The way of coloring of ZrO2 ceramics?
The chemical co-precipitation method is to use zirconium salt, stabilizer salt and coloring ion salt solution to mix, through the reverse position with alkali or carbonate, altogether generate double oxide or salt precipitation, and then heat and decompose to obtain oxidation Composite powder, Japan Toh Fuisaki et al. (200 successfully developed a black zirconia ceramic containing 2% ~ 6% (wt) colorant. The colorant is a spinel structure (Co-Zn,) (Fe-, AL) ,)2O4,(0≤x≤0.5,0≤y≤0.5). Co, Zn, FeAl colored zirconium oxide is obtained by co-precipitation method. This black zirconium oxide has a deep black color with jewel luster, and the color is very good for sintering. It is not sensitive to temperature changes and can be sintered at 1300~1500C without changing the color of the product.The chemical co-precipitation process is more complicated, but the obtained powder has high purity and excellent performance. However, the disadvantage of this method is that the complex co-precipitation ions of colored zirconia lead to complex reactions in the later sintering process. The zirconia stabilizer may react unexpectedly with colored ions, which affects the performance of the final colored zirconia product. On the other hand, it also affects the color rendering optical performance of the colored ions. In addition, this method is prone to agglomeration during the reaction process, and the dispersion of the prepared powder is poor, which affects the performance of the ceramic. In order to avoid the agglomeration of the powder, in the powder preparation process, the dispersant, surfactant and auxiliary agent are appropriately added to control the dispersibility and particle size of the powder.
(3)High temperature carburizing/nitrogen method
The high-temperature carburizing/nitriding method is to process the zirconia ceramics into shape and degreasing, and then carry out a low-temperature unprotected atmosphere bisque treatment, and then the treated zirconia cord-fired body is sintered at a high temperature under vacuum protection conditions. When placing the sample during sintering, a graphite crucible is used, and graphite paper is placed on the surface of the sample, and the carbon evaporated at high temperature is used to infiltrate the oxide surface to realize the black coloring of the oxide bonded ceramic (Zhong2005). The disadvantages of this method Yes: High requirements for equipment and vacuum environment: The color is mainly on the surface of the oxidized product: the black is not bright enough, and it may gradually fade during use. Miol 200 from Asurabu, Switzerland, uses high-temperature plasma nitriding to prepare golden oxide Hao ceramics. The sample of annual pottery is placed in a reaction vessel. The vessel contains ammonia and emotional gases. The mixed gas, nitrogen, hydrogen and the combined gas of your body, or the mixture of these two mixed gases produces a plasma, which will cause the surface layer of the product to form zirconium nitride (ZrN) or zirconium oxynitride after about 15-240min .
Wang and Xie (2009) of Tsinghua University used a non-uniform precipitation method to synthesize colored zirconia ceramics to overcome the serious internal problems of colorant volatilization caused by the solid phase mixing method and the shortcomings of complex reactions and difficult to control. They successfully prepared ZrO2 ceramics in various colors such as blue, black, pink, and cyan. The method is to coat a layer of colored ion hydroxide on the surface of ZrO2 powder, which can greatly shorten the mass transfer distance of colored ions during sintering. Therefore, in the crucible prepared by the heterogeneous precipitation method, the volatilization of colored ions or the reaction with the crucible are basically not observed after sintering, and the color obtained is uniform and consistent. Shows the prepared brilliant blue zirconia ceramic ring. The scanning electron micrograph of its internal microstructure is shown in the figure. It can be seen that CoAl2O4 and spinel crystals with coloring function are dispersed in uniform zirconia crystal grains.
Excerpts from "Structural Ceramics"
Author: Tsinghua University Professor Xie