Abstract
This work aims to evaluate four different clays used in the production of BIIb type ceramic tiles in Sergipe State, Brazil. The clays were characterized by X-ray diffraction, X-ray fluorescence, thermogravimetric analysis, differential thermal analysis, particle size distribution, Atterberg limits and dilatometry. From the results, it was possible to detect calcite concentrations between 1.1 and 13.7% depending on the origin of the material. This information is essential for adjustments in the firing cycle and to predict the minimum energy for sintering. Ceramic bodies were formed by uniaxial pressing of 28 MPa into rectangular bodies with dimensions of 120 mm x 56 mm x 6 mm. These ceramic bodies were then fired at 1130 °C using a 23 min firing cycle and 3 min of soaking time. Water absorption and modulus of rupture in bending were measured and the microstructure was investigated by electron scanning microscopy. From the results, it was possible to observe a correlation between liquid phase formation and reduction of porosity in ceramic bodies sintered at 1150 ºC. Activation energies of the sintering process were determined from the dilatometric tests and the results showed that the decrease of calcareous content combined to the increase of flux content results in lower sintering temperatures, which can lead to lower energy costs.
Keywords:
clay; ceramic tile; characterization; calcite; activation energy
