title: Micromechanism in Self-Lubrication of TiB2/Al Composite.
abstract: The authors discovered the self-lubrication behavior of TiB2/Al composite and pointed out that the materials responsible for the self-lubrication behavior comes from the oxidation of TiB2. Atomic/friction force microscopy and first-principles calculations have been employed to study the self-lubrication microscopic mechanism of TiB2/Al composite. Atomic force microscopy confirms the existence of a soft film with nanometer thickness on the TiB2 surface, which was attributed to H3BO3 film. Friction measurements revealed much smaller friction force on this H3BO3 nanofilm than that on Al matrix. The detailed structure and interactions among H3BO3 molecules and between the H3BO3 sheet and substrate were explored by density functional theory based calculations. The details of adsorption of H3BO3 sheet on TiB2 and TiO2 surface were scrutinized and the potential of the relative movement between H3BO3 sheets were scanned and compared with that of graphite. The generation of H3BO3 film, the strong chemical adsorption of H3BO3 film on the surface of the composite, the strong hydrogen bonding in H3BO3 film, and small potential in the relative slide between H3BO3 sheets warrant the good self-lubricant properties of TiB2/Al metal matrix composites.
authors.affiliation: †State Key Laboratory of Urban Water Resource and Environment, Institute of Theoretical and Simulational Chemistry, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin, 150080, P. R. China.|§State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150080, P. R. China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: ‡Institute of Metal Matrix Composite Science and Engineering, Harbin Institute of Technology, Harbin, 150080, P. R. China.
authors.forename: Longtao
authors.initials: L
authors.lastname: Jiang
authors.affiliation: §State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150080, P. R. China.
authors.forename: Shengbin
authors.initials: S
authors.lastname: Lei
authors.affiliation: †State Key Laboratory of Urban Water Resource and Environment, Institute of Theoretical and Simulational Chemistry, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin, 150080, P. R. China.
authors.forename: Wei Quan
authors.initials: WQ
authors.lastname: Tian
authors.affiliation: ‡Institute of Metal Matrix Composite Science and Engineering, Harbin Institute of Technology, Harbin, 150080, P. R. China.
authors.forename: Gaohui
authors.initials: G
authors.lastname: Wu
keywords: H3BO3 sheets; TiB2/Al composite; first-principles calculations; friction measurements; hydrogen bond; self-lubrication microscopic mechanism