• Title/Summary/Keyword: 니오비움

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Aluminum Equivalent Filter As an Inexpensive Alternative to the Niobium Filter in Reducing Patient Dose (환자에게 주는 선량을 감소시켜주는 니오비움 필터의 대체물로서의 저렴한 알루미늄 필터)

  • Kim, Chang-Sean
    • Progress in Medical Physics
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    • v.6 no.2
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    • pp.3-12
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    • 1995
  • A 50 $\mu\textrm{m}$ thick niobium filter and its quantitatively determined aluminum equivalent filter were evaluated for effects on entrance skin dose, image quality, and x-ray tube loading for three different tube voltages in radiology. There was no significant difference in the reducion in entrance skin dose and increase in tube loading between two filters while keeping radiographic contrast on the film. For the clinical use of the aluminum equivalent filter as an alternative to the niobium filter in radiology, aluminum equivalent filter thickness at the mid energy range of radiology, 90 kVp, was measured and the filter was applied to the other kVp values, 73 and 125 kVps, to evaluate the effect on the entrance skin dose and tube loading. There was no significant difference between two filter cases at the selected kVp. The aluminum filter with equivalent thickness can be used as an inexpensive alternative to the niobium filter.

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Studies on the Selective Oxidation of Niobium Containing Mixed Metal Oxide Catalysts (니오비움 함유 복합 금속산화물 촉매의 선택산화반응에 관한 연구)

  • Kim, Young-Chul;Kim, Hyeong-Ju;Moon, Dong-Ju
    • 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.

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Kinetics of High Temperature Oxidation of a Nb-Added Zr Alloy in Steam (Nb첨가 지르코늄 합금의 고온산화 거동 연구)

  • 박광헌;유태근;김성권;김현길;정용환;김규태
    • Journal of the Korean institute of surface engineering
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    • v.34 no.6
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    • pp.585-591
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    • 2001
  • 니오비움 첨가 지르코늄 합금(Zr-1%Nb)의 고온 수증기에서 산화속도에 관한 연구를 수행하였다. 산화온도는 $700-1200^{\circ}C$이다. 대기압수증기에서 산화될 때, Zr -1%Nb은 2차법칙을 따르는 것으로 나타났으며, 이는 $900^{\circ}C$이하에서 3차법칙을 따르는 지 르칼로이 -4와 상이한 형태를 보이고 있다. $900^{\circ}C$이상에선 산화속도가 지르칼로이 -4보다 약간 낮으며, 산화후 금속층의 경도가 증가하였다. 경도증가로 보아 인성의 감소가 예상되며, 따라서 니오비움 첨가 지르코늄 합금의 사고시 안전성에 대한 주의가 요구된다.

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The synthesis of ultrathin Nb-doped TiOx nanosheets (초박막 두께의 Nb-TiOx 나노시트 합성)

  • Lee, Sang Eun;Seo, Jun;Park, Hee Jung
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.30 no.5
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    • pp.194-199
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    • 2020
  • By controlling the composition of the metal-oxide nanosheet having a two-dimensional layered crystal structure, material properties and application can be extended. In this study, the composition of the nanosheet could be expanded from pure composition to doping composition by successfully synthesizing the TiO2 nanosheet doped with Nb. Specifically, the doping composition was designed when synthesizing the layered metal oxide as a starting material (K0.8Ti1.73-xNbxLi0.27O4, x = 0, 0.03, 0.07) and chemical exfoliation was performed. By doing this, it was possible to obtain the Nb-doped TiOy ultrathin nanosheet. The size of the nano sheet was 2 ㎛ or less based on the long length in the x-y direction, and the thickness was about 1 nm. Nb-doping was confirmed by XRD and SEM-EDS analysis.

티타늄 알루미나이드 합금의 산화연구

  • 이원식;이재희
    • Proceedings of the Korean Vacuum Society Conference
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    • 1999.07a
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    • pp.48-48
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    • 1999
  • 티타늄 알루미나이드 합금은 이들의 강도나 고온 특성 때문에 초음속 비행기의 구조물질이나 수소를 연료로 사용하는 비행기의 엔진물질로 각광받고 있다. 그러나 티타늄 알루미나이드 합금들은 이들이 갖는 규칙적인 미세구조로 인하여 실온에서 낮은 연성을 나타내는 단점이 있다. 실온에서 낮은 연성을 갖는 티타늄 알루미나이드 합금의 단점은 텅스텐, 물리브덴, 니오비움, 탄타륨, 바나디움 등의 베타 안정화 물질들을 첨가함으로서 어느정도 극복되고 있다. 따라서 티타늄 알루미나이드 합금이 초음속 비행기의 구조 물질이나 수소를 사용하는 엔진 물질로 사용되기 위해서는 이 물질들의 산화연구가 필수적이다. 지금까지 티타늄의 산화연구에서 알루미늄이나 니오비움의 역할에 대해서는 여러 연구자들이 연구를 한 바 있다. Chaze와 Coddet는 알루미늄이 티타늄에서 산소의 용해도를 감소시키고, Chen과 Rosa는 니오비움이 티타늄에서 산화물 형성율을 낮춘다는 것을 각각 알아냈다. 그러나 지금까지 티타늄 알루미나이드의 산화연구는 충분하지 못했다. 지금까지 티타늄 알루미나이드의 산화연구에서 밝혀진 산화운동학의 내용은 가열온도와 가열시간에 따라 크게 다른 두 개 혹은 그 이상의 산화물을 갖는다는 것이다. 본 연구의 목적은 여러 가지 티타늄 알루미나이드 합금의 산화특성을 밝히는 것이다. 이를 위하여 첫 번째 실험은 실온 공기 중에서 자연적으로 산화된 여러 가지 티타늄 알루미나이드 합금들($\alpha$2,$\beta$,${\gamma}$)을 초고진공($\leq$10-11Torr)속에 넣고, 시료의 온도를 실온에서 100$0^{\circ}C$까지 변화시키면서 AES(Auger Electron Spectroscopy)와 ISS(Ion Scattering Spectroscopy)를 사용하여 각각의 온도에서 여러 가지 시료들의 표면조성을 조사했다. 두 번째 실험은 티타늄 알루미나이드 시료를 고순도 공기(hydrocarbon$\leq$0.1^g , pp m) 중에서 각각 $600^{\circ}C$에서 100$0^{\circ}C$까지 가열하여 산화시켰다. 이 시료의 산화도는 각각의 가열온도에서 가열시간을 변하시키면서 TGA(Thermogravimetric Apparatus)로 측정했다. 실온 공기중에서 자연적으로 산화된 여러 가지 티타늄 알루미나이드 합금들을 초고진공속에 넣어 100$0^{\circ}C$까지 가열한 실험에서는 이들 시료에 포함된 알루미늄의 양에 따라서 표면 조성이 크게 다른 것을 알 수 있었다. 그리고 고순도 공기 중에서 100$0^{\circ}C$까지 가열하여 산화시킨 티타늄 알루미나이드 산화물의 산화기구는 명백한 3단계 포물선 산화의 특성을 나타냈다.

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Geology and Mineralization of Mwanza and Kongolo in DR Congo Tin belt (콩고민주공화국 무완자-콩골로 지역 주석광화대의 지질 및 광화작용)

  • Yang, Seok-Jun;Park, Sung-Won;Koh, Sang-Mo
    • Economic and Environmental Geology
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    • v.45 no.6
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    • pp.709-719
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    • 2012
  • Prospection was performed on the tin mineralized belt in Mwanza and Kongolo areas of Katanga, DR Congo. Most of deposits in Katanga areas are related to the granites which are located in Kibaran belt in NE and SW trends of mid Proterozoic. Metasedimentary rocks in the Kibaran belt are intruded by granites, and tin, niobium and tantalum deposits are especially developed along with tin-granite. Cassiterite, coltan and gold are developed in the pegmatite, quartz vein and greisen in related to the tin-granite in Mwanza and Katanga areas, and they are exploited by artisan in the smale scale. And we conducted the works with the alluviums and stream sediments in the case of no outcrops. With the results of analysis of samples, we will choose a few potential mineralized zones and con-tinue to prosepect precisely.

Fabrication and Operating Properties of Nb Silicide-coated Si-tip Field Emitter Arrays (니오비움 실리사이드가 코팅된 실리콘 팁 전계 방출 소자의 제조 및 동작 특성)

  • Ju, Byeong-Kwon;Park, Jae-Seok;Lee, Sangjo;Kim, Hoon;Lee, Yun-Hi;Oh, Myung-Hwan
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.7
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    • pp.521-524
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    • 1999
  • Nb silicide was formed on the Si micro-tip arrays in order to improve field emission properties of Si-tip field emitter array. After silicidization of the tips, the etch-back process, by which gate insulator, gate electrode and photoresist were deposited sequentially and gate holes were defined by removing gradually the photoresist by $O_2$ plasma from the surface, was applied. Si nitride film was used as a protective layer in order to prevent oxygen from diffusion into Nb silicide layer and it was identified that the NbSi2 was formed through annealing in $N_2$ ambient at $1100^{\circ}C$ for 1 hour. By the Nb silicide coating on Si tips, the turn-on voltage was decreased from 52.1 V to 32.3 V and average current fluctuation for 1 hour was also reduced from 5% to 2%. Also, the fabricated Nb silicide-coated Si tip FEA emitted electrons toward the phosphor and light emission was obtained at the gate voltage of 40~50 V.

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Surface Characterization of Anodized and Hydrothermal Treated Niobium Metal (양극산화와 열수처리한 니오비움 금속의 표면특성)

  • Won Dae-Hee;Kim Young-Soon;Yoon Dong-Joo;Lee Min-Ho;Bae Tae-Sung
    • 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.

Evaluation of Biocompatibility of Anodized and Hydrothermally Treated Pure Niobium Metal (양극산화와 열수처리한 순수 니오비움 금속의 생체활성 평가)

  • Won, Dae-Hee;Choi, Un-Jae;Lee, Min-Ho;Bae, Tae-Sung
    • 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).

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