• 전기화학회지
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• 제13권3호
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• pp.163-168
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• 2010

본 연구에서는 양극 산화를 통해 얻어지는 다공성 니오븀 산화물 제조에 양이온 계면활성제인 Cetyl Trimethyl Ammonium Bromide (CTAB)와 음이온 계면활성제인 Sodium Dodecyl Sulfate (SDS)의 영향을 비교 관찰하였다. SDS가 전해질에 첨가되어 제조된 다공성 니오븀 산화 막은 표면에 장시간 용출이 발생하지 않았고, 계면활성제가 첨가되지 않고 제조된 다공성 니오븀 산화막의 두께와 비교 하였을 때 두께가 두 배 이상 증가된 값을 얻을 수 있었다. 하지만 CTAB가 전해질에 첨가되어 제조된 다공성 니오븀 산화물의 표면에는 용출이 일어났다. 이러한 차이점을 양성으로 대전된 니오븀산화물과 음이온/또는 양이온 계면활성제 사이의 상호작용에 근거하여 설명하였다.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.839-842
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• 2012

We report for the first time the synthesis of niobium dioxide nanowires on a sapphire substrate by chemical vapor transport method. We identified single crystalline nature of as-synthesized nanowires by scanning electron microscopy and transmission electron microscopy. Niobium dioxide nanowires with their large surface-to-volume ratio and high activities can be employed for electrochemical catalysts and immunosensors. The Raman spectrum of niobium dioxide nanowires also confirmed their identity.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2675-2678
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• 2012

Studies on niobium anodization in the mixture of 1 M $H_3PO_4$ and 1 wt % HF at galvanostatic anodization are described here in detail. Interestingly, duplex niobium oxide consisting of thick barrier oxide and correspondingly thick porous oxide was prepared at a constant current density of higher than 0.3 $mAcm^{-2}$, whereas simple porous type oxide was formed at a current density of lower than 0.3 $mAcm^{-2}$. In addition, simple barrier or porous type oxide was obtained by galvanostatic anodization at a single electrolyte of either 1 M $H_3PO_4$ or 1 wt % HF, respectively. The formation mechanism of duplex type structures was ascribed to different forming voltages required for moving anions.

• 한국초전도ㆍ저온공학회논문지
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• 제23권4호
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• pp.1-5
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• 2021

Among elemental metals, niobium (Nb) has the highest superconducting transition temperature (T_c) at ambient pressure. Thus, Nb films have been used in superconducting electronics and radio frequency cavity applications. In this study, the depositional factors determining the crystallinity and T_c of Nb films were investigated. An Nb film grown at a sputtering temperature of 240℃ exhibited the maximum crystallinity of Nb and the minimum crystallinity of niobium oxide. X-ray photoelectron spectroscopy confirmed a maximum atomic percent of niobium and a minimum atomic percent of oxygen. A sputtering power of 210 W and a sputtering time of 50 min were the optimal conditions for Nb deposition, and the T_c of the optimized film (9.08 K) was close to that of bulk Nb (9.25 K). Transmission electron microscopy images of the thick film directly confirmed the removal of the typical in-plane compressive strain in the (110) plane caused by residual stress.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 춘계학술발표대회 및 제12회 신소재 심포지엄
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• pp.37.1-37.1
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• 2007

• 한국재료학회:학술대회논문집
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• 한국재료학회 2001년도 추계 학술발표강연 및 논문개요집
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• pp.180-180
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• 2001

• 공업화학
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• 제9권1호
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• pp.129-134
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• 1998

프로판의 아크릴로니트릴로의 가암모니아 산화반응을 $Nb_2O_5-V_{0.4}Mo_1Te_{0.1}$ 혼합촉매를 이용하여 연구하였다. 가암모니아 산화반응의 촉매적 활성은 강한 산성을 띠는 니오피움산화물을 몰리브덴계 산화물촉매($V_{0.4}Mo_1Te_{0.1}$)에 첨가함에 따라서 증가하였으며, 이때 아크롤로니트릴과 프로필린의 선택율은 일정하게 유지되었다. 최대의 활성은 $Nb_2O_5-V_{0.4}Mo_1Te_{0.1}$ 촉매 중 니오비움산화물이 25wt%가 되었을 때 얻었으며, 니오비움산화물은 프로판의 탈수소과정에 선택적인 촉매임을 알았다.

• 한국재료학회지
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• 제28권5호
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• pp.308-314
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• 2018

Among the fuel cell electrolyte candidates in the intermediate temperature range, glass materials show stable physical properties and are also expected to have higher ion conductivity than crystalline materials. In particular, phosphate glass has a high mobility of protons since such a structure maintains a hydrogen bond network that leads to high proton conductivity. Recently, defects like volatilization of phosphorus and destruction of the bonding structure have remarkably improved with introduction of cations, such as Zr4+ and Nb5+, into phosphate. In particular, niobium has proton conductivity on the surface because of higher surface acidity. It can also retain phosphorus content during heat treatment and improve chemical stability by bonding with phosphorus. In this study, we fabricate niobium phosphate glass thin films through sol-gel processing, and we report the chemical stability and electrical properties. The existence of the hydroxyl group in the phosphate is confirmed and found to be preserved at the intermediate temperature region of $150-450^{\circ}C$.

• 한국재료학회지
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• 제15권4호
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• pp.217-223
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• 2005

Thermal, electrical and mechanical properties of high purity niobium and tantalum refractory rare metals were investigated tn evaluate the physical purity. Higher purity niobium and tantalum metals showed lower hardness due to smaller solution hardening effect. Temperature dependence of electrical resistivity showed a typical metallic behavior. Remarkable decrease in electrical resistivity was observed for a high purity specimen at low temperature. However, thermal conductivity increased for a high purity specimen, and abrupt increase in thermal conductivity was observed at very low temperature, indicating typical temperature dependence of thermal conductivity for high purity metals. It can be known that reduction of electron-phonon scattering leads to increase in thermal conductivity of high purity niobium and tantalum metals at low temperature.

• 한국재료학회지
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• 제15권2호
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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.