Study On Preparation Of Porous Ceramic With Light And Low Thermal Conductivity By Hollow Spheres Secondary Foamed

Porous ceramics with special pore structure is a novel porous material, it is used to a broad application prospect including the metal filter, catalyst carrier, food and pharmaceutical industry, sound-absorbing, and water treatment. The characteristics of porous ceramics with high porosity would lead to a decrease in its strength, this limits the further development of porous ceramics.As a new typed lightweight material, alumina hollow spheres, owning rich source of raw materials, the advantages of cost-effective, easy to industrial production was greatly paid attention by all walks of life since it comes out. At present, the porous alumina ceramics is considered to be the most promising high temperature heat insulation material, and receives more and more attention. In this work, based on alumina hollow spheres as a part of the aggregate, alumina porous ceramics with different microstructure, high porosity and high strength were successfully prepared by the gel-casting process combined with foaming method.In this paper, alumina slurry with alumina hollow spheres and alumina body for the preparation technology of alumina were systematically studied. The gel process of slurry and the rheological behavior of slurry with alumina hollow spheres were investigated. And the influence rules of curing temperature, solid loading and the additive amount of dispersant on rheological behavior of slurry with alumina hollow spheres were studied. At the same time, how amount of foaming agent has influence on slurry foamed situation is investigated, finally, alumina bodies with different porous sizes were obtained.In addition, the evacuation-sintering process of alumina body is explored. During the sintering process, the buried powder, covered on the surface of alumina body can effectively reduce or even avoid crack. The physical properties of porous alumina ceramics with different sintering temperature and holding time were tested, including bulk density, porosity, pore diameter size, compressive strength and thermal conductivity etc. The results showed that the alumina hollow spheres prepared by the gel-casting process were macro-porous ceramics with micro-structured aperture, if sintering temperature is too high, it will lead to burnt, sintered body crack seriously; if temperature is too low, it will cause the problem that ceramic strength is not enough; the holding time determines the compressive strength of the ceramics, heat preservation time increased to3h while porosity slightly decreased, but the compressive strength has increased exponentially, significantly improve the reliability of ceramic in order to machine processing. The microstructure of alumina porous ceramics was observed by scanning electron microscope, with three dimensions of pore structure, and from the angle of grain size, degree of density discussing how the microstructures have influence on the change of the physical parameters and explain and analysis the rules.