Chengfeng Ye

Room-temperature ionic liquids: a novel versatile lubricant

Alkylimidazolium tetrafluoroborates are promising versatile lubricants for the contact of steel/steel, steel/aluminium, steel/copper, steel/SiO2, Si3N4/SiO2, steel/Si(100), steel/sialon ceramics and Si3N4/sialon ceramics; they show excellent friction reduction, antiwear performance and high load-carrying capacity.

Tribological Performance of Room-Temperature Ionic Liquids as Lubricant

The tribological performance of room-temperature ionic liquid of alkylimidazolium tetrafluoroborate was evaluated using an Optimol SRV oscillating friction and wear tester in air and a CZM vacuum friction tester in vacuum (1×10-3 Pa) using a steel/steel (SAE52100) contact. From the results, the ionic liquid exhibits excellent friction-reduction, antiwear proprieties, both in air and vacuum, which are superior to phosphazene (X-1P) and perfluoropolyether (PFPE). During friction, the ionic liquid forms a surface protective film mainly composed of FeF2 and B2O3, which contributes to low friction and wear.

Tribological behavior of sialon ceramics sliding against steel lubricated by fluorine-containing oils

Abstract The friction and wear behavior of sialon ceramics sliding against steel and lubricated by perfluoropolyethers (PFPE), tetrakis (3-trifluoromethylphenoxy)-bis(4-fluoro-phenoxy)-cyclotriphosphazene (X-1P) and ionic liquid (1-methyl-3-octylimidazolium tetrafluoroborate, coded as L108) were investigated. It was found that the three fluorine-containing lubricants reduced friction coefficient and wear volume effectively. The effectiveness of the three lubricants in reducing wear volume could be ranked as L108>X-1P>PFPE. The antiwear films mainly consisting of organic oxyfluoride or carbonfluoride species and silicon fluoride are all observed for the three lubricants, while the degradation of PFPE during friction might account for the higher wear volume therewith. The lowest friction coefficient 0.065 was recorded for L108 under load of 0.5–400 N. This is dependent on the physically adsorbed ionic liquid on the rubbing surface and the formation of BN under the harsh conditions.

Preparation and characterization of doped sol-gel zirconia films

Highly oriented CeO2-, Y2O3- and MgO-doped ZrO2 thin films have been successfully prepared by a sol-gel process by dip-coating an ethanol solution of zirconium oxychloride octahydrate and the corresponding inorganic dopants. The doped ZrO2 films contain only the zirconia tetragonal phase and show nano-scale morphology. Under low load, doped ZrO2 films sliding against a AISI 52100 steel ball display a good wear and friction performance. Best results have been obtained with the 13 mol% CeO2- doped ZrO2 film, which exhibits a friction coefficient as low as 0.22 and a wear-life over 5000 sliding cycles under 1 N load.

Preparation and characterization of self-assembled alkanephosphate monolayers on glass substrate coated with nano-TiO2 thin film

Abstract Self-assembled alkanephosphate monolayers on glass substrate coated with sol-gel TiO 2 thin film were prepared by means of molecular self-assembly process. The wetting behavior and structure of the alkanephosphate monolayers were characterized by means of contact angle measurement and X-ray photoelectron spectroscopic analysis. The friction behavior of the glass substrate coated with TiO 2 thin film and the alkanephosphate SAMs in sliding against an Si 3 N 4 ball was examined on a one-way reciprocating friction tester. As a result, water contact angle on alkanephosphate SAMs is at 90–104°. The SAMs of alkanephosphate are bonded to the TiO 2 covering layer on the glass substrate by way of monodentate and bidentate coordination. In n -monoalkanephosphate SAMs, the monodentate and bidentate of adjacent phosphate headgroups are linked by intermolecular hydrogen bonding. The SAMs of long chain n -monoalkanephosphate show considerably decreased friction coefficient in sliding against the Si 3 N 4 ball under low load, compared with the TiO 2 covering layer on the glass substrate.

A NOVEL SYNTHESIS OF HEXASUBSTITUTED CYCLOTRIPHOSPHAZENES

ABSTRACT Hexaaryloxyphosphazenes [N3P3(O-C6H4-R)6] (R=H, CH3, OCH3, C(CH3)3, CHO, COCH3, COOR, C6H5, NO2, F, etc) were readily obtained with ca 70% isolated yield in refluxing acetonitrile in the presence of anhydrous potassium phosphate. All compounds were characterized by means of elemental analysis, 1H-NMR, 31P-NMR spectroscopy.

Study of the tribological behaviors of [S-(2H-thiophen-2-yl)]-methyl-alkyl xanthates as additives in rapeseed oil

Abstract The xanthate derivatives of thiophen including [ S -(2H-thiophen-2-yl)]-methyl-ethyl xanthate (coded as TMEX), [ S -(2H-thiophen-2-yl)]-methyl-butyl xanthate (coded as TMBX) and [ S -(2H-thiophen-2-yl)]-methyl-octyl xanthate (coded as TMOX) were synthesized. The tribological behavior of the synthesized compounds as additives in rapeseed oil (RO) was investigated with four-ball friction and wear testers. The worn surfaces of the lubricated GCr15 steel were analyzed by means of X-ray photoelectron spectroscopy and scanning electron microscopy. The lubricating mechanisms were discussed on the basis of X-ray photoelectron spectroscopic and scanning electron microscopic analyses of the worn steel surfaces. It was found that the xanthate derivatives of thiophen as additives in RO improve the antiwear, friction-reducing properties and remarkably increase the load-carrying capacity of the base stock. X-ray photoelectron spectrometer (XPS) analytical results of the worn surfaces indicate that tribochemical reactions were involved for steel–steel pair lubricated with thiophen-rapeseed oil and the RO containing [ S -(2H-thiophen-2-yl)]-methyl-alkyl xanthates (coded as TMAX).