• Proceedings of the Korean Nuclear Society Conference
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• 1998.10a
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• pp.229-229
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• 1998

• Corrosion Science and Technology
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• v.13 no.4
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• pp.152-156
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• 2014

This study was undertaken to examine the electrochemical corrosion properties of an $Co_{80}Nb_{10}B_{10}$ and $Co_{82}Nb_8B_{10}$ amorphous alloys prepared by melt-spinning method under various conditions. The potentiodynamic polarization responses at various levels of pH (pH 2, pH 7, pH 12) showed that the corrosion current rate of $Co_{80}Nb_{10}B_{10}$ alloy is lower than that of $Co_{82}Nb_8B_{10}$ alloy in all levels of pH, implying the general corrosion resistance of the alloy with higher Nb content is better than that with higher Co content. The pitting potential of $Co_{80}Nb_{10}B_{10}$ alloy was also better than that of $Co_{82}Nb_8B_{10}$, evidenced by the higher pitting potential. Nb is thought to be effective in increasing the protectiveness of the passive film and hence to improve the corrosion resistance of Co-Nb-B alloys.

• Korean Journal of Materials Research
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• v.25 no.8
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• pp.376-385
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• 2015

The effects of Nb and Cr addition on the microstructure, corrosion and oxide characteristics of Zr based alloys were investigated. The corrosion tests were performed in a pressurized water reactor simulated-loop system at $360^{\circ}C$. The microstructures were examined using OM and TEM, and the oxide properties were characterized by low-angle X-ray diffraction and TEM. The corrosion test results up to 360 days revealed that the corrosion rates were considerably affected by Cr content but not Nb content. The corrosion resistance of the Zr-xNb-0.1Sn-yCr quaternary alloys was improved by an increasing Nb/Cr ratio. The crystal structure of the precipitates was affected by a variation of the Nb/Cr ratio. The Zr-Nb beta-enriched precipitates were mainly formed in the high Nb/Cr ratio alloy while $Zr(NbCr)_2$ precipitates were frequently observed in the low Nb/Cr ratio alloy. The studies of oxide characteristics revealed that the corrosion resistance was related to the crystal structure of the precipitate.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.107-108
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• 2006

The effect of WC or NbC addition on various properties of Ti(C0.7N0.3)-Ni cermets was investigated. The microstructure oj Ti(C0.7N0.3)-xWC-20Ni showed a typical core/rim structure, irrespective of the WC content, whereas the structure oj Ti(C0.7N0.3)-xNbC-20Ni was different and was dependent on the NbC content. The hardness (HV) and the fracture toughness (KIC) had a tendency to increase marginally, while the coercive force (HC) and the magnetic saturation $(4{\pi}{\sigma})$ decreased gradually with an increase in WC or NbC content in the systems studied. In addition, increasing WC content in Ti(C0.7N0.3)-xWC-20Ni system, decarburization was retarded, while denitrification was accelerated

• Korean Journal of Materials Research
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• v.9 no.5
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• pp.452-459
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• 1999

To develop advanced cladding materials, the effect of Nb addition on the microstructure and corrosion characteristics of Zr-0.8Sn-xNb alloys was investigated. As the Nb content increased, the grain size decreased and the volume fraction of precipitates increased. It was observed from the corrosion test at $360^{\circ}C$ that the corrosion resistance increased with decreasing Nb content. The best corrosion resistance was obtained in Zr-0.8Sn-0.2Nb alloy with high volume fraction of tetra-$ZrO_2$in the oxide. Therefore, it is suggested that Nb in theZr-0.85Sn-xNb system should be added within the solubility limit of Nb from the viewpoint of alloy design.

• Journal of the Korean institute of surface engineering
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• v.41 no.2
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• pp.57-62
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• 2008

Electrochemical properties of Ti-30Ta-$(3{\sim}15)$Nb alloys coated by HA/Ti compound layer have been studied by various electrochemical method. Ti-30Ta binary alloys contained 3, 7, 10, and 15 wt% Nb contents were manufactured by the vacuum furnace system. The specimens were homogenized for 24 hrs at $1000^{\circ}C$. The samples were cut and polished for corrosion test and coating. It was coated with HA/Ti compound layer by magnetron sputter. The HA/Ti non-coated and coated morphology of Ti alloy were analyzed by x-ray diffractometer(XRD) and filed emission scanning electron microscope(FE-SEM). The corrosion behaviors were investigated using potentiodynamic method in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The homoginazed Ti-30Ta-$(3{\sim}15wt%$)Nb alloys showed the ${\alpha}+{\beta}$ phase, and ${\beta}$ phase peak was predominantly appeared with increasing Nb content. The microstructure of Ti alloy was transformed from needle-like structure to equiaxed structure as Nb content increased. HA/Ti composite surface showed uniform coating layer with 750 nm thickness. The corrosion resistance of HA/Ti composite coated Ti-alloys were higher than those of the non-coated samples in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. Especially, corrosion resistance of Ti-Ta-Nb system increased as Nb content increased.

• Corrosion Science and Technology
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• v.8 no.4
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• pp.143-147
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• 2009

In biomedical implants and dental fields, titanium has been widely utilized for excellent corrosion resistance and biocompatibility. However, Ti and its alloys are nonbioactive after being implanted in bone. In this study, for the purpose of improvement in biocompatibility the anodic $TiO_2$ layer on Ti-xNb alloys were fabricated by electrochemical method in phosphate solution, and the effect of Nb content on the pore size, the morphology and crystallinity of Ti oxide layer formed by the anodic oxidation method was investigated. The Ti containing Nb up to 3 wt%, 20 wt% and 40 wt% were melted by using a vacuum furnace. The sample were cut, polished, and homogenized for 24 hr at $1050^{\circ}C$ for surface roughness test and anodizing. Titanium anodic layer was formed on the specimen surface in an electrolytic solution of 1 M phosphoric acid at constant current densities ($30mA/cm^2$) by anodizing method. Microstructural morphology, crystallinity, composition, and surface roughness of oxide layer were observed by FE-SEM, XRD, EDS, and roughness tester, respectively. The structure of alloy was changed from $\alpha$-phase to $\beta$-phase with increase of Nb content. From XRD results, the structure of $TiO_2$ formed on the Ti-xNb surface was anatase, and no peaks of $Nb_2O_5$ or other Nb oxide were detected suggesting that Nb atoms are dispersed in $TiO_2$-based solid solution. Surface roughness test and SEM results, pore size formed on surface and surface roughness decreased as Nb content increased. From the line analysis results, intensity of Ti peak was high in the center of pore, whereas, intensity of O peak was high in the outside of pore center.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.441-443
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• 2005

According as CCFL(Cold Cathode Fluorescent lamp) of light source in Backlight unit for Note PC (Personal computer) is presently needed to low power consumption and long life time, the development focus of CCFL is going on the discharge gas, phosphor and electrode material. First of all, discharge voltage characteristic of CCFL is closely connected with electrode material For low discharge voltage, the characteristic of electrode material is needed to low work function, low sputtering ratio and superior manufacturing property. We developed new CCFL with Nb/Ni Clad electrode superior to conventional CCFL. Because Nb/Ni Clad electrode with Ni material and Nb material, the electrical characteristic is superior to other electrode materials. The electrode of Nb/Ni Clad is composed that Ni of outside material has superior manufacturing property and Nb of inside material has low work function. Nb/Ni Clad of new electrode material is made by process of Rolling mill at high pressure and heat treatment. We compared electrical characteristic of Nb/Ni clad electrode with conventional Mo electrode by measurement. Mo electrode and Nb/Ni Clad electrode of cup type with diameter 1.1 mm and length 3.0mm are used to this experiment. Material content of Mo electrode is Mo 100%. But, Nb/Ni Clad electrode is composed by content of Nb 40% and Ni 60%. The result of comparison measurement between new CCFL with Nb/Ni Clad electrode and conventional CCFL was appeared that CCFL with Nb/Ni Clad electrode had superior characteristic than conventional CCFL. As a result of experiment, we completed Note PC with low power consumption and long life time by application of new CCFL with Nb/Ni Clad electrode.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.64-71
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• 2003

In order to evaluate the effect of alloying elements (Nb and Sn) on the wear resistance of advanced Zr fuel claddings, sliding wear tests have been performed in room temperature air and water and these results were compared with those of commercial alloys such as Zircaloy-4, A and B alloys. As a result, the advanced Zr fuel claddings have a similar wear resistance compared with the commercial alloys. The wear resistance of the advanced Zr fuel claddings is closely releted to the content of Nb and Sn even though the effects of transition elements are involved in deforming wear properties. In the tested specimens with similar Sn content, wear volume became down to a minimum at $0.4\;wt\;\%$ Nb, then rapidly increased at 1.0 wt Nb. This behavior results in the variation of grain size with alloying contents. But Sn did not have a significant effect on the wear volume of advanced Zr fuel claddings below $1.1\;wt\%$. The relationship between alloying elements and wear behaviour was evaluated and discussed using material compatibility factor.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.2
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• pp.88-95
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• 2022

Titanium alloy for bio-medical applications have been developed to reduce the toxicity of alloying elements and avoid the stress-shielding effect which is caused by relatively high elastic modulus compared to bone. Ti-39Nb-6Zr (TNZ40) alloy of elastic modulus exhibits around 40 GPa in the case of beta single phase. However, the strength of this alloy is lower than the other types of titanium alloys. Many research found that adding oxygen to beta-titanium alloys is beneficial for improving the strength through solid solution strengthening. In this study, TNZ40 ingots with addition of O were prepared by an arc remelting process (Ti-39Nb-6Zr-0.16O (wt.%), Ti-39Nb-6Zr-0.26O (wt.%)). Thermo-mechanical processing (i.e., heat treatment, cold swaging and aging heat treatment) has been performed under various conditions. Therefore, the aim of this study is to investigate the effect of oxygen content and ω phase formation on microstructure and mechanical properties.