New material lubricates itself

A highly durable and moreover self-lubricating material has seen the light of day at a thin film laboratory at Linköping University.

It is an alloy of boron suboxide and yttrium, BOY, and was grown by the physicist Denis Music. The discovery is put forward in his doctoral dissertation.

The element boron and its compounds have many interesting properties, but they have been difficult to exploit industrially because production involves extreme process conditions. To produce a crystal of boron suboxide requires a temperature of 2000 degrees and extremely high pressure. Denis Music solved the problem by adding the metal yttrium, and, using thin film technology, managed to create a crystalline surface layer of the materal at a mere 300-400 degrees.

The new material can be used in bearings and machine components of various kinds, especially in moist environments. When boron is exposed to water, boric acid is produced, forming a lubricating layer on the surface. This is of interest to the manufacturing industry, which is striving to limit the use of oils and cutting lubricants that are hazardous to health and the environment. Furthermore, BOY, unlike other boron alloys, conducts electricity.

Denis Music has worked with both computer simulations and laboratory experiments. Of some 30 metals tested in simulations, yttrium seemed to be the most promising. When it was tested in the lab, it proved to work.

“The combination of experimental work and simulations is becoming more and more central to materials research,” says Ulf Helmersson, professor of thin film physics and Denis Music’s thesis director.

The method used in the experiments is called ‘sputtering’ and is carried out in a vacuum chamber. When a powdered mixture of boron and yttrium is exposed to bombardment by energy-rich ions, single atoms are cast off and condense on a substrate. The result is a film that grows thicker as the process proceeds.

The material now has a patent pending, and the next step will be to further test its mechanical properties.