Types and applications of the hottest zirconia mat

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Types and applications of zirconia materials

zirconia is an inorganic non-metallic material with high temperature resistance, corrosion resistance, wear resistance and excellent electrical conductivity. It was applied in the field of refractory materials in the early 1920s. Until the mid-1970s, the advanced countries in Europe, America and Japan in the world have invested in the research and development of zirconia production technology and the production of zirconia series products, Further expand the application field of zirconia to structural materials and functional materials. At the same time, zirconia is also one of the high-performance new materials encouraged by the national industrial policy, and is now widely used in various industries

this paper summarizes the basic properties of zirconia and the types and applications of zirconia materials, and prospects the development prospect of zirconia marketing materials

1 basic properties of zirconia

pure zirconia has three crystal forms under normal pressure, monoclinic crystal system at low temperature, density of 5.65g/cm3, tetragonal crystal system at high temperature, density of 6.10g/cm3, cubic crystal system at higher temperature, density of 6.27g/cm the conversion relationship between them is as follows:

1170 2370 2715c

monoclinic Zr02 tetragonal Zr02 cubic Zr02 melt

Natural Zr 〇 2 and Zr 〇 2 obtained by chemical method belong to monoclinic.Clinoform system. The transformation between monoclinic and tetragonal crystal forms is accompanied by a volume change of about 7%. When heated, it changes from monoclinic Zr02 to tetragonal Zr02, with volume contraction. When cooled, it changes from tetragonal Zr02 to monoclinic Zr02, with volume expansion. However, this shrinkage and expansion do not occur at the same temperature. The former is about 1200 ℃, and the latter is about 1000 ℃

due to the volume change caused by the transformation of crystal form, it will cause cracking, so it is difficult to produce pure zirconia ceramics. Through practice, it is found that an appropriate amount of crystal form stabilizers Cao and MgO are added Y203, CE 〇 2 and other rare earth oxides can reduce the phase transition temperature of Zr02 below room temperature, so that high-temperature stable tetragonal and cubic zirconia can also exist in stable or metastable forms at room temperature, forming cubic and tetragonal stable zirconia (fsz) and partially stable zirconia (PSZ) without abnormal expansion and contraction

zirconia with different crystal forms will be produced with different stabilizer dosage in zirconia. Due to the change of volume and shape in the process of phase transformation, it can absorb energy, reduce the stress concentration at the crack tip, prevent crack propagation, and improve the bremsstrahlung of ceramic materials. Since then, the research and Application of zirconia phase change toughened ceramics have developed rapidly, mainly including three types: partially stabilized zirconia ceramics, Tetragonal zirconia polycrystalline ceramics, zirconia toughened ceramics

2 zirconia application field

2.1 zirconia refractories

zirconia has been used in the field of refractories since the early 1920s, and it still occupies a place in the field of refractories today

2.1.1 zirconia crucible

as mentioned above, the melting point of zirconia is as high as 27001c, and it will not react with molten aluminum, iron, nickel, platinum and other metals, silicates and acid slag even when heated to more than 1900 degrees Celsius. Therefore, crucibles made of zirconia materials can successfully smelt platinum, palladium, ruthenium, cesium and other platinum group precious metals and their alloys, and can also be used to smelt potassium, sodium, quartz glass, oxides and salts

2.1.2 zirconia refractory fiber

zirconia fiber is the only ceramic fiber refractory that can be used for a long time in an ultra-high temperature environment above 1600c. It has higher service temperature and better thermal insulation performance than alumina fiber, mullite fiber, aluminum silicate fiber, etc., and has stable high-temperature chemical properties, corrosion resistance, oxidation resistance, non-volatile and pollution-free. These excellent characteristics determine that zirconia fiber is a top-grade refractory fiber material. The zirconia fiber technology tackled by Nanjing University of technology has achieved a relatively mature preparation process

2.1.3 zirconia kiln material

zirconia is mainly used in the key parts of large-scale glass tank kilns as a refractory. The zirconia content of zirconia used in the early stage is only 33% - 35%, and the zirconia fire-resistant material containing 94% - 95% zirconia has been successfully developed by the subsidiary of Asahi nitrate in Japan, which is used on the top and key parts of the glass kiln, greatly improving the service life of the glass kiln

after melting and blowing zirconia, zirconia hollow balls of different sizes are obtained, and various high-grade insulating bricks are prepared, which avoids the dust pollution problem after the aging of ceramic fibers. The main manufacturers are Luoyang Refractory Research Institute and Shandong No. 2 refractory factory

2.2 zirconia structural ceramics

in 1975, rvie in Australia prepared partially stabilized zirconia with calcium oxide as a stabilizer, and used the effect of martensitic transformation toughening of zirconia for the first time to improve the toughness and strength, which greatly expanded the application of zirconia in the field of structural ceramics

2.2.1 zirconia ceramic bearing

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

at present, zirconia ceramic bearings have been adopted by micro cooling fans, and their product life and noise stability are better than traditional ball and sliding bearing systems. Foxconn took the lead in adopting zirconia ceramic bearings on computer cooling fans

2.2.2 zirconia ceramic valves

at present, the valves commonly used in various industries in China are metal valves, and the use of metal valves has a history of more than 100 years. During this period, although they have also experienced changes in materials and structures, due to the limitations of metal materials, the corrosion damage of metals has a considerable impact on the action period, reliability and service life of valve wear resistance, The action of mechanical and corrosion factors on the metal greatly increases the total wear of the contact surface. During the operation of the valve, the friction surface is worn and destroyed due to the simultaneous mechanical action and the chemical or electrochemical interaction between the metal and the environment. For the valve, the pipeline working climatic conditions are complex; The presence of hydrogen sulfide, carbon dioxide and some organic acids in oil, natural gas and reservoir water increases the destructive power of their surfaces, resulting in rapid loss of working capacity

zirconia ceramic valves have excellent wear resistance. Corrosion resistance, high-temperature thermal shock resistance, can be competent in this field

2.2.3 zirconia grinding material

zirconia grinding ball has high hardness, low wear rate, long service life, can greatly reduce the pollution of grinding raw materials, and can well ensure product quality. At the same time, zirconia material has high density and strong impact energy when used as grinding medium, which can greatly improve the grinding dispersion efficiency and effectively shorten the grinding time

good chemical stability determines its corrosion resistance, which can be used in acidic and alkaline media

the wear rate of zirconia ceramic grinding balls developed by the China Academy of building materials research and development is only 0.04/24h. They are widely used as grinding media in ball mills, vibratory mills, planetary mills, stirred mills and other mills

2.3 zirconia functional ceramics

2.3.1 zirconia ceramic ball beads for ball pen

China is a large pen making country. Four of every five pens in the world come from China, which has formed a market of nearly 80billion yuan/year. Generally, ball beads for ball pen are mainly stainless steel and tungsten carbide materials, but such ball beads often break, drop, die, dip, etc. in the writing process, At present, the "zirconia ceramic ball for ballpoint pen" jointly developed by Hebei Yonglong Bangda New Material Co., Ltd. and the State Key Laboratory of new ceramics and technology of Tsinghua University has overcome the above defects and filled the domestic gap. This scientific and technological achievement has been listed as the national key promotion new product of the National pen industry during the "Eleventh Five Year Plan"

2.3.2 zirconia ceramic cutting tools

zirconia ceramic cutting tools have the characteristics of high strength, wear resistance, no oxidation, no rust, acid and alkali resistance, anti-static, and will not react with food. At the same time, the knife body is as shiny as jade. It is an ideal tool in the world today. At present, the company has the national technical center, aviation materials research institute, national recognized laboratory The high-tech green cutting tools of the first-rate R & D institutions such as the postdoctoral workstation and the national aluminum alloy pressure processing engineering technology research center, the only one in the domestic aluminum processing industry. At present, the main products in the market include: zirconia ceramic knife, scissors, razor, scalpel, etc., which have become popular in Europe, the United States, Japan, South Korea and other places in recent years

2.3.3 zirconia high-temperature heating material

zirconia is an insulating material at room temperature, with a specific resistance of 1015 Ω Nan. When the temperature rises to 600 ℃, it can conduct electricity. When the temperature is above 1000C, it is a good conductor, which can be used as a high-temperature heating element at 1800C, and the maximum working temperature can reach 2400C. At present, it has been successfully used in heating elements and equipment in an oxidizing atmosphere above 2000c, Electrode materials for MHD power generation are also under active research

2.3.4 zirconia bioceramic material

the noble zirconia porcelain teeth in the porcelain tooth family. The quality of porcelain teeth directly affects its quality and the health of patients. Because the inner crown of porcelain teeth is made of different metal materials, the metal inner crown is easy to oxidize with oral saliva. Because there is no metal inner crown, the porcelain teeth made of zirconia have good transparency and excellent gloss, It can effectively avoid problems such as tooth allergy and gum black line, and has enough good shading ability, which can perfectly solve the dental beauty needs of patients with severe tetracycline teeth. Moreover, the strong bremsstrahlung of zirconia material makes up for the shortcomings of common porcelain teeth that are easy to skip. It has good biocompatibility, does not stimulate oral mucosal tissue, and is easy to clean. It is the best quality porcelain teeth at home and abroad at present

2.3.5 zirconia coating materials

zirconia thermal barrier ceramic coating materials stabilized by stabilizers such as high-performance Y2003 are mainly used in high-performance turbine aeroengines

2.3.6 zirconia communication materials

in recent years, with the development of emerging industries such as information and communication, its products are increasingly developing in the direction of high precision and miniaturization. The excellent mechanical properties, corrosion resistance and high insulation properties of toughened zirconia ceramics can be competent in this field. At present, zirconia ceramic pins and zirconia ceramic sleeves have been produced

in the ceramic PC type optical fiber movable connector, the zirconia pin body is its key component

2.3.7 zirconia oxygen sensor

in the automotive industry, oxygen sensors are essential for engines that use three-way catalytic converters to reduce emissions. At present, there are two types of oxygen sensors: titanium oxide type and zirconia type, of which zirconia type oxygen sensor is the most widely used

as early as the mid-1970s, Japan's automobile production technology was complete, but it was difficult to enter the U.S. market, but the United States formulated new policies to limit automobile exhaust pollution, which brought opportunities to Japan. Japanese scientists made zirconia into porous oxygen sensors, installed in the engine to automatically detect the proportion of oxygen and combustion gas in the engine, and automatically control the proportion of input gas and exhaust gas, So as to greatly reduce the harmful gases emitted by cars, and make Japanese cars enter the American market at one stroke

2.4 zirconia decorative materials

decorative ceramics in the traditional sense are made of ordinary silicate system materials, such as vases in display porcelain, ceramic painting boards, ceramic wall and floor tiles for indoor and outdoor decoration, etc. Zirconia decorative materials have created a new field of human beautification. At present, the main

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