• Progress in Superconductivity and Cryogenics
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• v.8 no.2
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• pp.25-28
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• 2006

The magnet system of KSTAR(korean Superconducting Tokamak Advanced Research) is consisted of 16 TF (Toroidal Field) coils and 14 PF (Poroidal Field) coils. Internal cooling CICC(Cable in Conduit Conductor) type conductor is used for both of TF and PF coil systems. The conduit material for $Nb_3Sn$ cable is Incoloy 908 and 316LN stainless-steel was used as conduit material for NbTi cable. $Nb_3Sn$ CICC is used for all TF coils and PF1-5 coils while NbTi CICC is used for PF6 and 7 coils. $Nb_3Sn$ and NbTi strands were made for KSTAR superconducting strand. They are satisfied with KSTAR superconducotr requirements. The $Nb_3Sn$ strands supplied from three companies; MELCO (Mitsubishi Electric Co.), OAS (Outokumpu Advanced Superconductor) and KAT (Kiswire Advanced Technology) were used. A special CICC jacketing system is developed for the KSTAR CICC fabrication which uses the tube-mill process consisted of forming, welding, sizing and squaring procedures. The. procedures for cabling and jacketing of CICC for TF and PF coils and their results including the geometrical specification and characteristics of strands are described.

• Molecules and Cells
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• v.20 no.1
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• pp.112-118
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• 2005

It was previously shown that AtNAP1 is a plastidic SufB protein involved in Fe-S cluster assembly in Arabidopsis. In this study, we investigated the effects of depleting SufB protein from plant cells using virus-induced gene silencing (VIGS). VIGS of NbNAP1 encoding a Nicotiana benthamiana homolog of AtNAP1 resulted in a leaf yellowing phenotype. NbNAP1 was expressed ubiquitously in plant tissues with the highest level in roots. A GFP fusion protein of the N-terminal region (M1-V103) of NbNAP1 was targeted to chloroplasts. Depletion of NbNAP1 resulted in reduced numbers of chloroplasts of reduced size. Mitochondria also seemed to be affected. Despite the reduced number and size of the chloroplasts in the NbNAP1 VIGS lines, the expression of many nuclear genes encoding chloroplast-targeted proteins and chlorophyll biosynthesis genes remained unchanged.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.333-336
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• 2005

The reduction behavior of $Nb_2O_5$ in aluminum containing self-reducing briquettes(SRNB) was investigated. The time required for slag/metal equilibrium was estimated as about 20 minutes from the addition of SRNB on to the surface of molten steel. The maximum yield of Nb was expected with the slag composition of $60\%CaO-40\%Al_2O_3$. When $CaCO_3$ was used as a flux, the oxidation loss of Al by $CO_2$ should be compensated, and the chemical equivalent ratio of Al to $Nb_2O_5$ of about 1.43 was required to maximize the yield of Nb.

• Korean Journal of Materials Research
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• v.2 no.1
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• pp.65-75
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• 1992

0.4wt%C steel added with V and/or Nb were forged and followed by air cooling. The structure-property relationships were examined and multiple regression analysis was conducted to quantify the magnitudes of effects of microalloying elements on the properties of the steels. All material's tensile strength are greater than $70kg/\textrm{mm}^2$, so they are equal to or superior to Q/T material's(S45C). Their impact energies are less than 40J, so they are 50% of Q/T material's. Increasing the content of V from 0.10 to 0.15 wt% had brought improvement in UTS about 20% but with some sacrifice of impact energy. These were the results from the precipitation strengthening by fine dispersion of VC in ferrite, increment of pearlite volume fraction and decrement of pearlite interlamellar spacings. However, increasing the content of Nb from 0.05 to 0.l0wt % slightly improved UTS and impact energy. NbC precipitates were more effective in suppression of austenite grain coarsening than VC precipitates. Combined additions of V+Nb were more effective to bring impact toughness than sole addition. Optimum combination of strength and toughness was accomplished wish 0.4C-1. 19Mn-0.05S-0.12V-0.07Nb steel.

• Journal of the Korean Magnetics Society
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• v.7 no.5
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• pp.250-257
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• 1997

The microstructure and magnetic properties of Fe-Nb-B-N thin film alloys, which produced by rf magnetron sputtering method in $Ar+N_2$ mixed gas atmosphere, were investigated. The $Fe_{70}Nb_{14}B_{11}N_5$ films, annealed at 59$0^{\circ}C$, exhibit soft magnetic properties: $4{\pi}M_s=16.5kG$ , $H_c=0.13Oe$ and ${\mu}_{eff}$ (1~10 MHz)=5, 000. The frequency stability of the Fe-Nb-B-N films has also been found to be good up to 10 MHz. The Fe-Nb-B-N thin film alloys annealed at 59$0^{\circ}C$ consist of three phase; fine crystalline $\alpha$-Fe phase with grain size of about 5~10 nm, Nb-B rich amorphous phase and Nb-nitride precipitates with the size of less than 3 nm. Annealed Fe-Nb-B films have two phases; $\alpha$-Fe grains with the size of about 10 nm and Nb-B rich amorphous phase. The addition of N decreased $\alpha$-Fe grain size due to the precipitation of NbN. The good magnetic properties of the Fe-Nb-B-N film alloys are due to fine $\alpha$-Fe grains resulting from the precipitation of NbN.

• Transactions of Materials Processing
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• v.30 no.6
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• pp.301-305
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• 2021

The role of Nb addition in the tension and corrosion responses of ferrite-based stainless-steel sheets processed by cold-rolling and annealing treatment at 1173 °K was studied to evaluate the possibility for commercialization. For this purpose, the grain sizes in the samples with and without Nb content were controlled to be reasonably identical by utilizing different heat treatments within the specific range for 60 seconds. The corrosion properties of both samples were evaluated based on the analysis of polarization curves. Room-temperature tension testing showed that the strength of the sample with Nb was much higher than that without Nb whereas the elongation of the sample with Nb was slightly lower than that without Nb. The polarization curves revealed that the addition of Nb contributed to the significant improvement in protective capabilities. We thought that such combinational behavior was mainly due to the formation of niobium carbides found in the ferritic matrix.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.581-585
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• 2006

Effects of V on both the formation of Ti-Nb-V carbonitrides and mechanical properties of Ti-Nb bearing low carbon HSLA steels were investigated. Hot rolling process was simulated by using Gleeble 3500 system with the steels containing three different levels of V ($0{\sim}0.1wt.%$). Vanadium precipitated as Ti-Nb-V carbonitrides at austenite region but it did not precipitate as VC during austenite to acicular ferrite or bainitic ferrite phase transformation. As V content increased, the amount of Nb precipitates was decreased but the average size of Ti-Nb-V carbonitrides was increased due to larger diffusivity of V than that of Nb. Coarsened Ti-Nb-V carbonitrides could act as heterogeneous nucleation site during ${\gamma}{\rightarrow}{\alpha}$ phase transformation, thus, acicular ferrite transformation was promoted as V content increased, resulting in increase of upper shelf energy.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.312-318
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• 2001

The mechanical and electrical properties of Cu-Nb filamentary nanocomposite fabricated by the bundling and drawing process were examined. The strength increased gradually with increasing Nb content while the ductility was insensitive to Nb content. The ratio of yield stresses at 293K and 75K are found to be 치ose to that of Young's moduli in various Cu-Nb nanocomposites, suggesting that athermal obstacles primarily control the strength. The fracture morphologies show ductile fractures irrespective of Nb contents. Secondary cracking along the interfaces between subelemental wires was occasionally observed and the frequency of secondary cracking increased with increasing Nb content. The conductivity and the resistivity ratio decreased with increasing Nb content. The decrease of the conductivity and the resistivity ratio(${\rho}_{293k}$/$\{rho}_{75k}$) can be explained by the increasing contribution of interface scattering.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.5
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• pp.260-266
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• 2003

In order to study the interfacial reaction between Nb thin sheet and Fe-C-(Si) alloy with different Chemical compositions, they were cast-bonded. The growth of carbide layer formed at the interface after isothermal heat treatment at 1173K, 1223K, 1273K and 1323K for various times was investigated. The carbide formed at the interface was NbC and the thickness of NbC layer was increased linearly in proportional to the heat treating time. Therefore, It was found that the growth of NbC layer was controlled by the interfacial reaction. The growth rate constant of NbC layer was slightly increased with increase of carbon content when the silicon content is similar in the cast irons. However, as silicon content increases with no great difference in carbon content, the growth of NbC layer was greatly retarded. The calculated activation energy for the growth of NbC layer was varied in the range of 447.4~549.3 kJ/moI with the compositions of cast irons.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.221-221
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• 2009