Synthesis and Characterization of PbO Films Grown by Pulsed Laser Deposition.
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SYNTHESIS AND CHARACTERIZATION OF PbO FILMS GROWN BY PULSED LASER DEPOSITION. 4 3 2 J.S. Zabinski(l), M.S. Donley,(') V.J. Dyhouse( ), R. Moore( ), and N.T. McDevitt( )
( 1 )WL/MLBT, Materials Directorate, WPAFB, OH 45433 ( 2 )Rcsearch Institute, University of Dayton, Dayton, OH 45469 ( 3 )Air Force Academy, USAFA CO 80840 ( 4 )RAMSPEC Research, 4399 E. Mohave Dr., Dayton, OH 45431 ABSTRACT Lead monoxide (PbO) is a potential solid lubricant for use at elevated The objective of this research was to grow temperatures in oxidizing environments. Film stoichiometry, crystallinity, thin films of PbO by Pulsed Laser Deposition (PLD). and chemistry were adjusted by varying substrate temperature and 02 partial pressure during deposition and the effects of changes in film properties on friction Chemistry and crystallinity were coefficients and wear lives were investigated. evaluated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Friction coefficients and wear lives were glancing angle X-ray diffraction (XRD). measured in dry nitrogen and at room temperature using a ball-on-flat tribometer. Films deposited at room temperature retained the crystal structure of the target The O/Pb ratio was increased by raising the 02 material, but were oxygen deficient. partial pressure and by increasing the substrate temperature during deposition; the Friction coefficients crystal structure and orientation changed with stoichiometry. ranged from 0.20 - 0.45 and the wear lives were typically less than those obtained from MoS2 films. INTRODUCTION Solid lubricants are needed to meet Air Force requirements for lubrication of future generation air and space vehicles where components may be exposed to high The most frequently used solid temperatures, vacuum, and intense radiation. However, both of these materials oxidize and lubricants are MoS2 and graphite. become poor lubricants when heated in air above about 350°C. PbO-based films have 0 While these been identified as good lubricants for use in air up to about 650 C [1-3]. films are effective at room temperature, their performance increases significantly above 260°C. Sliney and Johnson [3] evaluated lubricant films that were grown by melting and resolidifying PbO-SiO 2 mixtures onto steel substrates. Miyakawa et al. [4] demonstrated that PbO films can be effectively deposited by mechanical burnishing In addition, they show that PbO films provide lower and thermal spray techniques. friction coefficients and longer wear lives in vacuum and inert environments than in air. Research reported in this paper was directed towards identifying the conditions necessary for growing crystalline, stoichiometric PbO films using PLD and correlating chemical and physical properties to friction coefficients and wear lives. It has been shown that pulsed laser deposition and laser processing permit precise In addition, control of chemical and physical properties of lubricant materials [5-9]. films grown by PLD are dense, non-porous and their chemistry typically reflects that High energy speci
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