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Title: Improved Lubricating Performance by Combining Oil-Soluble Hairy Silica Nanoparticles and an Ionic Liquid as an Additive for a Synthetic Base Oil

This article reports on improved lubricating performance by combining oil-soluble poly(lauryl methacrylate) brush-grafted silica nanoparticles (hairy NPs or HNP) and an oil-miscible phosphonium-phosphate ionic liquid (IL) as a friction-reducing additive for a polyalphaolefin (PAO) oil. The HNP was synthesized by surface-initiated reversible addition–fragmentation chain transfer polymerization. At a total concentration of 2% and sufficiently high individual concentrations for HNP and IL in PAO, high-contact stress, ball-on-flat reciprocating tribological tests showed that the friction decreased by up to 23% compared with 2% HNP alone in PAO and by up to 35% compared to the PAO mixed with 2% IL. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis revealed that the tribofilm formed from the PAO containing 1% HNP + 1% IL was enriched with both Si and P, indicating that both hairy NPs and IL were involved in the tribochemical reactions. In addition, the O 1s and Si 2p peaks in the core-level XPS spectra exhibited significant shifts for the mixture of 1% HNP + 1% IL compared to those for 2% HNP, suggesting the possible formation of new covalent bonds. These results indicated that HNP and IL reacted with each other and also with the metalmore » substrate during the rubbing process, which likely strengthened the tribofilm and its bonding with the substrate and thus further improved the lubrication.« less
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  1. Univ. of Tennessee, Knoxville, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 10; Journal Issue: 17; Journal ID: ISSN 1944-8244
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
OSTI Identifier: