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 aluminum 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, whereas the [Cu]/ [Co] = 2 has a smoother surface. The analyses reveal that the increase of copper concentration in the synthesis process tends to promote the formation of octahedral Cu 2+ which minimizes the development of octahedral Cu + , and these octahedral Cu 2+ ions substitute the Co 2+ 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.

Adding impurities or doping through adsorption is an effective way to tailor the properties of graphene-based materials. The capability of making predictions with regard to the trends of elemental adsorption on graphene is crucial to a better understanding of the more complex adsorption cases. It also provides useful guidelines for fabricating 2D graphene materials with novel properties. In this review, we show trends of elemental adsorption on graphene with elements of the periodic table, based on previous studies and supplemented with our recent calculations. We also discuss the effects of atomic ratios on some properties of this element-adsorbed graphene system. Trends of properties studied include binding energy, most stable site, adatom height, migration energy, Fermi energy shift, graphene distortion, magnetization, charge transfer, and electronic energy band gap at Fermi energy. Certainly, there is ample scope to investigate the electronic structures of elemental adsorption on graphene based on period and group of the periodic table, and atomic ratio.

CrN has widespread applications as protective coatings, for example, in aircraft jet engines whereby their high hardness and good oxidation resistance render metal components resistant to harsh operating conditions. Alloying elements are commonly incorporated (doped) into the coatings to further enhance their thermomechanical properties. However, the effect of dopants on the electronic properties and their roles in modifying the grain boundary configurations remain unclear. Lack of such critical knowledge has hindered the development of design strategies for high performance CrNbased coatings. To address this challenging issue, in the present study nearedge X-ray absorption fine structure (NEXAFS) investigations of Cr 1−y Ni y N coatings at the Cr L 3,2 -edge (570−610 eV), Ni L 3,2 -edge (840−890 eV), and N K-edge (380−450 eV) regions were conducted using synchrotron radiation soft X-ray (SXR) spectroscopy in both Auger electron yield (AEY) and total fluorescence yield (TFY) modes. The chemical states in CrNiN were found to change with the increase of Ni content, manifested as a small chemical shift and moderate change of shapes of various absorption edges. The CrN grain size also became smaller with increasing Ni concentration. These findings help improve our understanding of local bonding structures, which could potentially lead to improved coating designs for highly demanding applications. ■ INTRODUCTIONInterests in transition metal nitrides have risen in the past few years due to their unique physical and mechanical properties that render them suitable for a wide range of technological applications in numerous devices. 1−13 For their superior strength, high corrosion, and oxidation resistance, these materials have been used in extreme pressure and temperature conditions, e.g., jet engine components. Moreover, dopants have been used to enhance their various physicochemical and mechanical properties such as hardness, oxidation resistance, inertness, diffusion resistance, and reflectance by the formation of dislocations, disorderness, vacancy, and atom substitution. 1,[3][4][5]9 In addition, incorporation of Si, Al, or Ti into the CrN matrix results in the reduction of grain sizes down to the nanoscale, which enhances the hardness of the thin films. 2 At the nanoscale, the formation of dislocations becomes difficult, and the hardness of the thin coatings is thereby controlled by the grain boundary. 14 Synchrotron radiation is emitted by very high-energy electrons circulating around a storage ring by a series of magnets separated by straight sections inside the synchrotron tunnels. Owing to their large skin depth in materials,

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