Mechanics of Deformation under Traction and Friction of a Micrometric Monolithic MoS2 Particle in Comparison with those of an Agglomerate of Nanometric MoS2 Particles

Abstract

Tribology of small inorganic nanoparticles in suspension in a liquid lubricant is often impaired because these particles agglomerate even when organic dispersants are used. In this paper we use lateral force microscopy to study the deformation mechanism and dissipation under traction of two extreme configurations (1) a large MoS 2 particle (*20 lm width) of about 1 lm height and (2) an agglomerate (*20 lm width), constituting 50 nm MoS 2 crystallites, of about 1 lm height. The agglomerate records a friction coefficient which is about 5-7 times that of monolithic particle. The paper examines the mechanisms of material removal for both the particles using continuum modeling and microscopy and infers that while the agglomerate response to traction can be accounted for by the bulk mechanical properties of the material, intralayer and interlayer basal planar slips determine the friction and wear of monolithic particles. The results provide a rationale for selection of layered particles, for suspension in liquid lubricants.

Microtribology and Friction-Induced Material Transfer in Layered MoS2 Nanoparticles Sprayed on a Steel Surface

“…There may be more than one reason for this effect and we intend to pursue this further in future using in situ Raman spectroscopy assisted tribology. In a previous article [41], we have reported that increasing the normal load shears slabs of increasing thickness, when a 20-lm particle is subjected to a shear traction, slip shear stress, however, remains insensitive to normal load. Thus, at high loads, high volumes of MoS 2 slabs are available to undertake generation and regeneration of transfer films over long sliding distances such that the incidences of metal-to-metal contact is reduced.…”

“…The LFM experiment showed that even when the contact is limited to within a small area (100 9 100 nm 2 on a 2 9 2 lm 2 particle surface) at more than 100 nN normal load the whole top surface of the particle slips as a slab against the lower part of the particle. A detailed account and analysis of single particle scratching of a large MoS 2 particle is presented elsewhere [41]. Figure 4 shows the friction coefficients observed in microtribometer experiments in the ambient.…”

Relationship Between Physical Structure and Tribology of Single Soot Particles Generated by Burning Ethylene

“…In a previous paper [51] we had proposed a model, based on mode II fracture mechanics, for a layered material removal process by LFM scanning. The model was validated for layered MoS 2 single particles by demonstrating that the thickness of removed material increases monotonically with applied normal load.…”

Microtribological Performance of Au–MoS2 and Ti–MoS2 Coatings with Varying Contact Pressure

“…lower coefficient of friction and lower wear rate) in humid environments and at higher contact pressure [32]. Other recent studies [34,35] have focused on lateral force microscopy of nanoparticles of MoS 2 .…”