Dehydroxylation and thermal transformations of raw clay during sintering

Powerful methods for determining the chemical and mineralogical makeup of unfired and fired clay materials include X-ray powder diffraction (XRD), chemical analysis, Fourier transform infrared (FTIR), dilatometry analysis, differential thermal analysis, thermogravimetric analysis (DTA-TG) and Scanning Electron Microscope (SEM).Using these analysis methods, it is possible to track the progression of mineralogical changes as firing temperatures increase from 300 to 1,200 .The objective of the present study is to investigate the impact of heat treatment on the structural and textural properties of clay minerals from the Tazoghrane area in Cap Bon, Tunisia.All clay samples contained crystalline phases, including illite, kaolinite, and smectite, along with quartz, K-feldspar, and calcite.The increase in firing temperatures leads to the destruction of clay minerals through dehydroxylation, resulting in the transformation of the clay's crystalline structure into an amorphous one.A structural reorganization occurs at high temperatures exceeding 900 , leading not only to the creation of spinel and anorthite but also to the formation of mullite and hematite.Spinel and mullite are generated in glass ceramics from siliceous and clay minerals through contact with other microstructure elements.