Aluminium Oxide Ceramic

This tiny off-white ‘bobbin’ is a ceramic called aluminium oxide, but it is nothing like your ordinary, china mug-type ceramic; this material is so hard that once it’s been fired and sintered it has to be cut using diamond tooling. The traditional ceramics that we recognise from our kitchens are objects made of clay and cements that have been hardened by heating at high temperatures, whereas advanced or ‘engineered’ ceramics like this one are made by sintering fine powders of pure chemical compounds formed between metallic (aluminium) and non-metallic (oxygen) elements, such as aluminium oxide, or metalloid (silicon) and non-metallic (carbon) elements, such as silicon carbide. Aluminium oxides or aluminas are generally white, but as you can see, this sample is creamy beige. Other examples of this material can be pink. The off-white colour of this sample could be derived from either impurities in the raw materials or sintering additives; aluminium oxide powder is often mixed with an organic binder to help it to keep its desired shape before it is fixed. This moulded powder is then heated to a very high temperature in a controlled atmosphere until its individual particles fuse together and form chemical bonds (sintering), shrinking and hardening it into a dense, strong ceramic. The result is a material with extreme strength, wear resistance, corrosion resistance, an ability to withstand high temperatures and biocompatibility. Because aluminium oxide ceramic’s main components are partially the same minerals found in bone structure, it is used for hip replacements, dental crowns and tooth implants.