Properties of Machinable Aluminium Nitride

Properties of Machinable Aluminium Nitride

Machinable aluminium nitride is a soft material that comes in two forms: BNP 2 and the more expensive Shapal M. Learn more here.

Machinable aluminium nitride is a technical ceramic that has many applications in high-performance and challenging environments. It has a high heat dissipation capability, as well as excellent mechanical and electrical properties. This is the preferred advanced ceramic material for power-generation industries as well as microelectronics. In both applications there is a vital requirement for rapid and efficient heat dissipation.

Such applications include insulators on high-voltage systems, diffusion furnace process parts and laser components. Aluminium nitride in both its forms – Shapal M and BNP 2 – has a hexagonal crystal structure that is an isomorph of wurzite, a polytype of zinc sulphide. Mineral acids and string alkalis will attack this material along its grain boundaries. The properties of Shapal M and BNP 2 are identical, and the two materials should be machined or otherwise worked in exactly the same way. The difference between them is just cost. BNP 2 is a cheaper version of machinable aluminium nitride.

 

Over the past decades, aluminium nitride has replaced beryllium oxide – a toxin – in semiconductor industry applications.

 

This material is stable up to temperatures of 700 degrees Celsius, at which point it begins to oxidise on the surface. Such a layer of surface oxide can be between 5 and 10 nanometres and is capable of protecting the material beneath to temperatures of around 1,370 degrees C. Once temperatures rise beyond this point, the material oxidises in bulk. When it is immersed in a hydrogen or carbon dioxide atmosphere, it is stable up to 980 degrees C.

 

Machining BNP2

Although aluminium nitride has a high resistance to attack from molten salts, which include cryolites and most chlorides, it does hydrolyse slowly when immersed in water. It has a flexural strength comparable with alumina – aluminium oxide – but its thermal conductivity is five times greater.

 

There are two main production processes for aluminium nitride ceramics. One involves a dry press followed by sintering or a hot press together with sintering aids. Dry pressing is the most cost-efficient process for producing bulk quantities of aluminium nitride. The thickness of the material produced ranges between 0.8 and 1.0 nanometres.

 

It is available in the form of sheets, rods, blocks and finished components. The most common colour from the material is grey, although it does come in a variety of other colours.

 

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