Porous Alumina Ceramics Prepared By Alcohol-water Based Gel Casting Process

Owing to superior properties of high temperature resistance, corrosion resistance, and good permeability, porous ceramics has been widely applied in filtration materials, catalyst carriers and other eco-friendly fields. As the environmental problem turns worse, higher demands are proposed to the technology of sintering porous ceramics.With alumina powder as raw materials and alcohol-water mixed solution as solvent, uniform alumina ceramics with high strength and three dimensional porous networks were fabricated by alcohol-water based gel casting process. This new method features in using low-surface-tension alcohol-water mixed solution as pore forming agent without additional foaming agent or solid pore-forming agent, which just need an ordinary drying process to achieve in-situ curing and pore structure evolution control of as-prepared uniform porous ceramics body. The influence of alcohol/water ratio, solid content and sintering temperature on the microstructure, pore structure and properties (such as bulk density, porosity, compressive strength and gas permeability rate) of porous ceramics were analyzed through SEM, mercury intrusion and other characterization methods. Main conclusions are as follows:1) Porous ceramics body prepared by alcohol-water based gel casting process enjoys3D connecting porous network which is made of alumina particles that wrapped polymer. The process of pore structure evolution is controllable, self-assembly and don’t need additional template.2) Using alcohol-water mixed solution as solvent combined with alcohol displacement drying process, as-prepared ceramics body with high porosity, low shrinkage rate and bulk density can be sintered effectively. As the ratio of alcohol to water increases, the shrinkage rate and bulk density of ceramics body would decrease. When the alcohol to water ratio increased from3:7to9:1with the certain solid content of10vol.%, the change of shrinkage rate is in21.93%-0.31%, and the bulk density is in the range of1.43g/cm3-0.72g/cm3. 3) By changing the alcohol-water ratio, solid loading, sintering temperature, the properties of products, such as porosity, pore size and distribution, flexural strength and gas permeability rate, could be adjusted. When alcohol-water ratio was7:3, solid loading was10vol%, sintering temperature was1600℃, optimal comprehensive performances were acquired:uniformly distributed pores with porosity of76.91%, pore size of1μ～4μm, flexural strength of9.68MPa, gas permeability of165.84m3/(m2·h·KPa).