Application Of Polysaccharide Gels In Ceramic Gel-casting Process

New ceramic colloidal forming has attracted wide attention because it can reduce themanufacturing cost of ceramic products as well as improve the reliability of ceramic partssuch as direct coagulation casting, gel casting process. Among them, green body with highstrenght, near net shape, complex shape and large size can be formed throught gel-casting, butthe acrylamide monomer is neurotoxic, which limits its further application. In this paper,gel-casting based on gel properties of natural polysaccharide polymer was used to achievein-situ consolidation of ceramic slurry, so as to realize the non-toxic gel-casting of ceramic.Gelation behavior of gellan gum and curdlan were studied, the application of the two kinds ofpolymer gel in gelcasting were discussed.The influence factors of temperature, concentration, ionic species on gellan gum andcurdlan gel behavior were studied, the effect of gellan gum on the rheological behavior ofalumina suspension was investigated. The gel-point of the two polysaccharose is about40centigrade, the gelation strength of gellan gum with cations is higher than that of curdlan,moreover, the concentration of gellan gum gelation is very low.Two kinds of polysaccharidegel were used in gelcasting of alumina and zirconia, bodies with excellent performance,compact structure were prepared throught the ceramic slurry consolidated based on the gelpoverties, which has the vital significance to the development of gel-casting.Curdlan was added into alumina or zirconia suspension, after the dissolving of thepolymers by heating. Gellan gum solution was added after heating the suspension. Then thesuspension with polysaccharose was casted into the non-porous mold. At the roomtemperature, the polysaccharose gelated as the temperature decreasing below the gel-piont,and the slurry coagulated. Kinds of green body with complex shape were formed by through this method, with smooth surface and homogeneous density distribution and net size. Dryingshrinkage of green body is about2%, compressive strength is about4MPa with0.5~1wtgellan gum or2~3wt%curdlan(based on water). Ceramics gained by50vol%suspension bythis method have sintered shrinkage about20%. The density of Alumina body is above98%,the bending strength can be above300MPa. The microstructure of the ceramic is dense,grains link closely, the grain size is uniform. Green body with complex shape and goodcharacteristic obtained througth gel-casting used gellan gum and curdlan.