Scientists at the US Department of Energy’s Argonne National Laboratory have found that nanoscale particles of boric acid can significantly improve the lubricity of engine oils, and thereby increase energy efficiency.
Boric acid is mostly used as a mild antiseptic and eye wash, but it has been known for some years that microscopic particles of the compound can reduce friction between surfaces in mechanical contact. In 1991 Argonne researcher Ali Erdemir showed that metals covered with a film of boric acid exhibited lower friction coefficients than Teflon.
Micro-scale suspensions of boric acid are, however, unstable, and separate out over time. What Erdemir has done is reduce the particle size to 50 nm, and created a stable suspension of boric acid in motor oil.
Laboratory tests show that the new suspensions can reduce by as much as two-thirds energy losses through friction, with obvious implications for fuel economy. “You’re easily talking about a four or five percent reduction in fuel consumption,” says Erdemir.
In a patent-pending process, Erdemir produces powders of boric acid by mechanical attrition, chemical precipitation, gas condensation and temperature evaporation of ethyl borates or methanol/ethanol solutions of boric acid.
With his industrial partners Erdemir is now focusing on the practicalities of using nano-boric acid as an engine oil additive. “Compared to micro-boric acid powders, there is no doubt that nano-boric acid powders will be more expensive,” he says. “Having said this, the amount needed to achieve adequate levels of lubricity will be much lower as well (perhaps less than 0.5 wt%).”
A number of environmental and other tests will now be carried out, and if nano-boric acid passes these Erdemir is confident that the additive will be available within two years. Erdemir is also looking at synthesising a liquid analogue of boric acid, which he hopes will provide equal or better performance in oils and fuels, and cost less.
Figure: The Sands of Boron, California, consist of spontaneously forming boron deposits, and the natural abundance of boric acid makes it a potentially cheap and environmentally friendly lubricant (credit: Argonne National Laboratory).
Article first published in Nanomaterials News.