Basic Info | Toughening Methods of Zirconia Ceramics

Zirconia (ZrO2) ceramics are special ceramics with unique physical and chemical properties, and their applications in electronic ceramics, functional ceramics and structural ceramics have developed rapidly. However, the fatal shortcomings of zirconia ceramic materials are brittleness, low reliability, and low repeatability, which seriously affect its application range. Only by improving the fracture toughness of zirconia ceramics, strengthening the material and improving its reliability and service life, can zirconia ceramics truly become a widely used new material.

Toughening technology of zirconia ceramics has been a hot spot in ceramics research. At present, ceramic toughening methods mainly include phase change toughening, particle toughening, fiber toughening, self-toughening, diffusion toughening, synergistic toughening, nano-toughening, etc.

Transformation_Toughening
Transformation-Toughening

Phase toughening

Phase toughening refers to the metastable tetragonal phase t-ZrO2 undergoing a phase change under the action of the stress field at the crack tip, forming a monoclinic phase, resulting in volume expansion, thereby forming compressive stress on the crack, hindering crack growth, and increasing the role of toughness. In addition, external conditions (such as laser shock, fatigue fracture toughness, low temperature, grain size and content, critical transition energy, etc.) have a great effect on the phase toughening of zirconia ceramics. If the phase transition produces large stress and volume changes, the product is prone to fracture. Therefore, the influence of external factors on the phase toughening of zirconia ceramics should be avoided during production.

Particle toughening

Particle toughening refers to the method of using particles as a toughening agent and adding it to ZrO2 ceramic powder. Although its effect is not as good as whiskers and fibers, if the particle type, particle size, content and matrix material are properly selected, there is still a certain strong effect. The advantage is that it is simple and easy to implement, and it will also improve the high-temperature strength and high temperature creep performance while toughening. The toughening mechanism of particle toughening mainly includes refinement of matrix grains and crack turning bifurcation.

zirconia-overview

Fiber toughening

The principle of fiber and whisker toughening is that the crystal close to the crack tip adds closing stress to the crack surface due to deformation, offsets the external stress at the crack tip, and passivates the crack propagation, thereby strengthening the toughness. In addition, when cracks are propagated, the frictional force must be overcome when the columnar crystals are pulled out, which also plays the role of toughening.

Self-toughening

Due to the existence of columnar crystals, cracks will be deflected during the fracture process of zirconia ceramics, which will change and increase the path of crack growth, thereby passivating the cracks, increasing the crack growth resistance and achieving toughening.

Diffuse toughening

Diffusion toughening mainly refers to the toughening of the ceramic matrix by the tetragonal ZrO2 particles. In addition to the phase toughening mechanism, there is also a diffusion toughening mechanism of the second phase particles. Before cracks propagate, the internal residual strain energy of the ceramic itself must first be overcome to achieve the purpose of toughening.

Microcrack toughening

Micro-crack toughening refers to adding a tough material at the crack stress tip to cause micro-cracks to achieve the purpose of dispersing stress, reducing the force of crack advance, and thereby increasing the toughness of the material. When a material undergoes a phase transition, it often results in residual strain energy effects and microcracks. Therefore, the effect of phase transition toughening is significant.

Composite toughening

Composite toughening refers to the simultaneous use of several toughening mechanisms during the actual toughening of ZrO2 ceramics, thereby improving the toughening effect of ZrO2 ceramics. In the actual application process, the specific toughening mechanism is selected according to the different properties of the zirconia ceramic material to be prepared.

Alumina-toughened-Zirconia
Alumina-toughened-Zirconia

Nano toughening

At present, there are three main academic viewpoints of nano-toughening, namely: the theory of refinement, trans-crystalline, and “pinning”.

  • The refinement theory believes that the introduction of nano-phases can suppress the abnormal growth of the matrix grains, refine the matrix structure uniformly, and improve the strength and toughness of the nano-oxide ceramic composites.
  • The trans-crystalline theory holds that in nanocomposite materials, the matrix particles are densified with the nanoparticles as the core, and the nanoparticles are encapsulated inside the matrix grains to form an “intracrystalline” structure. In this way, the effect of the main grain boundary can be weakened, transgranular fracture is induced, and transgranular fracture instead of intergranular fracture occurs when the material is fractured, thereby improving the strength and toughness of the nano-zirconia ceramic composite material.
  • The “pinning” theory believes that the nanoparticles existing in the grain boundaries of the matrix produce a “pinning” effect, which limits the occurrence of grain boundary slippage, pores, and creep. The enhancement of grain boundaries leads to the improvement of the toughness of nano-zirconia multiphase ceramic.

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

Advantages of Zirconia Ceramic Rods

Zirconium oxide ceramic rods have the common advantages of both metal and polymer materials, and they play a very important role because of their numerous advantages and applications. The production process of ceramic rods is cumbersome and requires production processes such as cutting, grinding, grinding and polishing. Despite this, ceramic rods are in high demand compared to other materials of the same type, which has a tendency to go higher because of its advantages.

zirconia-ceramic-rods

Excellent Weatherability

Ceramic rods using zirconia or alumina as production materials have obvious advantages over products of the same category. They are highly weather-resistant and have no effect on the surface and substrate of the ceramic rod, whether it is sunlight, rain or moisture. Corrosion-resistant ceramic rods are also very stable in color under ultraviolet light and are in good compliance with international standards in terms of impact resistance, strength, and elasticity.

Strong Stability

Ceramic rods are generally made of zirconia, which is currently a leading technology in the industry. First of all, a zirconia ceramic rod is simpler to clean, with good fire resistance, neither melting nor falling or exploding, and it can remain stable for a long time. Secondly, the ceramic rod is easy to maintain, no need to add any anti-corrosion paint or protective layer on the surface, it is easy to use and has a long service life.

High Abradability

The ceramic rods are made of high-precision materials, which enhance the mechanical strength and hardness of the ceramics during high-temperature firing. Therefore, the ceramic rod has a good performance in terms of impact resistance. After a long period of proof and a number of tests, the wear resistance is also strong, and the shape is not damaged in the long-term use. In a variety of harsh working environments, the advantages of ceramic rods are even more pronounced, making acid-resistant ceramic rods the best choice for harsh conditions.

kitchen-knives

Ceramic rods are widely used in various fields due to their weather resistance, stability, and high wear resistance. In addition to being able to be used in normal environments, the use of ceramic rods not only ensures the normal operation of the instrument, but also does not cause breakage, wear, corrosion, etc., nor damage to the instrument.

Stanford Advanced Materials (SAM) is a global supplier of pure metals, alloys, ceramics, minerals, and rare earth materials since 1994. We supply high-quality zirconia ceramic materials used in aerospace components, medical devices, surgical and dental implants, etc. Please visit http://www.samaterials.com for more information.

How is the Zirconia Industry Laid Out?

Globally, zirconia producers are mainly concentrated in a few countries, mainly including China, Japan, France, the United Kingdom, the United States, and Australia. Companies with comprehensive zirconia industrial layout include Saint-Gobain, Japan’s Tosoh, Japan’s First Element, Showa Denko, France’s Suvi, and Japan’s Sumitomo Osaka Cement. Among them, the main business of First Element is zirconium-based, and most of the other companies are large-scale integrated enterprises.

With zirconia as the main component, after adding rare earth elements (mainly cerium oxide) and other oxides, composite zirconia powders with different performance characteristics can be formed. The nature of the composite zirconia depends on the type of material or crystal structure to which it is combined. Depending on the specific needs of the application, different formulations of composite zirconia materials with different properties can be prepared using different formulations.

zirconia

In general, zirconia ceramics are divided into three categories: PSZ partially stabilized zirconia, also known as ceramic steel (with superior impact resistance); TZP tetragonal polycrystalline zirconia (better mechanical strength and fracture toughness); FSZ fully stabilized zirconia, crystalline phase cubic phase, with high temperature conductivity, but high thermal expansion coefficient and poor thermal shock resistance.

Catalyst

Since zirconia is the only metal oxide that has both acidic and basic and oxidizing and reducing properties and is also a p-type semiconductor, it is easy to generate oxygen vacancies. As a catalyst carrier, it can interact with the active component, so its supported catalyst has more excellent properties than other materials supported catalysts.

Precise ceramic parts

Zirconia ceramics can have excellent mechanical properties and fracture toughness, chemical resistance, and biocompatibility, so you can see the back of zirconia ceramic materials in industry and life.

Typical applications for zirconia ceramics: tools, dentures, bearings, etc.
Typical applications

Battery material

Solid oxide fuel cells (SOFC) are a new type of green energy that developed rapidly in the 1980s. Due to its high energy conversion efficiency (up to 65%) and the use of various fuels such as hydrogen, carbon monoxide, methane, etc., the system design is simple, and the pollution-free emission is low, which will be applied to the power generation system. The solid electrolyte is the core component of SOFC.

Schematic diagram of a solid fuel cell
Schematic diagram of a solid fuel cell

Zirconium oxide ceramics have become the most researched and widely used solid electrolyte materials because of their high ionic conductivity, good chemical stability, and structural stability.

Refractory

Zirconium oxide is an excellent special oxide refractory material and used at a high temperature (2300 ℃ – 2400 ℃). It has good chemical stability and is not easy to decompose, and is highly corrosive and resistant to acid and alkali slag. The industry uses zirconia-based refractories to produce refractory materials with excellent thermal shock resistance, corrosion resistance and wears resistance, which can make refractories have better performance and longer service life. It has been applied to the manufacturing process of industrial continuous casting steel and alloy materials and has important significance for improving the quality and cost of metal materials such as steel.

Zirconia foam ceramics for steel water filtration
Zirconia foam ceramics for steel water filtration

Optical material

Zirconium dioxide ZrO2 is a high refractive index, low absorptive material that can be used in coatings in the near-ultraviolet (<300 nm) to infrared (~8 μm) spectral regions. Nano-zirconia is added to the special coating material to increase the refractive index of the coating without changing the light transmittance. In the field of optical materials, in addition to being used as a coating, nano zirconia can also be used as a polishing material for optical lenses.

Electronic materials

For engines that use three-way catalytic converters to reduce pollution emissions, oxygen sensors are essential in the automotive industry. It uses the ceramic sensitive component to measure the oxygen potential in the exhaust pipe of the automobile, and calculates the corresponding oxygen concentration by the principle of chemical balance, and achieves the measuring component that monitors and controls the combustion air-fuel ratio to ensure the product quality and the exhaust gas emission standard. There are two types of oxygen sensors currently in use: titanium oxide and zirconium oxide. The core component is a porous zirconia ceramic tube, which is a solid electrolyte with sintered porous platinum (Pt) electrodes on both sides.

Plumbum zirconate titanate (PbZrxTi1-xO3, PZT) ceramics are a commercially important class of piezoelectric materials. Compared with other piezoelectric ceramics, PZT ceramics not only have high Curie temperature and piezoelectric coefficient, but also are easy to be doped and modified, and have good stability, so they have an important position in the electronic machinery manufacturing industry. They are the basic material for the preparation of most electromechanical devices such as sonar, hydrophone, ultrasonic generator, volt generator, and position trimmer.

Brake material

Ceramic materials have high heat resistance, thermal stability, and hardness. As an important member of advanced ceramics, zirconia ceramics certainly have similar characteristics. In view of the excellent quality of advanced ceramics, researchers have introduced it into friction materials to obtain longer-lasting and more durable friction materials under the most extreme working conditions. Today, more and more composite formulations for brake pads and clutch linings contain ceramic materials.

Many ceramic materials can be added to the brake material, including the zirconia ceramics we introduce today, in addition to silicon carbide, alumina, silica, and magnesia

Example of the microstructure of the brake pad material
Example of the microstructure of the brake pad material

Thermal spray material

Using thermal spraying technology, the ceramic coating is deposited on the metal collective, and the characteristics of high-temperature resistance, heat insulation, wear resistance, corrosion resistance and insulation of the ceramic are combined with the toughness, workability, the electrical and thermal conductivity of the metal material. The ideal composite coating product has become an important development direction in the field of composite materials and product development.

Aviation surface protection technology is a hotspot of thermal spraying for many years. The key components of aero-engines are high-temperature alloy turbine blades and turbine disks. The current engine turbine inlet temperature is close to or exceeds the melting point of the alloy, and such high temperatures will affect the function of the engine and dye. Therefore, an important development trend of superalloys is to coat the surface of the alloy with a high-melting ceramic coating (Thermal Barrier Coatings – TBCS) with good thermal insulation properties. At present, the most widely used TBCS is yttria-stabilized zirconia materials.

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

Application of Zirconia Electrolyte in Oxygen Sensor

With the gradual improvement of people’s awareness of environmental protection and energy conservation, many large and medium-sized enterprises, such as iron and steel metallurgy, petrochemical industry, thermal power plants, etc., have taken improving combustion efficiency, reducing energy consumption, reducing pollutant emissions, protecting the environment as an important way to improve product quality and enhance enterprise competitiveness.

oxygen-sensor

Generally speaking, the direct way to improve the combustion efficiency is to continuously monitor the composition of flue gas in the flue gas analysis instrument (such as flue gas analyzer, combustion efficiency tester, zirconia oxygen content detector), then analyze O2 content and CO content in flue gas, adjust the flow rate of combustion air and fuel, and determine better air consumption coefficient. Therefore, as an industrial tool to improve combustion efficiency, oxygen sensor’s response time and measurement accuracy become key performance indicators. Due to its simple structure, short response time, wide measurement range (from PPM to percentage), high operating temperature (600℃-1200℃) and small maintenance, zirconia oxygen sensor has been widely used in metallurgy, chemical industry, electric power, automobile, and other fields.

Principle of zirconia sensor

The figure below is the schematic diagram of oxygen measurement with an oxygen probe. Porous platinum (Pt) electrodes were sintered on the two sides of the zirconia electrolyte (usually a zirconia tube). At a certain temperature, when the oxygen concentration on both sides of the electrolyte is different, the oxygen molecules on the high concentration side (air) are adsorbed on the platinum electrode and combine with electrons to form oxygen ions, making the electrode positively charged. The oxygen ions then migrate through the oxygen ion vacancy in the electrolyte to the Pt electrode on the low oxygen concentration side, releasing electrons and transforming them into oxygen molecules, making the electrode negatively charged.

 

zirconia-sensor

This creates a certain electromotive force between the two electrodes. The zirconia electrolyte, the platinum electrode, and the gas with different oxygen concentrations on both sides constitute the oxygen probe, which is called the zirconia concentration difference cell. Then, by measuring the gas temperature and the output electromotive force, the oxygen partial pressure (concentration) can be calculated by the nengst equation, which is the basic detection principle of the zirconia oxygen sensor.

Common types of zirconia oxygen sensors

At present, the commonly used zirconia oxygen sensor includes a detection probe and direct insertion oxygen probe.

Detector probe

The sampling method is to introduce the measured gas into zirconia through a guide tube and then heat the zirconia to the working temperature (above 750℃) through a heating element. Zirconia is typically tubular and the electrode is porous platinum. Its advantage is that it is not affected by the temperature of the gas detected, and the oxygen content of the gas can be detected by using different flow guides at different temperatures.

This flexibility is used in much industrial on-line detection. Its disadvantages are slow response; the structure is complex and easy to affect the detection accuracy; when there are many impurities in the measured gas, the sampling tube is easy to be blocked; the porous platinum electrode is easy to be corroded by sulfur and arsenic or blocked by fine dust, etc. When the temperature of the detected gas is low (0-650℃), or when the measured gas is clean, it is suitable to use this detection method, such as oxygen measurement by nitrogen production machine and laboratory.

oxygen-sensors

Direct probe

Direct insertion method is to directly insert zirconia into the gas measured at high temperature and directly detect the oxygen content in the gas. It uses the high temperature of the measured gas to bring zirconia to its operating temperature without the need for additional heaters.

The key technology of direct insertion oxygen probe is the high-temperature sealing of ceramic material and the electrode. Due to the need to insert zirconia directly into the detection gas, the length of the oxygen probe is required to be relatively high. The effective length is about 500mm ~ 1000mm, and the special environment length is up to 1500mm, as well as high requirements for detection accuracy, working stability and service life. Therefore, it is difficult to adopt the whole zirconia tubular structure of the traditional zirconia oxygen probe with direct insert oxygen probe, and the zirconia and alumina tube connection structure with high technical requirements are mostly adopted. The sealing performance is one of the most important technologies for the zirconia oxygen probe. Currently, the most advanced connection mode in the world is the permanent welding of zirconia and alumina tubes together.

Compared with the method of sampling pattern detection, the direct insertion method has obvious advantages: zirconia directly contacts with gas; high detection accuracy; fast reaction speed and small maintenance.

Brief summary

The regulation of oxygen content is a powerful means to monitor combustion conditions and improve combustion efficiency, and the accuracy and time of the measurement of the sensor have put forward certain requirements. Zirconia, as a solid electrolyte, is used to transport conductive ions in oxygen sensors. At present, there are two kinds of zirconia oxygen sensors: detection type and direct insertion type. The direct insertion type probes are widely used because of their direct contact with the measured gas, high measurement accuracy and fast reaction time.

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.

Why Does Zirconium Explode? How to Solve It?

Zirconium (Zr) is estimated to make up about 0.017% of the lithosphere. Because zirconium is chemically active at temperatures only slightly above normal atmospheric temperatures, it exists only in a bound state. The most common ores are zircon (ZrO2) and barium lead (ZrSiO4).

The hafnium (Hf) coexists with zirconium in all its terrestrial ores. The content of hafnium fluctuates greatly, accounting for 2% (the total amount of hafnium and zirconium). The two elements are chemically closer than any other in the periodic table, and the similarities are so great that no difference in mass has been found to separate them.

Hafnium
Hafnium

Zircon

Zircon has been considered a gem since ancient times because it is usually found in large single crystals. However, most commercial deposits of zirconium ore are in beach sand, where the relatively heavy and chemically inert zirconium minerals are retained, while the lighter parts are broken down and washed away by water. India, Malaya, Australia and the United States are known to have large deposits of this sand. Harmful substances have been found in commercially useful deposits, first in Brazil and later in other places, including Sweden, India, and Italy, while some zirconium ores are also commercially mined in Madagascar, Nigeria, Senegal, and South Africa.

Zircon is used as a component of foundry sand, abrasive, and laboratory crucible zircon and zirconia refractories. It is found in ceramic compositions and acts as an emulsifier in glazes and enamels. Zirconium and zirconia bricks are used as glass linings, zirconia templates are also used for extrusion iron and non-ferrous metal molds and injection metal nozzle linings, especially for continuous casting.

zircon-crystals
Zircon-crystals

Zirconium metal

More than 90% of zirconium is now used in nuclear power generation because zirconium has a low neutron absorption cross-section and is highly resistant to corrosion in atomic reactors, provided it contains no hafnium. In addition, zirconium is used in the manufacture of cast iron, steel, and surgical instruments, as well as in arc lamps, fireworks, special solder, plastic pigments, etc.

The powdered zirconium metal is used as a “getter” in thermionic tubes that absorb traces of residual gas after it has been drained and expelled. The metal, in the form of filaments or wool, is also used as a filter for camera flashes. Block metals can be used in the lining of reaction vessels, either pure or alloyed. It is also used as lining for pumps and piping systems in chemical processes. Excellent zirconium and niobium superconducting alloys are used in the magnetic field of 6.7T.

Zirconium-metal-strip
Zirconium-metal-strip

Zirconium compounds

Zirconium carbide and zirconium diboride are hard, refractory, metallic compounds that have been used in metal cutting tools. Diboride is also used as the shell of open-hearth thermocouple with long life. Zirconium tetrachloride is used in organic synthesis and water repellent in textiles, and it is also useful as a tanning agent.

The metal hafnium has been used as a coating for the tantalum components of rocket engines, which must work at very high temperatures and under corrosive conditions. Because of its high thermal cross-section, it is also used as control rod material in nuclear reactors. In addition, hafnium is used in the manufacture of electrodes and filament bulbs.

The harm of zirconium

It is not accurate to say that zirconium compounds are physiologically inert, but most organisms seem to tolerate zirconium quite well compared to most heavy metals. Zirconium salts have been used to treat plutonium poisoning to replace the deposition of plutonium (and yttrium) in the skeleton and to prevent precipitation when early processing begins.

Zirconium-salts
Zirconium-salts

Some studies have shown that more than 20% of zirconia can be absorbed in rats for a long time without harmful effects. LD50 of rats injected with sodium zirconium citrate is about 171mg/kg. Other investigators found an intraperitoneal injection of LD50 rats with zirconium lactate 670mg/kg, barium zirconium 420mg/kg, and mice with sodium zirconium lactate 51mg/kg.

Zirconium compounds have been recommended for topical treatment of suede dermatitis and body deodorants, among which are zirconia carbide hydrate, zirconia hydrate, and sodium zirconium lactate. There have been some reports of persistent granulomas on the skin as a result of these applications.

More immediate interest in occupational exposure is the effect of inhaled zirconium compounds, which has not been studied as extensively as other approaches to drug administration. However, there are several experiments and at least one report on human exposure. In this case, a chemical engineer who had been at a zirconium and hafnium processing plant for seven years was found to have granulomatous lung disease. As no similar damage was found on all other employees, it was concluded that the situation was most likely due to relatively high levels of beryllium prior to zirconium contact.

Animal exposure to zirconium compounds has shown that severe persistent chronic interstitial pneumonia occurs in both zirconium lactate and barium zirconium at atmospheric concentrations of about 5mg/m3. Short exposure to sodium zirconium lactate at a higher air concentration of 4900mg/m3 resulted in peribronchoabscess, peribronchogranuloma, and lobular pneumonia. Despite the lack of literature on human zirconia pneumoconiosis, the authors of one study suggest that zirconium should be considered as a possible cause of pneumoconiosis and recommend appropriate precautions in the workplace.

A small number of studies on the toxicity of hafnium compounds indicate that their acute toxicity is slightly higher than that of zirconium salts. Like soluble zirconium salts, hafnium chloride-induced cardiovascular failure and respiratory arrest in cats at 10mg/kg.

Safety and health measures

  • Zirconium is burned as a fine powder in air, nitrogen or carbon dioxide. The spontaneous air explosion of these powders at concentrations of 45,000 to 300,000 mg/m3 may be caused by static electricity generated by the separation of the disturbed particles.
Zirconium-powder-in-flame
Zirconium-powder-in-flame
  • Metal powders should be transported and treated in a wet state; water is usually used for wetting. When the powder is dried before use, the amount used should be as small as possible and should be operated in a separate compartment to prevent the spread of the explosion.
  • All ignition sources including electrostatic charges should be eliminated. All surfaces in the area should be impermeable and seamless so that they can be washed down with water and completely free from dust. Any spilled powder should be washed with water immediately so that it has no chance to dry. Old paper and cloth contaminated with powder should be kept moist in a covered container until they are removed and burned, at least daily.
  • Dry powders should be treated with as little interference as possible, and then only sparkless tools should be used. Rubber or plastic aprons, if worn on overalls, should be treated with antistatic compounds. Work clothes shall be made of non-synthetic fibers unless effectively treated with antistatic materials.
  • All processes using zirconium and hafnium should be designed and ventilated to keep air pollution below exposure limits.

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

Applications of Zirconia in Structural And Functional Ceramics

Zirconia is a kind of inorganic nonmetallic material with high-temperature resistance, corrosion resistance, abrasion resistance, and excellent electrical conductivity. Since the mid-1970s, developed countries have invested heavily in the research and development of zirconia products, extending the application field of zirconia to structural and functional materials. Zirconia is also one of the new high-performance materials in the national industrial policy, which is widely used in various industries.

Applications of zirconia in structural ceramics

In 1975, R.G.Garvie, Australia, prepared partially stabilized zirconia with calcium oxide as a stabilizer, and improved the toughness and strength of zirconia for the first time, which greatly expanded its application in the field of structural ceramics.

1. Zirconia ceramic bearings

Zirconia ceramic bearing has the characteristics of wear resistance, corrosion resistance, high-temperature resistance, high cold resistance, oil-free self-lubrication, resistance to magnetoelectric insulation, etc. It can be used in an extremely harsh environment and special working conditions.

Zirconia-ceramic-bearings
Zirconia-ceramic-bearings

Zirconia ceramic bearings have been used in micro cooling fans, and the product life and noise stability are better than traditional ball and sliding bearing systems. Foxconn is the first company to use zirconia ceramic bearings in computer cooling fans.

2. Zirconia ceramic valve

At present, valves commonly used in various industries are made of metal materials. Due to the limitation of metal material itself, the corrosion damage of metal has a considerable impact on the working life, reliability and service life of valve wear resistance.

The working climate of valve pipeline is very complicated. Hydrogen sulfide, carbon dioxide, and some organic acids in oil, gas, and reservoir water increase the destructive power of their surfaces, rapidly disabling them. Zirconia ceramic valve has excellent wear resistance, corrosion resistance, high-temperature resistance, thermal shock resistance, so it is suitable for this field.

ceramic-ball-valve
Ceramic-ball-valve

3. Zirconia abrasive material

Zirconia ball has the advantages of high hardness, low wear rate and long service life, which can greatly reduce the pollution of grinding materials and ensure the quality of products. Besides that, zirconia material has high density and strong impact energy when used as a grinding medium, which can greatly improve the grinding dispersion efficiency. Good chemical stability determines its corrosion resistance and can be used in acidic and alkaline media.

Applications of zirconia in functional ceramics

1. Zirconia ceramic knives

Zirconia ceramic knife has the characteristics of high strength, wear resistance, no rust, no oxidation, acid and alkali resistance, anti-static, and no reaction with the food. Its body is as shiny as jade, which also makes it an ideal high-tech green knife. At present, the main products on the market are zirconia ceramic knife, scissors, razor, scalpel and so on, which has become popular in Europe, America, and Japan in recent years.

Zirconia-ceramic-knife
Zirconia-ceramic-knife

2. Zirconia high-temperature heating element

Zirconia is an insulating material at room temperature, its resistivity is as high as 1015 Ω cm, and it can conduct electricity when the temperature to 600 ℃. When the temperature reaches 1000℃ above, it is a good conductor and can be used as 1800℃ high-temperature heating element, with the highest operating temperature of 2400℃. At present, zirconia has been successfully used in heating elements and equipment with an oxidation atmosphere above 2000℃.

3. Zirconia bioceramics

The quality of ceramic tooth material directly affects its quality and patients’ health. The inner crown of porcelain teeth is made of different metal materials, which is easy to oxidize with saliva. Since there is no metal inner canopy, zirconia ceramic teeth have good transparency, excellent gloss, and effectively avoid tooth allergies and gum black lines.

Biomedical-uses-of-zirconia-ceramics
Biomedical-uses-of-zirconia-ceramics

4. Zirconia coating material

Zirconia thermal barrier ceramic coating material with a high-performance stabilizer such as yttrium oxide (Y2O3) is mainly used in high-performance turbine aero-engine. The thermal barrier coating uses ceramic insulation and corrosion resistance to protect the metal material, which can not only improve the fuel combustion efficiency but also greatly extend the life of the engine. Thermal barrier coating has important application value in aviation, aerospace, surface ships, large thermal power generation, and automobile power, etc. It is one of the most important technologies in modern national defense.

5. Zirconia oxygen sensor

Oxygen sensors are essential in the automotive industry for engines that use three-way catalytic converters to reduce pollution emissions. Currently, there are two kinds of oxygen sensors in use: titanium oxide and zirconia. Japanese scientists made a porous oxygen sensor out of zirconia, which is installed in an engine to automatically detect the ratio of oxygen to combustion gas in the engine, and automatically control the ratio of input gas and output gas, thus greatly reducing the harmful gas emissions from cars.

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

Why Are Zirconia Ceramic Teeth So Expensive?

The all-ceramic dental prosthesis has excellent mechanical properties, no gingival inflammation, and excellent biocompatibility, and it has no obstruction to X-ray rays. In addition, it has excellent wear resistance, corrosion resistance, and aesthetic properties of no gingival black edge and emulating natural teeth, all these make it the first choice of dental repair materials.

Zirconia ceramic teeth

At present, there are three kinds of materials used in all-ceramic dental restorations, namely, zirconia all-ceramic dental restorations, cast ceramic dental restorations and alumina all-ceramic dental restorations.

Among the three kinds of all-ceramic teeth, zirconia all-ceramic teeth are the strongest dental restorations. Its fracture toughness ratio is two or three times that of alumina all-ceramic, and it is not easy to break the teeth with it; secondly, it can be used for cosmetic dentistry and restoration of missing teeth. It can be used to repair multiple teeth, which can be used to repair even crowns, which can perfectly solve the problem that the strength of ceramic casting material is too poor to make continuous crown; moreover, its color is perfectly adjustable, so it can be used to make very realistic dentures.

zirconia-teeth

Zirconia denture, as such an excellent product, should have been favored by the public. But zirconia restorations are expensive, costing thousands or even thousands of dollars for a single crown, which makes it unaffordable for ordinary people.

Why are zirconia ceramic teeth so expensive?

The main reason for the high price of zirconia ceramic teeth is that the overall production cost of zirconia teeth is really high.

The zirconia prosthesis underwent a series of complex processes before it was put into the patient’s mouth to achieve its chewing, vocal and aesthetic functions, including raw material production of raw material manufacturers, production of zirconia block manufacturers, dental surgeons spare tooth mold, processing design, selection of the right zirconium block, cutting, dyeing, sintering, dyeing, polishing, dental doctor’s grinding, etc. As long as one of the above processes goes wrong, it will affect the currently visible quality of the restoration or the currently invisible but potential quality problems in the future.

Zirconium blocks used for all-ceramic teeth can cost anywhere from hundreds to thousands of dollars just from the cost of materials alone. From the above analysis, we can see that the proportion of the raw material cost is not large, but the difficulty of processing leads to an increase of the overall preparation cost.

crown

At present, the forming of zirconia ceramic crowns is dominated by CNC processing technology, which has advantages in product precision and processing efficiency. However, due to the material removal by cutting tools on zirconium plates (blocks) during processing, the cost of ceramic crowns remains high due to the waste of materials and the wear of cutting needles, and microcracks are easily introduced in the cutting process, leading to the failure of the restoration. The current zirconia denture is semi-machined, and the zirconia teeth processed by professional milling machine need to be used to repair the maxillofacial fossae and furrows with a crack drill or a ball drill to achieve a realistic effect. If the human ingenuity is lacked, it can also be said that it has a little personality in shape and edge treatment.

To sum up, the waste of raw materials and the high labor cost of advanced technical workers inevitably increase the preparation cost of zirconia teeth due to the inevitable mistakes in manual processing. Therefore, seeking a new dental ceramic prosthesis forming technology is the characteristic of dental ceramic research and the key point of the clinical prosthesis.

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.

Zirconia Ceramic Conversion Film Used in Automobile Coating Field

Phosphating is the most common pretreatment technology in the field of automobile coating. A phosphate conversion film is produced after phosphating the body steel plate, which can not only protect the base metal but also improve the adhesion between the metal and the coating. All cars are phosphated before they are painted.

Phosphating
Phosphating

However, the traditional phosphating process has the defects of high energy consumption and high pollution. In addition, nitrite in the phosphating bath has high carcinogenicity, and its storage and use requirements are high, which increases the burden of enterprises. Therefore, under the dual drive of environmental requirements and energy cost, the phosphorous-free film forming technology represented by the new zirconia conversion film technology has become the development consensus of green coating for automobiles.

Principle of film formation of zirconia ceramics

Zirconia ceramic film forming technology is one-step film forming, which means a surface treatment agent is used to treat the metal surface. The following diagram shows the film formation principle of a zirconia ceramic on the steel surface. The main materials are fluoro zirconic acid and zirconium salt. Zirconic acid and zirconium salt react directly with the metal substrate, and the zirconia ceramic film formed is attached to the surface of the metal substrate to play a role in corrosion protection.

Film formation process of zirconium salt conversion film on steel surface
The film formation process of zirconium salt conversion film on the steel surface

At present, the sol-gel is the main method to produce zirconia conversion film. The so-called sol-gel refers to the formation of the three-dimensional network configuration of colloidal particles crosslinked with each other, which can mechanically wrap a large number of solvents inside the aggregate, making it no longer flow and become semi-solid state and gel. When the density of sol particles in colloidal solution is higher than that in solution, the sol particles tend to sink under the action of gravity. If some parameters in the solution are changed to make the deposition rate of colloidal particles greater than the diffusion rate, the colloidal particles will rapidly precipitate out of the solution.

Characteristics of zirconia ceramic film

In terms of film properties, the ceramic coating formed by zirconia conversion film can completely replace the traditional phosphating film. In addition, zirconia conversion film also has the characteristic of light weight, while its film thickness is about 50nm. The film thickness means the low film weight, and the weight of the traditional phosphating film is usually 2-3g/m2, while that of zirconia conversion film is only 20-200mg/m2. The weight of zirconia conversion film varies according to the raw materials provided by the supplier, but in general, the weight of zirconia conversion film is about 200 times lower than that of traditional phosphating film.

In terms of technological process, the new zirconia conversion film technology is more simple and fast, and generally only takes about 30s to form a complete film, which can significantly reduce the cost of water consumption, wastewater treatment, energy, and manpower.

Ceramic-film
Ceramic-film

Moreover, the new process is suitable for a variety of metals (Fe, Zn, Al, Mg), so various plates can be mixed line processing. In the process of treatment, zinc-plated plate and aluminum plate without waste slag formation, only a small amount of slag produced in the treatment of cold-rolled plate. The resulting slag can be easily removed using a conventional phosphating system, without clogging the nozzle or adversely affecting coating properties or the appearance of the electrophoretic coating.

In daily process management, the bath of the new zirconia film forming technology is very stable and easy to control. At ordinary times, the temperature and PH value are only needed to be controlled in production, which does not need to be like zinc phosphating that requires regular daily testing of total acid, free acid and zinc, nickel, manganese content, and many other parameters, so a lot of process management costs are saved.

Zirconia film forming technology has been applied earlier in foreign countries. Henkel group of Germany has the absolute right to speak in this field. As early as 2002, Henkel was the first company to introduce zirconium pre-treatment materials suitable for a variety of plates; in 2008, GM used Henkel’s zirconium pretreated materials at its SanJose Dos Campos plant in Brazil; Henkel’s pretreatment materials were also used at Ford’s TwinCity plant during the same period.

Stanford Advanced Materials supplies high-quality zirconium and zirconia products to meet our customers’ R&D and production needs. Please visit http://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.

zirconia-powder
zirconia-powder

Ceramic Machining

Ceramic shell molding processes such as mobile phone 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 panel.

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 micron. Tape casting is used in the ceramic panel of MI 5 mobile phone and the ceramic fingerprint cover of various mobile phones.

MI5

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 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 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.

Zirconia Ceramics: A Hotspot in the Field of Micro-machinery

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 pump, microvalve, micro tweezers, and micro flowmeter applied in zirconia ceramics, and the micro-inertial measurement device, micro-whole analysis system, RF sensor, etc. used in the military field. Moreover, zirconia ceramic materials can be used as a micro burner, a microreactor, and a pressure sensor at high temperature and it can also be used as a composite, bone tissue scaffold, and other biomedical fields because of the good biological solubility.

Please visit http://www.samaterials.com for more information.