• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.125.2-125.2
• /
• 2015

The evolution of oxidation states of vanadium is monitored with ambient pressure X-ray photoemission spectroscopy. As the pressure of oxygen gas and surface temperature change, the formations of various oxidation states of vanadium are observed on the surface. Under 100mTorr of the oxygen gas pressure and 523K of sample temperature, VO2 and V2O5 are formed on the surface. The temperature-dependent resistance measurement on grown sample shows a clear metal-insulator transition near 350K. In addition, the measurement of Raman spectroscopy displays the structural change from monoclinic to rutile structures across the phase transition temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.05b
• /
• pp.70-73
• /
• 2002

Thin films of vanadium oxide($VO_{x}$) have been deposited by r.f. magnetron sputtering from $V_{2}O_{5}$ target in gas mixture of argon and oxygen. The oxygen/(oxygen+argon) partial pressure ratio of 0% and 8% is adopted. Crystal structure, chemical composition, molecular structure and optical properties of films sputter-deposited under different oxygen gas pressures and in-situ annealed in vacuum at $400^{\circ}C$ for 1h and 4h are characterized through XRD. RBS, FTlR and optical absorption measurements. The films as-deposited are amorphous and those annealed for time longer than 4h are polycrystalline. $V_{2}O_{5}$ and lower oxides co-exist in sputter-deposited films and as the oxygen partial pressure is increased the films become more stoichiometric $V_{2}O_{5}$. When annealed at $400^{\circ}C$, the as-deposited films are reduced to a lower oxide. It is observed that the oxygen atoms located on the V-O plane of $V_{2}O_{5}$ layer participate more readily in the oxidation and reduction process. The optical transmission of the films annealed in vacuum decreases considerably than the as-deposited films and the optical absorption of all the films increases rapidly between 400 and 550nm.

• Journal of the Korean Chemical Society
• /
• v.55 no.1
• /
• pp.81-85
• /
• 2011

$V_{0.9}Sb_{0.1}O_x$ systems, bulk and deposited on different supports (five types of $\gamma$-aluminas, $\alpha$-alumina, silica-alumina, silica gel, magnesium oxide), have been tested in the oxidative dehydrogenation (ODH) of iso-butane. Catalytic performance of VSb oxides has shown to be highly dependent on the support and the nature of the support decreasing in a series: $\gamma$-$Al_2O_3$ > $\alpha$-$Al_2O_3$ > Si-Al-O > $SiO_2$ $\approx$ MgO $\gg$ unsupported. Variation of the V-Sb-O-loading in the studied range of coverage (0.5-2 theoretical monolayer) only slightly influences the catalysts' activity and selectivity. The best catalytic performance of $\gamma$-alumina-supported $V_{0.9}Sb_{0.1}O_x$ systems can be explained by the optimal surface interaction between support and supported components resulting in the formation of well-spread amorphous active $VO_x$-component with vanadium in a high oxidation state.

• Transactions on Electrical and Electronic Materials
• /
• v.17 no.3
• /
• pp.139-142
• /
• 2016

β-AgVO₃ nanorods have been successfully synthesized using a soft chemistry route followed by heat treatment. They were characterized by X-ray diffraction and field emission scanning electron microscopy, and their electrochemical properties were investigated using cyclic voltammetry, impedance spectra, and charge-discharge tests. The results showed that the smooth-surfaced nanorods are very uniform and well dispersed, with diameters of ~100-200 nm and lengths of the order of several macrometers. The nanorods deliver a maximum specific discharge capacity of 275 mAh g^-1 at 30 mA g^-1. They also demonstrated good rate capability with a discharge capacity at the 100^th cycle of 51 mAh g^-1.