Tribo-Chemistry of Phosphonium-Derived Ionic LiquidsReport as inadecuate




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Tribology Letters

, Volume 40, Issue 2, pp 225–235

First Online: 30 May 2010Received: 01 April 2010Accepted: 15 May 2010

Abstract

The tribological properties of room temperature ionic liquids containing tetraalkylphosphonium cations were evaluated on the basis of the chemical structure of their salts. The tribochemistry of these ionic liquids was discussed on the basis of the results of tribo-tests and surface analyses. The tribological properties of the tetraalkylphosphonium salts examined in this work were observed to be better than those of 1,3-alkylimidazolium salts. The structure of the alkyl group in the phosphonium cation also has a slight effect on the tribological properties of the salts. During a friction test carried out under low-load conditions, the phosphonium cation was oxidized to phosphate to form a boundary film. This film inhibited the reaction of the bistrifluoromethanesulfonylamide anion that yielded metal fluoride on the rubbed surfaces. The combination of the phosphonium cation with a phosphate anion or thiophosphate anion resulted in a better lubricant than 1,3-alkylimidazolium bistrifluoromethanesulfonylamide. The reactions of the phosphate anion and thiophosphate anion yielded a phosphate boundary film that exhibited better tribological properties than those of the fluoride boundary film.

KeywordsIonic liquid Surface chemistry Lubricant chemistry Tribochemistry Structure–property relations AbbreviationsAESAuger electron spectroscopy

BF4Tetrafluoroborate

BMIM1-Butyl-3-methylimidazolium

JISJapanese Industrial Standards

PF6Hexafluorophosphate

R4PTetraalkylphosphonium

RT-ILRoom temperature ionic liquid

SUJ2Bearing steel assigned by JIS

TFSABistrifluoromethanesulfonylamide

XPSX-ray photoelectron spectroscopy

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Author: Ichiro Minami - Taketo Inada - Ryusuke Sasaki - Hidetaka Nanao

Source: https://link.springer.com/







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