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1

Theoretical investigation of vanadium oxide film with surface microstructure

Hong W., Wang Z., Chen Q., Sheng C., Gu G., Luo P., Xie Y.

Optica Applicata

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2017

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Vol. 47, nr 4

601--609

EN

This paper presents a method to design a surface microstructure of vanadium oxide to enhance optical absorption. This method, using a density of eigenfrequency, can be calculated by a planar wave expand method, to indicate the absorption efficiency of a dispersion material, which can be used as an approach method for further design. Based on this, a nanostructure-based vanadium oxide film is designed and simulated to validate this method. The simulation results show that the tendency of density of eigenfrequency is corresponding to the tendency of optical absorption enhancement. Moreover, this structure can achieve high optical broadband absorption when the material dispersion is considered. High optical absorption enhancement can be achieved by adjusting the geometrical parameters; our maximum overall enhancement absorption ratio was 31.84% at the metal phase, which can be attributed to the enhancement effect of a photonic band edge.

2

Structural and optical properties of vanadium oxides prepared by microwave-assisted reactive magnetron sputtering

Sieradzka K., Wojcieszak D., Kaczmarek D., Domaradzki J., Kiriakidis G., Aperathitis E., Kambilafka V., Placido F., Song S.

Optica Applicata

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2011

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Vol. 41, nr 2

463--469

EN

In this work, structural and optical properties of vanadium oxides have been presented. Thin films were manufactured by microwave-assisted magnetron sputtering process. Particles were sputtered from a vanadium target in Ar/O2 atmosphere. Oxygen partial pressure was changing from 3×10-4 to 7×10-4 Torr. After the deposition, the thin films were additionally annealed at 400 °C in ambient air in order to oxidize the films. Structural investigation was performed with the aid of X-ray diffraction measurements and Raman spectroscopy. The results obtained from both methods have revealed that as-deposited films were amorphous, while annealed films had V2O5 crystal form. Optical properties were determined by transmission measurements in the spectral range from 250 to 2500 nm. As-deposited films had low transmission (below 10%), but oxidization by additional annealing of the structure resulted in the increase of the transmission level up to about 20 and 43% at 650 nm wavelength for samples prepared under 3×10-4 and 7×10-4 Torr oxygen partial pressure, respectively. The analysis of the structure and optical properties of the thin films has revealed the influence of deposition parameters on the properties of vanadium oxides.

3

Oxidative Dehydrogenation of Propane over Mechanochemically Activated V2O5-Cr2O3 System

Wieczorek-Ciurowa K., Gomułczak A., Zazhigalov V. A.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 1-2

191-198

EN

High-energy ball milling of V2O5-Cr2O3 mixture (V/Cr molar ratio = 1/10) initially causes dispersion of vanadium oxide on the surface of chromium oxide grains resulting in an active phase-support system. The increase of both, the V/Cr ratio on the surface and acidity of active sites is observed. Thus, this system mechanically treated for only 30 minutes has lower selectivity of propane conversion to propylene than the non-milled one. Due to homogenization resulting from longer milling time, the vanadium layer on the surface is destroyed and therefore the lower V/Cr ratio on the surface and decrease in acidity are observed. Simultaneously, the formation of Cr2VO5.5 phase takes palce. It was concluded that these phenomena were responsible for a significant increase of selectivity in conversion of propane to propylene in contrast to the non-activated sample.

4

Dehydrogenation of Isobutane to Isobutene over V2O5/gamma-Al2O3 Catalysts: Effects of the Extent of Catalyst Reduction on Catalytic Performance

Ma H., Fu Y.-H., Li Y., Wang Z. -L., Zhu W. -C., Wang G.-J.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 7

903-908

EN

V2O5/_-Al2O3 catalysts for the dehydrogenation of isobutane to isobutene were prepared by impregnation and characterized by BET,H2-TPR, ESR and XPS. Based on our studies of the effects of the extent of catalyst reduction on catalytic performance, we conclude that the V2O5/_-Al2O3 catalytic activity for the dehydrogenation of isobutane is related to the valence state of vanadium present in the catalyst, in the order of V4+> V3+. Furthermore, V4+ species are the main active sites of this reaction under the present reaction conditions.

5

Solubility investigations in the K2SO4 + V2O5 + H2O system from 293 K to 323 K

Trypuć M., Chałat M., Mazurek K.

Polish Journal of Applied Chemistry

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2003

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Vol. 47, nr 4

287-293

EN

The mutual solubility of K2SO4 and V2O5 in water within temperature range of 293 K to 323 K was investigated employing the isothermal solution saturation method. The concentration of vanadium ions (V) was calculated using the spectrophotometric method with 4-(2-pirydylazo)-resorcinol agent while the potassium ion concentration was evaluated using the balance method in the form of K[[B(C6H5)4]. These results were used to plot a part of the polythermal section of the K2SO4 + V2O5 + H2O system .The data ere essential in determination of the optimum processing parameters to recover V2O5 from the used vanadium catalyst in the oxidation SO2 to SO3

PL

Rozpuszczalność K2SO4 oraz V2O5 w wodzie, zakresie temperatur 293 - 323 K, zbadano metodą izotermicznego nasycania roztworów. Stężenie jonów wanadanowych oznaczano spektrofotometrycznie przy użyciu 4-(2-pirydyloazo)-rezorcynolu, natomiast stężenie jonów potasowych metodą wagową w postaci K[B(C6H5)4]. Na podstawie uzyskanych wyników wykreślono wycinek politermy układu K2SO4 + V2O5 + H2O. Dane te są potrzebne do określenia optymalnych warunków wydzielenia V2O5 ze zużytego katalizatora wanadanowego po procesie utleniania SO2 do SO3.

6

Solubility investigations in the KCl + V2O5 +H2O system from 293 K to 323 K

Trypuć M., Chałat M., Mazurek K.

Polish Journal of Applied Chemistry

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2002

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Vol. 46, nr 2

135-141

EN

The mutual solubility of KCl and V2O5 in water within temperature range of 293 to 323 K was reported. These results were used to plot a part of the polythermal solubility surface for the KCl + V2O5 + H2O system. The data are essential in determination of the optimum operating parameters for the potassium metavanadate production process based on KCl and V2O5 in the presence of steam or oxygen.

7

Laser modification of the electrical properties of vanadium oxide thin films

Stefanovich G. B., Pergament A. L., Chudnovskii F. A., Kikalov D. O.

Opto-Electronics Review

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1999

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Vol. 7, No. 2

131-134

EN

The effect of laser irradiation on amorphous films of anodic vanadium oxide was studied using a YAG:Nd³⁺ laser at wavelength 1.06 µm. Irradiation was found to lower the electrical conductivity of the oxide films and modify significantly the parameters of electroforming and switching in metal/oxide/metal sandwich structures. The threshold energy for laser modification was measured to be ~ 0.3 mJ/cm². It is shown that the changes of the electrical properties are associated with structural (crystallization) and chemical (in particular, the reduction V₂O₅ → VO₂) transformations and that non-thermal photo-stimulated effects play an important role in the laser modification of the vanadium oxide thin films.