Researchers at Purdue University have created a new type of non-liquid lubricant—a novel graphene-zinc oxide composite—that has been shown to reduce friction and wear significantly under the extreme conditions found in various applications, from air compressors to missile systems. The new liquid-free composite is made from a slurry of graphene, zinc oxide, and the polymer polyvinylidene difluoride.
The nanosize zinc-oxide particles the team developed allow the lubricant to stick to the metal surface, and the polymer binds the whole mixture together, said chemical engineering graduate student Arthur Dysart. The lubricant has superior thermal conductivity, high strength and provides ultralow friction, said Vilas Pol, an associate professor of chemical engineering at Purdue University.
The graphene-rich lubricant demonstrates substantial friction and wear reduction (ca. 90%) compared to unlubricated sliding. The composite film is able to maintain its lubricating effects under extreme operating conditions including 15 N normal load and 450 m sliding distance.
… The excellent tribological performance of this graphene-rich composite is attributed to the adhesion effect from zinc oxide: zinc adheres graphene to the contact interface, maintaining improved tribological performance under high contact pressure. The durability and resilience of this adhesive coating suggest exceptional potential as a dry lubricant for high load-bearing applications.—Alazemi et al.
|This composite image depicts the makeup and performance of a new non-liquid lubricant developed by researchers at Purdue University. (Purdue University image/ Abdullah A. Alazemi) Click to enlarge.|
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 and 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. 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.—Farshid Sadeghi, Purdue’s Cummins Distinguished Professor of Mechanical Engineering
The researchers tested stainless-steel surfaces coated with the new lubricant. Findings were detailed in a research paper published in the journal Carbon.
The researchers found that the composite lubricant sets up a film that significantly improves friction and wear reduction. Raman spectroscopic analysis of wear scars revealed this persistent protective film on contact surfaces.
The research is ongoing, and future work is planned with industrial partners. The researchers applied for a patent through the Purdue Research Foundation’s Office of Technology Commercialization.
Abdullah A. Alazemi, Arthur D. Dysart, Steven J. Shaffer, Vilas G. Pol, Lars-Erik Stacke, Farshid Sadeghi (2017) “Novel tertiary dry solid lubricant on steel surfaces reduces significant friction and wear under high load conditions” Carbon doi: 10.1016/j.carbon.2017.07.030