Identification of the thermal phases in firing of kaolinite to mullite by using micro-Raman spectroscopy and curve-fitting

作者：Shoval Shlomo^*; Boudeulle Micheline; Panczer Gerard

来源：Optical Materials, 2011, 34(2): 404-409.

DOI：10.1016/j.optmat.2011.08.031

• Anatase
• Ceramic
• Cristobalite
• Metakaolinite
• Thermal analysis
• Pottery

Firing of kaolinite to mullite is an important process in ceramic industry. In the present study, Raman spectroscopy and curve-fitting are utilized for identification of the thermal phases in progressive firing of kaolinite to mullite up to 1300 degrees C. The results are compared to that observed by XRD. Many natural kaolinites consist of accessory anatase, and this mineral has strong Raman bands. Therefore, the spectra of anatase-free and anatase-containing kaolinites were analyzed. The Raman response is sensitive to the degree of the structural order of the thermal phases. Dehydroxylated kaolinite is detected at 500 degrees C by the disappearance of the Raman bands of the kaolinite. The metakaolinite at 700 degrees C and the spinel-type phase at 1000 degrees C have broad and weak Raman bands due to their short-range and poorly-order structure, respectively. Amorphous silica is observed at 1000 degrees C by the development of diagnostic broad and weak Raman bands. Mullite and cristobalite are detected at 1300 degrees C by the appearance of characteristic Raman bands. In firing of anatase-containing kaolinite, progressive thermal transform from anatase to rutile is observed at 1100-1300 degrees C by the appearance of Raman bands of rutile and by the decreasing of the anatase bands. The results can be applied in using micro-Raman spectroscopy as a non-destructive method for identification of thermal phases in the composition of modern and ancient ceramic.

• 出版日期2011-12