Sol-gel is a fabrication technique mainly used to make oxide ceramics, or polymer-ceramic composite materials. These materials can be in the form of powders, coatings, bulk monoliths or fibres. The two most common (i.e. economically viable) being powders and coatings.
Powders
The first significant industrial products of sol-gel technology were mixed oxide powders of radioactive elements such as uranium and thorium. Being a solution-based technique sol-gel produces no dust during fabrication, eliminating problems with the management of radioactive dust and decontamination of the preparation areas. Both these issues had previously demanded significant resource when conventional powder routes were used.
A second example of a sol-gel derived powder being used industrially is that of alumina for abrasive applications. Conventional melting and crushing gives a relatively low yield of alumina particles that are suitable for use in abrasive wheels and papers. Fabrication of these powders using sol-gel methods gives a much better yield because the grain size can be more readily controlled.
Coatings
Coatings of sol-gel derived materials are used in a variety of applications, for example as architectural coatings. One well known example of this is the European Patent House in Frankfurt, which has a sol-gel coating on the windows. The coating controls the transmission and adsorption of different wavelengths of light to give a uniform reflective appearance that is aesthetically pleasing, whilst also minimising the "greenhouse effect" in the building and reducing cooling costs during the summer.
Other examples of sol-gel coatings include the "self-cleaning" wing mirrors on some premium car brands, anti-reflective coatings on the interior mirrors of cars and corrosion protection coatings for metals.
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