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Open AccessReview

Dispersion of Nanoparticles in Lubricating Oil: A Critical Review

by Yan Chen 1, Peter Renner 2 and Hong Liang 1,2,*
1
Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843-3123, USA
2
J. Mike Walker ′66 Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123, USA
*
Author to whom correspondence should be addressed.
Lubricants 2019, 7(1), 7; https://doi.org/10.3390/lubricants7010007
Received: 10 December 2018 / Revised: 30 December 2018 / Accepted: 5 January 2019 / Published: 10 January 2019
(This article belongs to the Special Issue Industrial Tribo-Systems and Future Development Trends)
Nanolubricants have attracted great interest due to the promise of friction and wear reduction by introducing nanoparticles. To date, the foremost challenge for developing a new nanolubricant is particle suspension. To understand the mechanisms of nanoparticle dispersion and identify bottlenecks, we conducted a comprehensive review of published literature and carried out an analysis of dispersion based on available data from the past 20 years. This research has led to three findings. First, there are two primary methods in dispersion: formulation with dispersant and surface modification. Second, surfactant and alkoxysilanes are primary chemical groups used for surface modification. Third, functionalization using surfactant is found to be suitable for nanoparticles smaller than 50 nm. For larger particles (>50 nm), alkoxysilanes are the best. The existence of a critical size has not been previously known. To better understand these three findings, we conducted an analysis using a numerical calculation based on colloidal theory. It revealed that a minimal thickness of the grafted layer in surfactant-modified nanoparticles was responsible for suspending small nanoparticles. For larger nanoparticles (>50 nm), they were suitable for silanization of alkoxysilane due to increased grafting density. This research provides new understanding and guidelines to disperse nanoparticle in a lubricating oil. View Full-Text
Keywords: nanoparticles; nanolubricants; dispersion; suspension; functionalization nanoparticles; nanolubricants; dispersion; suspension; functionalization
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MDPI and ACS Style

Chen, Y.; Renner, P.; Liang, H. Dispersion of Nanoparticles in Lubricating Oil: A Critical Review. Lubricants 2019, 7, 7.

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