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The redox behaviour of several quaternary pyridinium corrosion inhibitors ("Quats") at glassy carbon (GC) electrodes has been investigated in neutral aqueous solutions. The primary emphasis is on n-butyl-3-(N-octylcarbamyl)pyridinium bromide, one of the Quats determined to have very good corrosion inhibition properties based on parallel weight loss experiments. It is demonstrated that the reduction of the Quats, which occurs in a two-electron reaction at potentials negative of -1.0 V vs. SSCE, results in the formation of a neutral product. This forms a porous film on the electrode surface, with clusters that expand and thicken as more Quat deposits, as confirmed by atomic force microscopy. The film charge density reaches a maximum of ~4 mC/[cm.sup.2], equivalent to more than 100 monolayers of Quat, after which no further Quat can be deposited, suggesting full surface coverage by a nonconducting product. The Quat multilayer can then be redissolved at potentials positive of ~ -0.2 V, during its oxidation back to its original solution-soluble form. Key words: quaternarized pyridinium compounds, reductive film deposition, glassy carbon, multilayer, corrosion inhibitors, cyclic voltammetry, AFM.

The domain structure of two selected single-crystal VO2 microrods (MRs) with different morphologies was mapped by pixelated Raman imaging through the metal-to-insulator transition (MIT) during heating and cooling schedules through 68 °C. The results show that MIT does not occur simultaneously and uniformly throughout the whole MR, and instead, it proceeds through alternating metal–insulator domains. Each structural domain possesses its own MIT transition temperature and hysteresis width. The variations in MIT characteristics among different domains of a single MR are probably ascribed to structural nonuniformity. The observed overall MIT transition and hysteresis width of a given VO2 single-crystal MR is an aggregate manifestation of the MIT properties of domains within the crystal. [ABSTRACT FROM AUTHOR]

NbOx thin films have been deposited on silicon (100) and quartz substrates by magnetron sputtering using a metallic Nb target in an optimized argon–oxygen atmosphere. This work investigates the dependence of structure–property relations on the key deposition parameters towards establishing optimum deposition conditions for the growth of NbOx polycrystalline films. It is found that a sputtering condition corresponding to DC power density 9.87 W cm−2, a substrate temperature of 720 °C, low gas pressures of 8 mtorr, a target to substrate distance of 45 mm gives thin films with good homogeneity and a high degree of crystallinity in the case of both NbO2 and Nb2O5. X-ray diffraction (XRD) and Raman spectroscopy confirmed the tetragonal phase of NbO2 and orthorhombic phase of Nb2O5 for similar deposition temperatures. Scanning electron microscopy (SEM) observations indicate that NbO2 has a unique nanoslice structure while Nb2O5 has a flake-like structure. The optical transmittance of the films has been investigated and found to be dependent on the oxygen gas content during deposition; the optical transmittance decreases with increasing O2 gas content. Optical constants of the films were calculated by fitting a suitable thin film transmittance model to experimental transmittance spectra using a modified Swanepoel technique. The nanohardness and stress in the films were measured by nanoindentation and an optical profilometer respectively. Nanohardness and stress in the film show no large dependence on the oxygen gas content except at high oxygen gas content. The nanohardness value of NbO2 films is approximately 6 GPa, and the Young's modulus is 150 GPa. The Nb2O5 films exhibit a nanohardness of 5.8–13 GPa and a Young's modulus of 137–161 GPa. [ABSTRACT FROM AUTHOR]

Erratum: Zhang, C. et al., The Effect of Substrate Biasing during DC Magnetron Sputtering on the Quality of VO 2 Thin Films and Their Insulator-Metal Transition Behavior. The authors would like to correct a typographical error in their paper [[1]]. Reference 1 Zhang C., Gunes O., Li Y., Cui X., Mohammadtaheri M., Wen S.-J., Wong R., Yang Q., Kasap S. The Effect of Substrate Biasing during DC Magnetron Sputtering on the Quality of VO2 Thin Films and Their Insulator-Metal Transition Behavior. [Extracted from the article]

In this work, VO 2 thin films were deposited on Si wafers (onto (100) surface) by DC magnetron sputtering under different cathode bias voltages. The effects of substrate biasing on the structural and optical properties were investigated. The results show that the metal-insulator transition (MIT) temperature of VO 2 thin films can be increased up to 14 K by applying a cathode bias voltage, compared to deposition conditions without any bias. The decrease in the transition efficiency and increase in the transition temperature are attributed to the enlarged grain size, increased defects, and the residual stress in the VO 2 thin films induced by biasing. The optical transmittance measurements for different thickness films indicate an attenuation coefficient of 3.1 × 10 7 m -1 at 2000 nm or an extinction coefficient of 4.9 in the metal phase. The optical transmittance vs wavelength characteristics point to an indirect bandgap of 0.6 ± 0.5 eV and significant scattering in the bulk and/or at the interface.