• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.120-122
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• 2003

We jointed Bi(Pb)-Sr-Ca-Cu-O multifilament tapes and evaluated their electrical properties. In order to improve connectivity of multifilarnents, single-filament tape was inserted between two multifilament tapes or multifilament was stepped by mechanical remove. The critical current ratio (CCR) and n-value of the jointed tapes were evaluated as a function of uniaxial pressure. It was observed that CCR and n-value were 24.8-29.0% and 2.5-2.8 for lap-jointed tape. On the other hand, the corresponding values were improved to 51.8-61.9% and 2.9-5.1 for three stepped jointed tape, and 63.4-67.9% and 3.4-4.2 for double MSM lap-jointed tape, respectively. These improvements are to be due to better interconnection between filaments of two tapes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.55-58
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• 2002

PIT method which is used at fabricating Bi-2223/Ag HTS wire includes a drawing process, conventional deformation method. Drawing of meta1(Ag) and ceramic (BiSrCaCuO) composite is also difficult and significant for uniform deformation. In this paper, parameters of uniform deformation was studied at Bi-2223/ Ag multifilamentary HTS wire. Powder and rod as a starting precursor was compared at 55 filament and 54 filament Bi-2223/Ag HTS wire, respectively. Micro-hardness and area COV of the filaments was also evaluated when the diameters were decreased through drawing operations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.31-34
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• 2003

($Ba_{0.6-x}Sr_{0.4}Ca_x)TiO_3$ (BSCT) (x=0.10, 0.15, 0.20) powder, prepared by the sol-gel method, were mixed with organic vehicle and the BSCT thick films were fabricated by the screen-printing techniques on alumina substrates using the BSCT paste. The structural and the electrical properties were investigated for various composition ratio and sintering temperature. BSCT thick film thickness, obtained by four printings, was approximately 110 ~ 120 ${\mu}m$. The Curie temperature and dielectric constant at room temperature were decreased with increasing Ca content. The relative dielectric constant, dielectric loss and tunability of the BSCT(50/40/10) specimen, which was sintered at $1420^{\circ}C$ and measured at 1MHz, were about 910, 0.46% and 9.28% at 5kV/cm, respectively.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.877-885
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• 1997

The dependence of strength, crack growth, fracture mode and degree of domain rearrangement of PZT ceramics on poling strength were studied. The PZT [(Pb0.94Sr0.06)(Zr0.46Ti0.54)O3+Nb(trace)] specimens were poled at 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 kv/mm, and the strength of the specimens was measured by 3 point flexure system. The bending strength of the specimen decreased in different modes according to the bending directions; xz, zx and yz plane direction with x axis of the poling direction in Cartesian coordinate system. The strength differences between the directions increased as the poling strength increased. The fracture mode transferred to intergranular fracture mode from transgranular one as the poling strength increased. The mechanical breakdown occurred when the poling strength higher than 3 kV/mm was applied to the specimen. It was observed that the crack length increased in the normal direction to the poling direction, however, decreased in the parallel direction to the poling direction when the poled PZT specimen was indented by the Vickers indenter. However, the crack produced by indentation continuously was continuously increased little by little after indentation on the specimen. The domain rearrangement occurred as the poling strength increased and the domains were rearranged more effectively when the electric field was continuously increased little by little.

• Journal of Surface Science and Engineering
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• v.49 no.6
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• pp.498-506
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• 2016

Electrochemical measurement using a LSCF6428 electrode was performed to estimate the oxygen potential gradient in the electrode layer and a long time stability test was performed by applied potential to learn the overpotential effect on the LSCF6428 electrode. By fitting the observed impedance spectra, it was obtained that the amount of faradic current decreased with distance from cathode/electrolyte interface. Oxygen potential gradient was estimated to occur within 1 um region from the cathode/electrolyte interface at an oxygen partial pressure of 10-1 bar. The segregation of cation rich phases in the LSCF6428 electrode suggests that kinetic decomposition took place. However, impedance response after applying the potential showed no changes in the electrode compared with before applying potential. The obtained results suggest that segregation of a secondary phase in a LSCF6428 cathode is not related to performance degradation for solid oxide fuel cells (SOFCs).

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3755-3760
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• 2012

Single crystals of lithium potassium phthalate (LiKP) were successfully grown from aqueous solution by solvent evaporation technique. The grown crystals were characterized by single crystal X-ray diffraction. The lithium potassium phthalate $C_{16}\;H_{12}\;K\;Li_3\;O_{11}$ belongs to triclinic system with the following unit-cell dimensions at 298(2) K;$a=7.405(5){\AA}$;$b=9.878(5){\AA}$;$c=13.396(5){\AA}$;${\alpha}=71.778(5)^{\circ}$;${\beta}=87.300(5)^{\circ}$;${\gamma}=85.405(5)^{\circ}$; having a space group P1. Mass spectrometric analysis provides the molecular weight of the compound and possible ways of fragmentations occurs in the compound. Thermal stability of the crystal was also studied by both simultaneous TGA/DTA analyses. The UV-Vis-NIR spectrum shows a good transparency in the whole of Visible and as well as in the near IR range. Third order nonlinear optical studies have also been studied by Z-scan technique. Nonlinear absorption and nonlinear refractive index were found out and the third order bulk susceptibility of compound was also estimated. The results have been discussed in detail.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.304-310
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• 2003

(Ba$\sub$0.6-x/Sr$\sub$0.4/Ca$\sub$x/)TiO$_3$(BSCT) (x=0.10, 0.15, 0.20) powder, prepared by the sol-Bel method, were mixed with organic binder and then BSCT thick films were fabricated by the screen printing techniques on alumina substrates using the BSCT paste. The structural and the dielectric Properties were investigated for various composition ratio and sintering temperature. The second phase appeared in BSCT(40/40/20) thick film sintered at 1450$^{\circ}C$. BSCT thick film thickness, obtained by four printings, was approximately 110∼120$\mu\textrm{m}$. The Curie temperature and dielectric constant at room temperature were decreased with increasing Ca content. The relative dielectric constant, dielectric loss and tunability of the BSCT(50/40/10) specimen, which was sintered at 1420$^{\circ}C$ and measured at 1MHz, were about 910, 0.46% and 9.28% at 5㎸/cm, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.30-33
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• 2003

YBCO coated conductor, also called the 2nd generation high temperature superconducting wire, consists of oxide multi-layer hetero-epitaxial thin films. Pulsed laser deposition (PLD) is one of many film deposition methods used to make coated conductor, and is the one known to be the best to make superconducting layer so far. As a part of the effort to make long length coated conductor, the optimum deposition condition of YBCO film on single crystal substrate (SrTiO3) was investigated using PLD. Substrate temperature, oxygen partial pressure, and laser fluence were varied to find the best combination to grow high quality YBCO film.

• Journal of Hydrogen and New Energy
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• v.21 no.5
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• pp.412-418
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• 2010

Steam reforming of n-hexadecane, a major component of diesel over Ni-based hydrotalcite-like catalyst was carried out at $900^{\circ}C$ at atmospheric pressure with space velocity of $10,000h^{-1}$ and feed molar ratio of steam/carbon=3.0. Ni-based hydrotalcite catalyst was prepared by a solid phase crystallization (spc) method and characterized by $N_2$-physisorption, CO chemisorption, TPR., XRD, and TEM techniques. It was found that spc Ni/MgAl catalyst showed higher catalytic stability and inhibition of carbon formation than Ni/$\gamma-Al_2O_3$ catalyst under the tested conditions. The results suggest that the modified spc-Ni/MgAl catalyst after optimization may be applied for the SR reaction of diesel.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.45-48
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• 2000

High dielectric (Ba,Sr)TiO$_3$ thin films were etched in an inductively coupled plasma (ICP) as a function of C1$_2$/Ar gas mixing ratio. Under Cl$_2$(20)/Ar(80), the maximum etch rate of the BST films was 400$\AA$/min and selectivities of BST to Pt and PR were obtained 0.4 and 0.2, respectively. We investigated the etched surface of BST by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and x-ray diffraction (XRD). From the result of XPS analysis, we found that residues of Ba-Cl and Ti-Cl bonds remained on the surface of the etched BST for high boiling point. The surface roughness decreased as Cl$_2$ increases in Cl$_2$/Ar plasma because of non-volatile etching products. This changed the nature of the crystallinity of BST. From the result of XRD analysis, the crystalliility of etched BST film maintained as similar to as-deposited BST under Ar only and Cl$_2$(20)/Ar(80). However, (100) orientation intensity of etched BST film abruptly decreased at Cl$_2$ only plasma. It was caused that Cl compounds were redeposited on the etched BST surface and damaged to crystallinity of BST film during the etch process.