Sintering behavior of porous wall tile bodies during fast single-firing process

Abstract

In ceramic wall tile processing, fast single-firing cycles have been widely used. In this investigation a fast single-firing porous wall tile mixture was prepared using raw materials from the North Fluminense region. Specimens were obtained by uniaxial pressing and sintered in air at various temperatures (1080 - 1200°C) using a fast-firing cycle (60 minutes). Evolution of the microstructure was followed by XRD and SEM. The results revealed that the main phases formed during the sintering step are anorthite, gehlenite and hematite. It appears that the sintering process is characterized by the presence of a small amount of a liquid phase below 1140°C. As a result, the microstructure of the ceramic bodies showed a network of small dense zones interconnected with a porous phase. In addition, the strength of the material below 1140°C appeared to be related to the type and quantity of crystalline phases in the sintered bodies.