• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.77-80
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• 2006

Structural phase transformations of silicon during nanoindentation were investigated in detail at the atomic level. The molecular dynamics simulations of nanoindentation on the (100), (110) and (111) surface of single crystalline silicon were simulated, and this supported the theoretical prediction of the anisotropic behavior of structural phase transformations. Simulations showed that microscopic aspects of phase transformation varied according to the crystallographic orientation of the contact surface and were directly linked to the slip system.

• Macromolecular Research
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• v.11 no.3
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• pp.152-156
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• 2003

We investigated epitaxial relations of phase transitions between the lamellar (L), hexagonally perforated layers (HPL), and gyroid (G) morphologies in styrene-isoprene diblock copolymer (PSI) and polyisoprene (PI)/PSI blend using rheology and small angle X-ray scattering (SAXS) techniques. In HPLlongrightarrowG transitions, six spot patterns of G phase were observed in two-dimensitional SAXS pattern. On the other hand, in direct L-longrightarrowG transition without appearance of HPL phase, the polydomain patterns of G phase were observed. From present study, it was understood that direct LlongrightarrowG transition of blend may be suppressed by high-energy barrier of transition and mismatches in domain orientation between epitaxially related lattice planes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.851-856
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• 2003

We have investigated the material and electrical properties of $Bi_{4-x}La_xTi_3O_{12}$ (BLT) ferroelectric thin film for ferroelectric nonvolatile memory applications of capacitor type and single transistor type. The 120nm thick BLT films were deposited on $Pt/Ti/SiO_2/Si$ and $SiO_2/Nitride/SiO_2$ (ONO) substrates by the sol-gel spin coating method and were annealed at $700^{\circ}C$. It was observed that the crystallographic orientation of BLT thin films were strongly affected by the excess Bi content and the intermediate rapid thermal annealing (RTA) treatment conditions regardeless of two type substrates. However, the surface microstructure and roughness of BLT films showed dependence of two different type substrates with orientation of (111) plane and amorphous phase. As increase excess Bi content, the crystallographic orientation of the BLT films varied drastically in BLT films and exhibited well-crystallized phase. Also, the conversion of crystallographic orientation at intermediate RTA temperature of above $450^{\circ}C$ started to be observed in BLT thin films with above excess 6.5% Bi content and the rms roughness of films is decreased. We found that the electrical properties of BLT films such as the P-V hysteresis loop and leakage current were effectively modulated by the crystallographic orientations change of thin films.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.1
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• pp.1-12
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• 2020

In this study, thin foil fabrication using Ni/Ni₃Al single crystal was performed by cold-rolling. It was found that the cold-rolling behavior was strongly dependent on the initial crystallographic orientation rather than morphology of Ni₃Al precipitates. The deformation banding was formed in the case of (100)[001]- and (210)[001]-oriented specimens at 83% reduction in thickness. However, the effects of Ni₃Al precipitates morphology on the microstructure evolution of Ni/Ni₃Al single crystals during cold-rolling were not so serious comparing with the effects of initial crystallographic orientation. Therefore, it could be concluded that the deformation behavior of Ni/Ni₃Al single crystals at serious strain level was strongly dependent on the initial crystallographic orientation rather than the morphology of Ni₃Al precipitates, whereas the initial deformation behavior was related to both crystallographic orientation and the morphology of Ni₃Al precipitates.

• Journal of Sensor Science and Technology
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• v.28 no.6
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• pp.341-344
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• 2019

Liquid crystal (LC) mesophase materials manifest a variety of phase transitions. The optical properties of LCs are highly dependent upon the phase and orientation of the optical axis with respect to the polarization of incoming light. Studying the LC phase transitions is significantly important for a wide range of scientific and industrial applications. In this study, we demonstrate the propagation velocity of the phase boundary between the nematic and isotropic phase of 4-Cyano-4-pentylbiphenyl (5CB) liquid crystal for different electric fields using a polarized optical microscope. The results demonstrate that the propagation velocity of the phase boundary exhibits a peak value for a specific voltage, attributed to the supercooling of the isotropic phase of the LC. The analysis of the propagation velocity for different electric fields also provides a simple optical platform to measure the thermal anisotropy and voltage dependent thermal properties of the homogeneously aligned LC.

• Korean Journal of Materials Research
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• v.1 no.1
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• pp.54-61
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• 1991

YBCO films deposited on MgO(100) and Si(100) by rf-magnetron sputtering using stoichiometric single target were annealed under oxygen atmosphere at $880^{\circ}C$ for 1 hr. The microstructure and superconducting properties of YBCO thin films depended on the composition of pre-annealed thin films. Basal planesuperconducting particles grown on MgO(100) substrate had small and rod-like shade due to preferred orientation, while superconducting film grown on the basal plane-superconducting particles showed round-shape particles. If pre-annealed thin film had nonstoichiometric composition, liquid phase was formed during the heat treatment, which made it easy for particles to grow in the preferred orientation and thus to form textured structure. But the thin films with the textured structure did not show good superconducting properties, especially $T_c$, since the liquid phase transformed into second phase in the grain boundary during the cooling. The effect of the second phase on $T_{c, \;zero}$ was greater than that on $T_{c, \;on}$.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.93-103
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• 2011

Precipitation behavior of high-nitrogen duplex Fe-24Cr-7Mn-4Ni-4Mo-0.43N stainless steel aged at $850^{\circ}C$ was investigated using scanning transmission electron microscopy. Based on the analyses of selected area diffraction patterns, four kinds of precipitates (intermetallic sigma (${\sigma}$) and chi (${\chi}$), $Cr_2N$ and secondary austenite) were identified. At the ferrite/austenite phase boundary, the ${\sigma}$ phase and secondary austenite were formed via ${\alpha}{\rightarrow}{\gamma}+{\sigma}$ eutectoid reaction. The precipitation of $Cr_2N$ occurred at the austenite grain boundary as well as the interior of the ferrite. The intermetallic ${\chi}$ phase also formed within the ferrite and showed a cube-cube orientation relationship with the ferrite. Further aging produced a lamellar structure composed of $Cr_2N$ and austenite along the ferrite/austenite boundary and enhanced the precipitation of the ${\chi}$ phase. The crystallographic features of the precipitates were also examined in terms of the orientation relationship with the austenite or ferrite matrix.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.717-727
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• 2006

The present study experimentally investigated the effect of flow direction and other flow parameters on two-phase flow distribution of refrigerants at a T-junction, and also suggested a prediction model for refrigerant in a T-junction by modifying previous model for air-water flow. R-22, R-134a, and R-410A were used as test refrigerants. As geometric parameters, the direction of the inlet or branch tube and the tube diameter ratio of branch to inlet tube were chosen. The measured data were compared with the values predicted by the models developed for air-water or steam-water mixture in the literature. We propose a modified model for application to the reduced T-junction and vertical tube orientation. Among the geometric parameters, the branch tube direction showed the biggest sensitivity to the mass flow rate ratio for the gas phase, while the inlet quality showed the biggest sensitivity to the mass flow rate ratio among the inlet flow parameters.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.162-169
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• 2004

High temperature uniaxial compression tests in the alpha single phase region were carried out on the Ti -43mo1%Al intermetallic compound, in order to obtain oriented lamellar microstructure. The compression deformation temperatures and strain rates are from 1573k to 1623k and 1.0x10$^{-4}$ s to 5.0x10$^{-3}$ s, respectively. Fully lamellar microstructure was observed after the uniaxial compression deformation in a single phase region followed by cooling to room temperature. Lamellar colony diameter depended on strain rates and test temperatures. The diameter varied between 8601m and 300fm. Stress-strain curve showed a work softening and the size of lamellar colony diameter varied depending on peak stresses. This shows the occurrence of dynamic recrystallization. Texture measurements after the uniaxial compression deformation, showed the development of fiber during dynamic recrystallization. It is seen that the area for the maximum pole density existed in 35 degrees away from the compression plane. The texture sharpens with a decrease in strain rate

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.174-176
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• 1996

In the YBCO matrix, 10wt.% Y$_2$BaCuO$\_$5/ (211 phase) was added, the final 211 content of YBCO made by MTG process could reach about 20wt.% which was the optimum value for the critical current density. And also 10wt.% Ag was added in the matrix of YBCO, which was nearly about the saturate solubility of silver in textured YBCO. SmBaCuO crystal was grown by the melted-condensed process. A 5${\times}$5${\times}$2㎣ single crystal of SmBaCuO was used to be the seed in the preparation of YBCO. It was proved the orientation of YBCO was the same as the orientation of the SmBaCuO seed. The oxygen absorption of bulk oriented YBCO was studied and the heat treatment of oxygen absorption would be in flowing oxygen, at 400$^{\circ}C$ for about 24 hours. the magnetic hysteresis loops were measured by Vibrating Smaple Magnetometer and the J$\_$c/ was calcuated by means of Bean's model.