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.
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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|
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