title: Ultrasmooth submicrometer carbon spheres as lubricant additives for friction and wear reduction.
abstract: Ultrasmooth submicrometer carbon spheres are demonstrated as an efficient additive for improving the tribological performance of lubricating oils. Carbon spheres with ultrasmooth surfaces are fabricated by ultrasound assisted polymerization of resorcinol and formaldehyde followed by controlled heat treatment. The tribological behavior of the new lubricant mixture is investigated in the boundary and mixed lubrication regimes using a pin-on-disk apparatus and cylinder-on-disk tribometer, respectively. The new lubricant composition containing 3 wt % carbon spheres suspended in a reference SAE 5W30 engine oil exhibited a substantial reduction in friction and wear (10-25%) compared to the neat oil, without change in the viscosity. Microscopic and spectroscopic investigation of the carbon spheres after the tribological experiments illustrated their excellent mechanical and chemical stability. The significantly better tribological performance of the hybrid lubricant is attributed to the perfectly spherical shape and ultrasmooth surface of carbon sphere additive filling the gap between surfaces and acting as a nanoscale ball bearing.
authors.affiliation: School of Mechanical Engineering, Purdue University , 585 Purdue Mall, West Lafayette, Indiana 47907-2088, United States.
authors.forename: Abdullah A
authors.initials: AA
authors.lastname: Alazemi
authors.forename: Vinodkumar
authors.initials: V
authors.lastname: Etacheri
authors.forename: Arthur D
authors.initials: AD
authors.lastname: Dysart
authors.forename: Lars-Erik
authors.initials: LE
authors.lastname: Stacke
authors.forename: Vilas G
authors.initials: VG
authors.lastname: Pol
authors.forename: Farshid
authors.initials: F
authors.lastname: Sadeghi
keywords: carbon spheres; friction; lubricant additives; wear reduction