White corundum (α-alumina) has a wide range of applications in the field of functional ceramics due to its high melting point, high hardness, excellent chemical stability and insulation properties. The following is an analysis of its specific application directions and advantages:
1. Electronic ceramics
Substrates and packaging materials
White corundum is used to manufacture ceramic substrates (such as Al₂O₃ ceramics with an Al₂O₃ content of 96% to 99.6%) for high-frequency electronic devices (such as LEDs and microwave devices). Due to its high thermal conductivity (about 30 W/m·K) and low dielectric loss, it is suitable for high-frequency signal transmission.
Insulating components
High-voltage switches, vacuum tube insulation rings, etc. use its high resistivity (>10¹⁴ Ω·cm) and arc resistance.
Advantages: High purity (Na₂O content <0.1%), avoiding electrical performance degradation caused by impurities.
2. Wear-resistant ceramics
Mechanical seals and bearings
The hardness (HV~2200) and wear resistance of white corundum ceramics make it suitable for harsh environments such as chemical pumps and high-speed bearings, and its service life is 5~10 times longer than that of metal materials.
Wear-resistant coating
White corundum powder is applied to the metal surface by plasma spraying to enhance wear resistance.
Advantages: Corrosion resistance (acid and alkali resistance) is better than silicon carbide and silicon nitride.
3. High-temperature ceramics
Thermocouple protection tube and furnace lining
White corundum can withstand 1800℃ for a long time (2000℃ for a short time) and is used for the protection of high-temperature furnace temperature measuring elements or sintering furnace lining.
Refractory materials
As an additive to improve the thermal shock resistance and strength of other refractory materials.
Advantages: Low thermal expansion coefficient (8×10⁻⁶/℃) and good thermal shock resistance.
4. Bioceramics
Dental and orthopedic implants
High-purity white corundum (such as 99.5% Al₂O₃) is used for artificial joints and dental implants, with excellent biocompatibility and no rejection.
Advantages: high surface finish (Ra<0.02μm), reducing tissue friction damage.
5. Optical and transparent ceramics
High-pressure sodium lamp tubes
Transparent alumina ceramics (transmittance>95%) are used for high-brightness lighting and are resistant to high-temperature sodium vapor corrosion.
Laser window materials
White corundum ceramics have good light transmittance in the ultraviolet to infrared bands.
Key processes: ultrafine powders (particle size <0.1μm) and vacuum sintering are required to obtain high density.
6. Sensor ceramics
Gas/humidity sensor matrix
Porous white corundum ceramics are used as carriers to load sensitive materials (such as ZnO, SnO₂), taking advantage of their stability and high specific surface area.
Advantages: Chemical inertness, avoiding reaction between the matrix and sensitive materials.
7. Other functional applications
Catalyst carrier
Porous Al₂O₃ with high specific surface area is used for automobile exhaust purification (such as three-way catalyst).
Nuclear industry shielding material
Absorbs neutron radiation and is resistant to high temperature irradiation.
Key points of the process
Powder preparation: It is necessary to control the α-Al₂O₃ crystal transformation (usually obtained by calcining aluminum hydroxide or aluminum sulfate).
Sintering aid: Add MgO (0.1%~0.5%) to inhibit abnormal grain growth and improve density.
Molding technology: Dry pressing, isostatic pressing or injection molding, selected according to the complexity of the component.