Properties and Application Fields of Alumina Ceramics
There are 12 kinds of homogeneous polymorphs of Al2O3, but there are mainly 3 kinds that are used more, namely α-Al2O3, β-Al2O3 and γ-Al2O3.
α-Al2O3 is a trigonal crystal system with the most compact structure, low chemical activity, good high temperature stability, excellent electrical properties and the best mechanical properties.
β-Al2O3 is a polyaluminate mineral with a high content of Al2O3. Its chemical composition contains a certain amount of alkaline earth metal oxides and alkali metal oxides, and it can also exhibit ionic conductivity.
γ-Al2O3 is a spinel-type cubic structure. Unstable at high temperature, 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.
Application.
1. Mechanical.
The bending strength of Al2O3 porcelain sintered products can reach 250 MPa, and the hot-pressed products can reach 500 MPa. The Mohs hardness of Al2O3 ceramics can reach 9, and it has excellent anti-wear properties, so it is widely used in the manufacture of tools, ball valves, grinding wheels, ceramic nails, bearings, etc. Among them, Al2O3 ceramic tools and industrial valves are the most widely used.
The optimal cutting speed of Al2O3 ceramic tools is higher than that of ordinary carbide tools, which can greatly improve the cutting efficiency of different materials. With a lot of research by scientific workers, other components are added to form two-phase or Al2O3-based composite ceramics and whisker-reinforced ceramics that exist in the matrix in the form of solid solution. These technologies make up for the deficiencies of pure Al2O3 ceramics, thereby improving its cutting performance and durability.
Al2O3-carbide ceramic tool, is to add a certain carbide in Al2O3, to improve its strength, wear resistance, impact resistance and high temperature performance. Due to the addition of metal, improve the connection strength of Al2O3 and carbide, improve the performance, this kind of ceramic tool is suitable for processing hardened steel, alloy steel, manganese steel, chilled cast iron, nickel and cobalt based alloy and non-metallic materials.
2. Electronics/Electricity.
In terms of electronics and electricity, there are various Al2O3 ceramic bottom plates, substrates, ceramic films, transparent ceramics, and various Al2O3 ceramic electrical insulating porcelain parts, electronic materials, magnetic materials, etc. Among them, Al2O3 transparent ceramics and substrates are the most widely used.
At present, transparent ceramics are an important frontier of research and application in the field of materials. As an emerging material, transparent ceramics have high thermal conductivity, low electrical conductivity, high hardness, high strength, low dielectric constant and dielectric loss, wear resistance and corrosion resistance in addition to their wide range of light transmittance. A series of advantages such as good sex.
Al2O3 ceramic substrates have excellent properties such as high mechanical strength, good insulation, and high light protection, and are widely used in multilayer wiring ceramic substrates, electronic packaging and high-density packaging substrates.
3. Chemical.
In chemical applications, Al2O3 ceramics also have a wide range of uses, such as Al2O3 ceramic chemical filler balls, inorganic microfiltration membranes, corrosion-resistant coatings, etc. Among them, Al2O3 ceramic membranes and coatings are the most studied and applied.
4. Medical.
In medicine, Al2O3 is more used to make artificial bones, artificial joints, artificial teeth, etc.
Advantages: Al2O3 ceramics have excellent biocompatibility, biological inertness, physical and chemical stability, high hardness and high wear resistance, and are ideal materials for the preparation of artificial bones and artificial joints.
Disadvantages: high brittleness, low fracture toughness, high technical difficulty in machining, complicated process, etc.
5. Architectural/Sanitary/Ceramic.
In building sanitary ceramics, products can be seen everywhere, such as Al2O3 ceramic lining bricks, grinding media, rollers, ceramic protection tubes and Al2O3 refractories. Among them, Al2O3 ball milling media is the most widely used.
6. Others.
Al2O3 ceramics is one of the most studied and widely used materials among new materials. In addition to the above applications, it is also widely used in other high-tech fields, such as aerospace, high-temperature industrial furnaces, composite reinforcement and other fields.
