• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.129-134
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• 1998

Conversion of propane to acrylonitrile via ammoxidation was studied using physically mixed catalysts composed of $Nb_2O_5(10{\sim}30wt%)$ and $V_{0.4}Mo_1Te_{0.1}$. Catalytic activities of ammoxidation were improved by adding strong acidic niobium oxide to $V_{0.4}Mo_1Te_{0.1}$, the selectivities to acrylonitrile+propylene being remained constant. The maximum activity was obtained at the mixing ratio 25wt% niobium oxide in $Nb_2O_5-V_{0.4}Mo_1Te_{0.1}$. Niobium oxide was found to be a selective catalyst for the oxidative dehydrogenation of propane.

• Journal of the Korean Electrochemical Society
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• v.14 no.4
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• pp.196-200
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• 2011

The formation of niobium oxide microcones on niobium substrates was investigated in NaF to the HF electrolytes. This condition builds on the uniqueness of the microstructures niobium oxide. The dimensions and integrity of the bulk microstructures were found to be strongly dependent on potential, temperature, electrolyte composition, and anodization time. The anodic oxide was initially amorphous at all temperatures, but crystalline oxide nucleated during anodization. From XRD patterns of the anodized specimens, the microcones consisted of crystalline $Nb_2O_5$. We demonstrated niobium oxide microcone structures with nanorods. The anodized niobium oxide microcone texture revealed nanorod bundles. The surface of $Nb_2O_5$ microcones is very regular and has a nano-scale. The surface morphologies of the nanorods were examined using FE-SEM. EDS analyses show that the anodically prepared niobium oxide consists of $Nb_2O_5$. The aim of this study is to find the condition of forming the favorable nanorods by anodization method.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.817-820
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• 2009

To meet the high current load requirement from the high energy density realized by metal oxide and high power density graphite, we propose a novel hybrid supercapacitor consisting of Nb2O5 and KS6 graphite in 1.0 M LiPF6-EC:DEC (1:2). This new system exhibits a sloping voltage profile from 2.7 to 3.5 V during charging and presents a high operating voltage plateau between 1.5 and 3.5 V during discharging. The cell was tested at a current density of 100 mA/g with a cut-off voltage between 3.0 and 1.0 V. This novel energy storage system delivers the highest initial discharge capacity of 55 mAh/g and exhibits a good cycle performance.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.79-88
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• 2005

This study was performed to investigate the surface properties of electrochemically oxidized pure niobium by anodic oxide and hydrothermal treatment technique. Niobium specimens of $10\times10mm$ in dimension were polished sequentially from #600, #800, #1000 emery paper. The surface pure niobium specimens were anodized in an electrolytic solution that was dissolved calcium and phosphate in water. The electrolytic voltage was set in the range of 250 V and the current density was 10 $mA/cm^2$. The specimen was hydrothermal treated in high-pressure steam at 300$^{\circ}C$ for 2 hours using an autoclave. Then, specimens were immersed in the Hanks' solution with pH 7.4 at 37$^{\circ}C$ for 30 days. The surface of specimen was characterized by scanning electron microscope(SEM), energy dispersive X-ray microanalysis(EDX), potentiostat/galvanostat test, and cytotoxicity test. The results obtained was summarized as follows; According to the result of measuring corrosion behavior at 0.9% NaCl, corrosion resistance was improved more specimens treated with anodic oxide than in hydrothermal treated ones. The multi-porous oxide layer on surface treated through anodic oxidation showed a structure that fine pores overlap one another, and the early precipitation of apatite was observed on the surface of hydrothermal treated samples. According to the result of EDX after 30 days deposition in Hanks' solution, Ca/P was 1.69 in hydrothermal treated specimens. In MTT test, specimens treated through anodic oxidation and hydrothermal treated ones showed spectrophotometer similar to that of the control group. Thus no significant difference in cytotoxicity was observed (P>0.05).

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.625-629
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• 2011

In this study, we show that by anodization of Nb in NaF electrolytes microcone niobium oxide layers can be formed under a range of experimental conditions. It is found that a single NaF electrolyte leads to the formation of microcones. At 1 M NaF, 40 V, 1 h, well-ordered microcones were generated on Nb discs. XRD results show that the initially formed anodic oxide is amorphous, but an amorphous to crystalline transition occurs during anodization. For the formation of favorable microcones, it is considered that proper parameters such as electrolyte concentration, voltage, anodizing time are necessary according to the kind of electrolytes.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.134-138
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• 2005

This study was performed to investigate the surface properties of electrochemically oxidized pure niobium by anodic oxide and hydrothermal treatment technique. Niobium specimens of $10mm\times10mm\times1.0mm$ in dimension were polished sequentially from $\#600,\;\#800,\;\#1000$ emery paper. The surface of pure niobium sperimens was anodized in an electrolytic solution that was dissolved calcium and phosphate in water. The electrolytic voltage was set in the range of 250 V and the current density was $10mA/cm^2$. The specimen was hydrothermal treated in high-pressure steam at $300^{\circ}C$ for 2 hours using an autoclave. And all specimens were immersed in the in the Hanks' solution nth pH 7.4 at $37^{\circ}C$ for 30 days. The surface of specimen was characterized by surface roughness, scanning electron microscope(SEM), energy dispersion X-ray analysis(EDX), X-ray photoemission spectroscopy(XPS) test. The value of surface roughness was the highest in the anodized sample and $0.41{\pm}0.04\;{\mu}m$. The results of the SEM observation show that oxide layers of the multi porosity in the anodized sample were piled up on another, and hydroxyapatite crystal was precipitate from the surface of the hydrothermal treated sample. In the XPS analysis, O, Nb, C peak and small amounts of N peak were found in the polished specimens while Ca and P peak in addition to O, Nb, C and peak were observed in the hydrothermal treated sample.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.245-251
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• 2017

Niobium doped zirconium oxide (Nb-Zr-O:NZO) thin films were fabricated on Si substrates by a sol-gel technique with an annealing temperatures of $500{\sim}1000^{\circ}C$ in air ($N_2:O_2=3:1$) for 20 minutes. It was found that the NZO film is based on tetragonal $ZrO_2$ polycrystalline structure with the Nb 5+ ion state and there is almost no diffusion of Nb or Zr to Si substrate. The relative dielectric constant for the NZO film with the Nb composition of 30 mol% and annealed at $800^{\circ}C$ was around 40. The root mean roughness was 1.02 nm. In addition, the leakage current of NZO films was as low as $10^{-6}A/cm^2$ at 4.4 V.

• Corrosion Science and Technology
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• v.2 no.2
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• pp.68-74
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• 2003

The effects of Niobium on the structure and properties(especially electric properties) of passive film of Zirconium alloys in pH 8.5 buffer solution are examined by the photo-electrochemical analysis. For Zr-xNb alloys (x = 0, 0.45, 1.5, 2.5 wt%), photocurrent began to increase at the incident energy of 3.5 ~ 3.7 eV and exhibited the $1^{st}$ peak at 4.3 eV and the $2^{nd}$ peak at 5.7 eV. From $(i_{ph}hv)^{1/2}$ vs. hv plot, indirect band gap energies $E_g{^1}$= 3.01~3.47 eV, $E_g{^2}$= 4.44~4.91 eV were obtained. With increasing Nb content, the relative photocurrent intensity of $1^{st}$ peak significantly increased. Compared with photocurrent spectrum of thermal oxide of Zr-2.5Nb, It was revealed that $1^{st}$ peak in photocurrent spectrum for the passive film formed on Zr-Nb alloy was generated by two types of electron transitions; the one caused by hydrous $ZrO_2$ and the other created by Nb. Two electron transition sources were overlapped over the same range of incident photon energy. In the photocurrent spectrum for passive film formed on Zr-2.5Nb alloy in which Nb is dissolved into matrix by quenching, the relative photocurrent intensity of $1^{st}$ peak increased, which implies that dissolved Nb act as another electron transition source.

• Journal of Korea Foundry Society
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• v.30 no.5
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• pp.179-186
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• 2010

To elucidate the effects of alloying elements on the characteristics of microstructure and high temperature oxidation of cast austenitic stainless steel, a thermodynamic calculation, a cyclic oxidation test, a X-ray diffraction, a scanning electron microscopy-back scattered electron, a electron probe microanalysis were conducted. The thermodynamic calculation for the effect of vanadium (V) addition on the formation of various precipitates leads to a decrease of chromium (Cr)-rich $M_{23}C_6$ carbides due to the formation of M (C, N) carbo-nitrides containing V and / or niobium (Nb). The V added alloy increased the resistance to high temperature oxidation due to a decrease of Cr-depleted zone deteriorating the oxidation resistance and due to the V-enriched oxide layer formed in inner oxide layer blocking the outward transport of cations.

• Journal of the Korean Chemical Society
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• v.35 no.6
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• pp.625-629
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• 1991

The electrical conductivity of the Niobium Oxide-Lead Oxide systems containing 2.5, 5.0, 7.5, and 10.0 mol% of Lead Oxide has been measured in a temperature range 700${\sim}$$1100^{\circ}C$ under oxygen partial pressure of 2.0 ${\times}$ $10^{-1}$${\sim}$1.0 ${\times}$ $10^{-5}$ atm. The electrical conductivities of the system decreased with increasing PbO mol% and varied from $10^{-5}$ to $10^{-1}$ $ohm^{-1}$ $cm^{-1}$. The activation energy for conductivity was about 1.70 eV. The oxygen pressure dependence of electrical conductivity revealed that the system was a mixed conductor between ionic and electronic conductivities at high oxygen pressures and a n-type electronic conductivity with oxygen pressure dependence of -1/4 order at low oxygen pressures. The defect structure and electrical conduction mechanism of the system have been discussed with the data obtained.