The Effects of Impurities and Vapors at Very Low Pressures on the Sliding Properties of Molybdenum and Tungsten Disulfide
Report Number: AFML-TR-70-127 p. 67
Author(s): Haltner, Arthur J.
Corporate Author(s): General Electric Company, Spaces Sciences Laboratory
Laboratory: Air Force Materials Laboratory
Date of Publication: 1970-07
Pages: 56
Contract: AF33(615)-5278
DoD Project: 7343
DoD Task:
Abstract:
The friction of molybdenite (naturally occurring molybdenum disulfide) sliding in ultrahigh vacuum is generally half that observed in air under comparable conditions. In contrast, synthetic molybdenum disulfide (three different preparations) and tungsten disulfide (from three sources) have been shown to have friction levels in ultrahigh vacuum that are as high as and often higher than values observed in air. When these samples are exposed to a gas mixture at 10-5 torr containing significant concentrations of hydrocarbons, friction levels drop to levels similar to those observed for molybdenite in ultrahigh vacuum. Tungsten disulfide has been studied in the presence of controlled atmospheres of pure vapors at reduced pressurues. Of the vapors studied, most (water vapor, oxygen, mercury, ethylene, acetone, methyl ethyl ketone, ethyl acetate, and methanol) had little or no effect on friction. But at 10-5 torr n-amyl or isoamyl alcohol lowered the friction coefficient to less than 0.09. When a specimen of molybdenite containing 10% by weight of molybdenum dioxide was studied in ultrahigh vacuum, the friction coefficient was near 0.25 and dropped to 0.07 when gas containing hydrocarbons was admitted to the chamber. These observations are consistent with the hypothesis that the high friction levels for synthetic dichalcogenides in ultrahigh vacuum are related to the presence of one or more impurities at the sliding interface.
Provenance: Lockheed Martin Missiles & Fire Control
Author(s): Haltner, Arthur J.
Corporate Author(s): General Electric Company, Spaces Sciences Laboratory
Laboratory: Air Force Materials Laboratory
Date of Publication: 1970-07
Pages: 56
Contract: AF33(615)-5278
DoD Project: 7343
DoD Task:
Abstract:
The friction of molybdenite (naturally occurring molybdenum disulfide) sliding in ultrahigh vacuum is generally half that observed in air under comparable conditions. In contrast, synthetic molybdenum disulfide (three different preparations) and tungsten disulfide (from three sources) have been shown to have friction levels in ultrahigh vacuum that are as high as and often higher than values observed in air. When these samples are exposed to a gas mixture at 10-5 torr containing significant concentrations of hydrocarbons, friction levels drop to levels similar to those observed for molybdenite in ultrahigh vacuum. Tungsten disulfide has been studied in the presence of controlled atmospheres of pure vapors at reduced pressurues. Of the vapors studied, most (water vapor, oxygen, mercury, ethylene, acetone, methyl ethyl ketone, ethyl acetate, and methanol) had little or no effect on friction. But at 10-5 torr n-amyl or isoamyl alcohol lowered the friction coefficient to less than 0.09. When a specimen of molybdenite containing 10% by weight of molybdenum dioxide was studied in ultrahigh vacuum, the friction coefficient was near 0.25 and dropped to 0.07 when gas containing hydrocarbons was admitted to the chamber. These observations are consistent with the hypothesis that the high friction levels for synthetic dichalcogenides in ultrahigh vacuum are related to the presence of one or more impurities at the sliding interface.
Provenance: Lockheed Martin Missiles & Fire Control
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