The influence of texture on elastic and thermophysical properties of kaolin- and illite-based ceramic bodies

Abstract

The influence of technological texture in illite- and kaolin-based ceramic bodies was studied on textured experimental samples. Strong texture was created by spreading (layering) a wet plastic mass. The texture was confirmed by XRD analysis. Anisotropy of Young's modulus (E), thermal diffusivity (a), and relative length changes (ε) was studied as a function of firing temperature in the interval 20–1200°C. Anisotropy was assessed based on the values of E, a, and ε in two directions – parallel (axial direction, “||”) and perpendicular (transversal direction, “⊥”) to the basal planes of illite/kaolinite crystals. Up to 500°C, the ratio E||/E⊥≈2.9 and a||/a⊥≈2.0 for the illite-based samples and E||/E⊥≈6.9 and a||/a⊥≈2.7 for the kaolin samples. Above 800°C, the anisotropy of E and a decrease, but do not disappear entirely even after the firing at 1200°C. It was found, that the firing shrinkage is more significant in transversal direction, which is more pronounced in kaolin samples. The results were compared with hand molded and extruded samples, showing a very strong axial texture in extruded samples. Compared to illite, kaolin is more prone to develop a significant technological texture.