zirconia powder – Zirconium Metal

Zirconia Ceramic Phone Backplane Stands Out in 5G Era

By the end of 2018, 154 mobile operators around the world are carrying out 5G technology tests or trials, and the number of countries participating in 5G has been expanded to 66. With the advent of 5G era, the mobile phone industry will usher in a new round of reform, and the mobile phone backboard market is facing a reshuffle.

Zirconia ceramic phone backplane stands out

5G era requires faster signal transmission, 1 to 100 times faster than 4G. 5G communications will use a spectrum of more than 3Ghz, with shorter millimeter-wave wavelengths. Compared with the metal backplane, ceramic backplane has no interference to signal and has incomparable superior performance of other materials, which is favored by mobile phone manufacturers.

The contrast of the backplane of several kinds of mobile phones

Among all-ceramic materials, zirconia ceramic has the advantages of high strength, high hardness, acid and alkali resistance, corrosion resistance and high chemical stability, as well as the characteristics of scratch and wear resistance, no signal shielding, excellent heat dissipation performance, and good appearance. Therefore, it becomes a new mobile phone body material after plastic, metal, and glass. The application of zirconia ceramic in the mobile phone is mainly two parts: backplane and fingerprint identification cover.

Preparation and difficulty analysis of zirconia cell phone ceramics

The preparation of zirconia ceramic backplane mainly includes the preparation, molding, sintering, grinding and polishing process of zirconia ceramic powder, in which the preparation of zirconia ceramic powder is the most important and most difficult part of the whole process.

Technological difficulties

The phone backplane powder of zirconia ceramic is nanocomposite zirconia. In the preparation of ceramics, the quality requirements include that the particle size distribution is normal, the particle shape is close to circular, the dispersion is good, and the purity is high. The preparation methods of nano-composite zirconia powders include the hydrothermal method, precipitation method, alcohol-brine hydrolysis method, and low-temperature gas-phase hydrolysis method.

The quality of powder directly affects the intrinsic quality and performance of finished products. High purity, ultra-fine particle size, narrow particle size distribution, and good dispersibility are important bases for evaluating the quality of ceramic powders. The powder agglomeration and surface modification of nano-composite zirconia have become two major problems. With the development of technology, researchers have found corresponding solutions.

Firstly, the agglomeration of zirconia powder is a big problem. Gan Xuexian et al. investigated the final depolymerization effect by designing and using different grinding equipment and process parameters. With d50＝1.355μm zirconia powder as the research object, when using vertical ball mill, vertical ball mill and horizontal sand mill as the grinding equipment, serving with φ2mm zirconia ball as the grinding medium, with m medium: m material = 5:1 medium material ratio grinding for 15h, detection zirconia slurry size after grinding, the results show that: the horizontal sanding machine has the best grinding effect, and the d50 of zirconia slurry is 0.303μm. When the horizontal sand mill is adopted as the grinding equipment, the grinding effect is best under the conditions that the ratio of medium material (m medium: m material) is 4:1, the solid content of slurry (w) is 45%, the linear speed is 10m•s-1, and the grinding time is 25h.

Secondly, in terms of surface modification of zirconia powder, Yue Liang et al. drew the following conclusions through experiments: the sintering activity of zirconia powder was significantly improved after horizontal stirring grinding and manual granulation, and the sintering density was close to 99.5% at 1400℃; after grinding zirconia powder, the bending strength of sintered samples was lower than that of the original powder mainly because of the large size defect. Therefore, it is necessary to have appropriate granulation technology to improve the powder forming performance; it is suggested that improving the stability of phase transition is beneficial to obtaining high-performance zirconia powders.

Stanford Advanced Materials supplies high-quality zirconia products to meet our customers’ R&D and production needs. Please visit https://www.samaterials.com/ for more information.

How is Zirconia Ceramic Cell Phone Panel Produced?

With the advent of the era of 5G signals, intelligent wearable devices are bound to shift from metal to glass and ceramics. Especially, in the mobile phone panel industry, more and more mobile phone manufacturers began to use zirconia ceramic material. So what is the manufacturing process of zirconia ceramic cell phone panel?

Ceramic powder

Microcrystalline zirconium is generally used as the raw material for the shell of 3C products. Zirconia powder is the most widely used ceramic material for the shell of 3C products due to its good appearance treatment effect and the advantages of phase change toughening.

Ceramic Machining

Ceramic shell molding processes such as mobile phones and smart wear mainly include injection molding, dry pressing molding, and tape casting. Injection molding is similar to plastic injection molding, which is mainly used to produce small and sophisticated ceramic parts with complex shapes. In general, the larger the size, the less advantageous the injection molding; dry pressing mainly produces flat products with high production efficiency; tape casting is an important forming method for thin ceramic materials. The above three molding methods can be used to produce mobile phone panels.

1. Injection molding

Ceramic Injection Molding (CIM) is a new process for ceramic parts manufacturing combining polymer Injection Molding with ceramic manufacturing.

2. Dry Pressing

Dry compression molding is a method to make the powder into a certain shape of the blank body by applying external pressure through the plunger of the press. Due to the moisture content of powder under 7%, the subsequent sintering time is reduced, so the forming efficiency is high and the cost is low, but the density is not uniform.

3. Tape casting

Tape casting is an important forming method for thin ceramic materials with high productivity and automation, but the shrinkage rate of firing is as high as 20-21%. It can be used to prepare high-quality ceramic films with a thickness of 10-1000 microns. Tape casting is used in the ceramic panel of MI 5 mobile phones and the ceramic fingerprint cover of various mobile phones.

4. Debinding and sintering

Debinding is the removal of organic matter from the body of an injection-molded billet by heating or other physicochemical means.

Under the action of high temperature, with the extension of time, the green body finally becomes a hard polycrystalline sintered body with a certain microstructure, which is called sintering. Sintering is a process to reduce the pores in the forming body, enhance the combination of particles and improve mechanical strength.

5. Postprocessing

The panel of 3C products, such as mobile phones and smart wearers, has very high requirements on the surface effect of engineering ceramics, such as smooth and clean surface, precise geometric size, fingerprint protection, and so on. This requires a complex post-processing process, including CNC machining, grinding, polishing, laser /PVD, AF processing, etc.

The above is all about the production process of the zirconia ceramic cell phone panel, I hope it can provide a reference for you. Stanford Advanced Materials supplies high-quality zirconia products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.

An Overview of Colored Zirconia Ceramics

Zirconia ceramics, with high strength, high toughness, wear resistance, corrosion resistance and other excellent properties, are widely used in mold, tools, ceramic bearings, electronic components, biomedical materials, and other fields. At present, with the wide application of zirconia ceramics in the field of electronic products, especially as the backboard of mobile phones, its single color has restricted its application and cannot meet people’s requirements on the appearance of structural devices. Therefore, the development of rich colors can greatly expand the application of zirconia ceramic materials in the field, which has broad prospects for development.

Overview of colored zirconia ceramics

With the 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 color phase (such as CoO, Cr2O3, Fe2O3, etc.) can be evenly distributed in the ceramic matrix. The color zirconia ceramics must have a stable crystal structure, bright and uniform color, high temperature and good chemical stability without damaging its inherent properties.

For colored zirconia ceramics, the capillary force, electrostatic attraction and van der Waals force between particles are prominent due to the small size, large surface area and high surface energy of the particles forming the matrix and colorizing phase. In this environment, nano-powder particles are easily agglomerated into a larger particle body, which leads to a significant decrease in the relatively good physical and chemical properties of nano-complex phase ceramics. Therefore, the agglomeration phenomenon must be overcome to prepare zirconia ceramics with good properties and diverse colors, so that the color phase is evenly dispersed in the ceramic matrix material.

Preparation of colored zirconia ceramics

The preparation methods of color zirconia ceramics mainly include solid phase mixing, chemical co-precipitation, liquid phase impregnation, and high-temperature carburization.

Solid-phase mixing

Color zirconia powders were prepared by solid-phase mixing with ball milling technology. It mixes oxide particles such as the colorant and mineralization agent with stable zirconia nanometer powder in a certain chemical proportion and grinds them into balls. Solid particles are refined in this process, resulting in micro-cracks, lattice distortion, and surface energy increase that are conducive to the realization of the low-temperature chemical reaction.

Chemical co-precipitation

After the solution of a zirconium salt, stabilizer salt and colorant ion salt is mixed, hydroxide or carbonate precipitation is generated by the reaction with alkali or carbonate, and then the zirconia composite powder is obtained by heating and decomposition. In coprecipitation, metal cations in a solution precipitate together to form a mixture due to an excess of precipitants. Under special circumstances, the composite oxides or their precursors that are required to be deposited must conform to a certain stoichiometric ratio, and cations are required to generate precipitation in a certain proportion.

Liquid phase impregnation

Liquid phase impregnation will firstly extract and degrease zirconia ceramic blank with connected pore structure after injection molding and then place it in a solution containing chromophore ions for impregnation. The colorized ions infiltrate into the surface of the billet through the pores of the solution, and the depth of infiltration is controlled by the length of infiltration time. In addition, the blank body obtained by water extraction and degreasing is directly used for infiltration, because the blank body after water extraction and degreasing will form a uniformly connected void structure, which facilitates the uniform distribution of chromophore ions in the blank body. Uniform color zirconia ceramics can be prepared only if they can be soaked completely.

High temperature carburizing/nitrogen

High-temperature carburizing is mainly used to prepare black zirconia ceramics. The technological process is to process zirconia ceramic into a blank, normal degreasing, dewaxing, at low temperature without protective atmosphere element burning treatment, and then the processed zirconia green blank under vacuum protection conditions for high-temperature sintering. Graphite crucible is used to place the workpiece during sintering, and graphite paper is placed on the workpiece surface. The black coloring of zirconia ceramics was realized by graphite infiltration into the zirconia surface at high temperatures.

Applications of color zirconia ceramics

The backplate of a mobile phone

Zirconia ceramic used in mobile phone backplate has no interference, no magnetic, strong reception signal, as well as color diversity, besides, it can also be used for fingerprint identification module ceramic cover plate.

Smart wearable appearance parts

Zirconia ceramic material has the advantages of scratch resistance, scratch resistance, no shielding, warm and moist hand texture, good corrosion resistance and bio-compatibility. It is applied to intelligent wearable appearance parts.

Ceramic knives

Zirconia ceramic knives have excellent characteristics such as ultra-high strength, abrasion resistance, sharp edge, no rust, no odor, and durability.

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Main Factors that Affect the Performance of Ceramics

The main raw material of zirconia ceramics is high purity zirconia powder, and its performance and content have a great impact on zirconia ceramics. Besides that, the properties of zirconia ceramics are affected by other factors. In order to prepare high-performance zirconia ceramics, we should control the main influencing factors, including raw material size, molding method, and sintering.

Forming method

Zirconia ceramics with low porosity and high density have excellent jointing properties. High density means that the grains in the ceramic body are closely arranged, and it is not easy to form a destructive breakthrough point when subjected to external loads or corrosive substances.

The forming method is the key to obtaining the calcium density of the ceramic embryo body. Zirconia ceramics are usually formed by means of dry pressing, isostatic pressing, and hot die-casting. Different methods have different characteristics and have different effects on sintering properties as well as the microstructure of curing rate ceramics. Generally, grouting and hot die-casting are the main technologies for products with complex shapes, while dry compression molding can be adopted for products with simple shapes. Generally speaking, the density of dry-pressed products is better than that of hot-die-cast products.

The particle size of the raw material

The particle size of raw material has a great influence on the properties of products. Only when the raw material is fine enough can the final finished product be fired into a microstructure, which makes it have good wear resistance. The finer the zirconia powder particles are, the more active they are and the sintering can be promoted.

Due to the difference between corundum and glass phase linear expansion coefficient, the stress concentration at the grain boundary can reduce the risk of cracking. The fine grain can also hinder the development of micro-cracks, and it is not easy to break into transgranular, which is conducive to improving fracture toughness and abrasion resistance.

Sintering

Sintering of ceramic is the densification process of raw ceramic at high temperatures. With the increase in temperature and time, the adhesion between powder particles and the strength of sintered body increase, the aggregation of powder particles becomes a strong polycrystalline sintered body with a certain microstructure, and the required physical/mechanical properties of products or materials are obtained. The densification rate and the final structure of the sample often reflect what kind of heat treatment process it has gone through.

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How is the Zirconia Ceramic Made?

As the most important type of advanced ceramics, zirconia ceramic material is an important basic material for the development of the modern high-tech industry. Zirconia is widely used in the market, and its specific applications include the solid fuel cell, automobile exhaust treatment, dental materials, ceramic cutting tools, and zirconia fiber core plug.

However, as mobile 5G era approaches at any time, zirconia ceramics become the hot spot of the industry again due to its characteristics such as warm feeling, anti-scratch and wear resistance, no signal shielding, and excellent heat dissipation performance.

Zirconia is insoluble in water, sulfuric acid, hydrochloric acid, and nitric acid. It is slightly soluble in hydrofluoric acid and concentrated sulfuric acid when heated. Pure zirconia is an insulator at room temperature. Adding a stabilizer can increase its conductivity and show ionic conductivity at high temperatures. There are three crystal types of zirconia. The crystal parameters and the schematic diagram of the structure of the three crystal types are shown below.

Zirconia ceramics have high hardness, wear resistance, high-temperature thermal stability and impact resistance. The preparation of high-performance zirconia ceramics depends on high-quality zirconia powder and optimized sintering process parameters.

Preparation of high-quality zirconia powder

The preparation methods of high-quality zirconia powder mainly include the physical method and the chemical method. The physical methods include high-temperature spray pyrolysis, spray induction coupled plasma pyrolysis and freeze-drying; chemical methods include gas phase, liquid phase, and solid-phase method. Among them, the liquid phase synthesis method has high efficiency, fine powder particle quality, and simple equipment, so it has been widely used.

The sintering method

Sintering process parameters include sintering temperature, sintering pressure and sintering time. Ceramic materials with very different microstructures and properties can be obtained when the same ceramic materials adopt different sintering processes. At present, the sintering process of zirconia ceramics at home and abroad has pressureless sintering, hot pressing sintering, hot isostatic sintering, and discharge plasma sintering. Pressureless sintering, also known as traditional atmospheric sintering, is the sintering of a prefabricated ceramic body under atmospheric pressure and high-temperature conditions; hot press sintering is a sintering method for applying axial pressure to the powder in the mold; spark plasma sintering (SPS), also known as plasma-activated sintering, is a new rapid sintering technology.

Stanford Advanced Materials supplies high-quality zirconia powder and related products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.