Study On Preparation And Properties Of Alumina Porous Ceramics

Lightweight and high strength porous ceramic materials as essential structural materials and functional materials play an important role in more and more engineering technical fields due to their characteristics of lightweight and unique pore structures.At present,the preparation of novel porous ceramic materials with low shrinkage,high porosity,high specific surface area,high strength and being regulated by pore structure to meet the application requirements,has been a hot and difficult research topic.The main purpose is to improve the properties of porous alumina ceramics,such as porosity,compressive strength,specific surface,and to reduce their shrinkage.The effect of low rate sintering Kirkendall effect on in situ hollowing of aluminum powder and the sintering mechanism of low rate sintering are studied.A new type of low shrinkage porous alumina ceramic material with hollow pore wall structure was prepared by atomic diffusion of micron aluminum powder in the sintering process based on the Kirkendall effect and ice template method.When the solid content is 30 wt%,the porosity of samples is86.4±1.7%,the shrinkage is-0.2±0.2%,and the compressive strength is 7.6±1.1 MPa.Porous alumina ceramic with two-stage pore structure,high strength and high porosity was prepared by combining the Kirkendall effect of aluminum powder with direct foaming method.When the porosity reaches 90%,the compressive strength of porous alumina ceramics can be as high as 12.3±3.8 MPa,which is 3 and 6 times higher than that of porous ceramics prepared by pure alumina ceramic powder system with the same porosity,and 1 wt%～2 wt%boehmite added to the slurry can make the slurry shear thinning so as to be suitable for 3D printing to prepare samples with small volume density and low shrinkage.Furthermore,in order to increase the specific surface area of alumina porous ceramics,the experimental method of water-in-oil is used in this paper.Boehmite paticles as raw materials were used to fabricate the porous alumina ceramic spheres with high specific surface area,which have diameters in range of 2–6 mm,average mesoporous sizes of 4–8 nm,and excellent specific surface areas of 400–500 m² g^-1.What’s more,we discussed the effects of water-oil ratio,rotation speed,sintering temperature on the morphology,porosity,compositions,pore size distribution,shrinkage rate of porous alumina ceramics.