title: Alkyl-chain-grafted hexagonal boron nitride nanoplatelets as oil-dispersible additives for friction and wear reduction.
abstract: Hexagonal boron nitride (h-BN), an isoelectric analogous to graphene multilayer, can easily shear at the contact interfaces and exhibits excellent mechanical strength, higher thermal stability, and resistance toward oxidation, which makes it a promising material for potential lubricant applications. However, the poor dispersibility of h-BN in lube base oil has been a major obstacle. Herein, h-BN powder was exfoliated into h-BN nanoplatelets (h-BNNPs), and then long alkyl chains were chemically grafted, targeting the basal plane defect and edge sites of h-BNNPs. The chemical and structural features of octadecyltriethoxysilane-functionalized h-BNNPs (h-BNNPs-ODTES) were studied by FTIR, XPS, XRD, HRTEM, and TGA analyses. The h-BNNPs-ODTES exhibit long-term dispersion stability in synthetic polyol ester lube base oil because of van der Waals interaction between the octadecyl chains of h-BNNPs-ODTES and alkyl functionalities of polyol ester. Micro- and macrotribology results showed that h-BNNPs-ODTES, as an additive to synthetic polyol ester, significantly reduced both the friction and wear of steel disks. Elemental mapping of the worn area explicitly demonstrates the transfer of h-BNNPs-ODTES on the contact interfaces. Furthermore, insight into the lubrication mechanism for reduction in both friction and wear is deduced based on the experimental results.
authors.affiliation: Chemical Science Division, CSIR-Indian Institute of Petroleum (CSIR-IIP) , Mohkampur, Dehradun 248005, India.
authors.forename: Sangita
authors.initials: S
authors.lastname: Kumari
authors.forename: Om P
authors.initials: OP
authors.lastname: Sharma
authors.forename: Rashi
authors.initials: R
authors.lastname: Gusain
authors.forename: Harshal P
authors.initials: HP
authors.lastname: Mungse
authors.forename: Aruna
authors.initials: A
authors.lastname: Kukrety
authors.forename: Niranjan
authors.initials: N
authors.lastname: Kumar
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sugimura
authors.forename: Om P
authors.initials: OP
authors.lastname: Khatri
keywords: boron nitride nanoplatelets; chemical functionalization; dispersion; exfoliation; friction