A coating material made of carbon reduces friction not just by providing a slippery surface, but also by keeping the points of contact warm.

Marcus Björling of Luleå University of Technology in Sweden and his team coated steel balls with 'diamond-like carbon' — a material in which the carbon atoms have a bonding pattern similar to that of diamond. They rolled the balls against a metal disk with an oil lubricant in between, and showed that the carbon coating acts as an insulator, lowering the viscosity of the lubricant and thus reducing the friction between the ball and the disk.

The findings could encourage the development of lubricant coatings made from insulating materials.

Tribol. Lett. http://doi.org/qtm (2014)