Alumina (Al2O3) Electrical Insulators - Properties and Applications by Precision Ceramics

Precision Ceramics, a division of McGeoch Technology, is a company dedicated to the engineering of technical ceramics. From procurement and supply through to technical design and specialist machining, we offer a complete service.

Our reputation for quality and service is truly international with specialist ceramic components engineered by Precision Ceramics finding their way into an ever-widening array of worldwide applications in industries as diverse as aerospace, opto-electronics and nuclear power.

In both new applications and in areas where technical ceramics are already being used, Precision Ceramics has the necessary expertise and in-depth knowledge to quickly find the best way forward for any potential application from prototypes through to full-scale production of components. And once fully up and running, we can easily take the process one stage further by offering expert advice in the engineering of more demanding materials.

The company operates to the very highest quality standards and holds BS5750 Part 1, ISO9000 and BASEEFA approval.

Characteristics of Alumina and Aluminium Oxide

Alumina is the more common name of Aluminium Oxide (Al2O3) and is a hard wearing material used for many applications. Once fired and sintered, it can only be machined using diamond-grinding methods.

Aluminium oxide is an electrical insulator but has a relatively high thermal conductivity (40 W/m K). In its most commonly occurring crystalline form, called corundum or á-aluminium oxide, its hardness makes it suitable for use as an abrasive and as a component in cutting tools.

Properties of Aluminium Oxide

Aluminium oxide is responsible for metallic aluminium's resistance to weathering. Metallic aluminium is very reactive with atmospheric oxygen, and a thin passivation layer of alumina quickly forms on any exposed aluminium surface. This layer protects the metal from further oxidation. The thickness and properties of this oxide layer can be enhanced using a process called anodising.

Corrosion Resistance of Aluminium Oxide

A number of alloys, such as aluminium bronzes, exploit this property by including a proportion of aluminium in the alloy to enhance corrosion resistance. The alumina generated by anodising is typically amorphous, but discharge assisted oxidation processes such as plasma electrolytic oxidation result in a significant proportion of crystalline alumina in the coating, enhancing its hardness.

Applications of Aluminium Oxide

Alumina's combination of hardness, high temperature operation and good electrical insulation makes it useful for a wide range of applications. Alumina is the most commonly used type of ceramic and is available in purities up to 99.9%. Typical applications inlcude electrical insulators; seal faces; valve seats.

Alumina Bead as Electrical Insulators

For many years fish spine beads have been used as a practical method of insulating wires with the beads interlocking together to provide continuous electrical insulation. Traditionally, the beads have been manufactured from a porcelain which although excellent for electrical purposes has not been mechanically strong or dense enough to be used in vacuum chambers or similar scientific instruments.

Precision Ceramics has now launched a range of standard fish spine beads, all manufactured from high purity alumina and therefore vacuum compatible and fully dense.

This information has been sourced, reviewed and adapted from materials provided by Precision Ceramics.

For more information on this source, please visit Precision Ceramics.

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