• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.341-342
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• 2008

The dynamics of nano particles in LC medium under an external electric field is of theoretical and technological interest. In this work, the dynamical characteristics of fullerene $(C_{60})$ particles in liquid crystal (LC) medium under dc electric field have been investigated. This effect was studied for homogeneously aligned nematic LC cells driven by in-plane field. The $C_{60}$ was found to be aggregated in a form of cluster inside the LC medium. Hence polystytene was used to protect the aggregation of $C_{60}$ in LC medium. When the electric field was applied, the fullerenes start to move in direction of applied electric field. The density of $C_{60}$'s particles at the electrodes increase with increase in the value of applied electric field. The dynamical motions of fullerene $(C_{60})$ particles in liquid crystal (LC) suggest that fullerene can be designed for electrophoretic displays (i.e., electronic ink).

• Composites Research
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• v.30 no.6
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• pp.350-355
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• 2017

The new liquid crystalline (LC) epoxy was designed by substituting the phenylcyclohexyl (PCH) mesogen moiety with an alkyl chain at the 2,5 position of the diglycidyl terephthalate. The mesomorphic properties were evaluated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). All LC epoxy derivatives exhibited an enantiotropic smectic phase upon heating and cooling process. The LC phase temperature range was widened by mixing the eutectic mixture of LC epoxies. Interestingly, the cured LC epoxy exhibited the highest thermal conductivity of $0.4W{\cdot}m^{-1}{\cdot}K^{-1}$. The novel LC epoxy with high thermal conductivity might be used as a composite material for electronic and display devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.370-370
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• 2007

The liquid crystal (LC) aligning capabilities treated on the Organic overcoat thin film surfaces by ion beam irradiation and rubbing method was successfully studied for the first time. The Organic overcoat layer was coated by spin-coating. In order to characterize the LC alignment, the microscope, pretilt angle, thermal stress, and atomic force microscopy (AFM) image was used. The good LC aligning capabilities treated on the Organic overcoat thin film surfaces with ion beam exposure of $45^{\circ}$ above ion beam energy density of 1200 eV can be achieved. But, the alignment of defect of NLC on the Organicovercoat surface at low energy density of 600 eV was measured. The pretilt angle of NLC on the Organic overcoat thin film surface with ion beam exposure of $45^{\circ}$ for 1 min at energy density of 1800eV was measured about 1.13 degree. But, low pretilt angles of NLC on the Organic overcoat thin film surface with ion beam exposure at energy density of 600, 1200, 2400, and 3000 eV was measured. Also, the pretilt angle of NLC on the rubbed Organic overcoat thin film surfaces was measured about 0.04 degrees. Finally, the good thermal stability of LC alignment on the Organic overcoat thin film surface with ion beam exposure of $45^{\circ}$ for 1 min can be measured.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.58-65
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• 2022

The field of liquid crystal display (LCD) is constantly in the spotlight and the process of depositing an alignment layer in the LCD manufacturing process is very important to obtain excellent performance such as low-power driving and high-speed response to improve LCD performance. Therefore, research on liquid crystal (LC) alignment is being actively conducted. When manufacturing LCD, it is necessary to consider the effect of the alignment layer thickness as one of the factors affecting various LCD performances. In addition, previous studies confirmed the LC alignment characteristics correlate with the rotation speed in the spin coating process. Therefore, the electro-optical properties of the LCD were investigated by manufacturing a polyimide alignment layer by varying the rotation speed in the spin coating process in this study. It was confirmed that the thickness of the polyimide alignment layer was controlled according to the spin coating conditions. The average transmittances of anti-parallel LC cells at the spin coating speed of 2,500 rpm and 3,000 rpm are about 60%, which indicates that the LC cell has relatively higher performance. At the spin coating speed of 3,000 rpm, the voltage-transmittance curve of twisted nematic (TN) LC cell was below 1.5 V, which means that the TN LC cell operated at a low power. In addition, high-speed operating characteristics were confirmed with a response time of less than 30 ms. From these derived data, we confirmed that the ideal spin coating speed is 3,000 rpm. And these results provide an optimized polyimide alignment layer process when considering enhanced future LCD manufacturing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.280-281
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• 2006

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a Titanium dioxide ($TiO_2$) thin film by rf magnetron sputtering system for 15min under various rf power. A very low pretilt angle by ion beam exposure on the $TiO_2$ thin film was measured. A good LC alignment by the ion beam alignment method on the $TiO_2$ thin film surface was observed at annealing temperature of $200^{\circ}C$, and the alignment defect of the NLC was observed above annealing temperature of $250^{\circ}C$. Consequently, the low NLC pretilt angle and the good thermal stability of LC alignment by the ion beam alignment method on the $TiO_2$ thin film by sputter method as various rf power condition can be achieved.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.529-534
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• 1994

The lethal concentration(LC50) of several micropollutants for three species of the fish Paralichthys olivaceus, Mugil cephalus and Sebastes schlegeli were determined by acute toxicity tests. For the determination of definitive test concentrations, the fish were exposed to three test material concentrations spaced at order-of-magnitude intervals based on a logarithmic ratio in range finding tests. LC50 was determined by five concentrations of test material in a geometric progression by means of range finding tests. The 96hr-LC50 values(mg/l) were estimated by the graphical interpolation of probability-logarithm transformations. These indicated that the order of sensitivities to three kind of micropollutants was Mugil cephalus > Paralichthys olivaceus > Sebastes schlegeli.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2860-2870
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• 1994

When crack are detected in aged turbine rotors of power plants, information on fracture resistance of the aged material at operating temperature is needed for determination of critical loading condition and residual life of the turbine. In this study, fracture toughness (J$_lc$) and tearing modulus(T$_mat$) of virgin and thermally degraded 1Cr-1Mo-0.25V steel, which is one of the most widely used rotor steels, were measured at 538.deg. C according to ASTM E813 and ASTM E1152, respectively. Five kinds of specimen with different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C.$ It was observed that J$_lc$ and T$_mat$ value decreased as the degradation level increased. Analysis of microstructures using a scanning electron microscope showed that the decrement of J$_lc$ is related to segregation of impurities at grain boundaries. It was also verified that the DC electric potential drop method is accurate and reliable for crack length monitoring at elevated temperature.

• Journal of the Korean Applied Science and Technology
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• v.13 no.2
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• pp.29-37
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• 1996

The phase separated structure and the electo-optical properties of the polymer /liquid crystal(LC) composite films including a dye were investigated. The phase separated structure of the polymer /LC / dye composite film(GH composite film) including below 2wt% dye against LC was almost same with the composite film which does not include dye. But the electro-optical properties of the GH composite film strongly depended on weight fraction of the dye against the LC. The response time of the GH composite film increased with the increase of the dissolved dye in LC because the dye acts as a registivity for the orientation of LC molecules by the electric filed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.133-134
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• 2021

Limestone-calcined clay-Cement (LC3) concrete provides a solution for sustainability, durability, and profitability of concrete industry. This study shows experimental studies of the macro properties (residual compressive strength), the meso properties (mesoscopic images), and micro properties (thermogravimetric (TG) analysis, X-ray powder diffraction (XRD), FTIR spectra, Raman spectra, Mercury intrusion porosimetry, and SEM) of LC3 paste with various mixtures and at high elevated temperatures (20 ℃, 300 ℃, 550 ℃ and 900 ℃). We find (1) Regarding to macro properties, LC3 cementitious materials are at a disadvantage in compressive strength when the temperature is higher than 300 ℃. (2) Regarding to meso properties, when the temperature reached 550 ℃, all samples generated more meso cracks. (3) Regarding to micro properties, first, as the substitution amount increases, its CH content decreases significantly; second, at 900 ℃, for samples with calcined clay, a large amount of gehlenite crystalline phase was found; third, at elevated temperatures (20 ℃, 300 ℃, 550 ℃ and 900 ℃), there is a linear relationship between the residual compressive strength and the cumulative pore volume; fourth, at 900 ℃, a large amount of dicalcium silicate was generated, and damage cracks were more pronounced. The experimental results of this study are valuable of material design of fire resistance of LC3 concrete.

• Electrical & Electronic Materials
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• v.10 no.5
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• pp.461-466
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• 1997

In this paper, we developed the new non-rubbing liquid crystal (LC) alignment techniques in the cell with slanted non-polarized ultraviolet (UV) light irradiation on polyimide (PI) film. It is shown that the uniform alignment for nematic (N) LC is obtained by using slanted non-polarized UV light irradiation on PI surface. We successfully obtained that the pretilt angle of NLC is generated about 3.3 degree in the cell with slanted non-polarized UV light irradiation with 70 degree on PI surface, for the first time. It is considered that the pretilt angle generation in NLC is attributed to interaction between the LC molecular and the PI, which is broken the polymer by slanted non-polarized UV irradiation. Therefore, we concluded that the uniform LC alignment is attributed to anisotropic dispersion force due to photo depolymerization with slanted non-polarized UV light irradiation on PI surface.