TY - JOUR
T1 - Shear-Induced Structural Changes and Origin of Ultralow Friction of Hydrogenated Diamond-like Carbon (DLC) in Dry Environment
AU - Manimunda, Praveena
AU - Al-Azizi, Ala'
AU - Kim, Seong H.
AU - Chromik, Richard R.
N1 - Funding Information:
P.M. acknowledges technical assistance from Line Mongeon, Wu, Ken and David Liu of the Facility for Electron Microscopy Research at McGill University. P.M. and R.R.C. thank the Natural Science and Engineering Research Council (NSERC) of Canada Discovery Grants program for financial support. A.A. and S.H.K. were supported by the National Science Foundation (Grant No. CMMI-1131128 and 1435766). The authors acknowledge Osman Eryilmaz and Ali Erdemir at Argonne National Laboratory for kindly providing DLC samples used in this study.
PY - 2017/5/17
Y1 - 2017/5/17
N2 - The origins of run-in and ultralow friction states of a sliding contact of hydrogenated diamond-like carbon (H-DLC) and sapphire were studied with an in situ Raman tribometer as well as ex situ analyses of transmission electron microscopy (TEM), Raman spectroscopy, and nanoindentation. Prior to ultralow friction behavior, H-DLC exhibits a run-in period. During the run-in period in dry nitrogen atmosphere, the transfer film was formed and its uniformity and thickness as well as structure were varied. The duration and friction behaviors during the run-in depended on the initial surface state of the H-DLC coatings. A comparative study of pristine and thermally oxidized H-DLC revealed the role of surface oxide layer on run-in friction and transfer film formation. Attainment of the ultralow friction state appeared to correlate with the uniformity and structure of the transfer film evolved during the run-in, rather than its final thickness. TEM cross-section imaging of the wear track and the counter surfaces showed a trace of nanocrystalline graphite and a thin modified surface layer on both rubbing bodies. The comparison of hardness and reduced modulus of the wear tracks and the unworn surfaces as well as the ex situ Raman spectra suggested the densification of the wear track surfaces. Combining the in situ and ex situ analysis results, a comprehensive model was proposed for the formation and structure of the ultralow friction sliding contact of H-DLC.
AB - The origins of run-in and ultralow friction states of a sliding contact of hydrogenated diamond-like carbon (H-DLC) and sapphire were studied with an in situ Raman tribometer as well as ex situ analyses of transmission electron microscopy (TEM), Raman spectroscopy, and nanoindentation. Prior to ultralow friction behavior, H-DLC exhibits a run-in period. During the run-in period in dry nitrogen atmosphere, the transfer film was formed and its uniformity and thickness as well as structure were varied. The duration and friction behaviors during the run-in depended on the initial surface state of the H-DLC coatings. A comparative study of pristine and thermally oxidized H-DLC revealed the role of surface oxide layer on run-in friction and transfer film formation. Attainment of the ultralow friction state appeared to correlate with the uniformity and structure of the transfer film evolved during the run-in, rather than its final thickness. TEM cross-section imaging of the wear track and the counter surfaces showed a trace of nanocrystalline graphite and a thin modified surface layer on both rubbing bodies. The comparison of hardness and reduced modulus of the wear tracks and the unworn surfaces as well as the ex situ Raman spectra suggested the densification of the wear track surfaces. Combining the in situ and ex situ analysis results, a comprehensive model was proposed for the formation and structure of the ultralow friction sliding contact of H-DLC.
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U2 - 10.1021/acsami.7b03360
DO - 10.1021/acsami.7b03360
M3 - Article
C2 - 28459534
AN - SCOPUS:85019601734
SN - 1944-8244
VL - 9
SP - 16704
EP - 16714
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 19
ER -