Alumina (Aluminum Oxide)

Alumina is the more common name of Aluminum Oxide (Al2O3). It is a hard-wearing technical ceramic offering an excellent combination of both mechanical and electrical properties. It is well-suited for a wide range of industrial applications.

Alumina features high hardness, wear resistance, low erosion levels, high temperature resistance, corrosion resistance, and bio-inertness. Its high temperature stability and thermal conductivity make it particularly suitable for high temperature applications such as thermocouple protection in high temperature measurement. Precision Ceramics offers a comprehensive range of advanced ceramic tubes and insulators for this purpose.

Applications

Alumina is a very hard ceramic that is excellent at resisting abrasion and is ideal for wear-resistant inserts or products. It is commonly used as a high temperature electrical insulator, particularly the higher purity grades which offer better resistivity. It also offers good resistance to strong acids and alkalis at elevated temperatures, which makes it ideal for applications where resistance to corrosive substances is required. Some common applications include:

  • Electronic components & substrates
  • High temperature electrical insulators
  • High voltage insulators
  • Laser tubes
  • Machine components
  • Mechanical seals
  • Precision shafts and axles in high wear environments
  • Roller and ball bearings
  • Seal rings
  • Semiconductor parts
  • Shot blast nozzles
  • Thermocouple tubes
  • Tap plates
  • Valve seats
  • Wear components
  • Wire and thread guides
  • Ballistic Armor

Image Gallery

CeramAlloy Ultra Hard

Alumina-Zirconia (ZTA) ceramic composites are unique ceramic materials that exhibit a combination of high hardness, strength, wear and corrosion resistance characteristics compared to their alumina component. All this while still maintaining reasonably high fracture toughness specific to its zirconia component. In this video, we test and show the wear characteristics of CeramAlloy Ultra Hard.

Material Properties

  • Excellent electrical insulation properties
  • High hardness and mechanical strength
  • Wear and abrasion resistant
  • High thermal conductivity and thermal shock resistance
  • Low density
  • Resistant to strong acid and alkali attack at high temperatures
  • Transparent to microwave radio frequencies
  • High compressive and dielectric strength
  • Very specific thermal conductive and thermal expansion rates

Mechanical Properties

Density
Unit
g/cm3
Value
3.9
Compressive Strength
Unit
MPa
Value
2500
Tensile Strength
Unit
MPa
Value
260
Flexural Strength @ 20°C
Unit
MPa
Value
350
Flexural Strength @ 800°C
Unit
MPa
Value
250
Fracture Toughness KIc
Unit
MPa m1/2
Value
4.5
Young‘s Modulus E
Unit
GPa
Value
350
Poisson Ratio
Unit
-
Value
0.22
Hardness Knoop (1000g)
Unit
GPa
Value
14

Thermal Properties

Maximum Temperature
Unit
°C
Value
1700
Thermal Conductivity @ 20°C
Unit
W/mK
Value
28
Thermal Expansion a at 20–100°C
Unit
10-6/K
Value
8.4
Specific Heat
Unit
100°C
Value
880
Thermal Shock Parameter R1
Unit
K
Value
200

Electrical Properties

Dielectric Constant
Unit
1 MHz
Value
9.7
Dielectric Strength (6.35mm)
Unit
ac-kV/mm
Value
8.7
Dielectric Loss (tan delta 25° C)
Unit
1 MHz
Value
0.0001
Volume Resistivity @ 25°C
Unit
Ωcm
Value
1014
Volume Resistivity @ 500°C
Unit
Ωcm
Value
2x1010
Volume Resistivity @ 1000°C
Unit
Ωcm
Value
2x106

Related Materials

Ceramic Material - CeramAlum (Aluminum Nitride)

Aluminum Nitride

Aluminum Nitride (AlN) is an excellent material to use if high thermal conductivity and electrical insulation properties are required -- an ideal material for use in thermal management and electrical applications.

Ceramic Material - Shapal Hi-M Soft (Machinable Aluminum Nitride)

Shapal Hi-M Soft

Shapal Hi-M Soft is a hybrid type of machinable Aluminum Nitride (AlN) ceramic that offers high mechanical strength and thermal conductivity.

Alumina Machining

Alumina can be produced in a wide range of purities with additives designed to enhance its properties. Typical purities range from 90 to 99.9% although Precision Ceramics generally works with 99.7% material.

It can be injection molded, die pressed, isostatically pressed, slip cast, and extruded. Once fired and sintered, it can only be machined using diamond grinding methods. Advanced green and biscuit machining techniques developed by Precision Ceramics allow more complex components to be manufactured using traditional machining methods. In addition, Alumina can be readily joined to metals or other ceramics using metalizing and brazing techniques.

Alumina can be machined in green, biscuit, or fully dense states. While in the green or biscuit form, it can be machined relatively easily into complex geometries. However, the sintering process that is required to fully densify the material causes the alumina body to shrink approximately 20%. This shrinkage means that it is impossible to hold very tight tolerances when machining alumina pre-sintering. In order to achieve very tight tolerances, the fully sintered material must be machined/ground with diamond tools. In this manufacturing process, a very precise diamond coated tool/wheel is used to abrade away the material until the desired form is created. Due to the inherit toughness and hardness of the material, this can be a time consuming and costly process.

Precision Ceramics specializes in tight tolerance and highly complex work. We have extensive in-house machining facilities, including 4th & 5th axis machining centres, drilling, grinding, milling, polishing, sawing, tapping, threading and turning. This allows us to manufacture Alumina components to the highest specifications.

Precision Ceramics is your Alumina machining specialist for all your technical ceramic prototyping & manufacturing needs. We are always happy to use our many years of advanced ceramics experience to provide advice on materials, design, and application. If you would like to buy Alumina plates, rods, tubes or custom machined components, please contact us and one of our experts will be happy to assist you.

Frequently Asked Questions

  • image/svg+xmlimage/svg+xml
    What's the difference between Macor vs Alumina?

    Alumina is a very commonly used technical ceramic due to its versatile properties, however, because it is such a hard material extensive diamond grinding is often required making it costly to produce in small quantities. Macor Machinable Glass Ceramic is often a viable alternative that can allows for significantly reduced production costs. The following are some factors to consider when choosing between Macor and Alumina.

    Thermal Cycle

    Macor is vulnerable to thermal shock – if you have rapid heat up and cool down cycles Macor may not be appropriate. Shapal may be a viable alternative.

    Maximum Temperature

    Macor has a maximum use temperature of 1000C (unstressed) and 800C (stressed); Alumina does offer higher temperature capabilities.

    Wear Resistance

    The same feature that makes Macor machinable means that it has relatively poor wear resistance when compared with Alumina.

    Cost

    For smaller quantities Macor often offers significant price reductions than Alumina components.

  • image/svg+xmlimage/svg+xml
    What is Alumina used for?

    Alumina is a very hard ceramic and is excellent at resisting abrasion. It is ideal for wear-resistant inserts or products. Alumina is commonly used as a high temperature electrical insulator, particularly the higher purity grades which offer better resistivity. Alumina also offers good resistance to strong acids and alkalis at elevated temperatures and is ideal for applications where resistance to corrosive substances is required. Some common applications of Alumina include:

    • Electronic components & substrates
    • High temperature electrical insulators
    • High voltage insulators
    • Laser tubes
    • Machine components
    • Mechanical seals
    • Precision shafts and axles in high wear environments
    • Roller and ball bearings
    • Seal rings
    • Semiconductor parts
    • Shot blast nozzles
    • Thermocouple tubes
    • Tap plates
    • Valve seats
    • Wear components
    • Wire and thread guides
    • Ballistic Armor
  • image/svg+xmlimage/svg+xml
    What are the advantages of Alumina?

    Alumina, also known as Aluminum Oxide, is a hard wearing advanced technical ceramic material frequently used in a wide variety of industrial applications.  It features high hardness and wear resistance, low erosion levels, high temperature resistance, corrosion resistance, and bioinertness. Additionally, it can be highly polished making it useful for precision sealing applications like pumps and pistons.  Alumina is an excellent high temperature ceramic material due to its high temperature stability. It is the most commonly used type of advanced ceramic and is available in purities ranging from 95 – 99.9%.

    Some of the key advantages of Alumina include:

    High Temperature Ability – Alumina can be used in both oxidizing and reducing atmospheres up to 1650°C (2900°F) and in vacuum environments up to 2000°C (3600°F).

    Abrasion Resistant – Alumina is a very hard ceramic and is excellent at resisting abrasion. It is ideal for wear-resistant inserts or products.

    Electrical Insulator – Alumina is commonly used as a high temperature electrical insulator, particularly the higher purity grades which offer better resistivity.

    Chemical Resistance – Alumina offers good resistance to strong acids and alkalis at elevated temperatures and is ideal for applications where resistance to corrosive substances is required.

    Additional properties and advantages of Alumina include

    • High hardness
    • Wear & abrasion resistant
    • High compressive strength
    • High mechanical Strength
    • Resists strong acid and alkali attack at high temperatures
    • Excellent electrical insulation properties
    • Decent thermal conductivity
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    What is the name of Al2O3?

    Al2O3 is the chemical formula for Aluminium oxide, which is a chemical compound of aluminium and oxygen. It is commonly called alumina.