- Effects of Nano FexC Addition on Superconducting Properties of MgB2
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Dong-Gun Lee, Ji-Hyun Lee, Byung-Hyuk Jun, Soon-Dong Park, Young-Rang Uhm, Hai-Woong Park, Chan-Joong Kim
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J Korean Powder Metall Inst. 2012;19(2):146-150.
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DOI: https://doi.org/10.4150/KPMI.2012.19.2.146
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- The effects of nano Fe_xC addition to superconducting properties of in situ processed MgB_2 superconductors was examined. 0.1 wt.% and 1 wt.% nano Fe_xC powders were mixed with boron and magnesium powders by ball milling. The powder mixtures were made into pellets by uniaxial pressing. The pellets were heat-treated at 700°C-900°C in argon atmosphere for MgB_2 formation. It was found by powder X-ray diffraction that the raw powders were completely converted into MgB_2 after the heat treatment. The superconducting transition temperature (T_c) and critical current density (J_c), estimated from susceptibility-temperature and M-H curves, were decreased by nano Fe_xC addition. The T_c and J_c decrease by nano Fe_xC addition are attributed to the incorporation of iron and carbon with MgB_2 lattices (Fe substitution for Mg and C substitution for B) due to the high reactivity of the nano Fe_xC powder.
- Estimation of a Lattice Parameter of Sintered Ni-W Alloy Rods by a Neutron Diffraction Method
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Chan-Joong Kim, Min-Woon Kim, Soon-Dong Park, Byung-Hyuk Jun, Serk-Won Jang, Baek-Seok Seong
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J Korean Powder Metall Inst. 2008;15(3):239-243.
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DOI: https://doi.org/10.4150/KPMI.2008.15.3.239
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- Ni-W(1-5 at.%) alloy rods were made by powder metallurgy process including powder mixing, compacting and subsequent sintering. Ni and W powder of appropriate compositions were mixed by a ball milling and isostatically pressed in a rubber mold into a rod. The compacted rods were sintered at 1000°C-1150°C at a reduced atmosphere for densification. The lattice parameters of Ni-W alloys were estimated by a high resolution neutron powder diffractometer. All sintered rods were found to have a face centered cubic structure without any impurity phase, but the diffraction peak locations were linearly shifted with increasing W content. The lattice parameter of a pure Ni rod was 3.5238AA which is consistent with the value reported in JCPDS data. The lattice parameter of N-W alloy rods increased by 0.004AA for 1 atomic % of W, which indicates the formation of a Ni-W solid solution due to the substitution of nickel atoms by tungsten atoms of larger size.
- Superconducting Properties of Mg(B1-xCx)2 Bulk Synthesized Using Magnesium and Glycerin-treated Boron Powder
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Yi-Jeong Kim, Byung-Hyuk Jun, Soon-Dong Park, Kai Sin Tan, Bong-Goo Kim, Jae-Min Sohn, Chan-Joong Kim
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J Korean Powder Metall Inst. 2008;15(3):182-187.
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DOI: https://doi.org/10.4150/KPMI.2008.15.3.182
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- Carbon was known to be one of effective additives which can improve the flux pinning of MgB_2 at high magnetic fields. In this study, glycerin (C_3H_8O_3) was selected as a chemical carbon source for the improvement of critical current density of MgB_2. In order to replace some of boron atoms by carbon atoms, the boron powder was heat-treated with liquid glycerin. The glycerin-treated boron powder was mixed with an appropriate amount of magnesium powder to MgB_2 composition and the powder pallets were heat treated at 650°C;and;900°C for 30 min in a flowing argon gas. It was found that the superconducting transition temperature (T_c) of Mg(B_1-xC_x)_2 prepared using glycerin-treated boron powder was 36.6 K, which is slightly smaller than T_c(37.1 K) of undoped MgB_2. The critical current density (J_c) of Mg(B_1-xC_x)_2 was higher than that of undoped MgB_2 and the T_c improvement effect was more remarkable at higher magnetic fields. The T_c, decrease and J_c increase associated with the glycerin treatment for boron powder was explained in terms of the carbon substitution to boron site.
- Synthesis of Yba2Cu3O7-y Superconductor using a Low Purity BaCO3 Powder
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Chan-Joong Kim, Soon-Dong Park, Jung-Suk Choi, Byung-Hyuk Jun, Jong-Baik Moon, Sang-Heon Lee, Tae-Hyun Sung
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J Korean Powder Metall Inst. 2008;15(1):6-12.
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DOI: https://doi.org/10.4150/KPMI.2008.15.1.006
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- [ YBa_2Cu_3O_7-y ](123) powders were synthesized by the solid state reaction method using two different purity BaCO_3 powders (99.75% and 99.7% purity) and Y_2O_3 (99.9%) and CuO (99.9%) powders. The effect of BaCO_3 purity on the formation of a 123 phase and the superconducting properties were investigated. The mixtures of raw powders were calcined at temperature ranges of 800°C-880°C in air and finally made into a single grain samples by a melt processing with top seeding. It was found that a 123 phase was well formed at temperature above 870°C, but the purity effect on the 123 formation was negligible. The single-grain 123 samples prepared from the different BaCO_3 powders showed the same T_c value of 90.5 K and similar J_c values about 104;A/cm2 at 0 T and 77 K, and 103;A/cm2 at 2 T and 77 K. This result indicates that the low purity, cheap price BaCO_3 powder can be used as a raw material for the fabrication of single-grain, high-J_c superconducting levitator.
- Texture and Mechanical Properties of Ni-W Alloy Tapes Fabricated from Powder Mother Billets
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Min-Woo Kim, Byung-Hyuk Jun, Bong-Ki Ji, Kyu-Dong Jung, Chan-Joong Kim
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J Korean Powder Metall Inst. 2007;14(1):13-18.
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DOI: https://doi.org/10.4150/KPMI.2007.14.1.013
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- The mother Ni-W (1-5 wt.%) alloy billets for coated conductor substrate were fabricated by powder metallurgy process. The tensile test results for the sintered Ni-W rods showed the increase of mechanical strength and decrease of ductility with increasing W content due to the solid solution hardening. All the fracture surfaces of the tested specimens showed the typical ductile fracture mode of dimple rupture due to the local necking. The Ni-W alloy billets were made into tape by cold rolling. After the appropriate heat treatment for recrystallization, the brass texture formed by the cold rolling was converted to the complete cube texture. The in-plane and out of plane texture of the tapes estimated by x-ray pole figure were smaller than 9 degree and 7 degree, respectively. The effect of the W addition on the texture development seems not to be significant.
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Citations
Citations to this article as recorded by  - Production of textured ribbons based on Ni–W paramagnetic alloys
V.A. Finkel
Functional Materials.2013; 20(1): 103. CrossRef
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