title: (Ag,Cu)-Ta-O ternaries as high-temperature solid-lubricant coatings.
abstract: Ternary oxides have gained increasing attention due to their potential use as solid lubricants at elevated temperatures. In this work, the tribological properties of three ternary oxides-AgTaO3, CuTaO3, and CuTa2O6-were studied using a combination of density-functional theory (DFT), molecular dynamics (MD) simulations with newly developed empirical potential parameters, and experimental measurements (AgTaO3 and CuTa2O6 only). Our results show that the MD-predicted friction force follows the trend AgTaO3 < CuTaO3 < CuTa2O6, which is consistent with the experimentally measured coefficients of friction. The wear performance from both MD and experiment exhibits the opposite trend, with CuTa2O6 providing the best resistance to wear. The sliding mechanisms are investigated using experimental characterization of the film composition after sliding, quantification of Ag or Cu cluster formation at the interface during the evolution of the film in MD, and DFT energy barriers for atom migration on the material surface. All our observations are consistent with the hypothesis that the formation of metal (or metal oxide) clusters on the surface are responsible for the friction and wear behavior of these materials.
authors.affiliation: †School of Engineering, University of California Merced, 5200 North Lake Road, Merced, California 95343, United States.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Gao
authors.affiliation: ‡National Institute for Nanotechnology, National Research Council of Canada, 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada.
authors.forename: Alberto
authors.initials: A
authors.lastname: Otero-de-la-Roza
authors.affiliation: §Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76207, United States.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Gu
authors.affiliation: §Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76207, United States.
authors.forename: D'Arcy
authors.initials: D
authors.lastname: Stone
authors.affiliation: §Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76207, United States.
authors.forename: Samir M
authors.initials: SM
authors.lastname: Aouadi
authors.affiliation: ∥Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada.|⊥Chemistry and Chemical Biology, School of Natural Sciences, University of California Merced, 5200 North Lake Road, Merced, California 95343, United States.
authors.forename: Erin R
authors.initials: ER
authors.lastname: Johnson
authors.affiliation: †School of Engineering, University of California Merced, 5200 North Lake Road, Merced, California 95343, United States.
authors.forename: Ashlie
authors.initials: A
authors.lastname: Martini
keywords: copper tantalate; friction; high temperature; silver tantalate; solid lubricants; ternary metal oxides; wear