Alkylamine-Grafted Molybdenum Disulfide Nanosheets for Enhanced Dispersion Stability and Lubricity Properties

Abstract

The unique structure and ultralow interlayer shear strength give molybdenum disulfide (MoS2) materials a broad prospect for energy savings, economic benefits, and extended operating life of lubrication systems. Herein, we prepared an effective integration strategy to prepare novel small-sized and chemically grafted MoS2 to solve the problems of poor dispersibility and easy agglomeration of MoS2. The MoS2 powder was stripped and oxidized to generate active centers using acid oxidation and high-speed ultrasonic crushing to obtain two different types of alkylamine chemically, covalently grafted, oxidized MoS2 nanosheets as lubricant additives to achieve friction reduction and antiwear. The chemical changes and structural characteristics of different types of alkylamine molecules upon covalent interaction with oxidized MoS2 were investigated in detail by FTIR, XPS, TGA, XRD, and TEM analyses. The results showed that the alkylamine-grafted MoS2 oxide nanosheets had good dispersion in 15# industrial white oil, and friction experiments confirmed that the alkylamine-grafted MoS2 oxide (MoS2–O-OLA) nanosheets exhibited better friction and wear resistance such that, compared with pure 15# industrial white oil, the 0.02 wt % MoS2–O-OLA nanosheets could significantly reduce friction (36.2%) and wear (22.4%). The field-emission scanning electron microscopy (FESEM) and EDS analyses of the wear surface showed that MoS2–O-OLA nanosheets play an important role in improving tribological properties by generating interlayer slippage at the steel ball contact interface, thereby forming surface protection and a uniform oil film.

MoS2 Nanomaterials as Lubricant Additives: A Review

“…Meng et al [125] analyzed the lubrication mechanism using molecular dynamics simulations, which showed that an increase in normal pressure promotes interlayer slip and reduces the friction coefficient between the MoS 2 nanosheets. Wang et al [126] used alkylaminegrafted MoS 2 oxide nanosheets (MoS 2 -O-OLA) dispersed in 15# industrial white oil for friction experiments, confirming that MoS 2 -O-OLA nanosheets exhibited better friction and wear resistance, resulting in a significant reduction of friction (36.2%) and wear (22.4%) by 0.02 wt% MoS 2 -O-OLA nanosheets as compared to pure 15# industrial white oil. MoS 2 -O-OLA nanosheets played an important role in improving tribological properties by generating interlayer slip at the steel ball contact interface, resulting in surface protection and a uniform oil film.…”

Tribological performances of MoS2/C60 nanocomposite as lubricating additive in dioctyl sebacate

“…The S atoms exposed on the crystal surface have strong adhesion to the metal surface, making MoS 2 well adhered to the metal surface (Hu et al , 2010). Numerous studies have confirmed the excellent performance of MoS 2 as a lubricant additive in reducing friction (Xu et al , 2015a; Hu et al , 2010; Wu et al , 2018; Liu and Zhou, 2017; Tang et al , 2013; Wang et al , 2023). However, MoS 2 nanoparticles are prone to agglomerate and settle in solution due to their large surface energy and specific surface area, which in turn affects their dispersion stability, lubricity and heat transfer properties (Hou et al , 2020; Sahoo and Biswas, 2010).…”

“…The S atoms exposed on the crystal surface have strong adhesion to the metal surface, making MoS 2 well adhered to the metal surface (Hu et al, 2010). Numerous studies have confirmed the excellent performance of MoS 2 as a lubricant additive in reducing friction (Xu et al, 2015a;Hu et al, 2010;Wu et al, 2018;Liu and Zhou, 2017;Tang et al, 2013;Wang et al, 2023). However, MoS 2 nanoparticles are prone to…”

“…One typical method to improve molybdenum disulfide’s dispersion stability is surface modification (Tang et al , 2013; Wang et al , 2023; Spear et al , 2015). However, this approach does not significantly affect the compressive capacity of the lubricant film.…”