How is it that we propose nano particles in lubricants, for instance, engine oil. To what extent does the particle size in relation to viscosity affect the metal surfaces. Is it a trade off due to increased heat transfer rate?
yes you can disperse nanoparticles in a suitable high boiling solvent to form a stable colloidal dispersion which can be used for lubrication.
Dear Dr. Olatunde Olanrewaju,
in the industry, most of the surfaces in mutual contact (i.e., bearings, seals and gears) are lubricated with specific oils in order to control friction and wear. Many scientific researches have been published on the tribological properties of nanoparticles-based lubricants and the phenomena regarding any mechanical system in relation to friction and wear, strongly depends upon the characteristics of the nanoparticles, such as shape, size and concentration within the lubricant.
Even a small concentration of nanoparticles (a few tenths of a percent by weight) could be sufficient to improve the tribological properties of the system. When the load between the sliding parts is small (low load conditions), friction reduction is mainly ascribable to the bearing-like behavior of nanoparticles, that roll between the contact surfaces, keeping their shape intact; for high load conditions, a coating, induced by the presence of nanoparticles, is deposited on the crests of surface roughness and it can reduce direct contact between the asperities, thus, minimize wear.
Because of the nature (inorganic and refractory) of the nanoparticles generally used as filler, the optimal performances achieved by the nano-lubricant can also be maintained in the working conditions at high temperature, thus avoiding the typical degradation of the traditional organic additives.
A major challenge to face, in order to scale up the use of nanoparticles as filler for lubricants, is related to their dispersion within fluids, that is often not uniform. Their small size, in fact, causes the attractive forces to rule over the other types of forces. This phenomenon generally causes aggregation and precipitation of nanoparticles. This issue shows that nanoparticles in lubricants need to be dispersed with other methods in order to optimize their stability, most likely they need to be surface-functionalized with organic treatments.
Source at: https://www.tec-star.com/nanoparticles-in-lubricants/?lang=en
In order to have more details, I suggest you to have a look at the following papers/notes:
-Dispersion of Nanoparticles in Lubricating Oil: A Critical Review
Yan Chen, Peter Renner and Hong Liang
Lubricants, 7(1), 7 (2019)
Available at: https://www.mdpi.com/2075-4442/7/1/7/htm
-How Can Nanoparticles Help in the Flow of Lubricants?
By Dr. Liji Thomas, MD – AZONANO Company (2019)
Available at: https://www.azonano.com/article.aspx?ArticleID=5218
-Effect of nanoparticles as lubricant additives on friction and wear behavior of tetrahedral amorphous carbon (ta-C) coating
Xiang Li*, Motoyuki Murashima, Noritsugu Umehara
Jurnal Tribologi, 16, 15-29 (2018)
Available at: https://jurnaltribologi.mytribos.org/v16/JT-16-15-29.pdf
-Roles of nanoparticles in oil lubrication
P. Noorunnisa Khanam & Mariam Al Ali AlMaadeed
Tribology International, Vol. 102, Pages 88-98 (2016)
Available at: https://www.sciencedirect.com/science/article/pii/S0301679X16301116
Good reading and best regards, Pierluigi Traverso.
Thank you for the detailed and insightful responses
Dear Gbadamosi-Olatunde Olatunde Bilikis Olanrewaju
Nanoparticles of hexagonal boron nitride can be the best choice in this regard. It has a tensile strength of ~ 1.3 TPa and stable in the air upto 400 C.
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