Nanotribological Properties of Fluorinated, Hydrogenated, and Oxidized Graphenes

Recently, the tribological properties of graphene have been intensively examined for potential applications in micro- and nano-mechanical graphene-based devices. Here, we report that the tribological properties can be easily altered via simple chemical modifications of the graphene surface. Friction...

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Bibliographic Details
Published in:Tribology letters 2013-05, Vol.50 (2), p.137-144
Main Authors: Ko, Jae-Hyeon, Kwon, Sangku, Byun, Ik-Su, Choi, Jin Sik, Park, Bae Ho, Kim, Yong-Hyun, Park, Jeong Young
Format: Article
Language:English
Subjects:
Adhesion tests
Anisotropy
Chemical treatment
Chemistry and Materials Science
Correlation analysis
Corrosion and Coatings
Density functional theory
Elastic constants
Elastic properties
Energy dissipation
Flexibility
Fluorination
Friction
Graphene
Hydrogenation
Materials Science
Mathematical analysis
Nanocomposites
Nanomaterials
Nanostructure
Nanotechnology
Organic chemistry
Original Paper
Physical Chemistry
Solid surfaces
Surfaces and Interfaces
Theoretical and Applied Mechanics
Thin Films
Tribology
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Summary:Recently, the tribological properties of graphene have been intensively examined for potential applications in micro- and nano-mechanical graphene-based devices. Here, we report that the tribological properties can be easily altered via simple chemical modifications of the graphene surface. Friction force microscopy measurements show that hydrogenated, fluorinated, and oxidized graphenes exhibit, 2-, 6-, and 7-fold enhanced nanoscale friction on their surfaces, respectively, compared to pristine graphene. The measured nanoscale friction should be associated with the adhesive and elastic properties of the chemically modified graphenes. Density-functional theory calculations suggest that, while the adhesive properties of chemically modified graphenes are marginally reduced down to ~30 %, the out-of-plane elastic properties are drastically increased up to 800 %. Based on these findings, we propose that nanoscale friction on graphene surfaces is characteristically different from that on conventional solid surfaces; stiffer graphene exhibits higher friction, whereas a stiffer three-dimensional solid generally exhibits lower friction. The unusual friction mechanics of graphene is attributed to the intrinsic mechanical anisotropy of graphene, which is inherently stiff in plane, but remarkably flexible out of plane. The out-of-plane flexibility can be modulated up to an order of magnitude by chemical treatment of the graphene surface. The correlation between the measured nanoscale friction and the calculated out-of-plane flexibility suggests that the frictional energy in graphene is mainly dissipated through the out-of-plane vibrations, or the flexural phonons of graphene.
ISSN:1023-8883
1573-2711
DOI:10.1007/s11249-012-0099-1