In situ high temperature X-ray diffraction study on high strength aluminous porcelain insulator with the Al2O3-SiO2-K2O-Na2O system

The high strength aluminous porcelain insulator with a mineral composition of kaolinite, corundum, microcline, quartz, small amounts of albite and anatase was investigated by in situ high temperature XRD (HTXRD) from 25 °C to 1300 °C. The amount change and reaction of minerals contained in the porcelain insulator were presented vividly. The full process occurred in successive stages: 1) kaolinite decomposed into amorphous metakaolinite in the temperature range of 500-600 °C; 2) metakaolinite kept amorphous form up to about 1000 °C; 3) at about 1000 °C, amorphous metakaolinite generated primary mullite; 4) after bout 1200 °C, microcline began to melt, forming an alkaline liquid phase which facilitated the growth of primary mullite into secondary mullite; 5) the alkaline liquid phase could etch β-quartz, resulting in the reflection intensity of β-quartz decreasing; 6) corundum was very stable in the whole heating process.