Using a new quartz-made reactor, large amounts of fullerene-like (IF) MoS 2 nanoparticles were synthesized by reacting MoO 3 vapor with H 2 S in a reducing atmosphere. The nanoparticles were found to be of high crystalline order; with an average size of 70 nm and consist of more than 30 closed shells. Extensive tribological testing of the nanoparticles in two types of synthetic oils-poly-alpha olefins (PAO)-was carried out and compared to that of bulk (2H platelets) MoS 2 and IF-WS 2 . These tests indicated that under high pressure and relatively low humidity, the IF-MoS 2 exhibited a friction coefficient as low as 0.03 and the smallest wear rate of the measured systems. However, its performance was found to be lower in comparison to IF-WS 2 after 2500 cycles, due probably to its inferior chemical stability. This study indicates that the tribological performance of the IF nanoparticles depends strongly on their crystalline order and size.
Composite coatings of Co + fullerene-like WS2
nanoparticles on stainless steel substrate were obtained through electroless deposition, using
DMAB (dimethyl borane complex, 97%) as the reducing agent, and by electroplating in acidic
solution. Phase analysis results show that the coatings consist of Co and the fullerene-like
WS2
nanoparticles alone. Tribological measurements show reduced wear and friction of the
composite coatings as compared with the pure cobalt film or the stainless steel substrate.
Metals and alloys of low melting points (<430 °C) can be melted in hot silicone oil to form two immiscible liquids. Irradiation of the system with ultrasonic energy induces acoustic cavitation in the oil, which disperses the molten metals into microspheres that solidify rapidly upon cooling. This method has been applied to seven pure metals (Ga, In, Sn, Bi, Pb, Zn, Hg) and two eutectic alloys of gold (Au-Ge and Au-Si). The morphology and composition of the resulting microspheres were examined by SEM and EDS. Eutectic Au-Si formed also crystalline Au nanoparticles, which were separated and studied by HRTEM.
A new physical method is described for the preparation of metal microspheres by ultrasonic cavitation of low-melting point metals (<380 °C) immersed in hot silicone oil. The ultrasonic radiation causes dispersion of the molten metals into spheres, which solidify rapidly on cooling. This method is illustrated for the synthesis of Pb and Au–Si eutectic alloy.
In this work chromium-rich coatings impregnated with fullerene-like (IF)-WS2 nanoparticles were deposited on stainless steel substrates. The coatings were obtained from a trivalent chromium bath at pH 2 by galvanostatic electrodeposition. Zinc and cobalt salts were added to the aqueous solution in small amounts serving as cationic growth promoters. Photodeposition of tin-palladium nanoparticles was used as seeding enhancer for the co-deposition of the fullerene-like nanoparticles. The coatings were characterized by a number of techniques and were found to show a decreasing gradient of the IF nanoparticles towards the film-substrate interface. Tribological tests showed that in contrast to the substrate and the pure metal coating, the IF-containing films exhibit low friction and wear.
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