Raman and X-ray Diffraction Data on Anatase in Fired Kaolins
Abstract:The Raman spectra of many kaolins are dominated by bands from ancillary anatase. Fired samples of a commercial anatase-bearing kaolin from the Jari River deposit in Brazil showed significant variations of Raman spectra as a function of the firing temperature. The spectra showed the full range of anatase bands up to a firing temperature of 900ºC. From 950ºC the background increased significantly, leading to an unfavorable signal/noise ratio that allowed observation of only the most intense (Eg) band at ~144 cm-1. X-ray diffraction (XRD), however, confirmed that this band, which persists up to 1200ºC, results from anatase. Two factors may be responsible for the high thermal stability of anatase in this sample: its relatively large particle size of ~120 nm and possible reactions with Si and Al that become liberated during kaolinite breakdown. W hen evaluated with circumspection, Raman and XRD data on anatase can serve as 'thermometers' to elucidate the thermal history of fired anatase-bearing kaolins and other anatase-bearing clays.
Document Type: Research Article
Publication date: December 1, 2003
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