Zirconia – Page 2 – Zirconium Metal

3 Manufacturing Methods of Zirconium-containing Refractories

What is Zirconium-containing Refractory Material?

Zirconium-containing refractory materials are made of zirconia (ZrO2) and zircon (ZrSiO4) as raw materials. “Zirconium-containing” usually refers to materials containing the following zirconium products: zirconia, zircon, zirconium mullite and zirconium corundum. Zirconium-containing products have good corrosion resistance to various molten metals, acidic reagents and liquid glass.

Zirconium-containing refractory materials can be divided into the sintered, fused cast, and non-fired products based on different manufacturing methods.

What are the Different Manufacturing Methods?

Sintered Zr-Containing Refractory Product

The basic steps to manufacture zirconium-containing sintered bricks are to prepare raw materials, press green bodies, and sinter at high temperatures.

Another method is to obtain blanks by granulation, kneading, machine pressing or extrusion molding, and the clinker fired at high temperature is used as aggregate, and the clinker fine powder is used for batching, kneading, molding, drying, and sintering to finally obtain the finished product.

Cast Zr-Containing Refractory Product

1) Use zircon concentrate or industrial zirconia and industrial alumina powder as raw materials.

2) Add sodium oxide, calcium oxide, boron oxide and rare earth metal oxides as additives.

3) The powder is melted at a temperature above 2500°C by means of electric arc melting, cast in a mold, cooled, annealed, and machined.

Non-fired Zr-Containing Refractory Product

The manufacturing process of zirconium-containing refractory products without firing is simple, and the product qualification rate is high.

1) Use stabilized zirconia clinker or zircon as raw material.

2) Use water glass, phosphoric acid, phosphate, or sulfate as the cementing agent.

3) Mix the raw materials and cementing agents, and undergo high-pressure molding and low-temperature heat treatment to make zirconium-containing non-fired materials.

The heat treatment temperature varies with different binders. When aluminum dihydrogen phosphate is used as the cement, the heat treatment temperature is about 300°C; when phosphoric acid is used as the cement, the heat treatment is carried out at a temperature of about 600°C.

What Are These Products Used for?

Zirconium-containing refractory products can be widely used in metallurgy, building materials, the chemical industry, machinery and other professional fields due to their high refractoriness, mechanical strength and chemical stability.

Zirconia bricks can be used in thermal equipment in the building materials industry and metallurgical industry, such as billet continuous casting sizing nozzles, submerged nozzles and slag lines in long nozzles.
Zircon bricks are resistant to low-alkali glass corrosion. They can be used for the kiln wall of the glass melting furnace, as well as the arch feet of the upper structure of the glass melting furnace or the intermediate transition layer between silica bricks and corundum bricks.
Zirconia-mullite fused cast bricks can be used in heating furnaces, soaking furnaces in the metallurgical industry, glass melting furnaces in the building materials industry, etc.
Zirconium corundum bricks have good resistance to melt erosion. As a high-grade abrasive, it has a good grinding effect on steel, cast iron, heat-resistant steel, and various alloy materials.

If you want to know more about zirconium material, we would like to advise you to visit Stanford Advanced Materials (SAM) for more information.

10 Common Zirconium Products and Their Applications

1. Zirconium Silicate

Zirconium silicate is an important variety in traditional zirconium products. The product is made of zircon sand, which can be obtained after grinding, calcining and powdering. It is a high-quality and cheap opacifying agent for ceramic glazes.

Zirconium silicate is mainly used for color glazes of architectural ceramics, daily-use ceramics and electric porcelain. It is also widely used in high-grade refractory materials, precision casting, emulsified glass and other industries.

2. Zirconium Carbonate

Zirconium carbonate is a source of zirconium that is insoluble in water but is easily transformed into other zirconium compounds. It is mainly used as an additive for cosmetics, waterproofing agent, flame retardant, opacifying agent, and surface aid for fibers and paper, and can also be used to prepare zirconium-cerium composite catalytic materials. It is an important raw material in the textile, papermaking, paint, and cosmetic industries, and its consumption has been increasing in recent years.

3. Zirconium Oxychloride

Zirconium oxychloride is the main raw material for the production of other zirconium products such as zirconium dioxide, zirconium carbonate, zirconium sulfate, composite zirconium oxide, and the separation of zirconium and hafnium to prepare metal zirconium and hafnium. In addition, it can be used in textiles, leather, rubber additives, metal surface treatment agents, paint drying agents, refractory materials, ceramics, catalysts, fire retardants, and other products. The primary source material for zirconium oxychloride is zircon sand.

4. Fused Zirconia

Fused zirconia is mainly used in the production of glazes and refractory materials. Due to the high content of impurities in fused zirconium, its use is sometimes limited.

5. Zirconium Sulfate

Zirconium sulfate is an intermediate raw material for the production of zirconium chemicals and metal zirconium and hafnium. It is also an important raw material for the production of leather tanning agents, wool treatment agents and paint surface oxidants. Additionally, it can be used as a catalyst carrier, amino acid and protein, precipitant and deodorant.

Consumption Structure of Zirconium Products

6. Zirconium Dioxide

Zirconium dioxide, or zirconia, is a non-toxic, odorless white solid. It has sufficient stability in alkaline solutions and many acidic solutions. ZrO2 ceramic is suitable for precision ceramics, electronic ceramics, optical lenses, glass additives, electrolytic zirconia bricks, ceramic pigments, enamel, artificial gemstones, refractory materials, grinding and polishing and other industries and products.

7. Composite Zirconia

Composite zirconia, referring to stabilized zirconia, is a non-toxic, odorless white powder. It has stable chemical properties and controllable specific surface area. It is the basic raw material for the manufacture of various special ceramics, advanced refractory materials, optical communication devices, and new energy materials.

8. Nuclear Grade Zirconium

Nuclear-grade zirconium is mainly used as the structural material of nuclear-powered aircraft carriers, nuclear submarines, and civil power reactors, and the cladding of uranium fuel elements. It is an important strategic metal.

9. Industrial Grade Zirconium

Industrial-grade zirconium is mainly used in the production of chemical acid and alkali-resistant equipment, the military industry, the electronics industry, pipeline valve materials, special high-strength, and high-temperature alloy materials, and getters for electric vacuum and lighting bulb industries.

10. Metallurgical Grade Zirconium

Metallurgical grade zirconium is used as a firearms sponge zirconium combustion agent and is also suitable for alloy additives and metallurgical deoxidizers, the chemical industry, civilian flash fireworks, etc.

Comparison of zirconia ceramic teeth and metal ceramic teeth

Broken or missing teeth usually require fillings. The two conventional options are zirconia ceramic teeth and metal-ceramic teeth. This article will analyze the difference between the two and help those in need to choose the one that suits them.

Metal ceramic teeth

Metal-ceramic crowns are accepted by most patients because of their good strength, but they have many disadvantages. The metal substrate is easily oxidized to form gray oxides, which are scattered and deposited on the edge of the gums, causing the gums to turn gray and affecting the appearance; at the same time, metal porcelain teeth may have a strong stimulating effect on the gums, and even cause gum swelling, bleeding, allergies and other symptoms; the color of the metal-ceramic crown should be covered with opaque porcelain, so that the ceramic crown can block the light to a certain extent, thus affecting the aesthetics of the teeth.

Zirconia all-ceramic teeth

At present, there are many types of all-ceramic dental materials, such as leucite, lithium-based porcelain, alumina, zirconia, etc. There are also a variety of fabrication methods, such as infiltrated ceramics, hot pressure casting ceramics, porcelain deposition, computer-aided design, and computer-aided fabrication. In comparison, among all all-ceramic restoration materials, zirconia material has higher flexural strength, so it is accepted by more and more patients and doctors.

Zirconium dioxide all-ceramic crown has its own unique advantages. Since there is no metal bottom crown, its restoration has permeability and aesthetics, which provides a guarantee for aesthetic restoration. At the same time, zirconium dioxide has strong biocompatibility and is non-irritating to the gums. Most patients will not experience symptoms such as gum swelling, bleeding, and allergies, which meet the clinical requirements.

Advantages of zirconium dioxide

(1) Good mechanical properties: it has a flexural strength greater than 900MPa, so it can also be used for the repair of posterior teeth and porcelain bridges with more than 6 units.

(2) Good biocompatibility: The zirconia all-ceramic crown itself does not contain metal, which can exclude metal allergic reactions; zirconia also has good biocompatibility.

(3) No obstruction to X-rays: There is no need to remove the dentures when performing cranial X-rays, CT, and MRI examinations, because zirconia ceramic teeth have no obstruction to X-rays.

(4) Good strength and density: Zirconium dioxide is widely used, especially in high-precision instruments, such as aviation equipment. Because of its good crack resistance and tough curing after cracking, it can be made into a porcelain bridge with more than 6 units, and it can also solve the problem that the all-ceramic system cannot be used as a long bridge.

(5) The color is comparable to real teeth: the color of the base crown of the ceramic is white, so the neck of the porcelain tooth will not become black and darkened for a period of time after the porcelain tooth is inserted, thus avoiding the problem of discoloration of the metal porcelain crown.

(6) Healthy biological material: Zirconium dioxide is an excellent high-tech biological material with good biocompatibility, which is healthy and safe to use.

(7) High-tech quality: Zirconium dioxide ceramic teeth are made by good computer-aided design, laser scanning, and then controlled by computer-aided program grinding.

Hopefully, the above analysis will help you a lot in making your choice between metal ceramic teeth and ceramic teeth.

What are Zirconium Containing Refractory Materials?

Description of zirconium-containing refractory products

Zirconium-containing refractory products refer to refractory products made of zirconia (ZrO2) and zircon (ZrSiO4) as raw materials, including zirconia products, zircon products, zirconium mullite, and zirconium corundum products. According to different production processes, zirconium-containing refractory products are divided into sintered products, fused cast products, and non-fired products. Zirconium-containing refractory products have the characteristics of high melting point, low thermal conductivity, and good chemical stability, especially good corrosion resistance to molten glass and liquid metal.

Properties of zirconium-containing refractory products

Dense, stabilized zirconia has a melting point of 2677°C and a service temperature of 2500°C. The bulk density fluctuates between 4.5 and 5.5 g/cm3 due to the purity of the raw materials and the different manufacturing methods. The bulk density of dense zirconia products can reach 5.75g/cm3. Sintered zirconia products do not chemically react with molten metal and liquid glass. Caustic alkali solutions, carbonate solutions, and acids (except concentrated H2SO4 and HF) do not chemically react to zirconia. When carbon reacts with sintered zirconia, zirconium carbide is formed only on the surface. Therefore, under the condition of oxidizing atmosphere, zirconia products can be used at high temperatures without chemical change.

The main component of zircon products is ZrO2•SiO. Zircon is decomposed into ZrO2 and SiO when heated at 1680℃. Quartz stone products have good corrosion resistance to various molten metals, acidic reagents, and liquid glass, but they are prone to erosion reactions when they come into contact with alkaline slag or alkaline refractory materials. Aluminum-zirconium-silicon (AZS) cast bricks and fired bricks have good resistance to glass liquid erosion, and can be used in the pool wall and upper structure of glass melting pool kilns.

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Uses of zirconium-containing refractory products

Zirconium-containing refractory products have high refractoriness, mechanical strength, and chemical stability. It can be widely used in metallurgy, building materials, the chemical industry, machinery, and other professional fields.

Zircon bricks have good resistance to acid slag, small corrosion loss, and slight sticking of slag. They can be used in the slag line of the ladle and have a long service life. Zircon products can also be used as continuous-casting intermediate tank base bricks, cushion bricks, and nozzle bricks. Zircon bricks are corrosion-resistant to low alkali glass and can be used in the kiln walls of glass-melting furnaces. It can also be used for the arch foot of the upper structure of the glass melting furnace or the intermediate transition layer between the silica brick and the corundum brick and is also an important material for the comprehensive masonry bottom.

Zirconia bricks can be used in thermal equipment for the building materials industry and metallurgical industry, such as sizing nozzles for billet continuous casting, submerged nozzles, and slag lines in long nozzles.

Fused-cast bricks with a ZrO2 content of more than 90% can be used for side walls, partition walls and flow holes of borosilicate glass melting furnaces and aluminosilicate glass melting furnaces. AZS-fired bricks and fused cast bricks can be used in soda-lime glass melting kilns, such as flow holes and side walls. The use of this brick to build liquid flow holes and side walls can reduce the contamination of glass liquid by refractory materials. In addition, zirconium mullite fused cast bricks can be used in the metallurgical industry heating furnaces, soaking furnaces, glass melting furnaces in the building materials industry, etc.

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Two Surface Treatment Technologies for Zirconium Materials

The surface of the zirconium rod and zirconium alloy must be clean and smooth before joining, heat treatment, electroplating and forming. This article introduces 2 types of surface treatment methods for zirconium materials.

Surface decontamination

Grease, oil, and lubricants produced during zirconium machining or other processing can be removed in a number of ways. Commonly used cleaning methods are

1) cleaning with alkaline or milky detergent in a soaking tank;

2) cleaning with ultrasonic vibration;

3) rinsing with acetone or trichloroethylene or steam degreasing and

4) cleaning with other cleaning agents.

Small stains can also be removed by hand wiping with some solvents such as acetone, alcohol, trichloroethylene, or a trichloroethylene substitute. In the electrolyte system, if the voltage and current can be controlled to avoid anodic polarization or spark discharge and pitting, positive or negative polarity decontamination can be used. Before heat treatment and bonding, the surface of the zirconium material must be cleaned to prevent metal contamination and the resulting deterioration of ductility.

Blast cleaning

Mechanical decontamination methods such as sandblasting, shot blasting, and evaporative cleaning can remove dirt and lubricants from zirconium and hafnium surfaces. Alumina, silicon carbide, silica and steel grit are ideal media for mechanical decontamination. The decontamination medium used should be replaced regularly to avoid increased workload due to particle passivation.

Grinding or shot peening may cause residual compressive stress and thermal deformation on the surface of the material, especially the surface of the sheet. Hot deformation may also occur during subsequent rolling and profile machining.

Blast cleaning is not a substitute for pickling. Blast cleaning cannot remove surfaces contaminated with interstitial elements such as carbon, oxygen, and nitrogen. In general, blast cleaning followed by pickling can ensure the complete removal of surface contamination and cold-worked layers, resulting in a smooth, shiny metal surface.

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What Are the New Sintering Methods of Zirconia Ceramics?

With the continuous development of science, sintering methods of zirconia ceramics are continuously introduced.

Electric field sintering

Electric field sintering refers to the sintering of the ceramic body under the action of a DC electric field. Some high-curie-point ferroelectric ceramics, such as lithium niobate ceramics, apply a DC field to both ends of the green body at their sintering temperature. After cooling to a temperature below the Curie point (Te-1210 ℃) and removing the electric field, you can obtain Piezoelectric ceramic samples.

Ultrahigh pressure sintering

Ultra-high pressure sintering is sintering at a pressure of several hundred thousand atmospheres or more. Its characteristics are that it cannot only make the material reach high density quickly, and have fine grains (less than 1um), but also change the crystal structure and even the atomic and electronic states, so that the material cannot be reached under the usual sintering or hot-pressing sintering process Performance, and can synthesize new artificial minerals. This process is relatively complicated and requires higher mold materials, vacuum sealing technology, and fineness and purity of raw materials.

Activated sintering

The principle of activated sintering is to use some physical or chemical methods to make the atoms or molecules of the reactants in a high-energy state before or during sintering. With the instability of this high-energy state, it is easy to release energy Low energy state. The physical methods used in activated sintering include electric field sintering, magnetic field sintering, sintering under the action of ultrasound or radiation, and so on; the chemical methods used are: chemical reactions based on redox reactions, dissociation of oxides, halides, and hydroxides, and atmospheric sintering. Activated sintering has the advantages of reducing the sintering temperature, shortening the sintering time, and improving the sintering effect.

For some ceramic materials, activated sintering is another effective texturing technique. There is also the use of substances in the phase change, dehydration and other decomposition processes, the atom or ion bond is destroyed, making it in an unstable active state. For example, increase the specific surface area; add substances that can generate new erbium molecules during the sintering process; add substances that can promote the sintering material to form a solid solution; increase the lattice defect substances, all of which are activated sintering. In addition, activated sintering also includes adding a small number of substances that can form an active liquid phase, promote the vitrification of materials, appropriately reduce the viscosity of the liquid phase, wet the solid phase, and promote solid-phase dissolution and recrystallization.

Activated hot sintering

Activated hot-pressing sintering is a new process developed on the basis of activated sintering. It utilizes an activated state with higher energy during the decomposition reaction or phase change of the reactants to perform hot-pressing treatment, which can be performed at lower temperature and lower pressure. It is a high-efficiency hot pressing technology to obtain high-density ceramic materials in a short time. For example, barium titanate, lead zirconium titanate, ferrite, and other electronic ceramics are made by hot pressing by the decomposition reaction of hydroxide and oxide; high-density beryllium oxide, thorium oxide and uranium oxide ceramics were prepared by hot pressing of carbonate decomposition reaction; high-density alumina ceramics are made by hot pressing during phase transition of some materials.

Stanford Advanced Materials (SAM) is a global supplier of pure metals, alloys, ceramics, minerals, and rare earth materials since 1994. Headquartered in Lake Forest, California, SAM specializes in providing high-purity chemicals (up to 99.99999%) for research institutes and technical grade materials for advanced industries, such as pharmaceutical, capacitor, metallurgy, semiconductor, and aviation. 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, 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.

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 Readability

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.

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 https://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 a 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 with 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.

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.

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.

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.

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

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.

Zirconia Ceramic Phone Backplane Stands Out in 5G Era

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

Zirconia ceramic phone backplane stands out

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

The contrast of the backplane of several kinds of mobile phones

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

Preparation and difficulty analysis of zirconia cell phone ceramics

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

Technological difficulties

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

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

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

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

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

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, reduced energy consumption, reduced pollutant emissions, protecting the environment as an important way to improve product quality and enhance enterprise competitiveness.

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 a 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, the oxygen sensors’ 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.

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 nengest 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.

Direct probe

The 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 the 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 a direct insert oxygen probe, and the zirconia and alumina tube connection structure with high technical requirements is 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.