Preparation method of colored zirconia ceramics

Zirconium oxide ceramic has high strength, high toughness, wear resistance, corrosion resistance and other excellent properties, and is widely used in molds, cutting tools, ceramic bearings, Electronic components, biomedical materials and other fields. At present, as zirconia ceramics are widely used in the field of electronic products, especially as mobile phone backplanes, their single color has restricted their application and cannot meet people's requirements for the appearance of structural devices. Therefore, developing rich and colorful colors can greatly It has greatly expanded the application fields of zirconia ceramic materials and has broad development prospects.

With the continuous development of technology, the synthesis methods of colored zirconia ceramics are becoming more and more diversified. The key to its preparation technology is that the colored phase (such as CoO, Cr2O3, Fe2O3, etc.) can be evenly distributed in the ceramic matrix. The researched and synthesized colored zirconia ceramics must achieve a stable crystal structure, bright and uniform colors, good high temperature and chemical stability, and not destroy its inherent properties.

For colored zirconia ceramics, due to the small particle size, large surface area, and high surface energy of the particles that constitute the matrix and colored phase, the capillary force, electrostatic attraction, and van der Waals force between particles are prominent. In this environment, the nanopowder particles are extremely It is easy to agglomerate into larger particles, resulting in a significant reduction in the relatively good physical and chemical properties of nanocomposite ceramics. Therefore, in order to prepare zirconia ceramics with good performance and various colors, it is necessary to overcome the agglomeration phenomenon and make the colored phase evenly dispersed in the ceramic matrix material.

The preparation methods of colored zirconia ceramics mainly include: solid phase mixing method, chemical coprecipitation method, liquid phase infiltration method, high temperature carburizing method, etc.

1. Solid phase mixing method

The solid phase mixing method uses mixing ball milling technology to prepare colored zirconia powder. It mixes and ball-mills oxide particles such as colorants and mineralizers with stable zirconia nanopowder according to a certain chemical ratio. The solid particle grains are refined during this process, and a process that is conducive to low-temperature chemical reactions occurs. Microcracks, lattice distortion, surface energy increase and other phenomena.

At present, the solid-phase mixing method is the main method for preparing colored zirconia ceramics. Its advantages are: simple process, low cost, convenient operation and easy industrialization. The disadvantages are: the agglomeration of nanoparticles cannot be overcome, the coloring phase and matrix nanoparticles are unevenly mixed, and the ball milling time is long. The ball milling medium or the atmosphere may cause serious pollution to the powder.

2. Chemical co-precipitation method

The chemical co-precipitation method uses zirconium salt, stabilizer salt and colored ion salt solution to mix, react with alkali or carbonate, etc. to jointly generate hydroxide or carbonate precipitate, and then heat and decompose to obtain zirconium oxide composite. Powder. In the co-precipitation method, the metal cations in the solution precipitate simultaneously due to the excess precipitant to form a mixture, and in specialIn this case, it is required that the precipitated composite oxide or its precursor must meet a certain stoichiometric ratio, and the cations will precipitate in a certain ratio.

The advantages of the chemical co-precipitation method are: the obtained zirconia powder has high purity and excellent performance. The disadvantage is that due to the complex co-precipitated ions of colored zirconia, the reaction in the later sintering process is complicated. The zirconia stabilizer may react unexpectedly with the colored ions, thus consuming a large amount of it. On the one hand, this affects the performance of the final colored zirconia products, and on the other hand, it also affects the color-developing optical properties of the colored ions.

3. Liquid phase infiltration method

The liquid phase infiltration method is to first extract and degrease the injection molded zirconia ceramic body with water to obtain a green body with a connected pore structure, and then place it in a solution containing colored phase ions for infiltration. The colored phase ions penetrate into the interior of the body from the surface of the green body through the pores; the depth of infiltration is controlled by the length of the infiltration time, and finally various colored zirconia ceramics with excellent properties are produced. In addition, the green body obtained by water extraction and degreasing is directly used for impregnation because after water extraction and degreasing, a uniform and connected void structure will be formed inside the green body, which facilitates the uniform distribution of colored phase ions in the green body. As long as the impregnation is complete, colored zirconia ceramics with uniform color can be prepared.

The advantages of the liquid phase infiltration method are that the process is simpler, and the prepared colored zirconia ceramics have obvious advantages in color uniformity and physical properties. In addition, the liquid phase infiltration method can make full use of injection molding to produce various complex-shaped zirconia green bodies, thereby producing various complex-shaped colored zirconia ceramics.

4. High temperature carburizing/nitrogen method

The high-temperature carburizing method is mainly used to prepare black zirconia ceramics. The process is to process the zirconia ceramics into blanks, perform normal degreasing and dewaxing, and then biscuit the processed zirconia ceramics at low temperature without protective atmosphere. The zirconium green body is sintered at high temperature under vacuum protection conditions. A graphite crucible is used to place the workpiece during sintering, and graphite paper is placed on the surface of the workpiece. Use graphite to penetrate the zirconia surface at high temperatures to achieve black coloring of zirconia ceramicscolor.

In addition, researchers used high-temperature plasma nitriding to prepare golden zirconia ceramic materials.

1. Mobile phone back panel

Zirconia ceramics used in mobile phone backplanes have no interference, no magnetism, strong signal reception, various colors and never fade. In addition, they can also be used for ceramic covers for fingerprint recognition modules.

2. Smart wearable appearance parts

Zirconia ceramic material is scratch-resistant, non-shielding, and feels warm and moist to the touch.It has texture, good corrosion resistance and biocompatibility, and is used in smart wearable appearance parts.

3. Ceramic knives

Zirconium oxide ceramic knives have excellent properties such as ultra-high strength, wear resistance, sharp edges, no rust, no odor, and durability.