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Surface electronic structure and mechanical characteristics of copper cobalt oxide thin film coatings: Soft X-ray synchrotron radiation spectroscopic analyses and modeling

Amri, A., Jiang, Z-T, Bahri, P.A., Yin, C-Y, Zhao, X., Xie, Z., Duan, X-F, Widjaja, H., Rahman, M.M. and Pryor, T. (2013) Surface electronic structure and mechanical characteristics of copper cobalt oxide thin film coatings: Soft X-ray synchrotron radiation spectroscopic analyses and modeling. The Journal of Physical Chemistry C, 117 (32). pp. 16457-16467.

Link to Published Version: http://pubs.acs.org/doi/abs/10.1021/jp404841m
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Abstract

Novel copper-cobalt oxide thin films with different copper/cobalt molar ratios – namely, [Cu]/[Co] = 0.5, 1 and 2 - have been successfully coated on aluminium substrates via a simple and cost-effective sol-gel dip-coating method. Coatings were characterized using high resolution synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy, in combination with nanomechanical testing and field emission scanning electron microscopy (FESEM). The surfaces of both [Cu]/[Co] = 0.5 and 1 samples consisted primarily of fine granular nanoparticles while the [Cu]/[Co] = 2 has a smoother surface. The analyses reveal the increase of copper concentration in the synthesis process tends to promote the formation of octahedral Cu2+ which minimizes the development of octahedral Cu+, and these octahedral Cu2+ ions substitute the Co2+ site in cobalt structure host. The local coordinations of Co, Cu and O are not substantially influenced by the change in the copper to cobalt concentration ratios except for the [Cu]/[Co] = 2 coating where the local coordination appears to slightly change due to the loss of octahedral Cu+. The present film coatings are expected to exhibit good wear resistance especially for the [Cu]/[Co] = 1.0 sample due to its high hardness/elastic modulus (H/E) ratio. Finite element modeling (FEM) indicated that, under spherical loading conditions, the high stress and the plastic deformation were predominantly concentrated within the coating layer, without spreading into the substrate.

Publication Type: Journal Article
Murdoch Affiliation: School of Engineering and Information Technology
School of Veterinary and Life Sciences
Publisher: American Chemical Society
Copyright: © 2013 American Chemical Society
URI: http://researchrepository.murdoch.edu.au/id/eprint/16836
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