Alumina in its various degrees of purity is a versatile material that offers a combination of good mechanical and electrical properties and probably the most important oxide ceramic for widely varying technical applications. Depending on the alumina purity, particular the purity ranging from 95% to >99.7%, these aluminum oxide ceramics have variety of properties:
* Good mechanical strength
* Good heat conductivity
* Good fire resistance
* Good corrosion and wear resistance
* Good sliding properties
* Very good electric insulation
It is suitable for a wide range of applications including seal rings, laser tubes, electrical insulators, threadguides, refractory devices, electronic substrates, thermocouple tubes, grinding media and wear components. It has a good strength and stiffness, very high hardness and resistance to wear. In addition it can be readily joined to metals or other ceramics using specially developed metallising and brazing techniques.
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Properties of Alumina ceramics (Al2O3) |
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Property |
Item |
Data |
Unit |
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99.8% alumina |
99% alumina |
95% alumina |
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|
Mechanical Characteristics |
Color |
Ivory |
Light yellow |
White |
|
|
Density |
3.93 |
3.85 |
3.7 |
g/cm3 |
|
|
Bending Strength |
370 |
310 |
300 |
MPa |
|
|
Compressive strength |
2,500 |
2,400 |
2,300 |
MPa |
|
|
Elastic Modulus |
390 |
340 |
320 |
GPa |
|
|
Fracture Toughness |
4 |
3~4 |
3~4 |
MPa m1/2 |
|
|
Weber Coefficient |
12 |
12 |
12 |
m |
|
|
Vickers Hardness (HV 0.5) |
1,850 |
1,600 |
1,400 |
MPa |
|
|
Thermal Characteristics |
Coefficient of Line Thermal Expansion |
7~8 |
7~8 |
7~ 8 |
10-6 K-1 |
|
Thermal Conductivity |
32 |
29 |
20 |
W/mK |
|
|
Thermal Shock Resistance (Put in Water) |
280 |
200 |
250 |
∆T °C |
|
|
Max Working Temperature |
1,750 |
1,600 |
1,500 |
°C |
|
|
Electrical Characteristics |
Volume Resistance at 20°C |
>1014 |
>1014 |
>1014 |
Ωcm |
|
Dielectric Strength |
15×106 |
15×106 |
15×106 |
V/m |
|
|
Dielectric Constant |
10 |
10 |
9 |
εr |
|
|
Dielectric Loss Angle at 20°C (One MHz) |
0.0001 |
0.0002 |
0.0004 |
tanδ |
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Chemical Characteristics |
Nitric Acid (60%) 90°C |
0.05 |
0.1 |
0.1 |
WT Loss mg/cm2/day |
|
Sulphuric Acid (95%) 95°C |
0.22 |
0.34 |
0.3 |
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Caustic Soda (30%) 80°C |
0.04 |
0.95 |
0.9 |
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