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Trapped Field Analysis of a High Temperature Superconducting Bulk with Artificial Holes
Guneik Jang,Mansoo Lee,Seungyong Han,Chanjoong Kim,Younghee Han,Byungjoon Park 한국자기학회 2011 Journal of Magnetics Vol.16 No.2
To improve trapped field characteristics of a high temperature superconducting (HTS) bulk, a technique to implement artificial holes has been studied. The artificial holes, filled up with epoxy or metal, may provide better cooling channel and enhance mechanical strength of the HTS bulk. Although many useful researches based on experiments have been reported, a numerical approach is still limited because of several reasons that include: 1) highly non-linear electromagnetic properties of HTS; and 2) difficulty in modeling of randomly scattered “small” artificial holes. In this paper, a 2-D finite element method with iteration is adopted to analyze trapped field characteristics of HTS bulk with artificial holes. The validity of the calculation is verified by comparison between measurement and calculation of a trapped field in a 40 × 40 ㎜ square and 3.1 ㎜ thick HTS bulk having 16 artificial holes with diameter of 0.7 ㎜. The effects of sizes and array patterns of artificial holes on distribution of trapped field within HTS bulk are numerically investigated using suggested method.
The Effect of Processing Parameters on HTS Tube Characteristics
Jung, Sengho,Jang, Guneik,Ha, Dongwoo,Sung, Taehyun The Korean Institute of Electrical and Electronic 2004 Transactions on Electrical and Electronic Material Vol.5 No.2
High-temperature Superconductor(HTS) tubes were fabricated in terms of different chemical compositions and various SrSO$_4$additions by centrifugal forming method. For powder melting by induction the optimum range of melting temperatures and preheating temperature were 1050$^{\circ}C$, 1100$^{\circ}C$ and 550$^{\circ}C$ for 30 min, respectively. The mould rotating speed was 1000 rpm. A tube was annealed at 840$^{\circ}C$ for 72 hours in oxygen atmosphere. The plates like grains more than 20 $\mu\textrm{m}$ were well developed along the rotating direction of mould regardless of initial chemical compositions and the amounts of SrSO$_4$in Bi2212. The specimen with Bi2212 composition exhibited T$\_$c/ of 83 K, while the specimens fabricated with other compositions are lower than 60 K. The measured I$\_$c/ and J$\_$c/ at 77 K(B = 0 T) in Bi2212 with 7 % SrSO$_4$ composition were about 680 A and 380 A/$\textrm{cm}^2$.
Mn-SnO<sub>2</sub>/Ag/Mn-SnO<sub>2</sub> 3중 다층막의 성능지수와 밴딩 특성
조영수,장건익,Cho, Youngsoo,Jang, Guneik 한국결정성장학회 2021 한국결정성장학회지 Vol.31 No.4
상온에서 PET 기판 위에 Mn-SnO<sub>2</sub>/Ag/Mn-SnO<sub>2</sub> 3중 다층막을 RF/DC 마그네트론 스파터링 방식으로 제조하였다. EMP 시뮬레이션 결과에 따라 Mn-SnO<sub>2</sub>의 막 두께는 40 nm, Ag 막 두께는 13 nm로 고정하였다. 550 nm 파장대역에서 측정한 3중막의 투과율은 82.9에서 88.1 % 범위였으며 면저항은 5.9에서 6.9 Ω/☐로 변화하였다. 가장 높은 성능지수(ϕ<sub>TC</sub>)는 48.1 × 10<sup>-3</sup> Ω<sup>-1</sup>로 나타났다. 곡률반경 4, 5 mm 조건에서 inner 밴딩과 out 밴딩의 굽힘시험을 10,000회 실시한 결과 Mn-SnO<sub>2</sub>/Ag/Mn-SnO<sub>2</sub> 3중막의 저항변화율은 약 1.5 %로 탁월한 기계적 유연성을 보였다. Typical Mn-SnO<sub>2</sub>/Ag/Mn-SnO<sub>2</sub> tri-layer films were prepared on a PET substrate by RF/DC magnetron sputtering method at room temperature. Based on EMP simulation, the thicknesses of the top and bottom Mn-doped SnO<sub>2</sub> layers were kept at 40 nm and the Ag layer was maintained at 13 nm for continuous electrical conduction. The experimentally measured optical transmittances at 550 nm wavelength were ranged from 82.9 to 88.1 % and sheet resistances were varied from 5.9 to 6.9 Ω/☐. The highest value of figure of merit, ϕ<sub>TC</sub> was 48.1 × 10<sup>-3</sup> Ω<sup>-1</sup>. Based on bending test under 4 and 5 mm of inner and outer curvature radius condition, tri-layer film resistance varies only by approximately 1.5 % after 10,000 bending cycles, showing excellent mechanical flexibility.
굴절율 조정층을 통한 SnO<sub>2</sub>/Ag/SnO<sub>2</sub> 막의 시인성 개선
김진균 ( Jingyun Kim ),장건익 ( Guneik Jang ) 충북대학교 산업과학기술연구소 2020 산업과학기술연구 논문집 Vol.34 No.2
SnO<sub>2</sub>/Ag/SnO<sub>2</sub> multi-layered thin films with refractive index matching layers were deposited on glass substrate by RF/DC magnetron sputtering system. In order to investigate the effect of IM (Index matching) layers, SiO<sub>2</sub>(n=1.51) and Nb<sub>2</sub>O<sub>5</sub>(n = 2.42) were inserted between SnO<sub>2</sub>/Ag/SnO<sub>2</sub> and glass substrate. Pattern visibility characteristics such as reflectivity (ΔR<sub>550nm</sub>) and color (Δb*) matching were systematically investigated. Reflectivities of SnO<sub>2</sub>(40nm)/Ag(10nm)/SnO<sub>2</sub>(30nm)/SiO<sub>2</sub>(10nm)/Nb<sub>2</sub>O<sub>5</sub>(10nm) multi-layer film measured on the top of multi-layer film stackup was 10.6% at 550 nm wavelength, However, reflectivities with IM layer only were 11.3%, suggesting that reflectivity variation was approximately within 1%. From the La*b* colour space represented by reflectivity spectra, the lightness (+L*) decreased from 91.5 to 89.9 and 91.2 to 89.4, whereas the yellowness (+b*) increased from 1.24 to 1.97 and 0.77 to 1.47, with increasing SnO<sub>2</sub> top layer thickness in multi-layer film.
혼합기체 O<sub>2</sub>/Ar+O<sub>2</sub> 농도 변화가 Mn 도핑된 SnO<sub>2</sub> 투명전도막의 상 안정성에 미치는 영향
김태근,장건익,Kim, Taekeun,Jang, Guneik 한국결정성장학회 2021 한국결정성장학회지 Vol.31 No.4
550 nm 파장대에서 O<sub>2</sub>/Ar+O<sub>2</sub> 혼합기체 농도비가 0에서 7.9 %로 변화 시 Mn 도핑된 SnO<sub>2</sub> 투명전도막의 투과율은 80.9에서 85.4 %로 밴드갭 에너지는 3.0에서 3.6 eV로 증가하였다. 비저항은 O<sub>2</sub>/Ar+O<sub>2</sub> 혼합기체 농도비가 0에서 2.7 %까지 증가 시 3.21 Ω·cm에서 0.03 Ω·cm으로 감소하다 이후 7.9 %로 증가 시에는, 52.0 Ω·cm으로 급격하게 상승하였다. XPS 분석결과 혼합기체 O<sub>2</sub>/Ar+O<sub>2</sub>에서 O<sub>2</sub> 농도의 증가로 Sn<sub>3d5/2</sub>의 결합에너지가 486.40에서 486.58 eV로, O<sub>1s</sub>의 결합에너지도 530.20에서 530.34 eV로 조금 변화하였다. 따라서 스파터링 방법으로 제조한 Mn 도핑된 SnO<sub>2</sub> 투명전도막에서 O<sub>2</sub> 농도변화에 따라 SnO와 SnO<sub>2</sub> 2개의 상이 공존하는 것을 확인하였다. The optical transmittance of Mn-doped SnO<sub>2</sub> monolayer film increased gradually from 80.9 to 85.4 % at 550 nm wavelengths upon increasing the O<sub>2</sub>/Ar+O<sub>2</sub> concentration rate from 0 to 7.9 % and the band gap energy changed from 3.0 to 3.6 eV. The resistivity tended to decrease from 3.21 Ω·cm to 0.03 Ω·cm, reaching a minimum at 2.7 %, and then gradually increased from 0.03 to 52.0 Ω·cm at higher O<sub>2</sub>/Ar+O<sub>2</sub> gas concentration ratio. Based on XPS spectra analysis, the Sn 3d<sub>5/2</sub> peak of Mn-doped SnO<sub>2</sub> single layer shifted slightly from 486.40 to 486.58 and O<sub>1s</sub> peak also shifted from 530.20 to 530.33 eV with increase the O<sub>2</sub>/Ar+O<sub>2</sub> concentration ratio. Therefore, the XPS spectra results indicate that a multiphase with SnO and SnO<sub>2</sub> coexisted in the sputtered Mn-doped SnO<sub>2</sub> monolayer film.