Gel-casting Process And Preparation Of Zirconia Solid Microspheres

Gel-casting process is a kind of technology of in situ coagulation forming technology,which combines traditional ceramic forming process with organic polymerization. Evenlymixed with organic monomers, ceramic powders are in situ solidficated by monomerspolymerization. And a green body with high-strength and good uniformity is obtained afterdrying. Near-net-shape and complicated ceramics can be obtained directly by the process, andit’s significant for preparation of difficult machining sintered ceramics.In this work, the preparing process of zirconia slurry with low-viscosity andhigh-stability and gel-casting process are studied.In the preparation of zirconia slurry, the relationship between the viscosity of slurry andammonium citrate used as disperser is studied by single-variable-control method. Zirconiaslurry with low-viscosity of9mPa·s is obtained and when0.55wt%ammonium citrate isadded, and the slurry is a kind of pseudoplastic fluid which presents the phenomenon of shearthinning. We also find that the rising temperature will accelerate the organic polymerization.The slurry at50C can be kept for only18min after ball-milling. In order to lengthen thelifetime of the slurry to at least2h, the slurry ball-milled should be cooled and preservedunder35C.In experiment, acrylamide (AM) used as monomer and methaacrylamide (MBAM)used as cross-linking agent polymerize by N,N ’-methylenebisacrylamide (TEMED), a kind ofcatalyst, to realize ceramic forming. The relationship among bending strength of green bodies,AM and the mass ratio between AM and MBAM is discussed. A green body with the bendingstrength of23.5MPa is obtained when2.00wt%AM is added, and the bending strengtharises to74.4MPa,3.17times than23.5MPa, when the additive amount of AM arises to8.00wt%. After burn-out and followed by sintering, a sample with density of5.97g·cm-3andrelative density of98.19%is obtained.Rapid expansion of paint, printing ink and medicine facilitates the development ofsub-millimeter milling mediums, especially zirconia solid microspheres. But its difficultpreparation and high price limit its use. In this work, microsphere green bodies of size0.25~0.4mm are obtained by a simple and easy method which combines gel-casting process with interfacial tension theory. And zirconia solid microspheres of size0.2~0.3mm with goodsphericity are prepared after polishing, burn-out and sintering.