Research Papers: Lubricants

The Effect of Nanoparticle Functionalization on Lubrication Performance of Nanofluids Dispersing Silica Nanoparticles in an Ionic Liquid

[+] Author and Article Information
Cengiz Yegin

Department of Materials
Science and Engineering,
Texas A&M University,
College Station, TX 77843
e-mail: cengiz.yegin@gmail.com

Wei Lu

Artie McFerrin Department of
Chemical Engineering,
Texas A&M University,
College Station, TX 77843
e-mail: weilu08@yahoo.com

Bassem Kheireddin

Artie McFerrin Department of
Chemical Engineering,
Texas A&M University,
College Station, TX 77843
e-mail: kheireddinb@gmail.com

Ming Zhang

Department of Polymer Engineering,
University of Akron,
Akron, OH 44325
e-mail: brightzhang@gmail.com

Peng Li

Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77843
e-mail: lipeng0503@gmail.com

Younjin Min

Department of Polymer Engineering,
University of Akron,
Akron, OH 44325
e-mail: ymin@uakron.edu

Hung-Jue Sue

Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77843
e-mail: hjsue@tamu.edu

Mufrettin Murat Sari

Technology Division,
Defense Science Institute,
Turkish Military Academy,
Ankara 06654, Turkey
e-mails: mufrettin@gmail.com;

Mustafa Akbulut

Artie McFerrin Department of
Chemical Engineering,
Texas A&M University,
College Station, TX 77843
e-mails: makbulut@tamu.edu;

1Corresponding authors.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received June 1, 2016; final manuscript received October 24, 2016; published online April 4, 2017. Assoc. Editor: Min Zou.

J. Tribol 139(4), 041802 (Apr 04, 2017) (8 pages) Paper No: TRIB-16-1180; doi: 10.1115/1.4035342 History: Received June 01, 2016; Revised October 24, 2016

Recently, ionic liquids (ILs) have received an increasing attention as lubricants owing to their intriguing properties such as tunable viscosity, high thermal stability, low emissions, nonflammability, and corrosion resistance. In this work, we investigate how the incorporation of octadecyltrichlorosilane (OTS) functionalized silica nanoparticles (NPs) in 1-butyl-3-methylimidazolium (trifluoromethysulfony)imide influences the tribological properties and rheological properties of IL under boundary lubrication and elastohydrodynamic conditions, respectively. It was found that the coefficient of friction was depended on the concentration of NPs in IL with a concave upward functional trend with a minimum at 0.05 wt.% for bare silica NPs and at 0.10 wt.% for OTS-functionalized silica NPs. For steel–steel sliding contact, the presence of functionalized NPs in IL at the optimum concentration decreased the coefficient of friction by 37% compared to IL and 17% compared to IL with bare silica NPs. While IL with bare NPs demonstrated a shear thinning behavior for all concentrations, IL with functionalized NPs showed a Newtonian behavior at low concentrations and shear thinning behavior at high concentrations. Overall, this study provides new insights into the antifriction and antiwear additives for lubrication systems involving ILs.

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Grahic Jump Location
Fig. 1

(a) Reaction scheme for the functionalization of SiO2 NPs with OTS, (b) TEM micrograph of bare SiO2 NPs, and (c) schematic illustration of the final product

Grahic Jump Location
Fig. 2

FTIR spectra of pure OTS, bare SiO2 NPs, OTS-functionalized SiO2 NPs within the frequency range of 400–4000 cm−1

Grahic Jump Location
Fig. 3

TGA thermogram of bare and OTS-functionalized SiO2 NPs between room temperature and 900 °C under nitrogen atmosphere. Heating rate is 10 °C min−1.

Grahic Jump Location
Fig. 4

(a) The sedimentation of 0.05 wt.% bare (left) and 0.1 wt.% OTS-functionalized SiO2 NPs in IL (right) after 24 h from preparation, (b) and (c) particle size distribution of bare and OTS-functionalized SiO2 NPs in IL measured by DLS right after preparation (t = 0) and after 1 h, respectively, and (d) particle size of the bare and OTS-functionalized SiO2 NPs in IL as a function of time. The existence of two data points for certain time points indicates the bimodal size distribution. Even if the actual concentration of NPs were lower for the case of functionalized NPs, they displayed a better colloidal stability.

Grahic Jump Location
Fig. 5

Effect of NP concentration on the friction coefficient of the OTS-functionalized SiO2 NPs

Grahic Jump Location
Fig. 6

Load versus friction force data for pure IL, IL with 0.05 wt.% bare silica NPs, and IL with 0.1 wt.% organosilane functionalized NPs

Grahic Jump Location
Fig. 7

Viscosity of the neat IL and IL with different concentrations of (a) SiO2 NPs and (b) OTS-functionalized SiO2 NPs as a function of shear rate

Grahic Jump Location
Fig. 8

SEM micrographs displaying morphologies of steel surfaces after shearing under three different lubrication conditions: (a) pure IL, (b) IL + 0.05 wt.% bare SiO2 NPs, and (c) IL + 0.1 wt.% OTS-functionalized SiO2 NPs. Low and high magnifications of the middle and edge parts of the wear track are shown.



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