Phase Transformation in Kaolin-Doloma Mixture

摘要

In order to obtain cordierite and anorthite based ceramics, doloma within a concentration ranged between 12 and 18 [wt%], was added to Kaolin. The mixed powders were sintered between 1000°and 1300°C. X-ray diffraction is used to investigate phase formation. It has been found that anorthite appeared first at lower temperatures, while the cordierite appeared just when mullite disappeared. The temperature, at which this phenomenon occurs, is lowered when doloma concentration increases. Between 1200 and 1250°C, anorthite and cordierite phase contents varied in an opposite way with doloma concentration variation. Mullite and spinel are detected as minor phases. These phases exist at temperature ranges 1000-1200°C and 1000-1300°C, respectively, while cristoballite appeared predominantly at 1100°C and disappeared gradually between 1150 and 1250°C with doloma concentration increase. The sintering of these materials is also studied. In spite of problems induced by cordierite crystallisation, nearly full density can be obtained below 1300°C.