• Journal of the Korean Magnetic Resonance Society
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• v.4 no.1
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• pp.1-11
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• 2000

Supported vanadium oxides are being used extensively as catalysts for a variety of reactions, including partial oxidations and ammoxidations. A series of vanadium oxide supported on TiO2-ZrO2 was obtained by impregnating ammonium metavanadate slowly into a mixed precipitateof Ti(OH)4-Zr(OH)4, followed by calcining in air at high temperatures. The prepared catalysts were characterized by 51V solid-state NMR. In the calcined catalysts 51V NMR studies indicated the peaks corresponding to distorted tetrahedral vanadia species at low V2O5 contents and octahedral vanadia species at high vanadia loadings. These results illustrate the suitability of 51V NMR as a unique quantitative spectroscopic tool in the structural analysis of vanadium(V) oxide catalytic materials.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.1-6
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• 2002

Silver doped vanadium pentoxides with a doping ratio Ag/V ranging from 0.03 to 0.11 were synthesized by sol-gel process, and $Li/Ag_xV_2O_5$ cell was investigated by the electrochemical methods. It appears to be amorphous layered material and entangled fibrous textures has been grown to form anisotropic corrugated fibrils. NMR measurements revealed that several different kinds of $Li^+$ ions exist in the lithium intercalated xerogel electrodes and the average cell potential was about 3.0V vs. $Li/Li^+$. The cell capacity of the silver doped $Ag_xV_2O_5$ xerogel cathodes was more than 359 mAh/g at discharge current 10mA/g and cycle efficiency $94\%$ was achieved.

• Proceedings of the Korean Magnetic Resonance Society Conference
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• 1999.06a
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• pp.15-15
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• 1999

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.311-317
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• 2003

Vanadium oxides supported on zirconia and modified with MoO₃were prepared by adding Zr(OH)₄powder into a mixed aqueous solution of ammonium metavanadate and ammonium molybdate followed by drying and calcining at high temperatures. The characterization of prepared catalysts was performed using FTIR, Raman spectroscopy and solid-state $^{51}V$ NMR. In the case of a calcination temperature of 773 K, for samples containing low loading of $V_2O_5$, below 15 wt %, vanadium oxide was in a highly dispersed state, while for samples containing high loading of $V_2O_5$, equal to or above 15 wt %, vanadium oxide was well crystallized because the $V_2O_5$ loading exceeded the formation of a monolayer on the surface of $ZrO_2$. The $ZrV_2O_7$ compound was formed through the reaction of $V_2O_5\;and\;ZrO_2$ at 873 K and the compound decomposed into $V_2O_5\;and\;ZrO_2$ at 1073 K, which were confirmed by FTIR spectroscopy and solid-state $^{51}V$ NMR. IR spectroscopic studies of ammonia adsorbed on $V_2O_5-MoO_3/ZrO_2$ showed the presence of both Lewis and Bronsted acids.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.180-186
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• 2018

We report the discovery of Li-rich $Li_{1+x}[(Ni_{0.225}Co_{0.15}Mn_{0.625})_{1-y}V_y]O_2$ as a cathode material for rechargeable lithium-ion batteries in which a small amount of tetravalent vanadium ($V^{4+}$) is selectively and completely incorporated into the manganese sites in the lattice structure. The unwanted oxidation of vanadium to form a $V_2O_5-like$ secondary phase during high-temperature crystallization is prevented by uniformly dispersing the vanadium ions in coprecipitated $[(Ni_{0.225}Co_{0.15}Mn_{0.625})_{1-y}V_y](OH)_2$ particles. Upon doping with $V^{4+}$ ions, the initial discharge capacity (>$275mA\;h\;g^{-1}$), capacity retention, and voltage decay characteristics of the Li-rich layered oxides are improved significantly in comparison with those of the conventional undoped counterpart.

• Resources Recycling
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• v.15 no.6 s.74
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• pp.10-15
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• 2006

As a basic study on recovery of valuable metals such as vanadium and nickel from metal oxide obtained from waste orimulsion ash, we conducted selectively leaching of vanadium and nickel using $Na_2CO_3$ leaching and ammoniacal leaching, respectively. The 97% of vanadium was selectively leached at an optimum experimental condition, 50g/L $Na_2CO_3$, pulp density 50g/L, and 35% $H_2O_2$ 50ml/L, $25^{\circ}C$... for 1 hr, whereas no nickel was leached. In ammoniacal leaching study, 95% of nickel was selectively leached at the optimal experimental condition, $NH_4OH\;2M,\;(NH_4){_2}SO_4$ 1.5M, pulp density 50g/L, 25, for 4 hr along with 3% of vanadium.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.211-216
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• 2010

$(NH_4)_{0.3}V_2O_5$ nanorods and $V_2O_5$ nanosheets have been synthesized by the reaction of $V_2O_5$ gel via homogeneous precipitation process employing urea and formic acid. The electrochemical and chemical characteristics of these nanomaterials have been investigated using TGA, SEM, FT-IR, XRD, and LSV. The interlayer distance of $(NH_4)_{0.3}V_2O_5$ was about $10.7{\AA}$, and that of $V_2O_5$ synthesized by using formic acid was $14.2{\AA}$. The surface morphology of $(NH_4)_{0.3}V_2O_5$ and $V_2O_5$ showed features that looked like nanorods and nanosheets, respectively. Specific capacity of $(NH_4)_{0.3}V_2O_5$ nanorods prepared at $95^{\circ}C$ was at least 280 mAh/g at 10 mA/g discharge rate.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.73.1-73.1
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• 2010

For the successful cold starting of a fuel cell engine, either internal of external heat supply must be made to overcome the formation of ice from water below the freezing point of water. In the present study, switchable vanadium oxide compounds as variable temperature-electrical resistance materials onto the surface of flat metallic bipolar plates have been prepared by a dip-coating technique via an aqueous sol-gel method. Subsequently, the chemical composition and micro-structure of the polycrystalline solid thin films were analyzed by X-ray diffraction, X-ray fluorescence spectroscopy, and field emission scanning electron microscopy. In addition, it was carefully measured electrical resistance hysteresis loop over a temperature range from $-20^{\circ}C$ to $80^{\circ}C$ using the four-point probe method. The experimental results revealed that the thin films was mainly composed of Karelianite $V_2O_3$ which acts as negative temperature coefficient materials. Also, it was found that thermal dissipation rate of the vanadium oxide thin films partially satisfy about 50% saving of the substantial amount of energy required for ice melting at $-20^{\circ}C$. Moreover, electrical resistances of the vanadium-based materials converge on an extremely small value similar to that of pure flat metallic bipolar plates at higher temperature, i.e. $T{\geq}40^{\circ}C$. As a consequence, experimental studies proved that it is possible to apply the variable temperature-electrical resistance material based on vanadium oxides for the cold starting enhancement of a fuel cell vehicle and minimize parasitic power loss and eliminate any necessity for external equipment for heat supply in freezing conditions.

• Journal of Powder Materials
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• v.30 no.6
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• pp.516-520
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• 2023

Highly safe lithium-ion batteries (LIBs) are required for large-scale applications such as electrical vehicles and energy storage systems. A highly stable cathode is essential for the development of safe LIBs. LiFePO₄ is one of the most stable cathodes because of its stable structure and strong bonding between P and O. However, it has a lower energy density than lithium transition metal oxides. To investigate the high energy density of phosphate materials, vanadium phosphates were investigated. Vanadium enables multiple redox reactions as well as high redox potentials. LiVPO₄O has two redox reactions (V⁵⁺/V⁴⁺/V³⁺) but low electrochemical activity. In this study, LiVPO₄O is doped with fluorine to improve its electrochemical activity and increase its operational redox potential. With increasing fluorine content in LiVPO₄O_1-xF_x, the local vanadium structure changed as the vanadium oxidation state changed. In addition, the operating potential increased with increasing fluorine content. Thus, it was confirmed that fluorine doping leads to a strong inductive effect and high operating voltage, which helps improve the energy density of the cathode materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.435-438
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• 2001

Thin films of vanadium oxide(VO$\sub$x/) have been deposited by r.f. magnetron sputtering from V$_2$O$\sub$5/ target in gas mixture of argon and oxygen. The oxygen/(oxygen+argon) partial pressure ratio is changed from 0% to 8%. Crystal structure, chemical composition and bonding properties of films sputter-deposited under different oxygen gas pressures are characterized through XRO, XPS, RBS and FTIR measurements. All the films prepared below 8% O$_2$ are amorphous, and those prepared without oxygen are gray indicating the presence of V$_2$O$\sub$$_4$/ phase in the films. V$_2$O$\sub$5/ and lower oxides co-exist in sputter-deposited films and as the oxygen partial pressure is increased the films become more stoichiometric V$_2$O$\sub$5/. The increase of O/V ratio with increasing oxygen gas pressure is attributed to the partial filling of oxygen vacancies through diffusion. It is observed that the oxygen atoms. located on the V-O plane of V$_2$O$\sub$5/ layer participate more readily in the oxidation process.