedron are bonded randomly by sharing oxygen atom. By the DTA analysis, the amount increase of Al2O3 composition in the pre-mullite caused the shift of first exotherm to low temperature. As a result of XRD analysis on the pre-mullite and leached sample calcined from 1200 ℃ to 1600 ℃, only mullite phase was created in the range from 70.5 wt% to 74.0 wt% alumina, which was identical with the Aksay''s range. The first exotherm at about 990 ℃ during the calcination of pre-mullite has been attributed to the formation of Al-O-Si spinel due to the liberation of amorphous silica. By means of the leaching experiment on the silica which coexisted with the spinel phase and the mullitization of leached sample, the amorphous silica liberated at about 990 ℃ was very essential for the mullitization. Insufficient or lack of amorphous silica can cause the formation of α-alumina with the O-Mullite by the calcination at about 1400 ℃.
Keywords: Mullite; Mullitization Sol-Gel Process; Spherical Powder; Mixed Solvent; Partial Hydrolysis
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[Cited By]
  1. Hwang UY, Lee JW, Park HS, Kim YR, Koo KK, HWAHAK KONGHAK, 41(4), 509, 2003
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