Alumina ceramic foam is a low-temperature foam ceramic, which is mainly used for filtering non-ferrous metal melts such as aluminum and aluminum alloy. It is the largest type of foam ceramic produced in China. At the same time, since the aluminum liquid casting is mostly a rod casting process, the size of the alumina ceramic foam filter is larger than that of zirconia and silicon carbide.
Because the filtered aluminum liquid has a lighter specific gravity, its performance requirements such as the strength of the ceramic foam filter – PAl are relatively low. The domestic alumina foam ceramic research time is early, the production process is mature, and the process requirements are not very high, the quality of the products produced by domestic manufacturers are relatively stable.
The main raw materials of alumina foam ceramics are α-alumina, kaolin, silica powder, feldspar, and aluminum dihydrogen phosphate. The α-alumina component accounts for more than 80%, and the proportion of slurry is 2.3 ~ 2.6 g/cm3. It is lighter and has lower requirements on the elasticity and strength of polyurethane sponge.
As a high-temperature foam ceramics, zirconia foam ceramics are mainly used in the filtration of high-temperature metal melts such as cast steel and high-temperature alloys. The overall consumption is not large, and there are few domestic manufacturers of such foam ceramics, such as AdTech ceramic foam filter- PZr. The technical difficulties in the production of zirconia foam ceramics mainly include the quality of the polyurethane foam sponge carrier, the control of zirconia sintering temperature, and the volume expansion caused by the zirconia crystal phase transformation. Among them, the sintering temperature of zirconia and the crystal phase transition of zirconia are technical problems, and the choice of polyurethane foam sponge carrier is a problem of raw material quality.
The true density of zirconia powder is 5.7 g/cm3 and its specific gravity is relatively large. The ceramic slurry composed of partially stabilized zirconia powder and additives has the characteristics of high specific gravity and good fluidity. In the foam ceramic sizing process, the polyurethane sponge carrier is required to have good slurry adsorption performance, good through-hole rate, thick sponge mesh and elasticity. Good and high tensile strength. The density of open-cell polyurethane sponge is only 0.03 ~ 0.05 g/cm3, and the sponge itself is not very elastic, and its strength is difficult to meet the requirements of the production process of zirconia foam ceramics.