Cordierite ceramic through glass and ceramic routes from kaolin and talc

Abstract

Based on kaolin and talc, cordierite was prepared through melt quench and ceramic process of two compositions. The sintering process of ceramics between 1000 and 1300 °C shows mainly the manifestation of cordierite with little ratios of spinel, enstatite, mullite and cristobalite. However, the sintering of their corresponding glasses between 1100 and 1200 °C shows the crystallization of cordierite as the main phases with little cristobalite and spinel. In microstructure, the sintering of ceramic samples gave nano size rounded- or rod- crystals either free or in clusters in glassy matrix but sintering of the corresponding glasses show clear euhedral to subhedral tetragonal to hexagonal crystals in submicron scale that are spread in residual glassy matrix. The density of the sintered ceramic samples was between 1.96 and 2.43 g/cm3 which corresponding to their porosity are between 29.34 and 5.46 % respectively, whereas as density of the sintered glasses were between 1.90 and 2.35 gm/cm3 which corresponding to their porosity between 36.20 and 3,30 % respectively. The sintered glass samples gave low and negative coefficient of thermal expansion values between 6.38 and -9.56 X 10-7 °C-1 (in the range ~ 24 -500 and 700 °C). The microhardness values were between 468 and 577 Kg/mm2. This cordierite ceramic can be used as refractoriness in electric heater supports, such as electric stove or heater cooling plate and ceramic heater base.