Researchers at two China universities said recently that nano-copper particles show early promise to become part of a new generation of industrial lubricant additives but that greater understanding and direct experimental evidence is still needed.
The group consists mostly of researchers with the School of Mechatronix Engineering at Xi’an Technological University in Xi’an, China. One researcher is also with the National United Engineering Laboratory for Advanced Bearing Tribology at the Henan University of Science and Technology in Luoyang, China.
In December they published a paper reviewing the research progress of anti-friction and anti-wear properties of nano-copper as a lubricating oil additive in recent years. Nano-copper consists of particles that are 1 to 100 nanometers in size.
Among the characteristics of nanoparticles are super sliding, extreme pressure and self-healing, which can improve the friction reduction and anti-wear performance of sliding components, when used as lubricating oil additives, according to the paper’s abstract. “The effectiveness and potential application of copper nanoparticles in improving the anti-friction and anti-wear properties of lubricating oil were presented, which has a good effect on the improvement of lubricating oil dispersion, stability and tribological properties,” the researchers found.
For the paper, the authors also summarize factors affecting the tribology properties of nano-copper particles in a lubricating oil system and the methods to enhance the dispersion stability and the lubrication mechanism of nano-lubricants. “The agglomeration of nanoparticles is the main problem facing the long-term stability of lubrication systems,” the researchers said, “although a large number of reports claim that the dispersibility has been improved by surface modification, polymer coating and mechanical dispersion and so on. Nano-copper particles have better dispersion stability after modification or freeze-drying treatment, and most studies aim at the overall dispersion of lubricating oil with nano-copper particle additives.”
They pointed out that with dispersion of nano-scale additives, it is difficult to form an acknowledged system, and the effectiveness of lubrication is uncertain under different working conditions. “The understanding of the industrial circle of the lubrication of the nanoparticles is still in the speculative stage, and there is a lack of unified understanding and direct experimental evidence,” they explained. “It limits the popularization and application of nanoparticles as lubricating oil additives in industry.”
What is lacking in theoretical analysis of nanoparticle lubricating oil additives, the authors noted, is corresponding simulation and theoretical simulation methods for the synergistic performance of nanoparticles and such common lubricating oil additives as zinc dialkyldithiophosphates, known as ZDDP.
“The lubrication condition of nano-copper oil additives mainly depends on the experimental means, and the suitable working conditions and evaluation methods of copper nanoparticles as lubricating oil additives have an important reference value for tribological performance optimization.” The paper is titled, “Research Progress of Nano Copper Lubricant Additives on Engineering Tribology, and was published on Dec. 12 in the MPDI Open Access Journals website.