Researchers at the Warwick Process Technology Group have devised a manufacturing technique for spun-fibre based ceramics that allows manufacturers to produce high tech ceramic fibres without the creation of very small diameter fibres that can be a health risk.

Fine ceramic fibres have been about for many years. They are used because fineness is a desirable property in a range of applications. Unlike the bulk forms of ceramic, fine fibres are strong and flexible and unlike coarser fibres they do not scratch and irritate the skin. They can be used for a host of applications, from forming the walls of high temperature furnaces to acting as light weight components in planes and cars, and they can also be incorporated into a composite material with the properties of the normally brittle and hard ceramic in a tougher and more handleable form.

Fine fibres have the best thermal insulation properties and good thermal shock resistance, and do not crumple up when heated and cooled over and over again. In the home we see them in the artificial coal in gas fires and around the heating elements on hot plates.

How fine they can be has returned as a major health issue, with new legislation having come in at the beginning of this year. Ceramic fibres finer than 1 micron diameter are now known to be carcinogenic, and fibres finer than 3 microns are respired into the lungs. Processes making these fine fibres produce a spread of diameters, and even the best current materials contain a large proportion of fibres which can be respired. Some products even contain both dangerously fine and irritatingly coarse fibre!

Now the problem of achieving the desirable properties of fine ceramic fibres in an absolutely safe product is being addressed by a research team of chemical engineers, materials scientists and chemists at the Warwick Process Technology Group. They have developed a process which can manufacture a range of these high tech ceramic materials free from dangerously fine, or irritatingly coarse, fibres.

The Fibres Research Group at Warwick use a Sol-Gel blow-spinning technique, which is configured to produce very even fibers with none less than 3 microns in diameter. Their methods also pay particular attention to the formation of the spinning sol to the extent that they can make fibres of magnetic, piezoelectric and conductive ceramics, as well as the high temperature refractory fibres usually associated with ceramic processing. The materials made by this process can create a range of high tech ceramics such as:

• Highly heat resistant materials for use in very high temperature furnaces

• Materials treated to act as microwave shields – for use in mobile phones for example

• High performance lightweight components for the automobile and aerospace industry

• Magnetic, piezoelectric and conductive fibres for use in composite materials

• Medical implants - even artificial muscles