Friction anisotropy in boronated graphite

•Friction anisotropy in boronated graphite is observed in macroscopic sliding condition.•Low friction coefficient is observed in basal plane and becomes high in prismatic direction.•3D phase of boronated graphite transformed into 2D structure after friction test.•Chemical activity is high in prismat...

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Bibliographic Details
Published in:Applied surface science 2015-01, Vol.324, p.443-454
Main Authors: Kumar, N., Radhika, R., Kozakov, A.T., Pandian, R., Chakravarty, S., Ravindran, T.R., Dash, S., Tyagi, A.K.
Format: Article
Language:English
Subjects:
Anisotropy
Basal plane
Friction
Friction anisotropy
Functional groups
Graphite
Planes
Surface characterization
Transformations
Tribology
Wear
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Summary:•Friction anisotropy in boronated graphite is observed in macroscopic sliding condition.•Low friction coefficient is observed in basal plane and becomes high in prismatic direction.•3D phase of boronated graphite transformed into 2D structure after friction test.•Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (002) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (110) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.
ISSN:0169-4332
1873-5584
DOI:10.1016/j.apsusc.2014.10.136