Nanotribological properties of composite molecular films: C{sub 60} anchored to a self-assembled monolayer
- Western Michigan Univ., Kalamazoo, MI (United States)
- Ford Research Lab., Dearborn, MI (United States)
- Univ. of Akron, OH (United States)
Tribological properties of molecular films composed of a fullerene monolayer chemically attached to the functional surface of self-assembled monolayers (C{sub 60}-SAM) were studied by friction force microscopy. We observed very high wear stability of composite fullerene films. The friction coefficient ({mu}) for these films varies in a wide range from 0.04{+-}0.02 at high loads and 0.06{+-}0.02 at the highest velocities tested (<1000 {mu}m/s) to 0.15{+-}0.03 at intermediate velocities and low loads. This non-monotonic velocity behavior is a striking feature of fullerene films as compared to steadily rising friction forces for alkylsilane monolayers (CH{sub 3}-SAM) and may be related to exceeding dissipation of energy during structural rearrangement of fullerene molecules. The friction coefficient of C{sub 60}-SAM films of 0.04-0.15 at various velocities and loads is much lower than {mu} for silicon surfaces (0.1-0.6) and is comparable to the friction coefficient of CH{sub 3}-SAM (0.02-0.05) and an azide-terminated monolayer, N{sub 3} -SAM (0.04-0.07), measured at the same conditions. This value is within an interval found in literature data for sublimed fullerene films (0.07-0.2). Our data allow ranking of the friction coefficients of the various surfaces studied here. This ranking is consistent with macroscopic pin-on-disk measurements on the same films, variation of water contact angles reflecting a trend of increasing hydrophilicity, and variation of the adhesive forces. 23 refs., 8 figs., 1 tab.
- OSTI ID:
- 374485
- Journal Information:
- Langmuir, Vol. 12, Issue 16; Other Information: PBD: 7 Aug 1996
- Country of Publication:
- United States
- Language:
- English
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