• 한국재료학회지
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• 제29권5호
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• pp.328-335
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• 2019

Nb-doped $TiO_2$(NTO) coated NiCrAl alloy foam for hydrogen production is prepared using ultrasonic spray pyrolysis deposition(USPD) method. To optimize the size and distribution of NTO particles based on good physical and chemical stability, we synthesize particles by adjusting the weight ratio of the Nb precursor solution(5 wt%, 10 wt% and 15 wt%). The morphological, chemical bonding, and structural properties of the NTO coated NiCrAl alloy foam are investigated by X-ray diffraction(XRD), X-ray photo-electron spectroscopy(XPS), and Field-Emission Scanning Electron Microscopy(FESEM). As a result, the samples of controlled Nb weight ratio exhibit a common diffraction pattern at ${\sim}25.3^{\circ}$, corresponding to the(101) plane, and have chemical bonding(O-Nb=O) at 534 eV. The NTO particles with the optimum weight ratio of N (10 wt%) show a uniform distribution with a size of ~18.2-21.0 nm. In addition, they exhibit the highest corrosion resistance even in the electrochemical stability estimation. As a result, the introduction of NTO coated NiCrAl alloy foam by USPD improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the foam and the electrolyte. Thus, the optimized NTO coating can be proposed for excellent protection of NiCrAl alloy foam for hydrocarbon-based steam methane reforming(SMR).

• 한국주조공학회지
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• 제22권3호
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• pp.114-120
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• 2002

A new titanium based alloy, Ti-10Ta-10Nb, has designed to examine the improved mechanical properties and biocompatibility. A specimen of titanium alloy was melted in a consumable vacuum arc furnace and homogenized at $1050^{\circ}C$ for 24 h. The effect of hot rolling on microstructure was estimated after rolling at $400^{\circ}C$ and $800^{\circ}C$ respectively. Surface of melted alloy by consumable vacuum arc melting was consisted of rough surface and it was changed to sound surface by coating of $ZrO_2$ slurry on copper mold surface. The hardness of Ti-10Ta-10Nb alloy increased with the amount of${\alpha}+{\beta}$ phase. Ti-10Ta-10Nb alloy showed $Widmanst{\"{a}}ten$ structure by hot rolling at $800^{\circ}C$ and in the rolling ${\beta}-region$ was negligible effects on microstructure refining.

• 대한치과기공학회지
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• 제24권1호
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• pp.95-104
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• 2002

For biomedical applications, Ti-X%Zr-Y%Nb-0.2%Pd(X:10$\sim$20, Y:2$\sim$8) alloys not containing harmful Al and V were newly designed, and the effect of alloy composition and heat treatment on the microstructure and mechanical properties was investigated. From the results, it was shown that the mechanical properties were enhanced with the addition of Zr or Nb. The effect of heat treating on room temperature strength was investigated by aging treatment after solution treatment. The mechanical properties of Ti-20%Zr-4%Nb-0.2%Pd alloy aged at 400$^{\circ}C$ for 10hrs was found to be superior to those of the pure Ti and Ti-6%Al-4%V ELI alloy.

• 대한치과기공학회지
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• 제23권1호
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• pp.55-64
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• 2001

This study is focusing on the improvement of problems of Ti-6Al-4V alloy. A new Ti based alloy, Ti-15Sn-4Nb, have designed to examine any possibility of improving the mechanical properties and biocompatibility. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at $100^{\circ}C$ for 24h. All specimens were solution treated at $812^{\circ}C$ and aged at $500^{\circ}C$ for 10h. The corrosion resistance of Ti alloys was evaluated by potentiodynamic polarization test and immersion test inl%Lactic acid solutions. Ti-15Sn-4Nb system alloys showed Widmanstatten microstructure after solution treatment which is typical microstructure of ${\alpha}+{\beta}$ type Ti alloys. Analysing the corrosion resistance of Ti alloys, it was concluded that the passive films of Ti-15Sn-4Nb system alloys are more stable than that of Ti-6Al-4V alloys. Also, the corrosion resistance of Ti-15Sn-4Nb system alloys was improved with adding elements, Hf. It was analysed that the passive film of the Ti-15Sn-4Nb alloy which was formed in air atmosphere was consisted of TiO2, SnO and NbO through X-ray photoelectron spectroscopy(XPS) analysis.

• 한국재료학회지
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• 제11권6호
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• pp.453-459
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• 2001

미세조직에 따라 기계적 성질 및 내산화성.내부식성 등의 제반 성질이 크게 변하는 Zr계 핵연료 피복관은 미세조직의 최적화가 중요하다. 이러한 미세조직은 합금원소의 고용도에 크게 의존하지만, Zr은 대부분의 용질합금원소의 고용도가 매우 작아서 측정이 곤란하였다. 본 연구에서는 핵연료 피복관 재료의 주요한 기본조성 재료인 Zr-0.8Sn 합금에 대한 Nb의 고용도를 TEP 측정방법을 이용하여 연구하였으며, 광학현미경과 전자현미경으로 미세조직을 관찰하여 이를 확인하였다. 균질화 처리온도가 증가함에 따라 고용된 Nb 함량이 증가하여 Zr-0.8Sn 합금의 TEP는 감소하는 경향을 보였다. 처리온도가 더욱 증가하면 TEP의 포화가 발생하였는데 이는 TEP에 영향을 미치는 고용된 합금원소의 함량 변화가 없기 때문이다. 따라서, TEP의 포화영역이 나타나기 시작하는 균질화 처리온도가 첨가된 Nb이 Zr-0.8Sn 합금에 모두 고용되는 시점이며, 이를 토대로 온도에 따른 Zr-0.8Sn 합금에서의 Nb 고용도 ($C_{Nb}$ )를 $4.69097{\times}10^{16}{\times}e^{-25300\times\;I/T}$(ppm.at.%)로 나타낼 수 있었다.

• 한국재료학회지
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• 제9권2호
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• pp.188-194
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• 1999

2원계 (Zr-xNb, Zr-xSnl 와 3원계 (Zr-O.8Sn-xNb, Zr-O.4Nb-xSnl Zr합금의 기계적 특성에 미치는 Nb와 Sn의 영향올 조사하기 위하여 인장시험 빛 마세조직 분석을 실시하였다. Nb와 Sn량이 많이 첨가될수록 2원계와 3원계 합금의 강도는 정진적으로 증가하는 경향을 보이는데, Nb와 Sn이 고용도 이상으로 첨가될 때 강도중가는 더욱 두드러진 것으로 냐타났다. 강도 증가현상을 고용강화, 석출강화, 결정립 미세화에 의한 강화, 집합조직에 의한 강화효과 관정에서 분석한 결과, 고용강화 효과가 가장 두드러지며 Nb와 Sn이 고용도 이상에서는 석출강화가 강도에 기여하는 것으로 냐타났다. 합금원소 첨가에 따른 결정립미세화도 강도에 약간은 영향을 미치는 것으로 사료된다. 그러나 집합조직은 합금원소 변화에 따라서 거의 변화가 없는 것으로 냐타났으므로 집합조직은 강도증가에 기여하지 않는 것으로 생각된다.

• 대한금속재료학회지
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• 제48권1호
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• pp.1-7
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• 2010

Experiments have demonstrated that the addition of a moderate amount of V to $Fe_{52}Co_{(20-x)}B_{20}Si_4Nb_4V_x$ amorphous alloy enhances the plasticity of the alloy. In particular, $Fe_{52}Co_{17.5}B_{20}Si_4Nb_4V_{2.5}$ alloy withstood a maximum of 8.3% strain prior to fracture along with a strength exceeding 4.7 GPa. Energy dispersive x-ray spectroscopy conducted on the $Fe_{52}Co_{17.5}B_{20}Si_4Nb_4V_{2.5}$ alloy exhibited evidence of compositional modulation, indicating that nm-scale phase separation had occurred at local regions. In this study, the role played by nm-scale phase separation on the plasticity was investigated in terms of structural disordering and shear localization in order to better understand the structural origin of the enhanced plasticity shown by the developed alloy.

• Journal of Magnetics
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• 제16권3호
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• pp.211-215
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• 2011

The dynamic magnetostriction characteristics of an Fe-based nanocrystalline FeCuNbSiB alloy are investigated as a function of the dc bias magnetic field. The experimental results show that the piezomagnetic coefficient of FeCuNbSiB is about 2.1 times higher than that of Terfenol-D at the low dc magnetic bias $H_{dc}$ = 46 Oe. Moreover, FeCuNbSiB has a large resonant dynamic strain coefficient at quite low Hdc due to a high mechanical quality factor, which is 3-5 times greater than that of Terfenol-D at the same low $H_{dc}$. Based on such magnetostriction characteristics, we fabricate a new type of transducer with FeCuNbSiB/PZT-8/FeCuNbSiB. Its maximum resonant magnetoelectric voltage coefficient achieves ~10 V/Oe. The ME output power reaches 331.8 ${\mu}W$ at an optimum load resistance of 7 $k{\Omega}$ under 0.4 Oe ac magnetic field, which is 50 times higher than that of the previous ultrasonic-horn-substrate composite transducer and it decreases the size by nearly 86%. The performance indicate that the FeCuNbSiB/PZT-8/FeCuNbSiB transducer is promising for application in highly efficient magnetoelectric energy conversion.

• Journal of Magnetics
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• 제19권4호
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• pp.327-332
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• 2014

The effect of minor element additions (Ca, Al) on microstructural change and magnetic properties of Fe-Nb-Cu-Si-B alloy has been investigated, in this paper. The Fe-Si-B-Nb-Cu(-Ca-Al) alloys were prepared by arc melting in argon gas atmosphere. The alloy ribbons were fabricated by melt-spinning, and heat-treated under a nitrogen atmosphere at $520-570^{\circ}C$ for 1 h. The soft magnetic properties of the ribbon core were analyzed using the AC B-H meter. A differential scanning calorimetry (DSC) was used to examine the crystallization behavior of the amorphous alloy ribbon. The microstructure was observed by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The addition of Ca increased the electrical resistivity to reduce the eddy current loss. And the addition of Al decreased the intrinsic magnetocrystalline anisotropy $K_1$ resulting in the increased permeability. The reduction in the size of the ${\alpha}$-Fe precipitates was observed in the alloys containing of Ca and Al. Based on the results, it can be concluded that the additions of Ca and Al notably improved the soft magnetic properties such as permeability, coercivity and core loss in the Fe-Nb-Cu-Si-B base nanocrystalline alloys.

• 한국주조공학회지
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• 제22권6호
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• pp.288-292
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• 2002

Ni-base amorphous alloys were manufactured using melt-spinning and Cu-mold die casting methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties were examined. The reduced glass transition temperature and the supercooled liquid region of $Ni_{51} Nb_{20} Zr_9 Ti_9 Co_8 Cu_3$alloy were 0.621 and 46 K respectively. $Ni_{51} Nb_{20} Zr_9 Ti_9 Co_8 Cu_3$ alloy was produced in the rod shape 3mm diameter using the Cu-mold die casting. Hardness, compression strength, elongation and elastic modulus of the alloy were 850 DPN, 2.75 GPa, 1.8% and 150 GPa respectively. Moreover, compression strength of 2.75 GPa was the highest value in the amorphous bulk alloy produced up to now.