Elaboration of cordierite ceramic starting from Algerian clays

Cordierite ceramic are elaborated by mixing a Algerian kaolin which is located in “Djebel Debbagh” region in the Algerian east, and hydroxide of magnesium. This kaolin named “DD3”, contains a large tenor of manganese oxide (MnO>;1.34 %) what gives a blackish colouring to this clay, which limit its utilization in luxury porcelain and sanitary ware where brightness and whiteness are required. However DD3 is composed mainly by kaolinite and gibbsite which is also bearer of alumina. Fusible compound such iron and alkalis are less than 1 %. Elaboration of cordierite is carried out by mixing magnesium hydroxide to DD3. Fumed Silica powder is added to respect the stoichiometric composition of cordierite. Magnesium hydroxide is prepared by precipitation from MgCl₂ and NH₄OH. The mixtures with various compositions of DD3 kaolin and magnesium hydroxide are pressed to give samples in form of pastilles, and sintered at temperatures ranging from 1200 °C to 1350 °C to determine the ceramics properties such apparent and specific density, linear shrinkage, water absorption. Formation of Cordierite phase and structural changes are investigated by X-ray diffraction (XRD), simultaneous thermal analysis (DTA-TG), and thermal dilatometry.