• 한국전기전자재료학회논문지
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• 제11권11호
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• pp.1028-1034
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• 1998

Bi-2223 superconductor is known as one of the candidates for practical superconducting wires. Ag-sheathed Bi-2223 superconducting wires were fabricated using the powder-in-tube(PIT) method. When the 19-filaments wire was immersed in liquid nitrogen(77K), maximum critical current density Jc of 62 A/$mm_2$ at 0T was achieved. The critical current density has been shown to depend on the mechanical properties such as tensile stress and bending strain in Ag-sheathed Bi-2223 superconducting wires. The tensile strain for Jc degradation onset was in the range of 0.12~0.3%. In the case of 19-filaments wire, the bending strain is estimated to be smaller than 0.3% for the reasonable Jc value. The observed degradation of the critical current density due to strain effect is inevitable and can be attributed to the formation of microcracks within the superconducting core.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.274-277
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• 2003

Critical current(Ic) degradation of HTS tapes after bending is one of the hottest issues in HTS development and application studies. Many people are measuring Ic degradations for effect of bending radius. However even if the bending radius is larger than the breaking radius a HTS tapes can be damaged by repetitive bending, which is unavoidable in the winding processes. Therefore, We studied the Ic degradation after repetitive bending. at 77K with self-field, of Bi-2223 tapes processed by "Powder-in-Tube" technique, which was made by America Superconductor Corporation(AMSC) and superconductiing tapes that strain is imposed measured critical current by temperature difference of L$N_2$ and normal temperature. Like this, critical current could measure that degradation about 1~3％ by temperature difference. These results will amount the most important basis data in power electric machine of superconductivity cable, magnet, etc that winding work is require.

• 한국지반환경공학회 논문집
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• 제23권9호
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• pp.5-16
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• 2022

최근 도시 및 지하공간 개발에 따라 지반재해가 증가하고, 사회문제로도 이어지고 있다. 이러한 문제를 해결하기 위해 일반적으로 그라우팅 공법이 사용되나, 낮은 침투성, 겔화특성 등의 재료적 한계와 인장저항력 부족 문제를 가지고 있어 지반의 역학적 성능을 개선하지 못하고 있다. 따라서 최근에는 섬유를 혼합한 그라우트재 연구 등 역학적 성능 개선을 위한 연구가 진행되고 있다. 그러나 일반적인 섬유는 교반 및 주입 시 주입구 막힘, 주입관 폐색 등의 문제를 유발해 실제 지반 주입에 많은 어려움을 가지고 있다. 이에 본 연구에서는 그라우트 인장보강재로 실제 주입이 가능한 CNT Powder를 사용해 'CNT-mixed grout재'를 고안하고, 역학적 거동 분석과 주입 가능성, 구근 특성, 적용성 분석을 수행하였다. 역학적 성능 시험결과 CNT Powder의 최적 함유량은 0.5 %로 확인되었고, 1차원 주입시험과 모형 구근 형성시험을 통해 적정 주입인자와 구근의 특성을 파악하였다. 수치해석을 통한 적용성 분석을 수행하여 CNT-Mixed grout재가 침하량과 소성영역 감소 등의 효과를 나타내어 지반에 주입 가능한 인장보강재로서 활용이 가능함을 확인하였다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.405-408
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• 1999

A prototype of solenoidal superconducting magnet using Bi-2223/Ag multi-filamentary tapes was fabricated and tested to investigate its performance. The Bi-2223/Ag tapes were prepared by powder-in-tube method. The dimensions of magnet, which was stacked with 9 double pancakes, were 90 mm in height, 74 mm in outer diameter and 40 mm in clear core. The axial maximum magnet field at the center of the solenoidal magnet was about 0.12 T, and the critical current of coil conductor was about 9 A at 77.3 K.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.10-13
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• 1999

For large scale applications of high temperature superconductor(HTS) such as transmission cables, motors and generators, long length of flexible HTS conductors is required. Currently, HTS tape that is capable of being fabricated in long length by industrial processes is the Bi-2223 HTS tape. In this study, we fabricated 19 filamentary Bi-2223($Bi_{1.8}$$Pb_{0.4}$$Sr_{2}$$Ca_{2}$$Cu_{3}$$O_{10+X}$) HTS tape with 100m length by PIT(Powder In Tube) process. Critical current(Ic) of this long length tape was measured 18.5 A at 77 K, self field and short sample Ic is 32.5 A at the same condition. Critical current of 100m length tape was decreased by about 1/3 compared to that of short tape. This was mainly resulted from the increase of non homogeneity in oxide layer.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권6호
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• pp.211-215
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• 2003

Alternating current (AC) losses of two Bi-2223 ([Bi, Pb] : Sr : Ca : Cu :O = 2:2:2:3) tapes [one untwisted (Tape I, twist-pitch of $\infty$ mm) and the other with a twist-pitch of 8mm (Tape II) ] were measured and compared. These samples, produced by the powder-in-tube (PIT) method, are multi-filamentary and have a Ag/Au and Ag matrix, respectively. Susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.72-75
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• 2003

HTS tubes were fabricated in terms of various SrSO4 additions by Centrifugal Forming Method. For powder melting by induction, the optimum temperature ranges of melting and preheating were 105$0^{\circ}C$~110$0^{\circ}C$ and 55$0^{\circ}C$ for 30min respectively The mould rotating speed was 1000rpm. A tube was annealed at 84 $0^{\circ}C$ 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 the amounts of SrSO4 in Bi2212. The measured Ic and Jc at 77K(B = 0T) in Bi2212 with 7％ SrSO4 composition were about 680A and 380A/$\textrm{cm}^2$.

• 대한기계학회논문집
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• 제13권3호
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• pp.528-537
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• 1989

The objective of this paper is to investigate effects of the specific heat and the diameter of suspending particles on the heat transfer coefficient of two phase turbulent flow with suspension of solid particles in a circular tube with constant heat flux. Heat transfer coefficients of two phase turbulent flow in pipe with suspension of graphite powder were measured with variations of particle sizes and solid-gas loading ratio. Measured data were compared with predictions by numerical analysis in which the turbulece models are closed on the first order level. Results show that heat transfer coefficient increases with increasing the solid-gas loading ratio and the specific heat of suspending material, however, it decreases as the average diameter of particles decreases below $24{\mu}m$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.488-491
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• 2000

Bi-2223/Ag superconducting wires have been mainly prepared by a powder-in-tube method. The drawing and the rolling are main processes to increase the core density and wire length. In the fabrication of long wire, especially, the drawing should be precisely controlled to assure the filament homogeneity. In this paper, the influences of drawing die angle, bearing length and reduction ratio on the sausaging and the critical current density of the wire are investigated. Single cored and multi-filamentary wires are fabricated by PIT method with different conditions. The core densities and sausaging in the wires are investigated and are discussed regarding their relationship to the I$_{c}$. It was made clear that the geometry of drawing die is sensitively dependent on the sausaging. The improvement of I$_{c}$ was achieved by reducing the die angle and high core density.ity.

• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.1978-1980
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• 2009

A mesostructured form of carbon was fabricated from a template of mesostructured silica by using pentane, an aliphatic hydrocarbon precursor. To synthesize the mesostructured silica, a buffered (pH of 6.5) mixture of nonionic Pluronic P123 surfactant, sodium silicate, and acetic acid were used. The impregnated silica with Fe$(CO)_5$ (wt 5%) and pentane was placed in a quartz tube, treated with pentane vapor at 800 ${^{\circ}C}$ for two hours to synthesize the mesostructured carbon. The XRD patterns of the carbon replica in the low/wide angle regions, its TEM images, and nitrogen adsorption-desorption isotherm revealed that the long-range framework order of mesostructure with the pore size centered on 2.8 nm was maintained to some extent mainly due to some portions of mesophase carbon that work as a support to fix the hexagonal frameworks by anchoring on the pore surface with an improved graphitic character. The dc conductivity of the mesostructured carbon in pressed powder form at 6.0 MPa was 2.08 S/cm.