• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.69-72
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• 2003

Bi-2223 superconducting wires were fabricated by stacking, drawing process with different precursor powders and different heat-treatment histories. The precursor powders were 2 kinds of Pb content. And a part of the tapes were experienced pre-annealing process which caused tetragonal structure of Bi-2212 phase to orthorhombic structure of it was during drawing process. We confirmed the transformation of Bi-2212 phase from tetragonal structure to orthorhombic structure and reduction of second phases. XRD and DC magnetization analysis were performed in order to investigate the fraction of Bi-2223 phase in Bi-2223/Ag HTS tape. We could achieve best Ic of 70 A class at the Bi-2223/Ag tape using low Pb content of precursor powder and experienced pre-annealing process. DC magnetization analysis was useful to investigate the fraction of Bi-2223 phase in the Bi-2223/Ag tape.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.51-56
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• 2005

We prepared orthorhombic $LiMnO_2$ by emulsion drying method. The thermo-gravimetric measurement and X-ray diffraction studies indicated that the orthorhombic $LiMnO_2$ phase was formed above $800^{\circ}C$ by oxygen evaporation process from $LiMn_2O_4$ and $Li_2MnO_3$. In this process, we could control the ordering of $LiMnO_2$ with heating rate. It was observed that electrochemical properties depended on the ordering of this material; the ordered one exhibited good capacity retention, whereas the disordered one suffered capacity fading upon cycling, especially in the 3 V region. Transmission electron microscopic (TEM) study showed that this difference is related with difference in the stress relieving effects in the samples.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1232-1233
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• 2006

To co-fire with commercial LTCC (Low Temperature Co-fired Ceramic) materials at $850^{\circ}C{\sim}880^{\circ}C$, different contents of $B_2O_3$ were added to the $Bi_2O_3-ZnO-Nb_2O_5$ (BZN) ceramics. According to the test results, the cubic phase of BZN was transformed into orthorhombic in all the test materials. $BiNbO_4$ phase was formed in test materials with $2{\sim}5wt%$ of $B_2O_3$ addition. The phase transformation of cubic BZN was controlled during the synthesis process with excess ZnO content. The Cubic and orthorhombic phases of BZN could coexist and be sintered densely at $850^{\circ}C/2hr$.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.231-236
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• 1999

Several series of morphologically controlled $MoO_3$/$SiO_2$ catalysts were prepared, characterized, and tested for hydrodesulfurization (HDS) of dibenzothiophene (DBT) activity. Molybdenum surface loaded with 4.0 atoms $Mo/nm^2$ was prepared as sintered hexagonal and sintered orthorhombic, as well as a novel "well dispersed hexagonal" phase. Characterization by XRD, Raman, and $O_2$ chemisorption results reveals that the dispersion of $MoO_3$ over silica depends on the final $MoO_3$ phase in the order of; sintered hexagonal < sintered orthorhombic < dispersed hexagonal phase. Temperature programmed reduction (TPR) results show that both bulk and dispersed microcrystalline of $MoO_3$ reduce to $MoO_2$ at $650^{\circ}C$ and to Mo metal at $1000^{\circ}C$. HDS of DBT was performed in a differential reactor at 30 atm over the temperature range $350{\sim}500^{\circ}C$. Activity of $MoO_3$/$SiO_2$ toward HDS of DBT is proportional to dispersion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.6
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• pp.558-561
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• 2004

The morphology of silica supported $MoO_{3}$ catalysts, which was prepared by impregnation of ammonium heptamolybdate(AHM) with various surface loadings up to 4 atoms $Mo/nm^{2}$, was studied using x-ray diffraction(XRD). All morphologies of silica supported $MoO_{3}$ appear to be thermodynamically driven. For high loaded catalysts there appeared three states: a sintered and well-dispersed hexagonal state at moderate temperature calcination($300^{\circ}C$), and a sintered orthorhombic state at high temperature calcination($500^{\circ}C$). Whereas the sintered orthorhombic phase is detected by XRD at loadings in excess of 1.1 atom $Mo/nm^{2}$, the well-dispersed hexagonal phase is not detected even until 4.0 $atomsMo/nm^{2}$. The higher apparent dispersion of the hexagonal phase may arise from some role of ammonia which results in a stronger $MoO_{3}-SiO_{2}$ surface interaction.

• Bulletin of the Korean Chemical Society
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• v.6 no.4
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• pp.183-186
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• 1985

The lattice vibrational calculation of orthorhombic hydrogen chloride is performed using physically realistic potential function which can reproduce the X-ray structure and heat of sublimation of the low temperature phase. The polar coordinates representation is introduced in order to describe the intermolecular interactions in a molecular crystal. The splitting in internal modes is calculated as 49 $cm^{-1}$ and the other modes are in good agreement with experimental results.

• Korean Journal of Materials Research
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• v.29 no.12
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• pp.753-756
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• 2019

Orthorhombic dysprosium manganite DyMnO₃ with single phase is synthesized using solid-state reaction technique and the crystal structure and dielectric properties as functions of temperature and frequency are investigated. Thermally activated dielectric relaxations are shown in the temperature dependence of the complex permittivity, and the respective peaks are found to be shifted to higher temperatures as the measuring frequency increases. In Arrhenius plots, activation energies of 0.32 and 0.24 eV for the high- and low-temperature relaxations are observed, respectively. Analysis of the relationship between the real and imaginary parts of the permittivity and the frequencies allows us to explain the dielectric behavior of DyMnO₃ ceramics by the universal dielectric response model. A separation of the intrinsic grain and grain boundary properties is achieved using an equivalent circuit model. The dielectric responses of this circuit are discerned by impedance spectroscopy study. The determined grain and grain boundary effects in the orthorhombic DyMnO₃ ceramics are responsible for the observed high- and low-temperature relaxations in the dielectric properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.585-588
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• 2003

Bi-2223 superconducting wires were fabricated by stacking, drawing process with different precursor powders and different heat-treatment histories. The precursor powders were 2 kinds of Pb content. And a part of the tapes were experienced pre-annealing process which caused tetragonal structure of Bi-2212 phase to orthorhombic structure of it was during drawing process. We confirmed the transformation of Bi-2212 phase from tetragonal structure to orthorhombic structure and reduction of second phases. AC magnetization analysis were performed in order to investigate the fraction of Bi-2223 phase in Bi-2223/Ag HTS tape. The cross sections of 55 filaments and 61 filaments were investigated after rolled in order to understand deformation mechanism of superconducting cores. We could achieve best Ic of 70 A class at the Bi-2223/Ag tape using low Pb content of precursor powder and experienced pre-annealing process. AC magnetization analysis was useful to investigate the fraction of Bi-2223 phase in the Bi-2223/Ag tape.

• Journal of the Korean Magnetic Resonance Society
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• v.2 no.1
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• pp.24-32
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• 1998

Drawn polyethylene was studied by 13C cross polarization magic angle spinning techniques. Solid-solid phase transition from orthorhombic to monoclinic crystalline phase by drawing was observed. In addition, using a synchronized magic angle spinning 2 dimension technique, we confirmed that macroscopic ordering of the polyethylene was produced by drawing.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.105-108
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• 2003

Long length of Bi-2223 superconducting wires were fabricated by stacking, drawing process with different precursor owders and different heat-treatment histories. The precursor powders were 2 kinds of Pb content. And a part of the tapes were experienced pre-annealing process which caused tetragonal structure of Bi-2212 phase to orthorhombic structure of it was during drawing process. We confirmed the transformation of Bi-2212 phase from tetragonal structure to orthorhombic structure and reduction of second phases. We designed and made a continuous Ic measurement system for Bi-2223/Ag HTS tape. We could achieve best Ic of 65 A at the Bi-2223/Ag tape using low Pb content of precursor powder and experienced pre-annealing process.