Crystallization kinetics of mullite formation in diphasic gels containing different alumina components (CROSBI ID 94870)
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Tkalčec, Emilija ; Ivanković, Hrvoje ; Nass, Ruediger ; Schmidt, Helmut
engleski
Crystallization kinetics of mullite formation in diphasic gels containing different alumina components
The crystallization kinetics of mullite formation in diphasic gels containing TEOS-derived amorphous silica and alumina component in different crystalline form and particle size has been studied using quantitative X-ray diffraction (QXRD) with 3:2 mullite as a standard and transmission electron microscopy (TEM). As the source of alumina component, aluminum nitrate nonahydrate, commercial gamma-Al2O3 and boehmite (gamma-AlOOH)were used. The results were consistent with previous studies which indicated that mullite forms initially by nucleation and growth. During the second slow stage of transformation, mullite with approximate 2:1 composition subsequently converts further into 3:2. This process is the fastest in the precursor with the smallest particle size of alumina, and the slowest in the sample with boehmite-derived alumina. In very fine scale of morphology the conversion of 2:1 mullite started even in the first stage of transformation.
Grain size; Kinetics; Mullite; Phase development; Sol-gel process
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