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.
Compared with traditional iron, copper, nickel, and other metal elements, zirconium has a lower density and smaller thermal expansion coefficient. In addition, zirconium has a low thermal neutron absorption cross-section (only 0.18×10-28 m2) and good corrosion resistance, which makes zirconium and zirconium alloys have a wide range of applications in the nuclear industry, aerospace and other special fields.
Zirconium and its alloys have been widely used as cladding materials in nuclear reactors. Zirconium and its alloys reflect neutrons back into the reactor more efficiently than stainless steel, greatly saving uranium fuel; Zirconium alloy has good corrosion resistance at high temperature and high-pressure steam of 300 ~ 400 ℃, which also makes the reactor have a long service life. Therefore, zirconium is regarded as the first metal in the atomic age.
Development status of zirconium and its alloys
Zirconium, which is found in the earth’s crust at about 220 g /t, ranks 20th, ahead of other common metals such as copper, nickel, lead, and cobalt. Initially, zirconium alloys were mainly used as cladding materials in the nuclear industry. In recent decades, zirconium alloys have been widely used in the chemical industry, medical industry, and some special fields.
Zirconium alloy for nuclear use
Zirconium alloys have been widely used in the nuclear industry because of their very low thermal neutron absorption cross-section and good resistance to high temperature and pressure corrosion. France, the United States, Germany, and Russia have developed a series of zirconium alloys for nuclear use. At present, Zr-2, Zr-4, Zr2.5nb and ZIRLO, E635, M5, and NDA zirconium alloys have been successfully applied in the nuclear industry. These newly developed zirconium alloys have lower radiation creep properties and better resistance to iodine stress corrosion. In addition, they are able to meet the requirements of high burnup of the fuel assemblies, increasing the service life of the assemblies to 30 years.
Corrosion-resistant zirconium alloy
Zirconium has excellent corrosion resistance against most organic acids, inorganic acids, strong alkalis, and some molten salts. Therefore, zirconium can be used to improve the service life of some key components in corrosive environments. Another way to improve the corrosion resistance of alloy parts is surface pretreatment. In industry, zirconium is placed in high-temperature air to obtain a dense oxide film, so as to improve the corrosion resistance and erosion resistance of zirconium and its alloys. The results show that the corrosion rate of zirconium treated by surface oxidation in sulfuric acid medium is only 5% of that of pure zirconium, but the erosion resistance is increased by twice.
At present, zirconium is widely used as corrosion-resistant material in the chemical industry, and it has been widely used in the heat exchanger, dike washing tower, reactor, pump, valve, and corrosion medium pipeline. For example, zirconium alloys have been used to produce concentrated and hydrolyzed tubes in hydrogen peroxide production lines, while zirconium pressure reducing valves, agitators and flow meters are used in fertilizer production, sewage treatment, and dye industries.
Biomedical materials are a new high-tech material in recent years, and biomedical alloys must have good compatibility and corrosion resistance with the environment of biological fluids. Zirconium is valued by researchers for its good biocompatibility, elastic modulus similar to bone and corrosion resistance. Ti6Al4V, a titanium alloy implanted earlier in hard tissues of the human body, has an elastic modulus of nearly 110 GPa, which is much higher than the elastic modulus of 15 ~ 30 GPa of natural bones of the human body.
High-strength zirconium alloy
In the fields of space exploration, deep-sea exploration, and high-speed railway, there are often some special operating environments, such as the alternating temperature environment of -200 ~ 200 ℃, continuous space irradiation, and relative motion of structural parts, etc. Under these special circumstances, long-serving structural components are often faced with fatigue damage, dimensional instability, atomic oxygen erosion, and friction wear. At present, the structural parts used in these special fields are mainly made of 20Cr, GCr15, and other alloy steel materials, which often have problems such as poor radiation resistance, easy damage of moving parts, high density, and high cost.
Compared with traditional alloy steels, zirconium and its alloys have several important potentials:
The thermal expansion coefficient of zirconium is small and the size structure is stable, so it has the potential to produce precise structural components;
It has the potential of resisting space radiation damage;
It has the potential to resist atomic oxygen erosion;
Therefore, zirconium and its alloys are expected to adapt to unconventional environmental conditions in special fields and have the potential to be used as structural components in special environments.
Zirconia ceramic materials are gradually being widely used in the field of micromachinery, because of its maintain excellent properties such as high-temperature resistance, oxidation resistance, acid and alkali corrosion resistance, hardness, etc.
The development of science and technology has made the miniaturization technology of zirconia ceramic materials become an important issue concerned by all countries, while the equipment tends to be miniaturized, and zirconia ceramics have a broad application prospect in the fields of automobile, medical treatment, aviation, aerospace, military, and environmental detection.
All countries in the world began to invest a lot of money, scientific research forces and too micromechanical system research. Organizations such as the National Natural Science Foundation of the United States and the Department of Defense attach great importance to MEMS（Micro-electromechanical Systems）technology and invest a lot of money in related research; The European Union has set up a multi-functional Microsystems research cooperation agency to strengthen interaction among countries; Japan has formulated the nano-manufacturing plan, the AI（artificial intelligence）technology plan, the microrobot plan, and established the micro machinery center and the micro machinery society; At present, there are more than 60 units engaged in MEMS research in China, and some scientific achievements have been made in the field of sensors and micro-actuators.
Zirconia ceramics are used in micro pressure sensors to detect engine inlet pipe pressure, micro accelerometers for vehicle safety airbag systems, and micro angular velocimeters for wheel sideslip and roll control. Microdevices such as micro pumps, microvalves, micro tweezers, and micro flowmeters applied in zirconia ceramics, and the micro-inertial measurement device, micro-whole analysis system, RF sensor, etc. are used in the military field. Moreover, zirconia ceramic materials can be used as a micro burner, a microreactor, and a pressure sensor at high temperatures and they can also be used as a composite, bone tissue scaffold, and in other biomedical fields because of their good biological solubility.
Alumina (Al2O3) is a very common technical ceramic material. Zirconia (ZrO2), including yttrium stabilized zirconia (YSZ), is also widely used in machinery industries. Since both of them are oxide materials and could be sintered without vacuum, they share a lot in manufacturing equipment and have a similar appearance. However, there are still quite a lot of differences between these two materials.
Price: alumina VS zirconia
The most significant difference between these two materials is the price. Cost for zirconia is more than doubled for even the best alumina material. One of the reasons is the cost of the raw material. Compared with Zirconium, Aluminum is far more abundant in the crust and it’s much cheaper. On the other hand, Yttrium oxide, widely used as a stabilizer for Zirconia, is a rare earth element with limited sources.
However, it is the cost of shaping zirconia that contributes the major part. The density of zirconia is much higher than alumina and the wear resistance of zirconia is far better than alumina. To ground down the same thicknesses for zirconia takes almost 10x more time than alumina and consumes more diamond tools. Also, since the thermal shock resistance for zirconia is poor and requires a higher sintering temperature, the sintering process also costs more than alumina.
Applications: alumina VS zirconia
As the wear resistance for zirconia is much better, it is frequently used as mortar and pestles, grinding jars and grinding media, bearing balls and ceramic parts in valves and pumps. Zirconia parts will last longer in machines and have less contamination than grinding jars. Zirconia is generally better in mechanical applications but alumina is a better bulletproof material due to the lower density.
Although zirconia could withstand higher temperatures, application in industrial furnaces is rare. The advantage in working temperature is not quite significant, while the cost for zirconia is much higher.
High-density ZrO2 also provides better corrosion resistance. Zirconia could survive longer in a highly corrosive environment and is considered better material in chemistry laboratories.
Generally, zirconia performs better if the density and heat shock resistance is not considered. Stanford Advanced Materials (SAM) is a trusted supplier of customized zirconia products, such as zirconia rods, zirconia crucibles, zirconia tubes, etc. Please visit http://www.samaterials.com for more information.
The Fingerprint recognition module is widely used in intelligent portable devices because of its fast, safe, convenient, and other advantages. However, due to the small area of the fingerprint module and complex application environment, it requires high identification sensitivity and speed, which also puts forward very high requirements for fingerprint identification chips and surface protection materials.
At present, there are two commonly used fingerprint identification schemes: pressing on the front of the sapphire cover and coating on the back.
Cost and Performance
In terms of cost and performance, sapphire has high hardness and corrosion resistance, but it has some weaknesses such as high cost and weak anti-falling ability, while the coated back fingerprint recognition scheme has the disadvantages of easy wear and sweat corrosion due to the low hardness of the coating.
Operation
In terms of operation, the two schemes have their own merits. The back fingerprint identification is convenient only for holding the index finger of the hand, while other fingers are inconvenient, and it can’t be used on a plane, it has to be picked up, too, which is not convenient in some special applications scenarios (such as driving). Meanwhile, the positive fingerprint is much smoother for the current hot fingerprint payment.
Appearance
In terms of appearance, the texture of backside fingerprint recognition is slightly poor, and it is easy to destroy the overall aesthetics of the backside putting fingerprints on the front not only makes the back of the phone more beautiful but also more in line with users’ habits and aesthetics.
Overall, a positive fingerprint is more popular with users, but it costs more. Many years of research have proved that zirconia ceramic cover products can be used for positive pressure fingerprint identification schemes.
The ceramic cover is zirconia ceramic (ZrO2), also known as the zirconium gem. It has superior hardness, toughness, insulation, heat conduction, and other advantages, showing abrasion resistance, fall resistance, corrosion resistance, high-temperature resistance, and other excellent characteristics, which is very suitable for pressing fingerprint identification module cover.
Zirconia ceramic is a cost-effective alternative to sapphire, and the zirconia product has been used in many well-known brands of mobile phones, which has the following advantages.
High hardness
The hardness of zirconia ceramics is 8.5 and that of single crystal alumina (sapphire) is 9, so they are quite similar in wear and scratch resistance.
High permittivity
The permittivity of zirconia is 32-35, which is three times that of sapphire, while all other materials are within 10. This characteristic is beneficial to improve the capacitance difference between the high and low levels of fingerprint identification module, so that fingerprint identification is more sensitive, the success rate is higher, and the speed is faster.
Thin in thickness
At present, the thinnest mass production thickness is as low as 0.1mm under the protection of falling strength of the zirconia protective layer, which is easier to identify than the thinnest sapphire cover with a thickness of 0.3mm. If the thickness is the same as that of sapphire, the strength and fall resistance of zirconia protective coating will be significantly better than that of sapphire.
Good processability
Zirconia ceramics are directly prepared by casting, polishing, and other ceramic processes. Its process is simple and its shape is easy to process, so it costs less than sapphire.
Zirconium, chemical symbol Zr, atomic number 40, melting point 1852°C, is one of the high melting point metals. Zirconium with special excellent properties, such as the resistance to high temperature, oxidation, corrosion, and abrasion, all of which made it a wide range of applications as the structured and functional ceramic material in many industrial sectors, especially in the high-tech industry.
Zirconium products and their applications
Zirconium silicate
Zirconium silicate is an important kind of traditional zirconium product. Products can be prepared with zircon sand as raw material, after grinding, calcination, and powder, is a kind of high-quality and inexpensive ceramic glaze opacifying agent, mainly used in ceramics and porcelain, building ceramics color glaze production, has been widely used in high-grade refractory materials, precision casting, emulsified glass and other industries.
Zirconium carbonate
Zirconium carbonate is mainly used as cosmetic additives and waterproof agents, flame retardants, sunscreen, fiber and paper surface additives, and can be used for preparing zirconium cerium catalytic composite material, is an important raw material for textile, papermaking, paint, cosmetics industry, the amount of growth in recent years.
Zirconium oxychloride
It can be used for other zirconium products such as two – zirconium oxide, zirconium carbonate, zirconium sulfate, zirconium and hafnium compound preparation and separation of zirconium and hafnium metal material, can also be used for textile, leather, rubber additives, metal surface treatment agent, coating driers, refractories, ceramics, catalyst, fire retardant, and other products.
Fused zirconia
Fused zirconia is mainly used in the production of glazes and refractories. Due to the high content of impurities in the fused zirconia, the use is limited.
Zirconium sulfate
It is the important raw material in the production of leather tanning agent, wool processing agent and paint surface oxidation agent, can be used as a catalyst carrier, amino acid, and protein, precipitant, and deodorant, intermediate raw materials are for zirconium chemicals and metal zirconium and hafnium.
Zirconium oxide
The white solid, non-toxic, tasteless, has enough stability of alkali solution and many acidic solutions, suitable for precision ceramics, electronic ceramics, optical lenses, glass additives, dissolving zirconia brick, ceramic pigment, glaze, artificial stone, refractory materials, grinding and polishing industry and products.
It is also known as semi-stable, stable zirconia is a white powder with non-toxic, tasteless, and stable chemical properties, the specific surface area is controllable, manufacturing all kinds of special ceramics, advanced refractories, new energy materials, optical communication devices, based on raw materials.
Zirconia structural ceramics
Using the composite zirconium oxide as the raw material, including two kinds of products such as zirconia grinding and zirconia structure, the structure of zirconia mainly includes the zirconia special ceramic valves, fiber optic connectors, ceramic knives, watches accessories, ceramic scissors, textile porcelain, etc.
Since Zirconium has very good chemical corrosion resistance, zirconium shapes, such as zirconium tubes and zirconium rods are used to make equipment for the chemical industry.
Nuclear grade zirconium
It is an important strategic metal used primarily for nuclear-powered aircraft carriers, nuclear submarines, and civilian power reactors, as well as the cladding of uranium fuel elements.
Industrial grade zirconium
It is mainly used for the production of industrial-grade zirconium – chemical corrosion resistance equipment, military industry, electronic industry, pipeline valve materials, special high strength and high-temperature alloy materials, electric vacuum, and lighting industry getter.
Firearm zirconium
It is also used in the combustion of the flame zirconium sponge, and also can be used in alloy additives and metallurgical deoxidizers, chemical industry, civil flash fireworks and so on.
To maintain their leading position in the field of aviation power in the 21st century, aero-engine companies around the world are seeking new ways to improve the performance of military and civil engines and maintain their competitiveness. Half of that will depend on material improvements, including low-temperature polymer composites and high-temperature ceramics; the other half relies on improving design guidelines, methods, and procedures.
As the key to the improvement of military engine materials is to rely on high-temperature ceramic materials, the military engine will be the primary verifier of ceramic technology. Why is it necessary to use chemical zirconia ceramics? The operating temperature of the existing engine is already very high, and the only way to increase the temperature again is through the fine design of the cooling air circuit or the increase of cooling air volume.
However, the effects of these methods follow the law of diminishing, and only by improving the working temperature of the material can the maximum effect be achieved. Because raising the operating temperature can improve working efficiency, reduce fuel consumption and obtain the maximum thrust, using the saved high-pressure air for cooling for circulation can also improve the thrust and efficiency. Another option is to reduce weight by choosing materials with greater specific strength and greater stiffness. At present, only ceramic materials have the potential in this respect.
The application of ceramics to aero-engines will be developed with new materials and manufacturing methods. Considering the brittleness of ceramic materials and the lack of design and use experience, the process will be very long, no less than 15-20 years of metal materials. The applications of chemical zirconia ceramics in aviation are as follows.
Chemical zirconia ceramics have high-temperature resistance, low density, good oxidation resistance, corrosion resistance and wear resistance. In the case of the cooling, the working temperature of chemical zirconia ceramics can reach 1600 ℃, the density is only 40% of that in the high-temperature alloy, and the same volume of parts can reduce the weight by about 60%, which can greatly reduce the centrifugal load of the high-speed rotor. The use of ceramics also simplifies the chemical zirconia by reducing or eliminating the cooling system, making the engine compact.
The increasing turbine inlet temperature is the key to improving the thrust-to-weight ratio of the aero-engine and reducing fuel consumption. Sages for example, when the ratio is 10 level, the temperature of the engine turbine can reach above 1500 ℃, while the use temperature of high-temperature alloys and intermetallic compounds highest is less than 1200 ℃. Therefore, the research of high-temperature chemical zirconia ceramics and their ceramic matrix composites becomes one of the key technologies for high thrust-weight ratio aero-engines.
Radar remains one of the most reliable means of detecting military targets in future wars. The essence of stealth technology is to reduce the target’s RCS（Radar Cross-Section）, that is, to select materials with good radar wave absorption to reduce its RCS.
Absorbing materials can be divided into coating type and structure type according to process and bearing capacity. The former has a poor bearing capacity and low strength, while the latter is a new functional composite chemical zirconia material, which has the characteristics of absorbing waves and can be directly used as the chemical zirconia material for aircraft.
We use the excellent mechanical and physical properties of chemical zirconia ceramics to carry out the research on absorbing materials, which can not only enhance the national defense force but also is an important aspect of expanding the application of chemical zirconia ceramics. Some new nano absorbents and their composites are being applied in this field, such as nano Silicon Carbide (SiC), nano nitride, carbon nanotube (CNT), and other nanocomposites.
In the mid-1980s, the United States developed an aerospace aircraft program that required both high-temperature tolerance and light mass. For this purpose, a variety of new high-temperature materials were developed, including advanced resin matrix composites, metal matrix composites, ceramic matrix composites, and carbon/carbon composites. Ceramic material is the preferred material for missile radome because of its excellent mechanical, thermal and electrical properties. The radome is the most widely used ceramic matrix composite material in missile structure.
Missile radome
The missile radome is located at the front end of the missile. Its function is to protect the navigation antenna from damage so that the missile can effectively hit the target. It is not only an important part of the aerodynamic shape of the missile but also the protection device of the antenna. During the flight of the missile, the radome should not only withstand aerodynamic heating and mechanical overload, resist the erosion of rain, sand, and other adverse working conditions, but also meet the stringent requirements of electrical performance proposed by the missile control loop. Therefore, the missile radome material should have the following properties:
Excellent dielectric properties
In the guidance system, the transmission efficiency and aiming error of the radome are very sensitive to the dielectric properties of the material and its relationship with temperature and frequency. It is required that the material has low dielectric constant (10) and dielectric loss, and the dielectric properties do not change obviously with temperature and frequency.
Good heat resistance and thermal shock resistance
The high Mach number of the missile can make the radome of instantaneous heating rate is as high as above 120 ℃ / s, so the material is required to have good thermal shock resistance, and the molecular structure of the material is required to be stable when the temperature is raised, and the material properties (such as dielectric properties and mechanical properties) change little to ensure that the radome can work normally when the temperature is raised.
High-strength structural properties
The strength of the radome material should be high and rigid enough to satisfy the mechanical stress and bending moment caused by the longitudinal or transverse acceleration of the aerodynamic forces in the spacetime of the missile flying at high speed.
Resistance to rain erosion
It plays a decisive role in the design allowable range of impact Angle and the sensitivity of aircraft in rain erosion.
Low-temperature sensitivity
The dielectric properties and strength properties of general materials change obviously when they work at high temperatures. Therefore, the properties of the radome material, especially the dielectric properties and strength, are affected by the temperature change as little as possible.
Ceramic-based missile radome
Ceramic-based missile radome materials mainly include silicon nitride-based, silicon oxide-based and phosphate-based materials. Silicon nitride ceramics have not only excellent mechanical properties and high thermal stability but also low dielectric constant. Its decomposition temperature is 1900 ℃, its erosion resistance is better than fused silica, and it can withstand 6 ~ 7 Ma rating of flight conditions. Silicon nitride ceramic composite radome is one of the main research targets in various countries, which has been identified as the most promising radome material by the test of the Georgia Institute of Technology. Yttria Stabilized Zirconia (YTZ), also known as yttria-zirconia, is the strongest ceramic material. This material offers the highest flexural strength of all zirconia-based materials, and the research on zirconia-based materials as missile radome is in progress.
Silica-based material
Because of the high flying Mach number of the missile and the relatively long heating time, if the radome of the medium-range missile is made of a single quartz ceramic material, it cannot meet the bearing requirement of thermal stress. In order to meet the requirements of medium and long-range ground-to-ground tactical and strategic missile radome, quartz glass, high-silica puncture fabric and orthogonal tri-directional quartz fabric reinforced silica matrix composites have been developed and successfully applied.
Phosphate-based materials
Phosphate matrix composite material is a kind of Russian characteristic permeable material, which is made by impregnating cloth or fabric with a phosphate solution and then curing under pressure. Aluminum phosphate has stable performance in 1500 ~ 1800 ℃. At present, such materials have been used in cruise missiles, anti-missile missiles, tactical missiles and space shuttles. The most obvious disadvantage of phosphate is that it is highly hygroscopic, so the surface of the composite material needs to be coated with an organic coating for moisture-proof treatment.
Silicon carbide ceramic matrix composites
Silicon carbide ceramic matrix composites have a series of excellent properties, such as low density, high-temperature resistance, ablation resistance, erosion resistance, and oxidation resistance, and it has a wide application prospect in the field of aerospace. Since the late 1980s, the United States has successfully developed a series of C/SiC, SiC/SiC ceramic matrix composites, which can be applied to the re-entry nose cone of missiles, the front end of wings and other heat-resistant structures.
Zirconia is a new structural ceramic material developed in the 1970s. It is widely used in metallurgy, electronics, chemical industry, machinery and other fields due to its abrasion resistance, corrosion resistance, high strength, and high melting point.
Zirconia ceramic material, the most important material in advanced ceramics, is an important basic material for the development of the modern high-tech industry. In particular, nano-oxide ceramics with their special structure and performance has become the focus of the industry. The following is a brief introduction to the powder materials needed to prepare nano zirconia ceramics.
Ni-P coated nano zirconia composite powders
The preparation process of Ni-P coated nano zirconia (ZrO2) composite powders is firstly to prepare nano-ZrO2 powders by the chemical precipitation method, and then to prepare Ni-P nano-ZrO2 powders by an electroless plating method. Since ZrO2 has no autocatalytic activity in the electroless nickel plating solution, it is necessary to pretreat ZrO2 nanoparticles. Generally, Pd2+ is directly adsorbed on the surface of ZrO2 powder by the one-step palladium catalysis method, and then Pd2+ is reduced to palladium in a reducing solution so that the surface of nanopowder has the catalytic activity of electroless nickel plating. The two-step sensitization-activation method is usually used in the pretreatment of non – conductive powders. However, it is difficult to remove the residual nickel ions in the powder after two-step treatment, which often brings adverse effects on the activity of the powder. At present, one-step palladium catalysis and in-situ palladium pretreatment are used.
At present, Ni-P coated nano zirconia composite powders have been widely used and studied in semiconductor nanomaterials.
Zirconia toughened alumina ceramic is one of the most widely studied structural ceramic materials. The toughening mechanism of zirconia toughening alumina ceramics is the refinement of matrix grain, the toughening of phase change, the toughening of microcrack, and the turning and bifurcation of crack. The properties of zirconia toughened alumina ceramics are mainly determined by the microstructure formed during sintering, and the microstructure is mainly determined by the powder state of raw materials. Therefore, the preparation of high-quality Al2O3/ZrO2 nanocomposite ceramic powders is the prerequisite for the preparation of zirconia toughened alumina ceramics with excellent properties. The preparation methods of Al2O3/ZrO2 nanocomposite ceramic powders mainly include the mechanical mixing method, multi-phase suspension mixing method, the sol-gel method, chemical precipitation method, etc.
Alumina is a kind of high-strength matrix in the composite ceramic system of zirconia toughening alumina, and the zirconia in the intercalation provides a phase change toughening mechanism. The use of ZrO2 phase change properties to toughen ceramic materials is still one of the main research topics of ceramic toughening in the future.
Zirconia toughened alumina composite ceramics have excellent corrosion resistance, thermal shock resistance, high strength, and toughness, as well as wide application prospects. Zirconia toughened alumina composite ceramics can be used to make ceramic cutters for the processing of cast iron and alloy, and the interface structure of engineering ceramics can be made to extend the service life of engineering materials. Alumina toughened with zirconia can be used to make wear-resistant ceramic balls. Due to its good biocompatibility, alumina can also be used as a biomedical material for the reconstruction and repair of hard tissues (teeth).
Boron nitride-zirconia composite powder
Boron nitride-zirconia composite powders were prepared by mechanical mixing method. Boron nitride, zirconia, and additives were used as the main raw materials. After mixing, the powders were ball-ground and mixed in an alcohol medium, and then the zirconia composite ceramics were sintered in a hot press sintering furnace. Due to the poor sintering capacity of pure boron nitride and its difficulty in sintering densification, CaO, B2O3, Al2O3, and ZnO are generally added as sintering AIDS.
Boron nitride-zirconia composite ceramics are characterized by high strength, high toughness, high thermal conductivity, low expansion, and excellent physical and chemical properties, such as chemical inertness and chemical corrosion, which are present in molten metals. In addition, it also has excellent thermal shock resistance, erosion resistance, wear-resistance and easy processing and other properties, which make the material suitable for thin strip continuous casting side seal plate, jet forming liquid guide pipe, the nozzle for metal spinneret, continuous casting functional refractories and other fields.
Nano cerium-zirconium composite oxide powder
The preparation methods of nano cerium-zirconium composite oxide powders include high-temperature roasting, the sol-gel method, coprecipitation method, hydrothermal method, and solid-phase reaction method. High-temperature roasting was carried out in a water-ethanol solvent, and the suspension consisted of dry Al (NO3) 3•9H2 O•Ce (NO3) 3•6H2O and monocline phase zirconia nano-powder was pyrolyzed by high-temperature, Al2O3 doped CeO2 coated monoclinal zirconia powders with a particle size less than 100 m were prepared.
Nano cerium-zirconium composite oxide materials are used as auxiliary catalysts, mainly used in automobile exhaust treatment, with good high-temperature stability, high REDOX ability, high oxygen storage, and release capacity.
Zirconium dioxide (ZrO2) is a kind of metal oxide material with many excellent properties such as high melting point (2700 ℃) and high boiling point, small coefficient of thermal conductivity, thermal expansion coefficient, high-temperature resistance, good wear resistance, corrosion resistance. Nano zirconia powders have many important applications because of their nanometer properties. Fine ceramics made of nano zirconia have some special properties under different conditions, such as insulator at room temperature, conductivity, sensitivity, and toughness at high temperature.
In the zirconium industry chain, the most widely used composite zirconia is the stable/partially stable zirconia formed by doping the corresponding rare earth elements according to different uses. The variety and content of the added rare earth elements can be adjusted to produce composite zirconia that meets the requirements of different uses, such as yttrium stabilized zirconia used as structural parts and zirconium and cerium eutectic used as catalysts. Compared with common zirconia, nano-scale composite zirconia has a smaller particle size and reaches the nanometer level. Its higher additional use value and the market scale of over ten billion are being rapidly developed.
Here are 10 applications of nanocomposite zirconia.
Denture material
Nano ZrO2 can obviously improve the room temperature strength and stress strength factor of ceramics, thus doubling the toughness of ceramics. The composite bioceramics prepared with nanometer ZrO2 have good mechanical properties, chemical stability, and biocompatibility. It is a promising composite bioceramics material, especially in the field of dental materials and artificial joints. Biomaterials refer to materials with natural organ tissue function or partial function, and they are the latest branch of biomedical science and have broad application prospects. Bioceramics have been widely used in the field of oral prosthodontics because of their excellent biocompatibility, stability, and aesthetics.
Zirconia toughened ceramic, as a new fine ceramic, has good mechanical properties (fracture toughness, strength, hardness, etc.), biocompatibility and stability, aesthetics, thermal conductivity, and formability, which can well solve the problem of insufficient strength and toughness of conventional all-ceramic crown materials. Secondly, as an excellent bioinert ceramic, it has excellent chemical stability both as an oral prosthesis and an implant, which fully meets the standard as an oral prosthesis material.
Joint prosthesis
The initial ceramic artificial joint is not perfect and has undergone four generations of process improvement so far, gradually becoming perfect. The fourth generation of the artificial ceramic joint is composed of several kinds of oxidized crystal materials such as zirconia, with good toughness and strength its performance is much better than that of the third generation of the ceramic joint. When zirconia is compounded, the crystal particles become smaller. More importantly, zirconia disperses and absorbs the energy of the fracture, inhibiting crack growth. Zirconia is the best prosthesis material currently used in clinical hip replacement, the ceramic material with the best wear resistance is the most ideal especially for middle-aged and young patients with high exercise.
Hip Joint Prosthesis. Source: www.researchgate.net
Oxygen sensor
The sensor made of zirconia has good electrical conductivity, which plays an important role in controlling automobile exhaust and boiler combustion in power plants. In the automotive industry, oxygen sensors are essential for the use of three-way catalytic converters in engines to reduce emissions and pollution. The Zirconia oxygen sensor is one of the most mature oxygen sensors with the largest output. It is one of the key components of the automobile emission control system, and its signal output characteristics directly affect the engine fuel economy and emission control.
The catalyst for automobile exhaust purification
The catalyst for automobile exhaust purification: carrier (alumina), co-catalyst (nano-coating to increase the specific surface area, as a hydrogen storage material), catalyst (general gasoline parking space platinum, palladium, rhodium, etc., diesel vehicles for vanadium, tungsten, titanium, etc.). Zirconium-cerium solid solution composite oxide is used as a cocatalyst and important coating material. In addition, zirconium-cerium solid solution is also widely used in sensor materials, polishing materials, fuel cells, structural materials, high-strength ceramics, and other fields.
Catalysts for chemical synthesis of aromatic hydrocarbons
Zirconia has long been used in the study of isomeric synthesis. Isomeric synthesis is a process in which syngas is converted into isobutene and isobutane (i-C4) in high selectivity, and it is mainly composed of metal oxides such as zirconia, thorium oxide and cerium oxide. Since Pichler et al. studied isomeric synthesis for the first time, zirconia has become the core of isomeric synthesis catalysis research due to its high i-C4 selectivity and non-radioactivity. This highly selective formation of i-C4 has been attributed to the fact that zirconia surfaces are both acidic, alkaline, oxidizing and reductive. If a single zirconia catalyst can convert syngas into aromatics or high-octane products in one step, the problem of mismatching of active centers in the catalytic system doped by metal and molecular sieve can be avoided, which has far-reaching significance for future energy development.
Ceramic core for fiber optic connector
Due to the excellent mechanical properties, chemical stability and extremely high precision of nano-yttrium oxide stabilize zirconia (nano-YSZ) powders, it can be used to prepare rare earth structure ceramic fiber core (precision needle) and sleeve for optical fiber connectors. It is the optical fiber passive device with the widest application range and the largest demand in the optical fiber network and is an important part of the information network infrastructure construction.
Mobile terminal products
As 5G, wireless charging and other new transmission methods approach, wireless frequency band becomes more and more complex, and metal case shielding will become a major bottleneck. The strict layout of 5G antenna requires the transformation of the existing metal housing material, and both ceramic and glass will be optional. Metal is also unfriendly to wireless charging. Most of the previous wireless charging technologies used electromagnetic wave raw materials, and metal would cause interference to the electromagnetic wave, which greatly reduced the charging efficiency. There are alternative materials such as plastics, glass, and ceramics. Plastic surfaces are prone to scratches, while glass is brittle, so ceramic materials, with their excellent physical properties, are gradually penetrating the appearance of smartphones.
The mi MIX is equipped with an all-ceramic body, and the microcrystalline zirconium ceramics, second only to sapphire hardness, is selected as the blank. It has a Mohs hardness of 8.5. Keys, knives and so on do not cause any wear and tear.
In fingerprint unlock applications, zirconia’s dielectric constant is three times that of sapphire, making the signal more sensitive. Compared with the 0.3mm sapphire cover plate used in iPhone Touch ID, the zirconia has higher recognition when the same thickness is used. It is expected that fingerprint recognition will become the standard of smartphones in the next 5-10 years.
Zirconia ceramic crucible
In the smelting of rare and refractory precious metals and alloys, the general materials are difficult to meet the requirements due to the need to heat to a higher temperature. Crucible made of zirconium oxide can be heated to 2430 ℃, the zirconium oxide thus become the first choice under the condition of high-temperature crucible pot zirconia materials.
Zirconia ceramic cutter
Ceramic cutters were used in the early 20th century, but their brittleness limited their range of use. However, its toughness has been greatly improved with the development of nanocomposite zirconia composite in recent years. Zirconia can be processed into various cutting tools, while the zirconia ceramic blades are made of special ceramic materials belonging to non-metallic materials. Zirconia ceramic tool not only has the advantages of traditional metal tools but also has the characteristics of no rust, health, wear resistance and so on, so it is known as ceramic steel.
Refractory material
Zirconia is often used as a refractory due to its high melting point, low thermal conductivity, and stable chemical properties. The advantages of refractory materials prepared with nano zirconia are more obvious, such as high-temperature resistance, high strength, good thermal insulation performance, and excellent chemical stability.
