Among the oxides with melting point over 2000 ℃, alumina is a more flexible and cheap material. Alumina ceramics are widely used, widely used and high-yield ceramic materials in oxide ceramics.
1、 Introduction of alumina ceramics
According to the research report, there are 12 kinds of homogeneous polycrystalline variants of alumina, but there are mainly three kinds of variants which are widely used, namely, Al 2O 3 α- Al2O3、 β- Al2O3 and γ- These three kinds of crystals have different structures, so their properties are very different.
α- Alumina is a cubic system, which has a compact structure, low chemical activity, good high temperature stability, excellent electrical and mechanical properties.
β- Alumina is a kind of polyaluminate mineral with high content of alumina. Its chemical composition contains a certain amount of alkaline earth metal oxides and alkali metal oxides, and it can also show ionic conductivity.
γ- Alumina is a spinel cubic structure. It is unstable at high temperature and has poor mechanical and electrical properties. But it has high specific surface area and strong chemical activity, and can be used as adsorption material after technical improvement.
3、 Application of alumina ceramics
In mechanical aspect: the bending strength of alumina ceramic sintered products can reach 250Mpa, and that of hot pressed products can reach 500MPa. The Mohs hardness of alumina ceramics can reach 9, and it has excellent wear resistance, so it is widely used in manufacturing cutting tools, ball valves, grinding wheels, ceramic nails, bearings, etc., among which alumina ceramic cutting tools and industrial valves are widely used.
(1) Pure alumina ceramic tool
The cutting speed of alumina ceramic tool is higher than that of cemented carbide tool, which can greatly improve the cutting efficiency of different materials. With a large number of scientific research, adding other components to form two phases or in the form of solid solution in the matrix of alumina matrix composite ceramics and whisker reinforced ceramics. These technologies make up for the deficiency of pure alumina ceramics, thus improving its cutting performance and durability.
(2) Composite alumina ceramic tool
In order to improve the strength, wear resistance, impact resistance and high temperature performance of Al2O3 carbide ceramic cutting tools, some carbides are added to them. This kind of ceramic tool is suitable for processing quenched steel, alloy steel, manganese steel, chilled cast iron, nickel base and cobalt base alloy and non-metallic materials.
(3) Toughened alumina ceramic tool
Toughening alumina ceramic tool is to add toughening or reinforcing materials into the alumina matrix. At present, the commonly used toughening methods are: ZrO2 phase transformation toughening, whisker toughening, second phase particle dispersion toughening and so on.
In Electronics / power: in electronics and power, there are various kinds of alumina ceramic substrates, substrates, ceramic films, transparent ceramics, as well as various kinds of alumina ceramic electrical insulating ceramics, electronic materials and magnetic materials, among which the transparent ceramics and substrates are widely used.
(1) Alumina ceramics transparent ceramics
At present, transparent ceramics is an important frontier in the field of materials research and application. As a new material, transparent ceramics not only have a wide range of light transmittance, but also have a series of advantages such as high thermal conductivity, low conductivity, high hardness, high strength, low dielectric constant and dielectric loss, good wear resistance and corrosion resistance.
(2) Alumina ceramic substrate
Alumina ceramic substrate has high mechanical strength, good insulation and high light resistance, which is used for multilayer wiring ceramic substrate, electronic packaging and high density packaging substrate.
In chemical industry: in chemical application, alumina ceramic also has a wide range of applications, such as alumina ceramic chemical filler ball, inorganic microfiltration membrane, corrosion-resistant coating, etc., among which the research and application of alumina ceramic membrane and coating are also more.
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