Properties and applications of alumina ceramics
Alumina is a flexible and inexpensive material in oxides with melting points in excess of 2000℃. Alumina ceramic is a ceramic material with wide application, wide application and large output in oxide ceramics.
Introduction to Alumina Ceramics
It has been reported that Al2O3 has 12 kinds of homogeneous polycrystalline variants, but there are mainly 3 kinds, which are -Al2O3, -Al2O3 and -Al2O3. These 3 kinds of crystals have different structures, so their properties are very different.
Alpha-al2o3 is a tripartite crystal system, which has the most compact structure, low chemical activity, high temperature stability, excellent electrical and mechanical properties.
-Al2O3 is a polyaluminate mineral with high Al2O3 content. Its chemical composition contains a certain amount of alkali earth metal oxides and alkali metal oxides, and can also present ionic conduction.
Gamma-al2o3 is spinel - shaped cubic structure. Unstable at high temperatures, poor mechanical and electrical properties. However, it has higher specific surface area and stronger chemical activity, and can be used as adsorption material after technical improvement.
Applications of alumina ceramics
The bending strength of Al2O3 porcelain sintered product can reach 250MPa, and the hot pressing product can reach 500MPa. The Mohs hardness of Al2O3 ceramics can reach 9, plus has excellent anti-wear performance, so widely used in the manufacture of tools, ball valves, grinding wheels, ceramic nails, bearings, etc., among which Al2O3 ceramic tools and industrial valves are the most widely used.
1, pure Al2O3 ceramic tool
The optimum cutting speed of Al2O3 ceramic tool is higher than that of ordinary carbide tool, which can greatly improve the cutting efficiency of different materials. With the extensive research of scientists, Al2O3 matrix composite ceramics and whisker reinforced ceramics are composed of two phases or solid solution. These techniques make up for the deficiency of pure Al2O3 ceramics, thus improving their cutting performance and durability.
2. Composite Al2O3 ceramic tool
Al2O3- carbide ceramic tool is added to Al2O3 to improve its strength, wear resistance, impact resistance and high temperature performance. This ceramic tool is suitable for processing hardened steel, alloy steel, manganese steel, cold cast iron, nickel-based and cobalt-based alloys, and non-metallic materials due to the addition of metal to improve the connection strength and service performance of Al2O3 and carbide.
3. Toughened Al2O3 ceramic tool
Toughened Al2O3 ceramic tool means to add toughened or reinforced material to Al2O3 matrix. At present, the commonly used toughening methods include: ZrO2 phase change toughening, whisker toughening, second phase particle dispersion toughening, etc.
In terms of electronics and power, there are various Al2O3 ceramic base plates, substrates, ceramic films, transparent ceramics and various Al2O3 ceramic electrical insulating porcelain pieces, electronic materials, magnetic materials, etc., among which Al2O3 transparent ceramics and substrates are most widely used.
1. Al2O3 transparent ceramics
At present, transparent ceramics is an important frontier in the field of materials research and application. As a new material, transparent ceramic has a wide range of light transmittance, high thermal conductivity, low electrical conductivity, high hardness, high strength, low dielectric constant and dielectric loss, good wear resistance and corrosion resistance and so on.
2. Al2O3 ceramic substrate
Al2O3 ceramic substrate has excellent properties of high mechanical strength, good insulation and high light protection. It is widely used in multi-layer wiring ceramic substrate, electronic packaging and high-density packaging substrate.
In terms of chemical applications, Al2O3 ceramics also have a wide range of uses, such as Al2O3 ceramic chemical filler ball, inorganic microfiltration membrane, corrosion resistant coating, etc., among which Al2O3 ceramic membrane and coating are the most studied and applied.
Al2O3 ceramic membrane
Membrane can be divided into organic polymer membrane and inorganic membrane, etc. Ceramic membrane has the following characteristics compared with organic polymer membrane:
In medicine, Al2O3 is mostly used to make artificial bones, joints, teeth and so on.
Advantages: Al2O3 ceramics have excellent biocompatibility, biological inertia, physical and chemical stability, high hardness, high wear resistance, is an ideal material for the preparation of artificial bone and artificial joints.
Disadvantages: high brittleness, low fracture toughness, high technical difficulty of machining, and complex technology.
In building sanitary ceramics, products can be seen everywhere, such as Al2O3 ceramic lining brick, grinding medium, roller, ceramic protective tube and Al2O3 refractory. Al2O3 ball grinding medium is most widely used.
Al2O3 ceramics is one of the most researched and widely used new materials at present. In addition to the above applications, Al2O3 ceramics is also widely used in other high-tech fields, such as aerospace, high temperature industrial furnace, composite reinforcement and other fields.