Research On Preparation Of Porous Ceramics By The Foam-gelcasting Method

The green bodies of porous ceramic with high porosity and low bulk density were fabricated by the gelcasting-foam method. This dissertation described the preparation of sully with high solid loading and low viscosity, control of the time of gelcasting, and the properties of porous ceramic fabricated by the gelcasting-foam method. By means of SEM, and DTA-TG, the effect of process factors on shaping and the intrinsic link between green body properties and its microstructure were studied in this dissertation.The dependence of suspension rheological properties on solid loading, various dispersants, pH value and milling time was researched in detail. ,Results showed that the dispersant of PMAA-NH₄ is more effective than TAC and its optimal content is 0.6vol%. The lowest viscosity of slurry can be achieved by adjusting pH value to 10. The slurry with high solid loading can be suit to gelcasting.Two different surfactant, anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant dodecyl trimethyl ammonium bromide (DTAB), were respectively added to slurry as foaming agent. The ability of foam generation and stabilities of foam at various concentrations were researched. The results showed that the surfactant of SDS is more efficient than DTAB. Sucrose was used to stabilize foams. Influence of sucrose concentrations on stabilities of foams was researched, and combined with the SEM photograph of green bodies, the mechanism of sucrose to stabilize foams was studied.Influence of monomer, cross-link agent, initiator and catalyst content on gelling time was investigated. After foam generation, the gelation can be sufficiently fast to prevent foam collapse by optimizing process parameters.In the presence of surfactant of SDS, the slurry was foamed by mechanical stirring. After foam generation, the foaming suspension was stabilized by the in situ polymerization of organic monomers. Porous ceramic materials with uniform pore size ,porosities more than 70%, pore size between 100～500μm and compressive strength more than 10MPa was prepared by optimizing firing process. Results showed that the best properties of porous ceramic materials can be prepared by sintered at 1200℃for a soaking time of 1h.