Fluorinated Nanocarbons for Lubrication

Pandorf, Thomas; Bilas, Philippe; Molza, Audrey; Legras, L.; Mansot, Jean-Louis; Guérin, Katia; Dubois, Marc

doi:10.1016/b978-0-12-803479-8.00014-0

Cited by 5 publications

(12 citation statements)

References 51 publications

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“…Thermal exfoliation of nanodiscs was then not successful and the resulting sample appear close to the precursors for which the tribological properties were studied. [8][9][10][11] Tribological tests were then performed only for exfoliated nanobers and graphite. Both the exfoliated structure and presence of residual uorine may act on the friction energy.…”

Section: Methodsmentioning

confidence: 99%

“…For such compounds, we showed in previous works that the friction reduction mechanisms are associated to a lowering of interparticles interactions due to the uorination of external graphene layers. [8][9][10] It has then to be noticed that the observed deuorination of the compounds during exfoliation does not deteriorate the lubricating performances of the tested materials. If considering the stability of m for raw and exfoliated materials and the weak uorination rate of Exf-FG and Exf-FCNF, the good friction properties seem to be related to the weakening of the interparticles interactions due to the exfoliation process rather than to the uorine content.…”

Section: Friction Propertiesmentioning

confidence: 95%

“…The mild uorination of graphitized carbon blacks and carbon nanobers allowed F/C atomic ratio of 0.08 and 0.05, respectively, to be achieved. [8][9][10][11] In comparison with raw nanocarbons, the decrease of the friction coefficient was then recorded for both CNFs and GCBs (0.09 AE 0.01 and 0.11 AE 0.01, respectively); for the cases of raw GCBs (0.12 AE 0.01) and CNFs (0.14 AE 0.01), the friction coefficients are higher and close to those obtained for graphite in air (0.10-0.15). The evolution of the friction coefficients of raw and exfoliated materials are reported in Fig.…”

Section: Friction Propertiesmentioning

confidence: 99%

“…7 For uorinated 0D, 1D and 2D nanocarbons, namely graphitized carbon blacks, nanobers and nanodiscs, which exhibit similar covalent CF bonding and a closed structure, good tribological properties were achieved whatever the uorine content and those nanomaterials appear as excellent precursors for the tribo-active phase in lubrication. [8][9][10][11] Indeed the friction coefficients of the uorinated nanocarbons ranged between 0.065 and 0.085, and are weaker than those of most solid lubricants (graphite). Accommodation of uorine atoms into the carbon lattice with a F/C atomic ratio higher than 0.15 results in easy cleavage for the cases of uorinated carbon blacks and nanobers.…”

Section: Introductionmentioning

confidence: 99%

“…Accommodation of uorine atoms into the carbon lattice with a F/C atomic ratio higher than 0.15 results in easy cleavage for the cases of uorinated carbon blacks and nanobers. [7][8][9][10][11] The aim of the present paper is to investigate the tribological properties of graphene materials, which are prepared by an easy operating, highly scalable, and low-cost method by applying a fast thermal treatment on highly uorinated carbons under argon atmosphere. This route differs from the three conventional synthesis methods to obtain uorinated graphene; all require mild conditions as follows: (i) reaction between raw graphene and uorinating agent such as XeF 2 or F 2 , (ii) exfoliation of (highly) uorinated graphite, (iii) uorination of graphene oxide (GO).…”

Section: Introductionmentioning

confidence: 99%

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Exfoliated fluorinated carbons with a low and stable friction coefficient

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Section: Friction Propertiesmentioning

confidence: 95%

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confidence: 99%

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Exfoliated fluorinated carbons with a low and stable friction coefficient

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An Insight into the Phase Transformation of WS₂ upon Fluorination

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reduces the TMDs and the gliding of the S planes results in the transformation from 2H to 1T. Functionalization by other electron donating species such as Re, Tc, and Mn can also induce the transformation. [7][8][9][10][11] The electron donated by the alkali metals alters the d electron count of the metal (Mo or W), and it splits in the octahedral coordination to have three unpaired electrons in the valence band d orbitals. However, the 1T phase is highly unstable and converts back into 2H phase with time and temperature. [12] Apart from alkali metals, several attempts have been made on the covalent functionalization of 2H and 1T phases by organic functional groups. [13][14][15][16] Sarkar et al. decorated the 2D layers with metal nanoparticles which changed the transfer characteristics of the 2D devices and demonstrated its capability as a gas sensor. [17] Theoretically, hydrogenation also converts the 2H semiconducting phase into the metallic phase. [18] A transformation from an n-type to a p-type semiconductor, a nonmagnetic to a magnetic material and a boost in the catalytic activity was achieved through controlled and selective doping of TMDs by transition metals. [19] An interesting deviation from extrinsic doping was intrinsic doping by the incorporation of islands of 1T in a lattice of 2H semiconducting nanosheets, where the The transformation from semiconducting to metallic phase, accompanied by a structural transition in 2D transition metal dichalcogenides has attracted the attention of the researchers worldwide. The unconventional structural transformation of fluorinated WS 2 (FWS 2 ) into the 1T phase is described. The energy difference between the two phases debugs this transition, as fluorination enhances the stability of 1T FWS 2 and makes it energetically favorable at higher F concentration. Investigation of the electronic and optical nature of FWS 2 is supplemented by possible band structures and bandgap calculations. Magnetic centers in the 1T phase appear in FWS 2 possibly due to the introduction of defect sites. A direct consequence of the phase transition and associated increase in interlayer spacing is a change in friction behavior. Friction force microscopy is used to determine this effect of functionalization accompanied phase transformation. FluorinationThe unique properties found in graphene and later in monolayers of other materials thrust the research on transition metal dichalcogenides (TMDs) as evidenced from the publications on TMDs in the past decade. [1][2][3][4][5] A distinctive property of TMDs is their polymorphic structural and electronic characteristics. For instance, in group 6 chalcogenides such as MoS 2 and WS 2 , when the sulfur (S) atoms occur on top of each other, it results in trigonal prismatic symmetry in the commonly called 2H semiconducting phase and the displaced S atoms results in octahedral symmetry in the 1T metallic phase. [6] Li or K functionalization

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Tuning C–F Bonding of Graphite Fluoride by Applying High Pressure: Experimental and Theoretical Study

et al. 2020

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C 2 F graphite fluoride has a unique mutable structure when subjected to external applied pressure. In the present study, we examine C 2 F using X-ray Raman scattering (XRS) up to 6.5 GPa coupled with theoretical simulations. Using the XRS technique, we follow the in situ high-pressure evolution of the energy loss corresponding to the C and F K-edge. Significant variations occur at 2.9 GPa, remain up to 6.5 GPa, and persist at ambient conditions after decompression. The permanent changes are related to an increased planarity of the graphitic layers and a modulation of the fluorine configuration. The all-electron density of a C 2 F-sp 3 slab obtained from the DFT simulation and the quantum theory of atoms in molecules reveals the appearance of bond-critical points between in-plane and out-of-plane F−F, suggesting an increasingly ionic character of the structure under biaxial isotropic strain. Pressure can be used as an alternative to chemical synthesis for tuning C−F bonding and metastabilizing new intercalated fluorine compounds with potentially improved electrochemical properties.

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Fluorinated Nanocarbons for Lubrication

Cited by 5 publications

References 51 publications

Exfoliated fluorinated carbons with a low and stable friction coefficient

Exfoliated fluorinated carbons with a low and stable friction coefficient

An Insight into the Phase Transformation of WS₂ upon Fluorination

Tuning C–F Bonding of Graphite Fluoride by Applying High Pressure: Experimental and Theoretical Study

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Fluorinated Nanocarbons for Lubrication

Cited by 5 publications

References 51 publications

Exfoliated fluorinated carbons with a low and stable friction coefficient

Exfoliated fluorinated carbons with a low and stable friction coefficient

An Insight into the Phase Transformation of WS2 upon Fluorination

Tuning C–F Bonding of Graphite Fluoride by Applying High Pressure: Experimental and Theoretical Study

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An Insight into the Phase Transformation of WS₂ upon Fluorination