The Study Of Gelcasting Of Forming Process Technology Of Al₂O₃ Ceramics

Gelcasting is a novel forming process of Al2O3 ceramic materials combined traditional materials with macromolecule chemical reaction. Gelcasting is an in-situ forming process in which slurry of ceramic powder in a solution of organic monomer is cast. The monomer mixture is polymerized in situ to form gelled parts at certain condition. The process is a promising technique for complex shapes of ceramic materials with high ingredient uniformity and high reliability of performance. Gelcast green bodies are strong and machinable.The technological character, conditions and affecting factors are discussed in the paper. The method of producing slurries of low viscosity and high solid loading is studied. The paper attaches importance to reducing the viscosity and improving solid loading in volume, the effects of pH value, dispersants, ball milling time and solid loading on the viscosity and the effects of solid loading on the three-point bending strength, fracture toughness, density and linear shrinkage are investigated. At the same time, the effects of gelling time on forming process are researched. Al2O3 slurry with 55vol% solid loading in volume and 690mPa ·s viscosity are prepared through optimization of all elements above parameters. The fine properties green bodies with 4% organic content, 31MPa three-point bending strength, 63% relative density, 2.2MPa · m1/2 fracture toughness and 3% linear shrinkage are prepared. In the paper, microstructure of green bodies formed by gelcasting of alumina and sintered samples are discussed. The results show that powders pile up densely, ingredient disperses uniformly and properties of microstructure are fine. Gelcasting reduces the number of pore and improves the dispersity of micropore. It benefits sintering densely and controlling the microstructure.