Preparation Of Fine-pore Al₂O₃ Foam Ceramics Filters By Polymeric Sponge Impregnation Process

The foam ceramics is a new innovative porous ceramic material, which has 70%⁹0% of the porosity and three-dimension network frame structure. Al₂O₃ foam ceramics filter with a fine-pore was prepared by polymeric sponge impregnation process in this study. The effects of surface modification of polyurethane sponges, binders, sintering process and slurry capability on performances of Al₂O₃ foam ceramics were studied.Surface modification of polyurethane sponges was carried out by different concentrations of CMC, calcium lignosulphonate, PEI. The results show that the effectiveness of the three kinds of surfactant on the properties of foam ceramics was in order to CMC, PEI, lignin. When the concentration of CMC is 1.5%, the best performance of foam ceramics is obtained. Its bulk density, compressive strength and porosity are respectively 0.49g·cm^-3, 2.40MPa, and 82.5%.The coating property, sintering appearance and sintering performance of alumina foamed ceramics treated by a composite binder are better than the ceramics treated by single binder. When the ratio of aluminium dihydrogen phosphate and CMC is 4:1, the best combination property of alumina foam ceramics can be prepared, the compressive strength is 1.72MPa, the thermal shock resistance is six times. For the silica sol-dextrin composite binder, when the ratio is 2:1, the compressive strength of the alumina foam ceramics is only 0.97MPa, and the thermal shock resistance is only 4 times.Sintering process has important effects on performance of samples. The physical and chemical changes are analysed by TG-DTA, XRD, SEM and so on. The results indicate thatα-A12O3 is major phase and porzite is minor phase in the sintered ceramic bodies. In this study, the best sintering temperature is 1400℃, holding time is 3h. Under these technology parameters, the compressive strength of fine-pore filters of Al₂O₃-based foam ceramics reaches at 2.71MPa.The density of foam ceramics increases with the increase of clay addition in the Al₂O₃-based foam ceramics. Therefore, the compressive strength and the thermal shock resistance of foam ceramics can be improved. However, excessive clay addition will result in the increase of the glass phase, so the compressive strength and the thermal shock performance will decrease. The performance of foam ceramics is best when the clay addition is 4%, meanwhile, the compressive strength reaches at 1.67MPa, and the thermal shock resistance reaches at 8 times.The compressive strength and thermal shock resistance of Al₂O₃-based foam ceramics are improved due to adding a certain amount of CeO₂ into the Al₂O₃-based foam ceramics. When the amount of CeO₂ is 3%, both the compressive strength and thermal shock resistance are best, and are respectively 1.70MPa and 9 times.