Tribological Properties of 2D Materials and Composites—A Review of Recent Advances

Abstract

This paper aims to provide a theoretical and experimental understanding of the importance of novel 2D materials in solid-film lubrication, along with modulating strategies adopted so far to improve their performance for spacecraft and industrial applications. The mechanisms and the underlying physics of 2D materials are reviewed with experimental results. This paper covers some of the widely investigated solid lubricants such as MoS2, graphene, and boron compounds, namely h-BN and boric acid. Solid lubricants such as black phosphorus that have gained research prominence are also discussed regarding their application as additives in polymeric materials. The effects of process conditions, film deposition parameters, and dopants concentration on friction and wear rate are discussed with a qualitative and quantitative emphasis that are supported with adequate examples and application areas and summarized in the form of graphs and tables for easy readability. The use of advanced manufacturing methods such as powder metallurgy and sintering to produce solid lubricants of superior tribological performance and the subsequent economic gain from their development as a substitute for liquid lubricant are also evaluated.

Layered 2D Nanomaterials to Tailor Friction and Wear in Machine Elements—A Review

“…[58] Thereby, the deposition process, as well as the composition and thickness of the interlayers, affect the resulting microstructure and overall hardness of the material system. [35,59] Another approach that allows the synthesis of large quantities of 2D materials, though with deterioration of their quality, is based on the carrier-liquid supported exfoliation method. [60] This method applies ultrasonication, mechanical shearing, and electrochemical processing of bulk crystals that are separated into single-or multi-layer flakes, which are dispersed in a carrier solution, such as ethanol [61] or water and spray-coated, [61] ink-jet printed, [62] or burnished onto the substrate.…”

“…For instance, BP embedded in a polymeric matrix or introduced as additives to liquid lubricants could be used as materials for sliding bearings, rolling bearing cages, or seals. [35] • Finally, the experimental testing chain is of crucial importance. An adequate reflection of the stress and kinematics occurring in laboratory model tests, which mimic the conditions under real working conditions (for instance of rolling portions instead of pure sliding), is an important prerequisite for the knowledge transfer from tribological screening tests into real-world applications.…”

“…[21] From a fundamental point of view, plentiful research work has been dedicated to exploring the underlying scale-dependent friction and wear mechanisms of graphene and its derivates, [22,23] TMDs, [24][25][26] h-BN, [27] BP, [7,28] and MXenes. [17,18,29,30] These research activities have brought up a number of review articles on the tribological performance of the individual 2D nanomaterials and their underlying mechanisms dependent on the corresponding scale [15,31,32] or the respective application such as lubricant additives, [20,33] reinforcement phases, [34,35] or solid lubricant coatings. [32,36] This summary makes it evident that the tribological performance of the 2D materials is well documented from a fundamental perspective.…”

Dialkyl Dithiophosphate-Functionalized Ti3C2Tx MXene Nanosheets as Effective Lubricant Additives for Antiwear and Friction Reduction

“…1,2 Liquid lubricants are widely used in most industrial applications owing to their practical friction reduction effect. 3 However, the performance of liquid lubricants is limited by the severe working environments, 4 which could result in equipment failure. Metal, metal oxide, graphite, and graphene-based nanomaterials could be used as lubricant additives for liquid lubricants, which could effectively improve the viscosity and rheological properties of the lubricant.…”

Experimental Study of the Lubrication Mechanism of Micro-Spherical Solid Particles between Flat Surfaces

“…Several studies have demonstrated that adding rigid nanoparticles to a liquid lubricant can result in decreasing friction force and wear damage in the boundary and mixed lubrication regions [5][6][7][8]. Previous experimental works have demonstrated that various forms of solid particles, of sizes ranging from 1 up to 50,000 nm, could be employed as lubricant additives for better tribological performance [9][10][11]. However, there is a lack of complete knowledge of the lubrication technique of these solid nanoparticles [12].…”