Possible Origin of D- and G-band Features in Raman Spectra of Tribofilms

Li, Yusheng; Jang, Seokhoon; Khan, Arman Mohammad; Martin, Tobias; Ogrinc, Andrew L.; Wang, Q. Jane; Martini, Ashlie; Chung, Yip‐Wah; Kim, Seong H.

doi:10.1007/s11249-023-01728-1

Cited by 12 publications

(2 citation statements)

References 105 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a result, it can be concluded that the Raman analysis alone may not be enough to conclude the carbon-based tribofilm nature and/or structure, especially the one from the oil-soluble additive where the oil decomposed product and/or surface's oxide particles can exert certain effects on the obtained spectra [121,122]. Similar concerns on characterizing carbon-based tribofilms using Raman were also raised in a very recent study [123], in which experimental evidence demonstrates that the D-and G-band features in Raman spectra of carbon-based tribofilms may originate from the photochemical degradation of carbonaceous organic matters induced by the Raman laser. Thus, the observation of the D-and G-band features in Raman spectra is not sufficient to confirm that DLC, a-C, or graphitic species are produced via tribochemical reactions assisted by interfacial friction or shear of organic molecules.…”

Section: Raman Spectroscopymentioning

confidence: 89%

Tribocatalysis Induced Carbon-Based Tribofilms—An Emerging Tribological Approach for Sustainable Lubrications

2023

View full text Add to dashboard Cite

To comply with the high demand for efficient and sustainable lubrications, carbon-based tribofilms and/or nanomaterials have emerged as a potential solution that can resolve the current major shortcomings of phosphorus- and sulphur-rich tribofilms and protective coatings. Although their employment is still in the early stages of realization and research, these tribofilms receive significant interest due to their capability to continuously and in situ repair/replenish themselves during sliding, which has been an ultimate goal of all moving mechanical systems. Structurally, these tribofilms are complex and predominantly amorphous or disordered with/without graphitic domains (e.g., graphene/graphite, onion-like carbon, etc.). Chemically, the compositions of these tribofilms vary significantly with environments, conditions, and material precursors. Yet, the structural properties of carbon-based tribofilms remain largely ambiguous, which precludes a full understanding of the mechanisms underlying the formation and lubrication performance. This review will summarize the current state-of-art research about the in situ carbon-based tribofilms that have been published since the pioneering works. Particularly, this work will highlight the recent approaches to generate these tribofilms, their associated lubrication performance, current understanding of the formation mechanics, common analytical approaches for these tribofilms, and the compatibility of these tribofilms with other additives. Together, the overall outlooks will be drawn, demonstrating the knowledge gaps and proposing further investigation tactics to tackle these emerging issues.

show abstract

Section: Raman Spectroscopymentioning

confidence: 89%

Tribocatalysis Induced Carbon-Based Tribofilms—An Emerging Tribological Approach for Sustainable Lubrications

2023

View full text Add to dashboard Cite

show abstract

“…Indeed, detection of these bands was used in all the post-2000 references cited above except for refs 11 to 13. Recently it has been suggested that these bands should not be taken as proving unequivocally that amorphous or graphitic carbon is produced during rubbing, since it is possible that other types of carbon-rich material may be converted into a graphitic structure during exposure to the intense laser beam used in Raman analysis [35]. This does not, of course, nullify the value of the method for demonstrating the presence of a carbonaceous tribo lm, simply the interpretation of this lm as having a graphitic content.…”

Section: Introductionmentioning

confidence: 99%

Influence of atmosphere on carbonaceous film formation in rubbing, metallic contacts

Zhang

Bolle

Wong

et al. 2023

Preprint

View full text Add to dashboard Cite

Many previous researchers have reported the formation of carbonaceous tribofilms from organic lubricants on rubbing metallic surfaces. This paper shows that a very important factor in the formation of such tribofilms is the presence or absence of molecular oxygen. When steel surfaces are rubbed in saturated hydrocarbon lubricants in the absence of oxygen, for example in nitrogen or hydrogen gas, carbonaceous films form very readily, resulting in low friction and wear. However, when a significant amount of oxygen is present, as is the case in air, carbonaceous tribofilms are not generally formed, so friction and wear are very high, with values comparable to those seen when no lubricant is present. In-situ Raman analysis combined with gas switching experiments shows that the carbonaceous films formed during rubbing when no oxygen is present are rapidly removed during rubbing in air, while tests in which lubricant is removed during a test in N2 indicate that the films are quite weak. This suggests that these carbonaceous films are being continually removed and replenished during rubbing in oxygen-free conditions. It is proposed that these carbonaceous films are formed from hydrocarbyl free radicals that are generated mechanochemically from hydrocarbon molecules during rubbing. In the absence of oxygen, these free radicals then react together to form a carbonaceous film. However, when oxygen is present, the hydrocarbyl free radicals react extremely rapidly with oxygen molecules to produce hydroperoxyl free radicals and so are no longer available to generate a carbonaceous tribofilm.

show abstract

Why is Superlubricity of Diamond‐Like Carbon Rare at Nanoscale?

Jang,

Colliton,

Flaih

et al. 2024

Small

View full text Add to dashboard Cite

Hydrogenated diamond‐like carbon (HDLC) is a promising solid lubricant for its superlubricity which can benefit various industrial applications. While HDLC exhibits notable friction reduction in macroscale tests in inert or reducing environmental conditions, ultralow friction is rarely observed at the nanoscale. This study investigates this rather peculiar dependence of HDLC superlubricity on the contact scale. To attain superlubricity, HDLC requires i) removal of ≈2 nm‐thick air‐oxidized surface layer and ii) shear‐induced transformation of amorphous carbon to highly graphitic and hydrogenated structure. The nanoscale wear depth exceeds the typical thickness of the air‐oxidized layer, ruling out the possibility of incomplete removal of the air‐oxidized layer. Raman analysis of transfer films indicates that shear‐induced graphitization readily occurs at shear stresses lower than or comparable to those in the nanoscale test. Thus, the same is expected to occur at the nanoscale test. However, the graphitic transfer films are not detected in ex‐situ analyses after nanoscale friction tests, indicating that the graphitic transfer films are pushed out of the nanoscale contact area due to the instability of transfer films within a small contact area. Combining all these observations, this study concludes the retention of highly graphitic transfer films is crucial to achieving HDLC superlubricity.

show abstract

Possible Origin of D- and G-band Features in Raman Spectra of Tribofilms

Cited by 12 publications

References 105 publications

Tribocatalysis Induced Carbon-Based Tribofilms—An Emerging Tribological Approach for Sustainable Lubrications

Tribocatalysis Induced Carbon-Based Tribofilms—An Emerging Tribological Approach for Sustainable Lubrications

Influence of atmosphere on carbonaceous film formation in rubbing, metallic contacts

Why is Superlubricity of Diamond‐Like Carbon Rare at Nanoscale?

Contact Info

Product

Resources

About