Researchers at Purdue University have created a new type of non-liquid lubricant which has been shown to significantly reduce friction and wear in various applications and extreme conditions.

The new liquid-free composite is made from a slurry of a material called graphene, zinc oxide and polyvinylidene difluoride. Graphene is an extremely thin layer of carbon that has many potential technological applications, including lubrication.

"It has superior thermal conductivity, high strength and provides ultralow friction," said Vilas Pol, an associate professor of chemical engineering at Purdue University.

The nanosized zinc-oxide particles the team developed allow the lubricant to stick to the metal surface, while the polyvinylidene difluoride polymer binds the mixture together.

Solid lubricants are needed for applications such as air compressors, equipment used in the food industry, space vehicles, gear-and-chain mechanisms, fasteners found in high-temperature environments, missile systems, high-speed printers, hydraulic motors in winches, cranes, military vehicles, high-performance shredders and drilling rigs.

"The fundamental causes of mechanical failure are friction and wear, so reducing these factors improves the performance and lifetime of many mechanical systems," said Farshid Sadeghi, a professor of mechanical engineering at Purdue University. "Despite recent advances, liquid lubricants cannot be used in situations of high temperature or low pressure such as a vacuum environment, so dry, solid-state lubricants are a viable alternative to their liquid counterparts in extreme operating environments."

Researchers tested stainless-steel surfaces coated with the new lubricant and found that the composite lubricant created a film that significantly improves friction and wear reduction. Spectroscopic analysis of wear scars revealed this persistent protective film on contact surfaces.

"The durability and resilience of this adhesive coating suggest exceptional potential as a dry lubricant for high load-bearing applications," Pol said.

For more information, visit www.purdue.edu.