Study On The Molding Process Of Monodisperse And Millimeter-grade Zirconia Ceramic Spheres

Both internal gelation process and gel-casting process for preparing monodisperse and millimeter-grade ZrO2 ceramic spheres were investigated in this paper. ZrO2 ceramic spheres prepared by these two processes had uniform sizes and perfect spheral shapes. The first process was internal gelation process. In this process, ZrOCl2?8H2O was used as raw material with hexamethylenetetramine (HMTA) and urea as solidified agents. Metal oxides, such as Y2O3 and MgO, were used as stabilized agents to prepare different constituents ZrO2 ceramic spheres. The second one was gel-casting process. In this process, precursor of zirconia stabilized by Y2O3 was used as raw material. Acrylamide (AM) and N, N′-methylenebisacrylamide (MBAM) were used as organic monomer and cross-linker. Poly (acrylic–acid– ammonium ) (PAA-NH4) was used as dispersant. Ammonium persulfate was used as initiator.The optimum process parameters were determined through our experiments. And the prepared samples were characterized by FT-IR, TEM, TG and DTA, SEM, XRD, BET, and so on. The experimental results showed that, in the first process, the optimum concentration of ZrOCl2?8H2O was1.6mol/L.The optimum ratios of HMTA to metal ions and urea to metal ions were 0.68 and 0.57. And molding temperature was 90oC. The final diameter of the ceramic spheres was between 600μm and 1200μm and directly determined by the diameter of the nozzle. Sintered at 1550oC, ZrO2 ceramic spheres prepared not only had perfect spheral shape and uniform size, but also had smooth and bright surfaces. The apparent density of ZrO2 ceramic spheres stabilized by Y2O3 was 5.10g/cm3. The mechanical strength was 900~1100g/per sphere. The specific surface area was 0.55~0.80m2/g. With MgO and/or Y2O3 as stabilized agents, the spheres had the characteristics of PSZ or TZP materials.In the second process, the optimum contents of solid loading and organic monomer were 29.5wt% and 20wt%, respectively. The content of initiator was in the range of 0.4wt%~0.6wt%. The molding temperature was between 80oC and 85oC. With the pH value controlled from 8 to 9, the slurry, which was added into 1.2wt%~1.6wt% PAA-NH4 as dispersant, was very steady. The gelled spheres prepared by this process had high mechanical strength. The final diameter of the ceramic spheres could be controlled in the range of 800~2000μm. Sintered at 1550oC,...