Re-doped fullerene-like MoS₂ nanoparticles in relationship with soft lubrication

Abstract

Inorganic, fullerene-like (IF) nanoparticles of tungsten disulfide (WS2) and molybdenum disulfide (MoS2) have been synthesised in the past and their useful tribological properties have been studied quite extensively. Rhenium doping of such nanoparticles was also reported and studied to some extent. Herein, further studies of the physico-chemical properties are reported in connection to lubrication under mild loads. Due to their self-repelling character, the doped nanoparticles form tessellated monolayers on certain substrates. When mixed in small amounts, the IF nanoparticles lead to a reduction in the viscosity of water-based gels. Furthermore, the added nanoparticles lead to a precipitous reduction in traction force (friction) under mild loads. The lubrication mechanism of such nanoparticles is briefly discussed.

An overview of the recent advances in inorganic nanotubes

“…The negative surface charge induced by the ionized Re atoms led to self-repelling nanoparticles, which showed little tendency to agglomerate, prompting exceedingly good tribological behavior. 142,143 Most naturally, tribological characterization cannot be easily experimented with individual nanoparticles. However, the progress with in-situ microscopy techniques brings this topic close to realization.…”

Electrophoretic Deposition of Hydroxyapatite Film Containing Re-Doped MoS2 Nanoparticles

“…Self-lubricating films containing these NP were obtained by co-deposition of the IF NP and various metallic films [ 24 , 25 , 26 ]. Recently, doping of IF-MoS 2 nanoparticles with minute amounts (<200 ppm) of rhenium atoms (Re:IF-MoS 2 ) was demonstrated [ 27 , 28 , 29 , 30 ]. Figure 1 a shows high-resolution scanning electron microscope (HRSEM) micrograph of the Re-doped IF NP powder.…”

“…Figure 1 b shows high-resolution transmission electron microscopy (HRTEM) image of one such nanoparticle made of some 20 closed and nested layers of MoS 2 . The crystalline perfection and atomically smooth (sulfur-terminated) surface of the IF NP contributes to their excellent mechanical [ 31 ] and tribological performance [ 27 , 30 ]. The synthesized nanoparticles are highly agglomerated (see Figure S1 ) and must be deagglomerated before use.…”

Doping of Fullerene‐Like MoS2 Nanoparticles with Minute Amounts of Niobium

“…Indeed Re‐doping (<1000 ppm) of fullerene‐like molybdenum sulfide (IF‐MoS 2 ) nanoparticles (NP) was recently accomplished . This resulted in vastly improved tribological behavior of the NP with friction coefficients nearing the superlubricity regime, offering them applications in a variety of medical technologies . On the other hand, substitution of Mo atoms by Nb atoms in the lattice contributes one extra hole to the valence band of MoS 2 per ionized acceptor state, lending the nanoparticle a p‐type character.…”