New ceramic materials have their unique advantages in performance. In terms of thermal and mechanical properties, it has high temperature resistance, heat insulation, high hardness, wear resistance, etc .; in electrical properties, it has insulation, piezoelectricity, semiconductority, magnetism, etc .; in terms of chemistry, it has catalysis, corrosion resistance, adsorption And other functions; in terms of biology, it has certain biocompatibility and can be used as biostructural materials. But it also has its disadvantages, such as brittleness. Therefore, research and development of new functional ceramics is an important field in materials science.
Belongs to a new type of material. Traditional ceramics mainly use natural rocks, minerals, clay and other materials as raw materials. The new ceramics use artificially synthesized high-purity inorganic compounds as raw materials, and are formed into inorganic materials with a fine crystalline structure through molding, sintering and other treatments under strict control. It has a series of superior physical, chemical and biological properties, and its application range is far from the comparison of traditional ceramics. Such ceramics are also called special ceramics or fine ceramics.
It is mainly divided into two categories: one is pure oxide ceramics, such as Al2O3, ZrO2, MgO, CaO, BeO, ThO2, etc .; the other is non-oxide ceramics, such as carbide, boride, nitride and silicide, etc. .
By performance and characteristics
Can be divided into: high temperature ceramics, super hard ceramics, high toughness ceramics, semiconductor ceramics. Electrolyte ceramics, magnetic ceramics, conductive ceramics, etc. With the continuous improvement of composition, structure and process, new ceramics are emerging one after another.
According to its application
They can be divided into engineering ceramics and functional ceramics.
Ceramics used in engineering structures are called engineering ceramics, which are mainly used at high temperatures, also called high-temperature structural ceramics. This type of ceramics uses alumina as the main raw material. It has the advantages of high strength at high temperature, high hardness, oxidation resistance, corrosion resistance, wear resistance, and ablation resistance. It can withstand high temperatures of 1980 ° C in air and is a space technology. , Military technology, atomic energy, industry and chemical equipment and other important materials. There are many types of engineering ceramics, but the most studied in the world, the most promising are silicon chloride, silicon carbide and toughened oxide three types of materials.
Piezoelectric ceramics are functional ceramics that can transform pressure into electrical energy. Even small pressures like acoustic wave vibrations can deform them, thus charging the ceramic surface. Using a piezoelectric ceramic column instead of a gas electronic lighter made of ordinary flint, it can light tens of thousands of times in a row.
The main components of transparent ceramics are magnesium oxide, calcium oxide, calcium fluoride and so on. Transparent ceramics not only transmit light, but also have high mechanical strength and hardness. Transparent ceramic is a good transparent bulletproof material, and can also be used to manufacture high-speed cutters on lathes, jet engine parts, tank observation windows, etc., and can even replace stainless steel.
Silicon nitride high-strength ceramics are known for their high strength, and can be used to manufacture gas turbine burners, blades, turbines, etc.
Precision ceramic ammoniated silicon replaces metal to manufacture heat-resistant parts of the engine, which can greatly increase the temperature of the workpiece, thereby improving thermal efficiency, reducing fuel consumption, saving energy, reducing the volume and weight of the engine, and replacing nickel, chromium, sodium, etc. Important metal materials, therefore, are considered a revolution for the engine. Silicon nitride can be prepared by a variety of methods. Industry generally uses high-purity silicon and pure nitrogen after 1600K reaction to obtain:
3Si + 2N2 = Si3N4 (condition 1600K)
The chemical vapor deposition method can also be used to make SiCl4 and N2 react under the protection of H2 atmosphere, and the product Si3N4 accumulates on the graphite substrate to form a dense Si3N4 layer. The silicon nitride obtained by this method has high purity, and the reaction is as follows:
SiCl4 + 2N2 + 6H2 → Si3N4 + 12HCl
New ceramics such as silicon nitride and silicon carbide can also be used to manufacture engine blades, cutting tools, mechanical seals, bearings, rocket nozzles, furnace pipes, etc., and have a very wide range of uses.
The ceramic materials manufactured by using the special functions of ceramics on the physical properties of sound, light, electricity, magnetism and heat are called functional ceramics. There are many types of functional ceramics with different uses. For example, according to the difference in the electrical properties of ceramics, electronic materials such as conductive ceramics, semiconductor ceramics, dielectric ceramics, and insulating ceramics can be made into capacitors, resistors, high-temperature and high-frequency devices in the electronics industry, and transformers. .
Using the optical properties of ceramics, solid laser materials, optical fibers, optical storage materials, and various ceramic sensors can be manufactured. In addition, ceramics are also used as piezoelectric materials, magnetic materials, base materials, etc. In short, the new ceramic materials cover almost every field of modern science and technology, and the application prospect is very broad.
Through hard research and development for many years, the product 99% AL2O3 bullet-proof ceramic with high performance had been successfully putted into mass production since 2003, which made our company become the first one in this industry domestic. This product is mainly applied in two fields— body protection and vehicle protection. Taking high purity α- Al2O3 powder as raw material, it is shaped by large-tonnage and two-sided pressing machine, and fired in computer-controlled ultra-temperature kiln. The product has these advantages：high hardness, moderate bulk density, strong impact resistance and high-performance of bulletproof. The bulletproof vests using the bulletproof ceramics of our company have reached the standard NIJ -0104.06 and passed the grade IIIV bullet-test held by National Bulletproof Equipment Testing Center. Through many years’ research, we can produce large whole bulletproof plate now. It has improved the bullet-proof performance greatly since the leaky joint formed by cobbling small ones couldn’t resist the bullet, while the whole plate solved the problem above effectively. So far, only our company has the capacity to arrange mass production in domestic market.
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Post time: May-08-2020