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This paper describes series of four-ball tribological and atomic force squeezing test results obtained under different contact pressures and sliding speeds (or squeezing speeds) and performed with poly-alpha-olefin suspended 0.5% weight percentage of different types of carboxylic acids. Results indicated that under a confined zone (contact pressures varied from 2.4~3.9 GPa), there is a critical turning speed at which the friction performances of carboxylic acid change dramatically. When the sliding speed exceeds the critical turning speed, carboxylic acid molecules or their incomplete decomposition products would adsorb, deposit, and spread in the friction surface, thus form an island–like aggregate tribofilm with an approximately thickness of 150 nm achieving a super–low wear. |
