title: Oil-Soluble Silver-Organic Molecule for in Situ Deposition of Lubricious Metallic Silver at High Temperatures.
abstract: A major challenge in lubrication technology is to enhance lubricant performance at extreme temperatures that exceed conventional engine oil thermal degradation limits. Soft noble metals such as silver have low reactivity and shear strength, which make them ideal solid lubricants for wear protection and friction reduction between contacting surfaces at high temperatures. However, achieving adequate dispersion in engine lubricants and metallic silver deposition over predetermined temperatures ranges presents a significant chemical challenge. Here we report the synthesis, characterization, and tribological implementation of the trimeric silver pyrazolate complex, [Ag(3,5-dimethyl-4-n-hexyl-pyrazolate)]3 (1). This complex is oil-soluble and undergoes clean thermolysis at ∼310 °C to deposit lubricious, protective metallic silver particles on metal/metal oxide surfaces. Temperature-controlled tribometer tests show that greater than 1 wt % loading of 1 reduces wear by 60% in PAO4, a poly-α-olefin lubricant base fluid, and by 70% in a commercial fully formulated 15W40 motor oil (FF oil). This silver-organic complex also imparts sufficient friction reduction so that the tribological transition from oil as the primary lubricant through its thermal degradation, to 1 as the primary lubricant, is experimentally undetectable.
authors.forename: Michael
authors.initials: M
authors.lastname: Desanker
authors.forename: Blake
authors.initials: B
authors.lastname: Johnson
authors.affiliation: Department of Chemistry, Texas A&M University at Qatar , P.O. Box 23874, Doha, Qatar.
authors.forename: Afif M
authors.initials: AM
authors.lastname: Seyam
authors.forename: Yip-Wah
authors.initials: YW
authors.lastname: Chung
authors.affiliation: Department of Chemistry, Texas A&M University at Qatar , P.O. Box 23874, Doha, Qatar.
authors.forename: Hassan S
authors.initials: HS
authors.lastname: Bazzi
authors.affiliation: Chemical Sciences and Engineering Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Delferro
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Marks
authors.forename: Q Jane
authors.initials: QJ
authors.lastname: Wang
keywords: friction reduction; lubrication; lubrication additive; oil degradation; silver complex