Mineral thennochemistry of bentonite and kaolin related to their possible application in the ceramic industry

Abstract

X-Ray Powder Diffraction (XRPD) analyses were carried out on the raw and fired clays for identification and study of mineral phases and their changes contained in the samples. The raw clays consisted of smectite, beidellite, kaolinite, dickite, illite, cristobalite, quartz and calcite. Clays fired at 950°C reflected the following mineral phases: cristobalite, spinel, quartz and kasilite. Upon further firing to 1250°C, spinel, cordierite, hematite, tridymite and mullite. Indistinguishable amorphous phases were also present in the fired clay samples. Equations of thermochemical reactions were advanced to support mineral phase transformations of the studied clays. The findings of the study confirm that despite the similarity of clays, when fired their end products are different due to their raw clay chemical and mineralogical compositions. The results further support the suitability of the studied clays for use in the ceramic industry. © 2008 Asian Network for Scientific Information.