Influence Factors on Mechanisms of Superlubricity in DLC Films: A Review

Yu, Qingyuan; Chen, Xinchun; Zhang, Chenhui; Luo, Jianbin

doi:10.3389/fmech.2020.00065

Cited by 41 publications

(18 citation statements)

References 103 publications

(160 reference statements)

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“…Stress-induced graphitisation can also occur because of the high contact pressure in sliding tests [9]. High hardness, surface smoothness, and viscoelasticity/viscoplasticity are properties that strongly influence the tribological behaviour of DLC coatings [14][15][16][17]. The passivation of dangling bonds by different agents (H, hydroxyl (-OH), carboxyl (-COOH), etc.…”

Section: Introductionmentioning

confidence: 99%

“…The passivation of dangling bonds by different agents (H, hydroxyl (-OH), carboxyl (-COOH), etc. ), graphitisation, and the formation of a self-generated easy-shearing transfer layer consisting of carbon-based structures, oxides, water, etc., are the main mechanisms explaining the excellent tribological properties of DLC and ta-C coatings, including superlubricity (COF < 0.01 [18]) [14,[19][20][21][22][23]. Hydrogen and oxygen thus play important roles in understanding the friction mechanisms of DLC and ta-C coatings.…”

Section: Introductionmentioning

confidence: 99%

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High-Temperature Tribological Performance of Al2O3/a-C:H:Si Coating in Ambient Air

et al. 2021

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The study investigates thermal stability and high temperature tribological performance of a-C:H:Si diamond-like carbon (DLC) coating. A thin alumina layer was deposited on top of the a-C:H:Si coating to improve the tribological performance at high temperatures. The a-C:H:Si coating and alumina layer were prepared using plasma-activated chemical vapour deposition and atomic layer deposition, respectively. Raman and X-ray photoelectron spectroscopy were used to investigate the structures and chemical compositions of the specimens. The D and G Raman peaks due to sp2 bonding and the peaks corresponding to the trans-polyacetylene (t-Pa) and sp bonded chains were identified in the Raman spectra of the a-C:H:Si coating. Ball-on-disc sliding tests were carried out at room temperature and 400 °C using Si3N4 balls as counter bodies. The a-C:H:Si coating failed catastrophically in sliding tests at 400 °C; however, a repeatable and reproducible regime of sliding with a low coefficient of friction was observed for the Al2O3/a-C:H:Si coating at the same temperature. The presence of the alumina layer and high stress and temperature caused structural changes in the bulk a-C:H:Si and top layers located near the contact area, leading to the modification of the contact conditions, delivering of extra oxygen into the contact area, reduction of hydrogen effusion, and suppression of the atmospheric oxidation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High-Temperature Tribological Performance of Al2O3/a-C:H:Si Coating in Ambient Air

et al. 2021

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“…The microscale friction occurs at the ideal small contact interface, and the intact nanosheet of graphene can get low friction ( Hod et al, 2018 ; Chen and Li, 2020 ). However, at the macroscale, the contact interface has large and plentiful factors that influence the frictional performance ( Cooper et al, 2019 ; Yu et al, 2020 ). In particular, graphene nanosheets have a high specific surface area and more easily absorb surrounding gas molecules when exposed to an atmosphere, which would easily affect macroscale tribological properties.…”

Section: Introductionmentioning

confidence: 99%

Environmental Molecular Effect on the Macroscale Friction Behaviors of Graphene

Wang

et al. 2021

Front. Chem.

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This study investigated the friction behavior of graphene in air and nitrogen atmosphere environments. The microstructural evolution caused by the variation of atmosphere environments and its effect on the friction coefficient of the graphene is explored. It is demonstrated that graphene can exhibit excellent lubricating properties both in air and nitrogen atmosphere environments. In air, a highly ordered layer-by-layer slip structure can be formed at the sliding interface. Oxygen and H2O molecules can make edge dangling bonds and defects passive. Thus the interaction between the nanosheets and the layers of nanosheets is weak and the friction coefficient is low (0.06–0.07). While the friction coefficient increases to 0.14–0.15 in a nitrogen atmosphere due to the interaction of defects generated in the sliding process, the nitrogen molecules with lone pair electrons can only make the nanosheets passive to a certain degree, thus the ordered slip structure is destroyed and friction is higher. This work reveals the influence of environmental molecules on the macroscale tribological performances of graphene and its effect on the microstructure at the sliding interface, which could shed light on the lubricating performance of graphene in environmental atmospheres and help us to understand the tribological behaviors of graphite at the macroscale.

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“…The materials with anti-wear and ultralow friction characteristics are the most desirable in mechanical engineering applications where the carbon based materials have potentials to play a major role. Since ultralow friction and negligible wear are demonstrated in ultrananocrystalline diamond (UNCD) and diamond-like carbon (DLC) films at ambient conditions, the research interest is ever increasing drastically over the recent past years [1,2,[11][12][13][14][15][16][17][18][19][20]3,[21][22][23][24][25][26][27][28][29][30]4,[31][32][33][34][5][6][7][8][9][10]. The formation of tribofilms which occurs due to the shear induced graphitization is one of the crucial factors for achieving ultralow friction in carbon materials [5,10,[20][21][22][23][24][25][26]35].…”

Section: Introductionmentioning

confidence: 99%

“…There are numerous reports available in the literature on the factors affecting the ultralow friction and wear of UNCD and DLC films. Among them, the surface roughness of tribo-contacts, contact pressure, tribo-environment, crystalline orientation, structural defects, mechanical properties, and surface chemistrypassivation by functionalization or the formation of secondary phase tribofilms due to tribo-chemical reactions at the sliding interface play significant role on tribological properties [14][15][16][17][18][19][20]. The chemical and microstructure analysis of the tribofilm can provide invaluable information about the tribochemical reactions at the interface and the wear mechanism.…”

Section: Introductionmentioning

confidence: 99%

Direct microscopic evidence of shear induced graphitization of ultrananocrystalline diamond films

et al. 2021

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The origin of ultralow friction and high wear resistance in ultrananocrystalline diamond (UNCD) films is still under active debate because of the perplexed tribochemistry at the sliding interface. Herein, we report a comparative study on surface topography and nanoscale friction of tribofilms, in wear tracks of two sets of UNCD films having different structural characteristics.Despite both the films display ultralow coefficient of friction, the UNCD films grown under Ar atmosphere (UNCDAr) exhibit a high wear resistance while the wear rate is higher for the films grown in N2 (UNCDN). Frictional force microscopic (FFM) investigations clearly reveal the manifestation of shear induced graphitization on both the films. However, the wear track of UNCDAr films have a large network of a few layer graphene (FLG) structures over the amorphous carbon tribofilms while only isolated clusters of FLG structures are present in the wear track of UNCDN films. Here, we demonstrate the direct micro-/nanoscopic evidence for the formation of large network of ~ 0.8 -6 nm thick FLG structures, as a consequence of shear induced graphitization and discuss their decisive role in ultralow friction and wear.

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Influence Factors on Mechanisms of Superlubricity in DLC Films: A Review

Cited by 41 publications

References 103 publications

High-Temperature Tribological Performance of Al2O3/a-C:H:Si Coating in Ambient Air

High-Temperature Tribological Performance of Al2O3/a-C:H:Si Coating in Ambient Air

Environmental Molecular Effect on the Macroscale Friction Behaviors of Graphene

Direct microscopic evidence of shear induced graphitization of ultrananocrystalline diamond films

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