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The manufacturing method of zirconia products

The manufacturing of zirconia products has processes such as casting and molding. When using the slurry casting method, first pulverize the stabilized zirconia in a steel ball mill. The ratio of material, ball, and water is 1:3:0.8. After ball milling for 80 hours, the fine powder smaller than 1.76μm accounts for about 60%. If the fineness is all less than 1μm, the milling time can be extended to 100-120h. The ball-milled powder is treated with hydrochloric acid for 48 hours, and the amount of acid added is 2.5-3 times that of the material. After pickling, wash with water to neutral, and then dehydrated and dried to moisture less than 0.15%. Use this material to configure a neutral slurry in a plastic or ceramic ball mill. Material: ball: water: glue is 1:1.5:0, 16:0.15, mixing for 8-10 hours. The mud density is about 2.2g/cm3, with good suspension and fluidity. The slurry is poured into a plaster mold. The density of the molded part is about 3.6g/cm3. The green body is fired at 1800°C and kept for 2-4h. The bulk density of sintered products can reach 5.65g/cm3, and the porosity is about 0.2%.

If the molding process is adopted, two kinds of zirconia materials that are stable at different temperatures can be used: one is zirconia that is stable at a temperature higher than 1700℃, which is crushed and passed through a 3.327mm sieve for use as aggregate; Zirconium oxide stabilized at 1450℃, finely ground for 48h, used as base material. The two materials are mixed according to the ratio of 60%-70% aggregate and 40%-30% base material, plus 4%-5% 2.5% methylcellulose aqueous solution as a binder, and uniformly mixed and formed. Finally, it is fired at 1800-1840°C in a neutral or oxidizing atmosphere. In order to improve the thermal shock resistance of products, sometimes partly stabilized zirconia is used as a compound. The so-called partial stabilization means that only a part of the zirconia is formed into a stable cubic solid solution during high temperature treatment with insufficient amount of stabilizer, while the remaining part still maintains the tetragonal crystal form of crystal transformation. Of course, in the microstructure, the distribution of these two crystal phases should be very uniform. For the blank formed with this material, during the heating or cooling process, the sudden change in volume due to crystal change can offset part of the volume change caused by natural expansion, thereby reducing the overall volume change and improving the integrity of the product. Thermal shock resistance, because the fully stabilized zirconia still has a high coefficient of linear expansion.

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