Influence of laser interference patterning on microstructure and friction behavior of gold/yttria-stabilized zirconia na
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ie Migot and David Horwatb) Department CP2S, Institut Jean Lamour, UMR 7198, École des Mines de Nancy, F-54042 Nancy, France (Received 31 August 2011; accepted 15 December 2011)
Laser interference patterning (LIP) and the hereby induced microstructure modifications have been investigated in gold/yttria-stabilized zirconia nanocomposite films. Transmission electron microscopy was used to study the influence of the laser treatment on the structure and microstructure of the samples. The impact of LIP on the friction coefficient has been evidenced. The initial microstructure consisted of gold nanograins homogeneously distributed in the yttria-stabilized zirconia matrix. A noticeable growth and coalescence of gold nanograins occurred near the surface in specific regions. Simultaneously, a foamy morphology, mostly consisting of gold crystals, was formed at the surface and is responsible for a drastic diminution of the friction coefficient after patterning. Furthermore, the influence of the film topography on the friction behavior is analyzed using Abbott–Firestone curves. In contrast to thermal annealing, the laser treatment proposed here is a fast procedure to partially relocate gold at the film surface and provide a local solid lubrication. I. INTRODUCTION
Innovation in materials science relies on the possibility to control the morphology, microstructure and chemistry of materials. Thereby, specific properties can be obtained. Noble metals are fascinating for various aspects, among which is their poor or absence of reactivity toward oxygen. The association of noble metals with other metallic elements can produce original microstructures and morphologies, more particularly upon thermal annealing and in the presence of oxygen.1,2 We showed recently that the electrical conductivity of noble metal-based oxides and nitrides can be tailored by laser interference patterning (LIP).3 Within this method, described in detail in,4 the interference of single laser pulses is used to tailor both the morphology and the microstructure of thin films.5 Due to a high local thermal gradient produced in a very short time, metallurgical effects like lateral grain growth,5,6 chemical decomposition3 or intermetallic phase precipitation7 are promoted. Gold is the only element that does not present a thermodynamically stable oxide under normal condition. In contrast, zirconium and Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] c) Present Address: Département CP2S, Institut Jean Lamour, UMR 7198, École des Mines de Nancy, F-54042 Nancy, France This paper has been selected as an Invited Feature Paper. DOI: 10.1557/jmr.2011.443 J. Mater. Res., Vol. 27, No. 6, Mar 28, 2012
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yttrium are highly reactive toward oxygen as they can form zirconia (ZrO2) and yttria (Y2O3). Therefore, upon synthesis of thin films constituted by Au, Zr, Y and O atoms, gold is expected to segregate in metallic form in an oxide matrix. The present st
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