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.

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A new type of composite metal–nanoparticle coating that significantly reduces the friction force of various surfaces, particularly archwires in orthodontic applications, is demonstrated. The coating is based on electrodeposited Ni film impregnated with inorganic fullerene-like nanospheres of tungsten disulphide. The first encouraging tests have shown reduction of up to 60% of the friction force between coated rectangular archwires and self-ligating brackets in comparison with uncoated archwires. The coating not only significantly reduces friction of commercial archwires but also maintains this low value of friction for the duration of the tests in comparison to archwires coated with nickel film without the nanoparticles. The coated surfaces of the wires were examined by scanning electron microscopy equipped with energy dispersive analyzer and by x-ray powder diffraction methods before and after the friction tests. Using these analyses, it was possible to qualitatively estimate the state of the Ni+IF-WS2 coating before and after the friction test compared to Ni coated wires without IF-WS2.

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If we compare the wear of the chrome-magnesite and the periclase-spinel products, it is clear that the chrome-magnesite products are penetrated to a greater extent by the iron oxides and SiO 2 than are the periclase-spinel products; the periclase-spinel products are mainly penetrated by iron oxides and to a lesser extent by the SiO 2 while the chrome-magnesite are penetrated by iron oxides and SiO 2 to approximately the same extent; in the chrome-magnesite products, by contrast with the periclase-spinel, the iron oxides are reduced to metal; the main form of the wear in products of both types is flashing, which occurs as the result of the formation of olivine of a complex composition, pyroxene, glass, magnetite, and magnetosioferrite, as observed to a greater extent in the chrome-magnesite products.Thus, in order to further improve the wear resistance of the periclase-spinel products, it is necessary to reduce their porosity and their concentrations of iron oxide and SiO 2. CONCLUSIONSThe interaction between zinc sinters and refractory products has been studied. The greatest resistance to the action of the zinc-sinter melt is found in the articles made from grade PShSP and MChVP products. In this case the structure and porosity of the products are found to have a significant effect on their wear resistance.The wear on chrome-magnesite and periclase-spinel products currently used to line Weltz furnaces is caused by the penetration of the refractory by iron oxides and SiO 2 forming olivine of a complex composition, pyroxene, glass, ferrites, and aluminates and silicates of zinc. In the periclase-spinel products, these processes occur to a lesser extent than in the chrome-magnesite ones.On the basis of the results from these studies it is recommended that the MChVP and PSpSP products be used in the linings of Weltz furnaces; the use of ChM and PSpSO products is not recommended.