Friction Properties of Fluorinated Graphitized Carbon Blacks

Abstract

International audienceThe tribologic properties of graphitized carbon blacks and their fluorinated derivatives are investigated as a function of the fluorination rate. Very low intrinsic friction coefficients are obtained for highly fluorinated compounds. The correlation of the tribologic results and structural investigations of the initial compounds by TEM strongly suggests that the friction mechanisms involve surface effects in the early stage of friction. Long-term tribologic experiments and Raman analyses point out an evolution of the structure and composition of the tribofilms during the friction process leading to similar friction properties of the tribofilms. Wear studies revealed that highly fluorinated derivatives appear less efficient than pristine and weakly fluorinated compounds

Synthesis of Fluorine‐Doped Hydrophilic Carbon Nanoparticles from Hexafluorobenzene by Femtosecond Laser Pulses

“…[5] There are three possible reasonsf or the hydrophilicity of our CNPs:1 )the building-up process forms an early uniform atom distribution;2 )C ÀFb onds on the surfaces as well as disordered structuresi nside CNPs enablet he CNPs to attract water;a nd 3) each CNP is well isolated (not agglutinated). By analogy with above suggestions, hydrophilicity could be expected for fluorinated carbon blacks, which have semiionic CÀFb onds, [3] if they are cracked into primary particles. However,a gglutinatedc arbon black, primaryp articles connected tightly by chemical bonds, requireamechanical process such as bead millingi no rder to crack them into primary particles.…”

“…[2] Basically,h igh fluorine doping is accomplished under severe synthetic conditions using very reactive reagents such as F 2 and HF. [2][3][4][5]12] Furthermore, the production of hydrophilic carbon materials also requires long-term oxidative acid treatments with heating to in-troduceO Ha nd/or COOH groups to the surface. [13] The addition of hydrophilic functional groups to the highly fluorinated carbons, such as carbon blacks (F/C = 0.89 [3] )a nd graphite (F/C = 0.83 [2] ), would not be useful under acidic conditions due to the liberationo ff luorine atoms.…”

“…The semi-ionic charactero fC ÀFb onds and the non-aggregating feature of the nanoparticles play key roles in the water-dispersible character of fluorine-doped carbon nanoparticles. We suggestt he following building-up process of carbon nanoparticles: the fragmentation of hexafluorobenzene initiated by the electrons generated in laser-inducedp lasma followed by the reconstruction of acarbon framework of nanoparticles.Doping fluorine atoms into carbonm aterials such as graphene, [1] graphite, [2] carbon black, [3] fullerenes, [4] ands ingle-wall carbon nanotubes [5] dramatically changes the material's electronic, mechanical, and chemical properties, such as redox, [6] surfacef riction, [3] solubility, [5] and catalytic activity, [7] making such materials useful. [8] Furthermore, the hydrophilic functionalizationo fn anocarbon materials makes them useful for biological and medical applications: fluorescent biomarkers suitable for living cell imaging, [9] 19 FM RI for in vivo imaging, [10] and drug delivery.…”

“…[2][3][4][5]12] Furthermore, the production of hydrophilic carbon materials also requires long-term oxidative acid treatments with heating to in-troduceO Ha nd/or COOH groups to the surface. [13] The addition of hydrophilic functional groups to the highly fluorinated carbons, such as carbon blacks (F/C = 0.89 [3] )a nd graphite (F/C = 0.83 [2] ), would not be useful under acidic conditions due to the liberationo ff luorine atoms. Then eed for simpler synthetic methods for the simultaneous functionalization of both fluorine incorporation and hydrophilicity in carbonm aterials is important for broader application of nanocarbon materials.In 2015, the different synthetic methods of fluorinated carbon nanoparticles (CNPs) were reported.…”

The Role of Solid Lubricants for Brake Friction Materials

“…The objective of using oil additives is to keep the ultra-low COF even under mixed lubrication conditions when asperities of the counter-bodies come into direct contact with each other [2]. This usually is achieved by crystallographically aligned solid lubricant films of either graphite [5][6][7] or MoS 2 and WS 2 [8][9][10][11][12], or by amorphous films which can flow in a fluid-like manner [13,14].…”