• Bulletin of the Korean Chemical Society
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• v.19 no.5
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• pp.544-548
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• 1998

A Monte Carlo simulation incorporated with the genetic algorithm is presented to describe the defect known as "transition from Y-to X-type deposition" of the cadmium arachidate Langmuir-Blodgett multilayer film. Simulation is performed based on the detachment models of XY-type deposition. The transition is simulated by introducing a probability of surface molecule detachment considering interaction between neighboring molecules. The genetic algorithm is incorporated into Monte Carlo simulation to get the optimum value of the probability factors. The distribution of layers having different thickness predicted by the simulation correlates well with the measured distribution of thickness using the small-angle X-ray reflectivity. The effect of chain length and subphase temperature on the detachment probability are investigated using the simulation. Simulation results show that an increase (or a decrease) of two hydrocarbon chain is roughly equivalent to the detachment probability to a temperature decrease (or increase) of 15 K.

• Journal of Mechanical Science and Technology
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• v.20 no.4
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• pp.545-553
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• 2006

Generally, the temperature drop under $0^{\circ}C$ on vaporizer surface creates frozen dews. This problem seems to increase as the time progress and humidity rises. In addition, the frozen dews create frost deposition. Consequently, heat transfer on vaporizer decreases because frost deposition causes adiabatic condition. Therefore, it is very important to solve this problem. This paper aims to study of the optimum design of used vaporizer at local LNG station. In this paper, experimental results were compared with numerical results. Geometries of numerical and experimental vaporizers were identical. Studied parameters of vaporizer are angle between two fins $(\Phi)$ and fin thickness $(TH_F)$. Numerical analysis results were presented through the correlations between the ice layer thickness $(TH_{ICE})$ on the vaporizer surface to the temperature distribution of inside vaporizer $(T_{IN})$, fin thickness $(TH_F)$, and angle between two fins $(\Phi)$. Numerical result shows good agreement with experimental outcome. Finally, the correlations for optimum design of vaporizer are proposed on this paper.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.11
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• pp.886-890
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• 2010

The polytetrafluoroethylene (PTFE) films are deposited on glass using conventional rf-magnetron sputtering method. Their hydrophobic properties are investigated for application as an anti-fouling coating layer on the screen of displays. It is found that the hydrophobicity of PTFE films largely depends on the sputtering conditions, such as Ar gas flow and deposition time during sputtering process. These conditions are closely related to the deposition rate or thickness of PTFE film. Thus, it is also found that the deposition rate or the film thickness affects sensitively the geometrical morphology formed on surface of the rf-spluttered PTFE films. In particular, the PTFE film with 1950 nm thickness deposited for 30 minute at rf-power 50 W shows a very excellent optical transmittance of over 90% and a good anti-fouling property and a good durability.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.778-783
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• 2003

For ac Plasma Display Panel (PDP), the lifetime should be guaranteed over 30000 hours. The lifetime is correlated with the deterioration characteristics for the weakest element in ac PDP. In this paper, in order to improve the lifetime of ac PDP, a short-term relative lifetime test method for a given element in the ac PDP is proposed. By this method, the effects of MgO thin film thickness and deposition rate on the relative lifetime of ac PDP are investigated. The relative lifetime is increased with MgO thin film thickness but it was almost saturated over 5000. The relative lifetime decreased with increase in the MgO deposition rate and increased with Xe% in the working gas of He+Ne+Xe..

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.268-268
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• 2012

Adsorption and desorption of toluene from bare and $TiO_2$-coated silica with a mean pore size of 15 nm was studied using breakthrough curves and temperature programmed desorption. Thicknesses of $TiO_2$ films prepared by atomic layer deposition on silica were < 2 nm, and ~ 5 nm, respectively. For toluene adsorption, both dry and humid conditions were used. $TiO_2$-thin film significantly improved toluene adsorption capacity of silica under dry condition, whereas desorption of toluene from the surface as a consequence of displacement by water vapor was more pronounced for $TiO_2$-coated samples with respect to the result of bare ones. In the TPD experiments, silica with a thinner $TiO_2$ film (thickness < 2 nm) showed the highest reactivity for toluene oxidation to $CO_2$ in the absence and presence of water. We show that the toluene adsorption and oxidation reactivity of silica can be controlled by varying thickness of $TiO_2$ thin films.

• Journal of the Korean institute of surface engineering
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• v.36 no.2
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• pp.155-160
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• 2003

The effect of the temperature, current density and deposit time on hard chromium deposition in trivalent chromium bath was investigated. Cathode current efficiency increased with increasing current density. Increasing bath temperature from $20^{\circ}C$ to $50^{\circ}C$, chromium deposits were produced in higher current density and the maximum current efficiency was increased. At the plating conditions of $40^{\circ}C$, $30A/dm\m^2$, the deposition thickness increased in proportion to increasing electrolysis time The rate is$ 90\mu\textrm{m}$/hrs. for 2 hours. Microhardness of chromium deposits increased with increasing bath temperature and decreasing current density, and it was constant with electrolysis time. All of bath conditions, microstructure of chromium deposits has nodular structure with some cracking pattern and nodule size increased with increasing deposit thickness.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.447-451
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• 2009

Continuous SiC fiber-reinforced SiC composites ($SiC_f$/SiC) were fabricated by electrophoretic deposition (EPD). Nine types of slurries with different powder contents, binder resin amounts and slurry pH were deposited on Tyranno$^{TM}$-SA fabrics by EPD at 135 V for ten minutes to determine the optimal conditions. Further EPD using the optimum slurry conditions was performed on fabrics with four different pyrolitic carbon (PyC) thicknesses. The density of the hot-pressed composites decreased with increasing PyC thickness due to the difficulty of infiltrating the slurry into the narrow gaps between the fibers. On the other hand, the mechanical strength increased with increasing PyC thickness despite the decrease in density, which was explained by the enhanced crack deflection with increasing PyC thickness. The $SiC_f$/SiC composites showed the highest density and flexural strength of 94% and 342 MPa, respectively, showing EPD as a feasible method for dense $SiC_f$/SiC fabrication.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.4
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• pp.70-76
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• 2022

Calcium-phosphate-based bioceramics are promising biomaterials for scaffolds because they can assist in bone regeneration. In this study, a laser sintering deposition system was developed, and 3D hydroxyapatite (HA) scaffolds were fabricated. The main process conditions of the HA scaffolds were laser power, table velocity, and laser focal distance. As the laser power increased, the line width, line height, and layer thickness also increased. Further, the line width, line height, and layer thickness decreased as the table velocity increased. As the laser focal distance increased, the line width increased, but the line height and layer thickness decreased. The fabricated green scaffolds were sintered at 1050 ℃ and 1150 ℃. The sintered scaffolds had a uniform and continuous interconnected shape, with pore sizes ranging from 850 to 950 ㎛ having 53% porosity. The compressive strength of the scaffolds decreased from 0.72 MPa (1050 ℃) to 0.53 MPa (1150 ℃). The biocompatibility of the scaffolds was investigated by analyzing the adhesion of osteoblast-like MG-63 cells cultured on the surfaces of the scaffolds. The results indicate that the scaffold sintered at 1050 ℃ had good mechanical and biological properties compared to that at 1150 ℃.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1301-1309
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• 1994

A study of heat transfer and thermophoretic particle deposition has been carried out for the Modified Chemical Vapor Deposition(MCVD) process. A new concept utilizing two torches is suggested to simulate the heating effects from repeated traversing torches. Calculation results for the wall temperatures and deposition efficiency are in good agreement with experimental data. The effects of variable properties are included and heat flux boundary condition is used to simulate the moving torch heating. A conjugate heat transfer which includes heat conduction through solid layer and heat teansfer in a gas in a tube is analyzed. Of particular interests are the effects of torch speeds and solid layer thicknesses on the deposition efficiency, rate and the tapered entry length.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.519-526
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• 1987

TiC was deposited onto several substrate steels by the Chemical Vapor Deposition technique from TiCl4-CH4-H2 gas mixtures in the horizontal resistance furnace. Deposition rates and morphologies of the coatings were investigated with the carbon contents. Deposition thickness increased linearly with the deposition time in the Presence of CH4 gas. The various interlayers of coating by EDS and X-ray Diffraction were proved as Cr7C3 and Fe3C. Chromium contents did not affect the preferred orientation of TiC deposit. The deposition was controlled by a mass transport and a surface reaction in case of 1 wt% C-5.25 wt% Cr steel irrespective of deposition temperature.