A molybdenum disulfide magnetic solid lubricant for ferromagnetic surfaces

Molybdenum disulfide (MoS2) has been used in industrial applications as a dry lubricant. Although this material initially improves anti-wear properties, as surfaces move against each other the lubricating particles tend to spread out from the asperity points. To reduce this spread of lubricant, MoS2 platelets were made magnetic by replacing the unsaturated or loosely bonded sulfur atoms (located mainly on the edges of the platelets) with magnetic elements such as Fe, Ni, or Co particles. Under appropriate experimental conditions these elements form stable bonds with the partially free Mo atoms of the edges and are protected from oxidation in air by the basal planes of the overlapping neighboring layers. When compared to the friction coefficient of pure MoS2, the incorporation of magnetic Fe particles for example, increases the friction depending on the Fe/Mo ratio, but the overall result is in an improved lubricant with unique magnetic properties when the Fe/Mo ratio is properly optimized. In this application at least one of the surfaces must be ferromagnetic to hold the lubricant in place.