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Quaternary sputtered TiAlSiN coatings were investigated for their high temperature structural stability, surface morphology, mechanical behaviors, surface chemical bonding states, solar absorptance and thermal emittance for possible solar selective surface applications. The TiAlSiN films were synthesized, via unbalanced magnetron sputtered technology, on AISI M2 steel substrate and annealed at 500 °C - 800 °C temperature range. SEM micrographs show nanocomposite-like structure with amorphous grain boundaries. Nanoindentation analyses indicate a decrease of hardness, plastic deformation and constant yield strength for the coatings. XPS analysis show mixed Ti, Al and Si nitride and oxide as main coating components but at 800 °C the top layer of the coatings is clearly composed of only Ti and Al oxides. Synchrotron radiation XRD (SR-XRD) results indicate various Ti, Al and Si nitride and oxide phases, for the above annealing temperature range with a phase change occurring with the Fe component of the substrate. UV–Vis spectroscopy, FTIR spectroscopy studies determined a high solar selectivity, s of 24.6 for the sample annealed at 600 °C. Overall results show good structural and morphological stability of these coatings at temperatures up to 800 °C with a very good solar selectivity for real world applications. [ABSTRACT FROM AUTHOR]

Nanostructured thin film coatings of copper oxide (Cu-oxide) were investigated to determine their physical structure, surface morphology, surface electronic bonding states, and optical properties. The Cu-oxide had been coated onto reflective aluminum substrates via a facile one-step sol–gel dip-coating route using a copper nitrate precursor. Characterizations were conducted using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and ultra-violet visible (UV–Vis) spectroscopic methods, and representative sol-gel reactions using copper nitrate precursor were proposed. The XPS spectra confirmed the presence of copper oxide elements. Further exploration of the Cu2 p 3/2 peak in XPS spectra revealed that the electronic structure of the copper component consisted of tetrahedral Cu(I) and octahedral Cu(II) with the presence of octahedral Cu(II) enabling coatings to have high absorption levels across the solar spectrum. The deconvolution of the O1 s spectra exhibited three curve-fitting components: the lattice O2−, surface oxygen, and subsurface O− species. FESEM results showed that the coating surface was an agglomerated copper oxide nanoparticles structure forming a porous structure. The optical band-gap of Cu-oxide thin film coatings, via the Tauc plot, was 2.7 eV. [ABSTRACT FROM AUTHOR]

Abstract The temperature dependence of phase composition and lattice parameters, for TiAl x N thin film coating, are experimentally investigated by in-situ synchrotron radiation X-ray diffraction (SR-XRD), at temperatures between 25 °C and 700 °C. Mechanical properties, such as: Young's modulus (E), hardness (H) and plastic deformation index (PDI) – were experimentally determined by nanoindentation, at 25 °C. Crystalline structural analysis, of SR-XRD results, indicates the major phases are TiN and AlN; with Ti 2 O and TiO 2 phases also present above 600 °C. The lattice constants increased with an increase in temperature. Atomic and phase compositions, at 25 °C, were also verified by X-ray photoelectron spectroscopy (XPS). Field emission scanning electron microscopy (FESEM) images display an increase in surface roughness and reduction in grain size, with increasing Aluminium percentage (Al%). Nanoindentation analysis showed a maximum hardness of 25.1 ± 1.5 GPa (sample containing 12% Al), which was subsequently reduced upon addition of more Aluminium. Finite element modelling (FEM), including von Mises stress distribution, indicates lower mechanical integrity, for samples with high Al% content. Highlights • Hardness increase upon the addition of small amounts of Aluminium doping. • Significant increase in resistance of plastic deformation with increasing doping. • High temperature in-situ analysis detected an increase in lattice parameters. • Film coatings with different doping exhibited different oxidation states. • Finite element modelling evaluated mechanical integrity of films under load. [ABSTRACT FROM AUTHOR]

Abstract Ce/Ti mixed metal oxide thin films have well known optoelectrical properties amongst several other physio-chemical properties. Changes in the structural and mechanical properties of magnetron sputtered Ce/Ti oxide thin films on Si (100) wafers with different Ce:Ti ratios are investigated experimentally and by modelling. X-ray Photoemission Spectroscopy (XPS) and X-ray diffraction (XRD) confirm the primary phases as trigonal Ce 2 O 3 and rutile form of TiO 2 with SiO 2 present in all prepared materials. FESEM imaging delivers information based on the variation of grain size, the mixed Ce/Ti oxides providing much smaller grain sizes in the thin film/substrate composite. Nanoindentation analysis concludes that the pure cerium oxide film has the highest hardness value (20.1 GPa), while the addition of excess titanium oxide decreases the hardness of the film coatings. High temperature in-situ XRD (up to 1000 °C) results indicate high thermal phase stability for all materials studied. The film with Ce:Ti = 68%:32% has a new additional minor oxide phase above 800 °C. Contact angle experiments suggest that the chemical composition of the surface is insignificant affecting the water contact angle. Results show a narrow band of 87.7–95.7° contact angle. The finite element modelling (FEM) modelling of Ce/Ti thin film coatings based on Si(100); Si(110); silica and steel substrates shows a variation in stress concentration. [ABSTRACT FROM AUTHOR]