AVS 59th Annual International Symposium and Exhibition
    Advanced Surface Engineering Monday Sessions
       Session SE+NS-MoA

Invited Paper SE+NS-MoA1
Layered Binary Metal Oxide Solid Lubricants for High Temperature Moving Assemblies

Monday, October 29, 2012, 2:00 pm, Room 22

Session: Nanostructured Thin Films and Coatings II: Multifunctional Properties
Presenter: S. Aouadi, Southern Illinois University Carbondale
Authors: S. Aouadi, Southern Illinois University Carbondale
D. Stone, Southern Illinois University Carbondale
A. Martini, University of California Merced
C. Muratore, Air Force Research Laboratory
A.A. Voevodin, Air Force Research Laboratory
Correspondent: Click to Email
Oxides exhibit an unparalleled variety of physical properties that give them great promise for many applications in optics, magnetism, and electronics. Oxides that possess layered crystal structure inherently display anisotropic properties as a result of their non-symmetrical crystal structure. This flexibility in their structural skeleton offers a great opportunity to create new materials with designed functionality. This paper provides an overview of the current research developments in understanding how a class of layered binary metal oxides is effective at reducing friction at moderate and high temperatures. Oxides, known to be abrasive at low temperatures, are particularly desirable lubricious materials at high temperatures considering that most materials will oxidize in air under these conditions. Four different, non-exclusive, mechanisms are reported to cause their enhanced lubricity: (1) oxide softening due to the working temperatures between 0.4-0.7 of the absolute melting temperature (Tm), (2) melting of the oxide by exceeding Tm, (3) the creation of a material with a lamellar crystal structure with weak interplanar bonds, and, (4) shearing due to dislocations or grain boundary sliding. We will focus on understanding the fundamental mechanisms that impart their advantageous material properties at high temperatures using computational (density functional theory and molecular dynamics simulations) and experimental tools (in situ Raman spectroscopy, X-Ray diffraction, scanning electron microscopy, and transmission electron microscopy). The frictional and wear properties of these materials, tested in various controlled environmental conditions, will be discussed in detail.