Preparation of low thermal expansion glaze for ceramic cookware body of direct flame type

Abstract

Ceramic flameware bodies have a low thermal expansion coefficient, excellent thermal shock resistance, low water absorption and high strength. It can be used for direct flame cooking on stove-top without cracking. Therefore, a glaze for ceramic cookware body requires thermal expansion coefficient value lower than or similar to that of the body to get compatibility between matrix and coating. This study focused on the glaze of cordierite/spodumene composite for ceramic cookware body which has low thermal expansion coefficient of 2.83x10^-6  /°C. The glazes in a Li₂O-CaO-MgO-AL₂O₃-SIO₂  system were calculated by varying the mole ratio of Al₂O₃, between at 0.483-0.653 and SiO₂, between of 4.308-4.508. The starting material including petalite, calcium carbonate, talc, alumina, silica and zirconium silicate were mixed via wet ball milling. The samples were coated onto the composite body and fired at 1275 °C with 1 h soaking time. Phase content was analyzed by XRD. Thermal expansion coefficient was tested by dilatometer. The crazing resistance was tested using an autoclave at 250 psi followed ASTM C424-80. The microstructure quantitative analysis and elemental archived by SEM&EDX technique, respectively. The results showed petalite and zircon as two main phases, providing thermal expansion coefficient with smooth and crack-free surfaces.