Effect of Water Adsorption on the Frictional Properties of Hydrogenated Amorphous Carbon Films in Various Relative Humidities

Ishikawa, Takumi; Choi, Junho

doi:10.1021/acs.langmuir.0c02416

Cited by 11 publications

(8 citation statements)

References 61 publications

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“…Recently, friction and wear have become one of the major factors causing material and energy consumption. Lowering friction coefficient and wear rate are of great importance for improving the efficiency of metal-working processes [1] and prolonging the service life of mechanical equipment [2]. The adoption of appropriate lubricants is a powerful and convenient means to solve the issues.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of N-doped carbon quantum dots as lubricant additive to enhance the tribological behavior of MoS2 nanofluid

Sun

Choi

et al. 2022

Friction

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In this study, a novel lubricant additive nitrogen-doped carbon quantum dot (N-CQD) nanoparticle was prepared by the solvothermal method. The synthesized spherical N-CQD nanoparticles in the diameter of about 10 nm had a graphene oxide (GO)-like structure with various oxygen (O)- and nitrogen (N)-containing functional groups. Then N-CQDs were added to MoS2 nanofluid, and the tribological properties for steel/steel friction pairs were evaluated using a pin-on-disk tribometer. Non-equilibrium molecular dynamics (NEMD) simulations for the friction system with MoS2 or MoS2 + N-CQD nanoparticles were also conducted. The results showed that friction processes with MoS2 + N-CQD nanofluids were under the mixed lubrication regime. And MoS2 nanofluid containing 0.4 wt% N-CQDs could achieve 30.4% and 31.0% reduction in the friction coefficient and wear rate, respectively, compared to those without N-CQDs. By analyzing the worn surface topography and chemical compositions, the excellent lubrication performance resulted from the formation of tribochemistry-induced tribofilm. The average thickness of tribofilm was about 13.9 nm, and it was composed of amorphous substances, ultrafine crystalline nanoparticles, and self-lubricating FeSO4/Fe2(SO4)3. NEMD simulation results indicated the interaction between S atoms in MoS2 as well as these O- and N-containing functional groups in N-CQDs with steel surfaces enhanced the stability and strength of tribofilm. Thereby the metal surface was further protected from friction and wear.

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Section: Introductionmentioning

confidence: 99%

Synthesis of N-doped carbon quantum dots as lubricant additive to enhance the tribological behavior of MoS2 nanofluid

Sun

Choi

et al. 2022

Friction

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“…However, the a-C:F films showed a significant dependence on the RH, as shown in Figure e. Our previous study investigated the frictional characteristics of a-C:H films with a polymer-like structure (PLC films) and observed that the friction coefficient increased as the RH increased, although the measured O/C ratio was similar . The study revealed that the higher the RH, the thicker the adsorption water layer formed on the surface of the PLC films, which induced a high shear force between the water layers owing to the hydrogen bonds at the surface.…”

Section: Resultsmentioning

confidence: 91%

“…Our previous study investigated the frictional characteristics of a-C:H films with a polymer-like structure (PLC films) and observed that the friction coefficient increased as the RH increased, although the measured O/C ratio was similar. 29 The study revealed that the higher the RH, the thicker the adsorption water layer formed on the surface of the PLC films, which induced a high shear force between the water layers owing to the hydrogen bonds at the surface. Kim et al 37 conjectured that water layers possess large cohesive energy owing to greater dipole interactions, providing a stronger physical barrier, which is expected to result in a larger friction coefficient.…”

Section: ■ Results and Discussionmentioning

confidence: 96%

“…The surfaces of the a-C:F film and the a-C:H mating material are oxidized when sliding in ambient air, forming C−O−C, C�O, and C−OH bonds at the sliding surface, 36 and the friction coefficient continues to increase owing to the increase in hydrogen bonds between the surfaces. Ishikawa et al 29 reported that when several water molecules are present at the sliding interface, the surface chemistry is significantly changed by oxidation during sliding, which increases the friction coefficient.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Barthel et al , studied the effects of adsorbed water molecules on the friction and meniscus force and reported the necessity of understanding the surface chemistry and adsorption of surrounding vapor molecules to understand their effects on adhesion, friction, and wear properties. In addition, Ishikawa et al reported the water adsorption properties of hydrogenated amorphous carbon (a-C:H) films with various microstructures using a quartz crystal microbalance (QCM) and showed that the friction properties of the films in the air could be explained by surface oxidation and the thickness of the adsorbed water layer. Hence, we believe that it is necessary to investigate the characteristics of water adsorption of a-C:F films to clarify their tribological properties in the air.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Water Adsorption Layers on the Friction Properties of Fluorinated Amorphous Carbon Films in Ambient Air

2022

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Fluorinated amorphous carbon (a-C:F) films with different microstructures were prepared with bipolar-type plasmabased ion implantation and deposition method by changing the negative bias voltage, and the tribological properties were investigated in ambient air. Their surface chemistry and water adsorption properties were investigated to determine their friction properties. Microstructural analysis results showed that, as the negative bias voltage increased, the density of the films decreased with the promotion of graphitization. The water adsorption properties evaluated using a quartz crystal microbalance showed that a large adsorbed water weight was observed for the films deposited at high negative bias voltages. In contrast, these films exhibited thin water adsorption layers from the measurements with an ellipsometer. These results indicate that water molecules are adsorbed on the film surface and permeate into the films, particularly for the films deposited at high negative bias voltages. The friction properties in ambient air depend significantly on their microstructure and relative humidity (RH). Regardless of the RH, the higher the negative bias voltage during film deposition, the lower the friction coefficient. Since several water molecules existed on the surface of the film deposited with a low negative bias voltage, its surface was oxidized during sliding, which increased the friction coefficient. In addition, the friction coefficient of the films increased at high RH. The number of water molecules adsorbed on the film increased as the RH increased, causing a high shear force owing to many hydrogen bonds and/or high capillary force at the friction interface.

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Tribological behavior of the friction film of polycrystalline diamond compact and different matching materials in drilling fluid

Gou,

Chen,

Luo

et al. 2023

Journal of Alloys and Compounds

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Effect of Water Adsorption on the Frictional Properties of Hydrogenated Amorphous Carbon Films in Various Relative Humidities

Cited by 11 publications

References 61 publications

Synthesis of N-doped carbon quantum dots as lubricant additive to enhance the tribological behavior of MoS2 nanofluid

Synthesis of N-doped carbon quantum dots as lubricant additive to enhance the tribological behavior of MoS2 nanofluid

Effect of Water Adsorption Layers on the Friction Properties of Fluorinated Amorphous Carbon Films in Ambient Air

Tribological behavior of the friction film of polycrystalline diamond compact and different matching materials in drilling fluid

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