Chemically functionalized graphene for lubricant applications: Microscopic and spectroscopic studies of contact interfaces to probe the role of graphene for enhanced tribo-performance

Ajay Chouhan; Harshal P Mungse; Om P Sharma; Raj K Singh; Om P Khatri

doi:10.1016/j.jcis.2017.11.072

Chemically functionalized graphene for lubricant applications: Microscopic and spectroscopic studies of contact interfaces to probe the role of graphene for enhanced tribo-performance

J Colloid Interface Sci. 2018 Mar 1:513:666-676. doi: 10.1016/j.jcis.2017.11.072. Epub 2017 Dec 2.

Authors

Ajay Chouhan¹, Harshal P Mungse², Om P Sharma³, Raj K Singh¹, Om P Khatri⁴

Affiliations

¹ CSIR - Indian Institute of Petroleum, Dehradun 248005, India; Academy of Scientific and Innovative Research (AcSIR), Chennai, India.
² Department of Materials Science and Engineering, Kyoto University, Kyoto 606 8501, Japan.
³ CSIR - Indian Institute of Petroleum, Dehradun 248005, India.
⁴ CSIR - Indian Institute of Petroleum, Dehradun 248005, India; Academy of Scientific and Innovative Research (AcSIR), Chennai, India. Electronic address: opkhatri@iip.res.in.

PMID: 29207349
DOI: 10.1016/j.jcis.2017.11.072

Abstract

Shear-induced transfer of graphene on the contact interfaces was studied by microscopic and spectroscopic analyses of steel balls lubricated with chemically functionalized graphene-based mineral lube base oil (SN-150). The 3,5-di-tert-butyl-4-hydroxybenzaldehyde (DtBHBA) grafted-graphene (Gr-DtBHBA) was prepared by two-steps approach using graphene oxide as a precursor. Chemical and structural features of Gr-DtBHBA are probed by FTIR, XPS, Raman, TGA, and HRTEM analyses. The van der Waals interaction between the tertiary-butyl group in the Gr-DtBHBA and hydrocarbon chains of mineral lube base oil facilitates the dispersion of Gr-DtBHBA in the SN-150 lube base oil, which is very important for the optimized performance of Gr-DtBHBA as a lubricant additive. The minute dosing (0.2-0.8 mg mL^-1) of the Gr-DtBHBA in the SN-150 lube base oil showed the significant reduction in the coefficient of friction (40%) and wear scar diameter (17%) under the rolling contact between steel balls. The microscopic and EDX analysis of the worn area suggested the role of Gr-DtBHBA nanosheets for enhanced tribo-performance of the SN-150 lube base oil. A detailed Raman study of the worn area of steel ball revealed the deposition of a graphene-based tribo thin film in the forms of irregular patches. The shear-induced deposition of graphene thin film on the contact interfaces reduced the friction and protected the tribo-surfaces against the wear.

Keywords: Contact interfaces; Friction; Graphene; Lubricant; Raman; Wear.