| Alumina sphere has excellent properties, such as high resistant to high temperature and high pressure, a low water absorption; a high corrosion resistivity, good stability. Because of some of these properties, alumina sphere has been widely applied to petroleum, chemical industry and environmental protection industries, excellent high temperature infrared materials and electronic materials. Yttrium oxide (Y2O3), as high-performance ceramic materials, has received a great attention in the field of high temperature infrared materials and electronic materials, due to its excellent physical and chemical properties, including a high melting, a high corrosion resistivity, and no birefringence phenomenon. Colloidal processing enables to effectively control the agglomeration of green bodies, minimize impurity and strength-degrading defects, form complex shapes and high-volume production. Colloidal processing includes gelcasting, gel centrifugal casting, and so on.To prepare green bodies with a high packing density and uniform microstructure, a well-dispersed suspension is essential. In this paper, aqueous suspensions of yttria powder were prepared by dispersing yttria powder into deionized water with the addition of different dispersant. Effects of the type of dispersant, the concentration of the dispersant on the stability of the suspensions were characterized by viscosity measurement. The best stable suspension of Al2O3 was obtained by addition of 0.4 wt% TAC. And then, the optimal total amount and ratio of the organic monomer and cross-linking agent was determined by viscosity measurement. The results show that when the mass ratio of organic monomer and cross-linking agent is 10:1 and the total amount is 15 wt%, the viscosity of the slurry is minimum. In the process of gelcasting, the temperature as a function of time was measured, which indicates the higher the content of catalyst and initiator, shorter gel curing time was obtained, but the effect is not as good as the initiator of the catalyst.The commercial Y2O3 powder as starting material, preparation of transparent ceramics was achieved by gel centrifugal method. Effects of concentration of TAC on the stability of the suspensions were characterized by viscosity measurement and sedimentation experiment, the results show that the optimum concentration of TAC is 3.5 wt%. The obtained green bodies were pretreated by various process before vacuum sintering. The results shows that the green bodies were pretreated by pre-sintering at 700℃for 4 h, pressing for 142 MPa pressure, and pre-sintering at 1300℃ for 4 h, and then the highest transmittance of ceramic was obtained after vacuum sintering at 1700℃ for 5 h. The prepared colloidal suspensions with various solid loadings were subsequently consolidated into green compacts via gel centrifugal method. The results show that the transparent ceramics with highest transmittance were achieved by using the 35 vol% Y2O3 suspension consolidated into green compacts, and sintered in vacuum at 1700℃ for 5 h.The commercial Al2O3 powder as starting material, study on gelcasting preparation of alumina spheres. The optimal parameter of preparation of alumina spheres was determined by the Characterization of the degree of sphericity and surface morphology of alumina spheres. The results show that the alumina spheres with optimal performance were obtained by following parameters:the processing temperature is 120℃, the methyl silicone oil as oily medium viscosity is 12500 cs. The measurement of the wear rate shows that:higher solid content, lower wear rate was obtained, the wear rate alumina spheres isostatic-pressed before vacuum sintering is better, but the effect is not very obvious. |
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