Thickness and surface force distributions in spreading region of molecularly thin lubricant film on magnetic disks

Intermittent sliding (stick–slip motion) between solids is commonplace (e.g., squeaking hinges), even in the presence of lubricants, and is believed to occur by shear-induced fluidization of the lubricant film (slip), followed by its resolidification (stick). Using a surface force balance, we measure how the thickness of molecularly thin, model lubricant films (octamethylcyclotetrasiloxane) varies in stick–slip sliding between atomically smooth surfaces during the fleeting (ca. 20 ms) individual slip events. Shear fluidization of a film of five to six molecular layers during an individual slip event should result in film dilation of 0.4–0.5 nm, but our results show that, within our resolution of ca. 0.1 nm, slip of the surfaces is not correlated with any dilation of the intersurface gap. This reveals that, unlike what is commonly supposed, slip does not occur by such shear melting, and indicates that other mechanisms, such as intralayer slip within the lubricant film, or at its interface with the confining surfaces, may be the dominant dissipation modes.

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Dependence of Pin Surface Roughness for Friction Forces of Ultrathin Perfluoropolyether Lubricant Film on Magnetic Disks by Pin-on-Disk Test

Advances in Tribology ◽

10.1155/2012/923818 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7

Author(s):

H. Tani ◽

Y. Mitsuya ◽

T. Kitagawa ◽

N. Tagawa

Keyword(s):

Surface Roughness ◽

Ion Beam ◽

Lubricant Film ◽

Friction Forces ◽

Magnetic Disks ◽

End Groups ◽

Cluster Ion ◽

Perfluoropolyether Lubricant ◽

Gas Cluster Ion Beam ◽

Pin On Disk

We fabricated supersmooth probes for use in pin-on-disk sliding tests by applying gas cluster ion beam irradiation to glass convex lenses. In the fabrication process, various changes were made to the irradiation conditions; these included one-step irradiation of Ar clusters or two-step irradiation of Ar and N2clusters, with or without Ar cluster-assisted tough carbon deposition prior to N2irradiation, and the application of various ion doses onto the surface. We successfully obtained probes with a centerline averaged surface roughness that ranged widely from 1.08 to 4.30 nm. Using these probes, we measured the friction forces exerted on magnetic disks coated with a molecularly thin lubricant film. Perfluoropolyether lubricant films with different numbers of hydroxyl end groups were compared, and our results indicated that the friction force increases as the surface roughness of the pin decreases and that increases as the number of hydroxyl end groups increases.

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Measurement of thickness of molecularly thin lubricant film by using ellipsometric microscopy

APMRC 2004 Asia-Pacific Magnetic Recording Conference, 2004. ◽

10.1109/apmrc.2004.1521932 ◽

2005 ◽

Author(s):

K. Fukuzawa ◽

T. Shimuta ◽

A. Nakada ◽

Hedong Zhang ◽

Y. Mitsuya

Keyword(s):

Lubricant Film ◽

Molecularly Thin Lubricant ◽

Measurement Of Thickness

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