“Special ceramics†refers to high-performance ceramics made from high-purity synthetic inorganic compounds and sintered by precision control technology. According to the characteristics of properties and materials, special ceramics are roughly divided into five categories: structural ceramics, functional ceramics, semiconducting ceramics, ceramic fiber reinforced ceramic matrix composites and cermets. In actual research and application, mainly based on structural ceramics and functional ceramics. The special ceramic industry is a low-carbon industry that uses high-tech development.
The basic characteristics of the special ceramics market China's functional ceramics account for 80% of the total sales of special ceramics, and the annual growth rate of 20%. Among functional ceramics, electromagnetic functional ceramics account for 80% of the ratio. That is, more than 60% of the special ceramics market is electromagnetic functional ceramics. Functional ceramics have been widely used in energy development, space technology, electronic technology, sensing technology, laser technology, optoelectronic technology, infrared technology, biotechnology, environmental science and other fields. With the development of modern science and technology such as aerospace, aviation, atomic energy and advanced energy, the demand for high-temperature and high-strength materials is becoming more and more demanding, and metal-based superalloys are often difficult to fully satisfy. Structural ceramic materials have much higher melting point and hardness than metal materials, and it also has good chemical stability, oxidation resistance and other good properties, so structural ceramics are more and more widely used in high temperature technology. In particular, in the field of traditional ceramic kiln, high load-bearing, high-temperature transmission, firing accessories, and insulating refractory materials such as alumina, silicon carbide roller, guillotine, mullite ceramic fiber, etc., China has the world's largest production. Capabilities and price/performance advantages.
Development status and prospects of special ceramics The research and production of special ceramics in China has been greatly developed in the past 30 years of reform and opening up, but it is still far from the developed countries in terms of practical application, production level and industrialization. It is estimated that by 2010 and 2015, the output value of China's special ceramics will reach 30 billion yuan and 45 billion yuan respectively, and the market demand is huge. There are more than 300 universities, research institutes and production enterprises engaged in the development of special ceramics in China, of which 63.6% are units for research and development of functional ceramics, and 36.4% are for research and development of structural ceramics. The Chinese Academy of Sciences, Shanghai Institute of Ceramics, and Tsinghua University have played an important role in promoting the research of special materials in China.
Special ceramics are widely used in industrial machinery equipment, gas appliance industry, automobile (motorcycle) industry, textile industry, electromechanical industry, medical equipment and other fields. With the development of the economy, the application range of high-tech ceramics has also expanded.
In the 21st century, a new generation of technological revolutions—bioengineering, new energy, information engineering, space development, and marine development—needs a lot of new materials. The underlying material undoubtedly plays an important role in these technological revolutions. In the development of materials, although ceramics appeared the earliest, they have always been based on metal materials and organic polymers, so they have been studied thoroughly and widely used. Because of this, the potential is relatively fully exploited. The history of special ceramics is relatively short, the depth and breadth of research is far less than that of metals and polymers, and specialty ceramics have many unique properties and great potential. Therefore, the probability of discovering new materials is very high.
Some special ceramics projects in 2009 have been researched. Since 2009, China's special ceramics have formed large-scale development projects including automotive ceramic brake pads, zirconia solid electrolyte research, nano ceramics forming, calcium cobalt oxide thermoelectric materials research, and titanium dioxide. Application of photocatalysis technology, biofunctional ceramics, etc. Breakthrough development in these fields will surely become a new way of industrialization development.
First, the automotive brake pad application project is becoming more and more demanding for high-speed vehicles. None of the friction materials currently used in China can fully meet the new requirements. This situation seriously restricts the braking performance of automobiles and even the automotive industry in China. The rapid development.
Compared with semi-metallic friction materials and non-asbestos friction material brake pads, ceramic brake pads have the advantages of small specific gravity, high melting point, high hardness, good chemical properties and corrosion resistance, and have been widely used in friction materials. Therefore, the development of new ceramic friction materials with stable friction performance, low wear rate, long service life, no noise and vibration has become a hot field in the research of friction materials.
2. Zirconia-based solid electrolyte project Solid oxide fuel cell (SOFC) is a new type of green energy that developed rapidly in the 1980s. Solid electrolyte is the core component of SOFC. SOFC requires electrolyte with high ionic conductivity, low electron migration number, chemical stability with electrode material and oxidized gas, and thermodynamic stability over a wide temperature and oxidation pressure range. Other battery components are matched in thermal expansion coefficient, and have good airtightness and suitable mechanical properties.
Zirconia ceramics have become the most researched and widely used class of electrolyte materials due to their high ionic conductivity, good chemical stability and structural stability. By improving the preparation process of zirconia-based electrolyte film, reducing the operating temperature and preparation cost of such materials, it is also an important direction for future research to realize industrialization.
3. Nano-ceramic forming Like the molding of ordinary ceramics, the forming method of nano-ceramics can be divided into two types: dry forming and wet forming. However, for coarse-grained powders of ordinary ceramics, the formation of nano-powders is often much more difficult because the nano-powder particles are small, and the contact points between the particles in the unit volume are much larger than those of ordinary powders, and each contact point Both may hinder the slip and rearrangement between the particles due to the action of friction, thereby affecting the increase in the density of the green body and the homogenization of the structure. More importantly, the nanoparticles are easily agglomerated by the action of van der Waals forces, resulting in an increase in the unevenness of particle packing in the green body and a decrease in the density of the green body. Moreover, if these agglomerates are not crushed or removed in the forming stage, it is easy to form differential sintering at the time of sintering, which results in an increase in sintering temperature and production of crystal grains, which is extremely disadvantageous for preparing nano ceramics. In addition, the surface of the nanoparticles is very easy to adsorb impurities, and may also affect the formation and even subsequent sintering and material properties. Therefore, finding suitable technical processes and obtaining agglomerates with little or no agglomeration, high relative density and uniform structure is an important task in the preparation of nanoceramics.
4. Calcium cobaltate thermoelectric materials research Thermoelectric materials have important application value in the field of temperature difference power generation and refrigeration because the equipment prepared by thermoelectric materials has the advantages of no vibration, no noise, small volume, light weight and no pollution to the environment. And a wide range of application prospects.
Calcium sulphate oxide is a new type of thermoelectric material, which has the advantages of not easy to deliquesce, good chemical stability and good thermoelectric performance. With the increasingly prominent energy and environmental issues, calcium cobalt oxide based thermoelectric materials will become a new hot spot in the field of green energy research due to its special functions in the utilization of low-grade energy such as industrial waste heat and environmental protection. However, calcium cobalt-based thermoelectric materials are not a substitute for traditional refrigeration and power generation technologies, and their industrial applications are required. The following research is needed: continue to study the effects of doping on the thermoelectric properties of materials, conduct research on nanocomposites, and strengthen Research on the fabrication process of devices to accelerate the practical process of thermoelectric materials.
V. Application of titanium dioxide photocatalysis technology Titanium dioxide photocatalysis technology originated in the 1970s. Nano-titanium dioxide has many excellent properties in terms of structure, photoelectricity and chemical properties. It can convert light energy into electrical energy and chemical energy, so that the reaction that is difficult or impossible to achieve under normal conditions can be smoothly carried out under mild conditions. . In particular, titanium dioxide as a photocatalyst has the characteristics of non-toxicity, low cost, and stable physical and chemical properties. The holes generated by photoexcitation and the further formed hydroxyl radicals can selectively oxidize organic pollutants and be completely mineralized without secondary pollution. It is very popular. With the development of photocatalytic technology and the improvement of the catalytic activity of nano-TiO2, its application fields are more extensive.
At present, “photocatalyst†has been adopted as a means of air purification for hospitals, public facilities and even taxis in developed coastal areas of China. Some car manufacturers use photocatalytic technology to process new cars before they are produced, and launch healthy cars. However, the separation of Ti02, the reactor model, the immobilization of the catalyst, and the improvement of visible light utilization efficiency still need further study.
Sixth, biological functional ceramics The basic requirements of biological functional materials are that they are harmless to health and are not destroyed by biochemical effects. That is, the physical, chemical and physiological properties of the material are required to be stable, no stimulation to biological tissues, corrosion and absorption by biological tissues, and good compatibility. At the same time, the human bones must withstand large stresses, requiring approximately 200 MPa of strength.
Many ceramic materials have these various requirements, so in the past 30 years, it is gradually replacing traditional biological hard tissue materials such as stainless steel, titanium alloys and other metal materials. Traditional metal biomaterials are easily dissolved and corroded in living organisms. Organic non-metallic biomaterials have low strength. The surface structure of the ceramic is hydrophilic, has excellent affinity with biological tissues, and has the advantages of light weight, high strength and high rigidity.
Biofunctional ceramics can be divided into seven aspects according to their use. First, artificial bone or artificial joint; second, artificial organ material of exercise system; third, morphological repair and orthopedic materials; fourth, artificial root and denture; fifth, adsorption material in artificial liver (activated carbon) Sixth, fixed enzyme carrier (porous glass); seventh, diagnostic test instrument temperature, gas, ion sensor and other sensor materials. Biofunctional ceramics play an irreplaceable role in protecting human health and beauty.
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