• Korean Chemical Engineering Research
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• 제44권3호
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• pp.259-264
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• 2006

염화반응에 의한 $TaCl_5$의 제조에서 반응생성물 중 $NbCl_5$, $TiCl_4$, $FeCl_2$ 등이 주요 불순물로 존재하게 된다. $TaCl_5$와 $NbCl_5$는 증류나 수소 환원법에 의해 쉽게 분리가 되므로, 반응생성물에서 $TaCl_5/NbCl_5$ 혼합물을 99.9％ 이상 순도로 분리하기 위해 2기의 연속식 증류공정을 사용하여 light한 성분과 heavy한 성분을 제거하는 공정을 구성하였다. 본고에서는 순차배열(direct sequence)과 비 순차배열(indirect sequence)으로서의 두 분리공정에 대한 비교연구를 상용성 화학공정모사기인 Aspen Plus 13.1을 이용해서 전산모사를 수행하였다. 비교결과 순차배열이 비 순차배열에 비하여 초기 장치투자비용이나 운전비용에서 좀 더 우수한 것으로 나타났다.

• 전기화학회지
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• 제5권4호
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• pp.183-188
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• 2002

The structure of species formed in $NbCI_5-I-ethyl-3-methylimidazolium$ chloride (EMIC) room-temperature molten salt (RTMS) was examined with the Raman spectroscopic measurement and ab initio molecular orbital calculation. The equilibrium structures of $NbCl_5,\;NbCl_6^-,\;Nb_2CI_{10},\;Nb_2CI_{11}^-,\;Nb_3CI_6^-,\;NbCI_6^--EMI^+\;(in\;which\;NbCI_6^-$ anion approaches $EMI^+$ cation with strong interaction) and $Nb_2CI_{11}^--EMI^+$ were obtained with the HF/LANL2DZ level of calculation. The harmonic frequencies at each equilibrium structure were compared with Raman spectra. The harmonic frequencies of $NbCI_6^--EMI^+,\; Nb_2CI_{11}^--EMI^+,\;and\;Nb_2CI_{10}$ were in good agreement with the Raman spectra of RTMS melts. In the $NbCI_5-EMIC RTMS$, the main species were $NbCI_6^-\;and\;EMI^+$. In the $NbCl_5-EMIC$ RTMS added $NbCl_5\;over\;50mol\%$, small amount of $Nb_2CI_{11}^-\;and\; Nb_2CI_{10}$ were also formed. The structures of anions and cation in the RTMS distorted from free ions with Coulomb force.

• 대한치과기공학회지
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• 제28권1호
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• pp.61-66
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• 2006

Titanium alloys have been used for dental materials due to it's very good biocompatibility. Ti-6Al-4V alloy instead of pure titanium is being widely used as biomaterials has some characteristics such as high fatigue strength, tensile strength and corrosion resistance. But it has been reported recently that the vanadium element expresses cytotoxicity and carcinogenicity and the aluminium element is related with dementia of Alzheimer type and neurotoxicity. The Ti-Nb alloys has designed and examined corrosion resistance. Ti-3wt.%Nb($\alpha$type), Ti-20wt.%Nb(${\alpha}+{\beta}$type) and Ti-40wt.%Nb($\beta$type) alloys were melted by vacuum arc furnace. The corrosion resistance of Ti alloys was evaluated by potentiodynamic polarization test in the solution of 0.9% NaCl and 5% HCl. The results can be summarized as follows: 1) For the corrosion test in the solution of 0.9% NaCl and 5% HCl, the corrosion behaviour of Ti-Nb alloys was similar to ASTM grade 2 CP Ti. 2) The corrosion resistance of Ti-20Nb alloy was better than that of CP-Ti, Ti-3Nb, Ti-40Nb alloy in 0.9% NaCl and 5% HCl, solutions.

• Bulletin of the Korean Chemical Society
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• 제28권7호
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• pp.1167-1170
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• 2007

A simple and convenient method for the addition of TMSCN to carbonyl compounds is described. NbCl5 is found to possess a strong Lewis acid property to transform carbonyl compounds smoothly to the corresponding cyanosilylether in high yields (up to 99 %) in solvent- free conditions.

• 한국자기학회지
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• 제25권5호
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• pp.139-143
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• 2015

CsCl 구조를 가지는 CoX(X = Ti, V, Nb) 이원화합물에서 (001) 표면계의 전자구조를 제일원리 전자구조 계산방법을 이용하여 계산하고 표면자성을 연구하였다. Co 원자로 끝나는 CoTi(001)계에서 표면 Co 원자의 자기모멘트는 가운데 층 Co 원자에 비해 상당히 증가한 $1.19{\mu}_B$였다. V 원자로 끝나는 CoV(001) 표면계에서 표면 V 원자의 자기모멘트는 가운데 층의 2.5배로서 $1.64{\mu}_B$이고, Co 원자로 끝나는 계에서 표면 Co 원자의 자기모멘트는 $1.34{\mu}_B$로 덩치 Co 원자에 비해 다소 감소하였다. CoNb(001)계에서 Nb 원자로 끝나는 계의 경우, 표면 Nb 원자의 자기모멘트는 가운데 층 Nb 원자에 비해 다소 감소한 $0.26{\mu}_B$였으며, Co 원자로 끝나는 표면계의 경우 자성이 사라졌다.

• 한국결정성장학회지
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• 제5권2호
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• pp.129-134
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• 1995

단결정 $KMnCl_3$, $LiNbO_3$ 및 $Mg-LiNbO_3$의 bulk 성질을 중성자 산란을 이용하여 측정하였다. 본 연구는 편광 빛을 사용하여 보이는 좋은 단결정이라도 이들의 bulk 성질을 정확히 파악하기 위하여는 중성자 산란으로 재측정하여야 함을 보여준다. 중성자 산란에서 나타나는 $KMnCl_3$, 의 큰 mosaic 분포는 이 결정이 단일 구역을 갖는 단결정이 아니고 축에 대해 작은 각으로 분포되어 있는 구역 군들이 상대적으로 여러 방향으로 존재함을 보여준다. $LiNbO_3$ 에서 나타는 작은 mosaic분포는 큰 구역들이 서로 가까이 정렬되어 있고 Mg가 첨가된 $LiNbO_3$ 는 잘 키워진 단결정으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제20권8호
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• pp.893-896
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• 1999

Novel citric acid based Ti, Nb and Ta precursors that are highly stable in the presence of water were developed. No alkoxides of Ti, Nb and Ta were utilized in the preparation, instead much less moisture-sensitive metallic Ti, NbCl5 and TaCl5 were chosen as starting chemicals for Ti, Nb and Ta, respectively. The feasibility of these chemicals as precursors is demonstrated in the powder synthesis of BaTi4O9, Y3NbO7 and LiTaO3. The water-resistant Ti precursor was employed as a new source of water-soluble Ti in the amorphous citrate method, and phase pure BaTi4O9 in powdered form was successfully synthesized at 800 ？. The Pechini-type polymerizable complex method using the water-resistant Nb and Ta precursors was applied to the synthesis of Y3NbO7 and LiTaO3, and both the powder materials in their pure form were successfully synthesized at reduced tempera-tures, viz. 500-700 ？. The remarkable retardation of hydrolysis of these water-resistant precursors is explained in terms of the partial charge model theory.

• 공업화학
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• 제5권5호
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• pp.862-870
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• 1994

출발물질로 $Pb(NO_3)_2$, $Mg(NO_3)_2$, $NbCl_5$를 선정하여 이들을 수용액상으로 $Pb(Mg_{1/3}Nb_{2/3})O_3$조성에 맞도록 각 수용액을 정확히 취하여 $Pb(Mg_{1/3}Nb_{2/3})O_3$ 1M용액이 되도록 조제하였다. 이 혼합용액은 상온에서 $PbCl_2$를 형성하므로 $70^{\circ}C$로 가열하여 $PbCl_2$를 용해시킨 후, 침전제 oxine을 가하여 pH 8~10에서 공침물을 얻었다. 이 침전물을 여과, 건조의 공정을 거처 $700{\sim}1000^{\circ}C$로 5시간 하소하여 $Pb(Mg_{1/3}Nb_{2/3})O_3$을 합성하였으며 합성된 분말은 평균입경이 $0.3{{\mu}m}$ 정도이고 모양은 구형이었다. 그리고 합성된 분말을 $2000Kg/cm^2$의 압력으로 성형하고, $1100{\sim}1200^{\circ}C$로 소성하여 이론밀도의 97.4%인 소결체를 얻었고 이때의 유전율은 1kHz에서 17000이고 유전손실은 상온에서 0.02%이었다.

• 대한치과기공학회지
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• 제23권2호
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• pp.223-230
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• 2002

Pure titanium and Ti6Al4V alloy have been mainly used as implant materials but the cytotoxicity of V, neurotoxicity of Al resulting in Alzheimer disease had been reported. This paper was described the influence of composition of Ti-Nb alloys with 3 wt%Nb, 20 wt%Nb on the microstructure and corrosion resistance. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at $1000^{\circ}C$ for 24hr. The alloys were rolled in $\beta$ and ${\alpha}+{\beta}$ regions. The corrosion resistance of Ti alloys were evaluated by potentiodymic polarization test in 0.9% NaCl and 5% HCl solutions. The results can be summarized as follows: 1. The microstructure was transformed from $\alpha$ phase to ${\alpha}+{\beta}$ phase by adding Nb 2. The hardness of Ti-20Nb alloy was greater than Cp- Ti, Ti-3Nb alloy. 3. The corrosion resistance of Ti-20Nb alloy was better than that of Cp-Ti, Ti-3Nb alloy in 0.9%NaCl and 5%HCl solutions.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 추계학술논문요약집
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• pp.299-300
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• 2018

Electrochemical behaviors of Nb ion in the $LiCl-KCl-NbCl_5$ molten salt were examined. Cyclic voltammograms with different scan rates and scan range at $450^{\circ}C$ showed possible electrochemical redox reactions which were identified by comparison to the literature data. Peak potentials for each redox reaction were consistent with the literature, but some redox reactions were not clearly defined due to the formation of subchloride compound in chloride salt. The electrochemical behaviors of Nb ion related to the subchloride formation as well as Nb metal deposition will be investigated for the future work.