High Lubricity of Re-Doped Fullerene-Like MoS2 Nanoparticles

Abstract

The electrostatic effects in tribological systems have been studied in the past, especially with regards to data storage media. Nanoparticles (NP) of WS 2 and MoS 2 with fullerene-like structure (IF) have been studied in the past and showed very good tribological behavior. Being semiconductors, their electrical properties can be controlled by, e.g., substituting the lattice Mo (W) atoms with Re (n-type conductivity) and Nb (p-type conductivity) atoms. In this study doping of IF-MoS 2 , and to a lesser degree IF-WS 2 , NP with small amounts (\ 1 at.%) of rhenium atoms has been studied. For this purpose two new synthetic approaches have been pursued. The doped nanoparticles were characterized by various techniques. In particular, the doping density was determined by ICP-MS technique. The resistivity of the nanoparticles was shown to decrease significantly with increasing doping level. In contrast to the undoped nanoparticles, the doped NP were shown to exhibit reduced agglomeration and produce stable suspensions in PAO-4 and PAO-6 oils. Extensive tribological measurements with these PAO oils formulated with 1 wt % of the doped NP showed friction coefficients as low as 0.01 in mixed lubrication conditions and negligible wear. Microscopy analysis of the tribological surfaces reveal very smooth but discontinuous and dense film of the doped NP on the tribological surfaces. It is proposed that the doped NP are negatively charged at their surface eliciting mutual repulsion, which has a remarkable influence on their rheological properties and their tribological behavior.

Formation of an adsorption film of MoS2 nanoparticles and dioctyl sebacate on a steel surface for alleviating friction and wear

“…Unlike the IF nano-MoS 2 spheres reported in Refs. [5,6], the MoS 2 layers in the sphere-like nanoparticles formed only partial close structure. Many crystal defects were observed at the brim of MoS 2 nanoparticles.…”

“…Previous studies have shown that the lubrication of MoS 2 was dependent on its size and morphology. Nanoscaled MoS 2 (nano-MoS 2 or n-MoS 2 ) particles usually present better properties than bulk microsized 2H-MoS 2 (micro-MoS 2 or m-MoS 2 ) [4][5][6][7]. Thus, much attention was focused on the synthesis and tribological properties of MoS 2 nanoparticles [8][9][10][11][12][13].…”

Direct observation by in situ transmission electron microscopy of the behaviour of IF‐MoS2 nanoparticles during sliding tests: influence of the crystal structure

“…For example, Rapoport et al . and Yadgarov et al . showed that the use of the Re‐doped IF‐MoS 2 nanoparticles in PAO oil resulted in a significantly lower coefficient of friction and wear compared with un‐doped IF‐MoS 2 , IF‐WS 2 or 2H‐MoS 2 particles.…”

“…One of the purposes of this novel synthesis strategy is linked to the attempt of reducing the agglomeration tendency of the nanoparticles. For example, Rapoport et al and Yadgarov et al 19,20 showed that the use of the Re-doped IF-MoS 2 nanoparticles in PAO oil resulted in a significantly lower coefficient of friction and wear compared with un-doped IF-MoS 2 , IF-WS 2 or 2H-MoS 2 particles. It was reported that Re atoms were acting as electron donors and, therefore, the Re-doped IF-MoS 2 particles should have a negative charge at the surface.…”

Effect of Dielectric Constant of Solvents on the Particle Size and Bandgap of La/SnO2‐TiO2 Nanoparticles and Their Catalytic Properties

“…nanomaterials play an important role in the fabrication of devices like telecommunication and optical components, solid‐state lasers, and many others . Therefore, it is of great interest to develop a facile synthetic method for the synthesis of high‐quality RE‐doped nanomaterials that have uniformity in size and shape . RE‐doped nanoparticles have been suggested as a promising new class of material with properties comparable to those of semiconductor quantum dots and organic dyes and with superior optical and chemical properties …”