It can be divided into oxide ceramics, nitride ceramics, boride ceramics, carbide ceramics and metal ceramics according to the different raw material composition.Among them alumina ceramics is one of the most important, its raw material is various specifications of alumina powder.
Application of alpha alumina in functional ceramics
Functional ceramics refers to the use of the electric, magnetic, the properties such as sound, light, heat, or the coupling effect, in order to realize some functions of advanced ceramics, its insulation, dielectric strength, piezoelectricity, thermoelectricity, semiconductor, ionic conductivity and superconductivity and various electrical properties, thus has various functions and the most widely used.It is widely used in TV sets and video recorders, capacitor dielectric ceramics, piezoelectric ceramics and sensitive ceramics for various sensors. It is also used in high pressure sodium lamp.
Spark plug insulation ceramics
Spark plug insulating ceramics is the single biggest application of ceramics in engine.Aluminum oxide is widely used in the world because of its excellent electrical insulation, high mechanical strength, high pressure resistance and heat shock resistance.-alumina for spark plugs is a regular low sodium alumina powder with a sodium oxide content of 0.05% and an average particle size of 325 mesh.
Integrated circuit substrates and packaging materials
Ceramic substrate materials and packaging materials are superior to plastics in the following aspects: high insulation resistance, high resistance to chemical corrosion, high tightness, can prevent moisture transmission, no reactivity, will not contaminate ultra-pure semiconductor silicon.Integration of substrate and packaging material required by alpha alumina performance: the thermal expansion coefficient 7.0 x10-6 / ℃, thermal conductivity of 20-30 w/k. m (room temperature), 9 a 12 (IMHz), dielectric constant dielectric loss 3 ~ 10-4 (IMHz), volume resistivity > Ω, 1012-1014 cm (room temperature
With the high performance and integration of integrated circuits, more stringent requirements are put forward for the substrate and packaging materials:
Higher thermal conductivity is required as the calorific value of the chip increases.
Low dielectric constant is required with the high speed of operation element.
Thermal expansion coefficient is required to be close to silicon.This leads to a higher requirement for alpha monoalumina, which develops towards high purity and fineness.
High pressure sodium lamp
The fine ceramics made of high purity ultrafine alumina are characterized by high temperature resistance, corrosion resistance, good insulation and high strength.Transparent polycrystal made of high purity alumina plus a small amount of magnesia, alumina language or iridium oxide and adopting atmosphere sintering and hot pressing sintering etc.
Application of alpha alumina in structural ceramics
Application of alpha alumina in bioceramics
Biological ceramic materials as inorganic biomedical materials, compared with metal materials, polymer materials have no side effects, and biological tissue has the advantages of good biocompatibility, corrosion resistance, has been more and more get people's attention, the biological research and clinical application of ceramic materials, has developed from short-term replacement and filling into a permanent planting, from the development of biological inert materials to bioactive materials and multiphase composite materials.
In recent years, alumina porous ceramics have been used for making artificial bone joints, artificial knee joints, artificial femoral head, other artificial bones, artificial tooth roots and bone fixation screws and corneal repair due to their chemical erosion resistance, wear resistance, good high temperature stability and thermoelectric properties.In the preparation process of alumina porous ceramics, the pore size is controlled by mixing alumina particles with different particle sizes, foam impregnation and spray drying.The aluminum plate can also be anodized to make directional nano-sized pores of channel type.
Compared with the above methods, the sol-gel method can further improve the control of pore size distribution, phase transition, purity and microstructure of alumina porous ceramics.The process of preparing alumina porous ceramics by sol-gel method is as follows: aluminum powder is hydrolyzed in aluminum chloride solution to obtain alumina sol, and the pore-forming agent is directly mixed with it, then the product is formed and fired.