The Preparation And Properties Of Porous Alumina Ceramic By Spray Drying

Porous ceramics have been used in heat separate, heat transfer, separation filters, catalyst supports, energy storage, electrodes, noise absorption, biomaterials, etc., and play important roles in many aspects, because they not only have the properties of the general ceramics,such as,high chemical stability, high stiffness, high temperature and corrosion resistance,and other excellent features, but also have low thermal conductivity, the choice of liquid and gas permeability, energy absorption or damping properties, etc.In this paper, alumina secondary particles are prepared by sub- micron powders through spray drying method, which have spherical structure containing depressed pore. In this process, the pore agent and alumina powders are dispersed and uniform. Then the aluina particles are molded by compression, and sintered into the porous alumina ceramics. This technique combined with the advantages of both the particle stacking technique and the pore agent adding technique, make the porous alumina ceramics with high porosity and high strength,which can be used as rigid insulation materials.This paper studied various process parameters of the preparation processing, tested the porosity and compressive strength of porous alumina ceramic, and observed the morphologies of particles and porous ceramics by a confocal laser microscopy. Experiment results indicates that when the pH value is 3, and binder content is 1%, the viscosity of the alumina slurry is less than 20mPa ? s, and is suitable for spray drying. As the slurry solid content Increasing, the size of the particle made by spray granulation increase, too. This makes the pore size among the particles increasing, eventually leading to the porosity of ceramic increasing, and strength declining. But when the solid content is more than 40%, the particles gradually approaches spherality, the volume of the depression in particle is reduced obviously, that make the porosity reducing, and the strength increasing. Increasing the content of pore agent and reducing the sintering temperature also can increase the porosity and reduce the compressive strength of porous ceramic.Orthogonal experiments show that the sintering temperatures of porous ceramics play the most important role on the ceramics'performance. And then, solid content have more effect than pore agent content on the porosity, and have less effect than agent porosity on the compressive strength. Considering the porosity of porous ceramics and strength, comprehensively, the ultimate optimal solution of the porous alumina ceramics is that the solid content is 40%, binder content is 1%, and the sintering temperature is 1400℃. Under this condition, the porosity of porous alumina ceramic is 60.8%, and compressive strength is 81.0MPa.