First, the development of zirconia
Since the 1975 Australian scholars K.C.Ganvil first proposed the volume effect of the Zr2O transformation and to achieve the new concept of toughened ceramics, of ZrO2 ceramic used as structural materials research is very active, from the transformation crystallography, thermodynamics, toughening mechanism and materials preparation system and process aspects of in an attempt to make ZrO2 Yao ceramics or toughened by ZrO2 Ceramic play a greater utility. The research reported that more of the material system and has certain effect of partially stabilized zirconia (PSZ); polycrystalline tetragonal zirconia (TZP); zirconia toughened alumina (ZTA); zirconia toughened mullite (ZTM); toughening Si3N4, SiC and superplastic zirconia and other toughening AlN, cordierite and spinel also have a story. Due to ZrO2 phase transformation toughening the Al2O3, Mo on the fracture properties of mullite, SiN4 and SiC also have varying degrees of increase, Si3N4 material KIC from about 4.8 5.8 increased to 7, Al2O3 material KIC. Increased from 4.5 to 9.8. Providing the guarantee of mechanical properties for the further application of these materials.
As early as 1789 Klaproth extracted from the precious stones of zirconia, but until the 40's of this century as a gas lamp used in industry. Since then, one after another in refractory materials, coloring and abrasive materials have been applied. In the recent ten years, a new product with good toughness and multi function has been developed, and the number of applications of ceramics has been increased.
Zirconia is a high temperature resistance, corrosion resistance, abrasion resistance and excellent electrical properties of inorganic non-metallic materials, in the early 1920s applies to in the field of refractories, until the mid-1970s. Since then, the advanced countries in Europe, America and Japan competing investment funding research and development of oxidation zirconium production technology and zirconia series products production, further extended to the application field of zirconia structural materials and functional materials. At the same time, zirconia is also in the national industrial policy encouraged one of the focus on the development of novel materials with high performance. At present, it is widely is applied in various industries.
Two, the properties of zirconia
Under normal pressure pure zirconium oxide has three kinds of crystal form, low temperature for the single crystal system, density 5.65g/cm3, high temperature tetragonal system, density 6.10g/cm3, higher temperature for the cubic system, the density of 6.27g/cm3, the transformation of the relationship between the following:
Natural ZrO2 and ZrO2 obtained by chemical method are in the form of a single crystal system. The transition between a single crystal and a tetragonal crystal is accompanied by a volume change of about 7%. When heated by a single ZrO2 to the tetragonal ZrO2, the volume shrinkage, cooling by the tetragonal ZrO2 into a single crystal, the volume expansion of ZrO2. But this contraction and expansion does not occur at the same temperature, the former is about 1200 degrees Celsius, which is about 1000 degrees Celsius.
Volume change generated due to the change of crystal type, resulting in cracking and so pure zirconia ceramic is very difficult to produce, through the practice found that adding an appropriate amount of crystal type stabilizer of Cao, MgO, Y2O3 and CeO2 and other rare earth oxides, ZrO2 phase transformation temperature can be reduced to below room temperature, so that the stability of high temperature tetragonal and cubic zirconia at room temperature can also exist in a stable or metastable form. No abnormal expansion, contraction of the cubic and tetragonal crystal form of stabilized zirconia (fsz) and partial oxidation of stable zirconia (PSZ) formation.
Zirconia with different amount of stabilizer, will produce a different crystal types of zirconia, phase transition in the process due to changes in size and shape, capable of absorbing energy, reduce the crack tip stress concentration, prevents the propagation of cracks, improve the toughness of ceramics, from zirconia phase transformation toughening ceramics research and application has been the rapid development, there are three types: partially stabilized zirconia ceramic; tetragonal zirconia polycrystal ceramic; zirconia toughened ceramics.
Three, the application of zirconia
1.zirconia refractory
Zirconium oxide has been used in the field of refractory materials from the beginning of 1920s, until today, it still has a place in the field of refractory materials.
Zirconia crucible
Such as the melting point of before the zirconia of up to 2700 DEG C, even heating to more than 1900 Celsius also not with molten aluminum, iron, nickel, platinum metals, silicate and acidic slag and other reaction, so made of zirconia crucible can successfully melting platinum, palladium, ruthenium, cesium and other precious metals platinum and its alloys, can also be used for smelting potassium, sodium, quartz glass and oxides and salts.
zirconia refractory fibre
Zirconia fiber is only a can be in more than 1600 DEG C, ultra high temperature environment, the long-term use ceramic fiber refractory material, compared with alumina fiber, Mo mullite fiber, aluminum silicate fiber and higher temperature and better thermal insulation performance, and high chemical stability, corrosion resistance, oxidation resistance, not easy to volatilization, no pollution. These excellent characteristics determine the zirconia fiber is a kind of top grade refractory fiber material by Nanjing University of Science and Technology research of zirconia fiber technology has been made more mature preparation technology.
Zirconia kiln material
Zirconia as a refractory material mainly used in key parts of large glass tank furnace, the early use of zirconia refractory, the zirconia content is only 33% ~ 35%, Japan's Asahi Glass Company successfully developed containing zirconia 94%~95% zirconia refractory material, will be its use in glass kiln at the top and key parts, greatly improving the life of glass kiln.
Zirconia melting, blowing to obtain the different sizes of zirconia hollow spheres prepared various high-grade heat insulation brick, avoid the ageing of ceramic fiber dust pollution problem, the major manufacturers have Luoyang Institute of refractories and Shandong the refractory material factory.
2.zirconia structural ceramics
In 1975 the Australian R.G.Garvie with calcium oxide as the stabilizer of partially stabilized zirconia, and for the first time using zirconia martensitic transformation toughening effect, improve the toughness and strength, greatly extends the application of zirconia in the field of structural ceramics.
Zirconia toughened ceramics is actually by the addition of different stabilizers consisting of partially stabilized zirconia, determine its crystal structure is tetragonal phase (metastable phase) as the main body of the containing cubic and monoclinic phase is composed of polycrystalline structure. It has characteristics of high toughness, high bending strength, high hardness and wear resistance, but also shows the application of the extensive. It has broad application prospects in the fields of machinery, electronics, petroleum, chemical, aerospace, textile, precision measuring instruments, precision machine tools, biological engineering and medical equipment.
Due to the partially stabilized zirconia has a low thermal conductivity, good strength and toughness, low elastic modulus, high thermal shock resistance, high operating temperature (1100 DEG C), so for manufacturing Disuoer engine spare parts, engine parts. It has a small size, light weight, high thermal efficiency, is an effective energy-saving engine. The application of ZrO2 toughened ceramic in internal combustion engine is successful. The goal of the United States adiabatic engine program is to cancel the water cooling system, to the combustion chamber heat insulation, the use of exhaust heat, improve thermal efficiency, reduce the weight of the engine. In the adiabatic engine, toughness zirconia also available as top cylinder liner, piston, valve conduit, an inlet and exhaust valve seat, bearings, a tappet rod, a cam, a cam follower and ` piston rings and other parts. The thermal efficiency of the ceramic adiabatic internal combustion engine has reached 48% (30% for the common internal combustion engine). Ceramic insulation of internal combustion engine to eliminate the 360 a radiator, a water pump, a cooling pipe of spare parts, the weight is reduced by 191 kg and toughening of ceramics in the revolving cylinder engine with rotor. Japan, the United States, Germany and other developed countries in the production of ductile zirconium oxide. At the same time also used to manufacture computer driven components, seals, aircraft engine cooling blades, etc..
Partially stabilized zirconia has high hardness and wear resistance, so it has a wide application in the field of abrasive and abrasive tools, such as ball mill ball and ball mill inner lining and wear-resistant parts, drawing die, etc.. In our country, more than half of the toughness of ceramics in the field of grinding, while the zirconia ball accounted for an absolute advantage.
Due to zirconia is not magnetic, not conductive, non rusting, wear resistance, so in the biomedical devices and tools in the field is widely used, such as used for medical surgical knife and cut tape magnetic material products, production of artificial bone and artificial joint, artificial teeth etc.. Recently some stable ZrO2 by powder metallurgy method, preparation of magnetic watch case, to avoid corrosion of the table and other instrument parts. Used to make a kitchen knife, scissors, screwdriver, hammer, axe, saw, which is more suitable for cutting the raw food and cooked food. Japan has developed a high cerium zirconium oxide toughening ceramic tool, the composite with Ce2O3 as a stabilizer to replace the metal ceramic, fracture toughness is 3 times the metal, cutting capacity increased by 1.5 times. Tetragonal zirconia CeO2 - ZrO2 can form a wide range of solid solution phase. Adding the mole fraction of 15 to 20%CeO2 can reduce the phase transition temperature of the tetragonal zirconia to below 25. Used in military to make bullet proof armor. In the iron and steel industry, the surface of the ceramic roller and guide roller is very small.
Structural ceramics, as a new application field of zirconia, have attracted more and more attention. China's current zirconia structural ceramics, 70% of the enterprises are made of alumina ceramic industry transformation from the. The application of partially stabilized zirconia in the Chinese market is at its initial stage of development. Mainly for: optical fiber connector and casing, zirconia grinding, cutting tools, textile and tobacco machinery plate etc.. Grinding media accounted for more than half of the share. The total market in 300 ~ 400 tons / year, which used to optical fiber connector in core and a sleeve, and a jumper of zirconia in 80 ~ 100 tons / year. For a long time, China's production process is not perfect, the product quality is not high, the powder performance is not good. Also did not pass the next homes customers processing technology, so the customer use only on trial, and can not be normal application, so most of the raw powder of the product is Japan occupied by the products, especially some of the high-end industries, such as optical fiber connector and advanced structural ceramics, almost all Japanese products.
Optical fiber connector and optical fiber jumper:
The fiber optic connector and the fiber jumper wire are the most widely used and the most widely used optical passive devices in the optical fiber network. One of the core parts of the multimode active fiber optic connector, the main part of which is the two zirconia ceramic bushing (i.e., the connector precision pin), which is used as the material of the Y2O3 stabilized tetragonal zirconia powder. Its main uses are:
Zirconia ceramic bearing
Zirconia ceramic bearings with the characteristics of anti magnetic electric insulation, wear resistance, corrosion resistance, oil-free self-lubricating, high temperature resistant, cold resistant etc., for extreme environment and special working conditions.
The zirconia ceramic bearings have been used in micro cooling fan, the product life and noise stability were superior to the traditional ball bearing and sliding bearing system, Foxconn's first computer cooling fan in the zirconia ceramic bearing.
Zirconia ceramic valve
At present, widely used in various industries in China's valve metal valves, metal valve also has a history of 100 years, although the period also experienced the change of material and structure, but due to metal material limitations, as has considerable influence with the life period, reliability and wear resistance of the valve metal corrosion damage, the role of mechanical and corrosion factors on the role of the metal has greatly increased the total contact surface wear, the valve operation, the friction surface due to the interaction of chemical or electrochemical and mechanical role and metals and the environment to wear and damage results, for the valve, the pipeline complex climatic conditions of work; oil, natural gas and oil water medium hydrogen sulfide, carbon dioxide and some organic acids, the destructive force of the surface increases rapidly from Loss of ability to work.
Zirconia ceramic valve excellent wear resistance, corrosion resistance, high temperature thermal shock resistance, can be competent in this field.
Zirconia abrasive material
Zirconia grinding ball has the advantages of high hardness, low wear rate, long service life, can significantly reduce the pollution of raw material grinding, can guarantee the quality of the products is very good, and zirconia material density, used as a grinding medium impact energy strong, greatly improve the grinding dispersion efficiency, can effectively shorten the grinding time.
Good chemical stability determines its corrosion resistance, can be used in acid and alkaline media.
The wear rate is only 0.04/24h, which is widely used as grinding media in the ball mill, vibrating mill, planetary mill and grinding mill, which is developed by China Building Materials Academy.
3.zirconia functional ceramics
Zirconia ceramic ball beads for ball point pen
The first market in our country is pens big country, the international every 5 pen 4 teams from China, has formed a nearly 800 million yuan / year, the general case, pen ball beads are mainly stainless steel and tungsten carbide material, but the ball in the writing process, often appear disconnected, drop beads, die beads, dip phenomenon, at present by the Hebei Province Yong long state of new materials Co., Ltd. and Tsinghua University new ceramic and process of National Key Laboratory of jointly developed the "ball point pen with zirconia ceramic ball beads" to overcome the above defects, to fill the domestic blank, the scientific and technological achievements have been listed as national pens industry "Eleventh Five" national focus on the promotion of new products [3].
Zirconia ceramic cutting tool
Zirconia ceramic tool has the characteristics of high strength, wear resistance, no oxidation, no rust, acid and alkali resistant, anti static, and the food will not react. At the same time, knife body luster, such as jade, is today's ideal world high-tech green cutting tool, the markets are the main products are: zirconia ceramic knife, scissors, razors, scalpels,, in recent years in Europe, America, Japan, Korea and other places has started to become popular.
Zirconia high temperature heating material
Zirconium oxide at room temperature for insulating materials, the specific resistance of up to 1015 Omega - cm, elevated temperature to 600 DEG C can be conductive, and in more than 1000 DEG C is a good conductor, 1800 DEG C high temperature heating element, the highest temperature can reach 2400 DEG C, has been successfully for 2000 DEG C in oxidation atmosphere of heating element and its equipment, electrode materials for MHD power generation also in positive research.
Zirconia bio ceramic material
Noble - KaoCiYa KaoCiYa zirconium oxidation family, porcelain material directly affects the quality and health of patients, because the inner crown porcelain teeth are composed of different metal materials made of metal crowns with saliva oxidized zirconia material without the metal in baked porcelain tooth the canopy, teeth good transparency, excellent gloss, more effective to avoid sensitive teeth and gum problems black line, with good color masking ability, can perfectly solve severe dental cosmetic needs tetracycline teeth of patients, and the strength and toughness of zirconia materials to make up for the lack of common and ordinary porcelain defects, good biocompatibility, no stimulation of oral mucosa, easy to clean, is currently the most high quality porcelain teeth.
Zirconia coating materials
Zirconia thermal barrier ceramic coating materials of high performance Y2O3 stabilizers, mainly used in high performance aero turbine engine.
Zirconia communication material
In recent years, with the development of information and communication and other emerging industries, its products are more and more to the high precision, miniaturization direction, zirconia toughened ceramics excellent mechanical properties, corrosion resistance and high insulating property can be competent in this field, at present already zirconia ceramic ferrule and zirconia ceramic sleeve products available. In the ceramic PC type optical fiber connector, two pin zirconia is one of the key parts.
zirconia oxygen sensor
Automobile industry use three-way catalytic converter to reduce pollution emissions of the engine, the oxygen sensor is essential, the oxygen sensor with two kinds of titania and zirconia, one of the most widely used is oxidation zirconia oxygen sensor.
Back in the mid seventies of the 20th century, the Japanese car production technology complete is difficult to enter the market in the United States, but the United States to develop a new policy restrictions on vehicle exhaust pollution has brought opportunities to Japan, Japanese scientists to zirconia made of porous oxygen sensor, installed in the engine automatically detect hair motivation in oxygen and combustion gas ratio and automatic control input gas and exhaust gas ratio, thus greatly reducing harmful gas emissions from motor vehicles, the Japanese car in one fell swoop into the American market.
4.zirconia decorative materials
Traditional decorative ceramic by ordinary silicate system materials, such as furnishings porcelain vase, ceramic board, indoor and outdoor decoration of ceramic wall and floor tiles and other. Zirconia decorative materials to create a new field of human beautify their own, is currently mainly used in simple accessories and with the application of the function of the.
Zirconia gem material
Zirconia gem materials are divided into two kinds of natural cubic zirconia and synthetic cubic zirconia.
Under the natural state of natural cubic zirconia extremely elusive found, determines that it is a rare gem material characteristics, form a natural cubic zirconia color is very rich, large pieces of high quality natural zircon prices never under the same diamond is very rare precious natural gems.
Synthetic cubic zirconia has good optical properties, and it is a cheap and beautiful diamond substitute.
Zirconia ceramic jewelry
Zirconia ceramic jewelry at present, there are mainly the following several types: (1) silver jewelry inlaid zirconia, in the scope of this zirconia is quite broad, including oxide zircon, zirconium oxide, high purity oxide zirconium, stable zirconium oxide, superfine zirconia, zirconium English sand, zircon powder, inlaid with Cubic Zirconia silver plated rhodium jewelry is especially popular with European customers of all ages. The favor of the ceramic accessories development of ceramic decorative material (2) pure zirconia wear jewelry, is currently the market is quietly rising for a class of products, the existing ceramic production company in research, development and sales of the products in the same industry forefront of the industry the government has also given highly attention, 2006 Beijing science and technology SMEs Technology Innovation Fund of gratuitous aid projects have color zirconia structural ceramics, the market there are nearly 300 kinds of new products, which include a variety of novel styles also include a variety of color bright color, and this kind of products in Europe and the United States, Japan and Hong Kong, China and other regions have a very good market, especially by the European market. (3) both application function of wear jewelry, typical products is ceramic watch watchcase, table circle, strap, and other products, watch international well-known brands Chanel/ Chanel, RADO/ radar has full ceramic styles, and the price is not cheap.
5.other applications of zirconium oxide
Zirconia and zirconia composite materials
And other composite materials form of multiphase materials, such as zirconium oxide and aluminum oxide, Mo mullite materials such as the formation of multiphase materials, than the single-phase materials with more excellent performance of the new material.
Ordinary ceramic additive
The application of ceramic glaze color: zirconia as well yellow green pigment dyeing assistant agent, if you want to get better performance of zirconium vanadium yellow pigment must be used texture pure zirconia, also in the glaze manufacturing, pure zirconium oxide can improve the glaze of high temperature viscosity and the expansion of the high temperature viscosity changes in the temperature range, good thermal stability, its content was 2% ~ 3%, improve the glaze of anti cracking performance, because of the high chemical inertness of zirconia, can enhance the glaze of chemical stability and resistance to acid and alkali erosion ability is sometimes used to make opalescent glaze.
Preparation of chromate raw materials
The raw material of the preparation of the zirconium acid salt is formed by the reaction of two zirconium oxide and some metal oxide or metal carbonate, which is a macromolecular structure and has various electric properties, and is used in the fields of high temperature, electronic components and the like.
Four, the development prospects of zirconia
The development of high performance structural ceramics has attracted the attention of the advanced countries in the world, and has become a very active field of research, investment and production, especially in Japan, the United States and other countries. China has always attached great importance to the development of new ceramic materials, and has achieved many significant results. In recent years, some companies have been able to produce high quality ultrafine zirconia powder, and most of the products are exported. But it should be seen that our country is still in a relatively backward level in the production of raw materials. Development in the future should be towards the development of ultra-fine, high purity, product manufacturing aspects should be toward the new features, the new application areas of development, and constantly expand the application of zirconium oxide.