Founder of TriboNet, Editor, PhD (Tribology), Tribology Scientist at ASML, The Netherlands. Expertise in lubrication, friction, wear and contact mechanics with emphasis on modeling. Creator of Tribology Simulator.
Reduce the Friction with Graphene Balls
Tiny, sub-micron sized particles are frequently used as additives in the lubricants to improve their frictional and wear behavior. These particles, due to their size, can enter the contact and protect the surfaces from the direct contact in the cases when the base lubricant is not capable of doing it, as in case of boundary lubrication. If their properties are favorable, the friction and wear may be reduced. On the other hand, tiny particles posses large surface area and tend to form aggregates. It is harder for larger aggregated particles to get into the contact to separate the bodies. Besides, agglomeration reduces the ability of the particles to evenly disperse in the lubricant, which also leads to unstable tribological performance.
Xuan Dou and his colleagues from Northwestern University developed such type of ultrafine particles, which can self-disperse in the lubricant, generating a stable suspension. They used graphene to produce tiny crumpled, paper like balls to use as an additive to polyalphaolefin base oil. These particles have favorable mechanical properties and exhibit chemical and thermal stability. On top of it, the use of these particles shows stable and moreover, superior tribological behavior compared to other widely used carbon based additives. It was also shown by experimental measurements, that the friction and wear coefficients are improved even compared to the commercial fully formulated oil.
It should be noted that the fully formulated oils are highly toxic due to their additives. Development of the graphene based substitute with comparable, or even superior, tribological properties, may also help to reduce the negative impact of the commercial lubricants on the environment.
More details can be found in the original article by Xuan Dou et al, Self-dispersed crumpled graphene balls in oil for friction and wear reduction.
Credit for image: By U.S. Army Materiel Command – https://www.flickr.com/photos/armymaterielcommand/6795812766, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=37863884
I give Jiaxing Huang, Associate Professor, Materials Science and Engineering, and his team at Northwestern credit for realizing the potential of graphene in lubricants; but Jiaxing needs to further realize that the object of the graphene is not to enhance the physical properties of the base oil, but to be the main focus of the tribological effort itself (base lubricant be damned).
There is still need in the base oil? Graphene by itself cannot be a good lubricant in the contact between steels, right?
Yes, there is a base oil, because the oil serves more purposes than just being a lubricant. The base oil acts as a heat transfer agent, and also serves to catch and eventually remove the products of incomplete combustion that act as contaminants. The motor oils also have pH buffers to deal with acids that build up over time. But, there is a very big (philosophical) difference between adding graphene to oil (ex situ) as a lubricant modifier (enhancing the base lubricant), and using graphene as an ISN technology (or better, synthesizing it in situ), where the base lubricant is merely the carrier for the ISN graphene-based technology. One of the benefits of ISN technology is that excess graphene acts as a tribological coating and heat transfer agent itself. Further, when surface asperities are eliminated through ISN, the base lubricant can be modified radically to reduce its viscosity and improve its fluidity; this greatly improving efficiency through lowering induced friction from the lubricant oils themselves.
I am wondering, if water could substitute the oil?