Effect of polishing waste additive on microstructure and foaming property of porcelain tile and kinetics of sinter-crystallization

Ceramic tiles were manufactured from an industrial powder batch of porcelain stoneware tiles with 0, 10, 30 and 50 mass% polishing waste and fired at 1100–1180 °C. The phase evolution and microstructure of ceramic tiles with the polishing waste were investigated by X-ray diffraction, differential thermal analysis and scanning electron microscope. The result showed that introduction of the polishing waste into porcelain tiles did not cause significant variations in the phase composition and facilitated the formation of mullite phase. The activation energies of mullite crystallization calculated by the Kissinger method were 780 ± 43, 828 ± 61, 493 ± 18 and 530 ± 30 kJ mol−1 for the porcelain tiles with 0, 10, 30 and 50 mass% polishing waste, respectively. In addition, the Avrami constant, n, gradually decreased with the increasing polishing waste content, indicating that the crystallization mechanism of mullite in porcelain stoneware tiles changed from two-dimensional crystallization to one-dimensional crystallization. The process of one-dimensional crystallization is more favorable to the formation of needle-shaped mullite and increases the length of mullite.