• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.59-64
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• 2001

The fluid flow, mass transfer and film thickness variation during a wafer spin coating process are numerically studied. Governing equations for the cylindrical coordinates are simplified using the similarity transformation and solved efficiently using the finite difference method. Concentration dependent viscosity and the binary diffusivity of the coating liquid are used in the analysis. The time variational velocity components of the coating liquid and the film thickness are analyzed according to the various spin speed. When the evaporation is considered, the flow decease in the early times due to the increase of the viscosity and the resultant flow resistance. Effects of the two film thinning mechanism, the flow-out and evaporation are also considered in the analysis.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.115-118
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• 2008

지금까지 액막두께나 air core 직경 변화 등과 같은 수력학적 과정에 대한 이론 실험적 연구가 많이 이루어져왔다. 스월 노즐에서 수치적 해석 등을 통해 이에 대한 몇 가지 이론식들이 확립되었지만, 아직까지 내부유동에 대한 실험적 연구 결과 등은 명백히 정립되어 있지 않고 있다. 본 연구에서는 스월 챔버 내의 air core를 가시화하고 액막두께를 측정하여 내부유동의 변화 및 안정성 등을 살펴보았다.

• 한국추진공학회지
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• 제12권6호
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• pp.30-37
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• 2008

지금까지 액막두께나 air core 직경 변화 등과 같은 수력학적 과정에 대한 이론 실험 연구가 많이 이루어져왔다. 스월 노즐에서 수치적 해석 등을 통해 이에 대한 몇 가지 이론식들이 확립되었지만, 아직까지 내부유동에 대한 실험적 연구 결과 등은 명백히 정립되어 있지 않고 있다. 본 연구에서는 스월 챔버 내의 air core 구조를 가시화하고 오리피스에서의 액막두께를 측정함으로써 접선방향유입구 조건에 따른 내부유동의 안정성 여부를 판단해볼 수 있었다.

• 대한기계학회논문집B
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• 제25권11호
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• pp.1483-1491
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• 2001

Enhancement of pulsed-laser ablation by an artificially deposited liquid film is presented. Measurements of ablation rate, ablation threshold, and surface topography arc performed. Correlation between material ablation and photoacoustic effect is examined by the optical beam deflection method. The dependence of ablation rate on liquid-film thickness and chemical composition is also examined. The results indicate that photomechanical effect in the phase explosion of liquid is responsible for the enhanced ablation. The low critical temperature of liquid induces explosive vaporization with localized photoacoustic excitation in the superheat limit and increases the ablation efficiency. Experiments were carried out utilizing a Q-swiched Nd:YAG laser at near-threshold laser fluences with negligible plasma effect (up to ∼100 MW/cm$^2$).

• 한국분무공학회지
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• 제7권4호
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• pp.1-8
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• 2002

This paper investigates the spray angle and the outline shape of the liquid sheet discharged from a simplex swirl nozzle. A theoretical model was proposed and the corresponding experimental data were presented for comparison. Axial and tangential velocities and thickness of the liquid sheet at the nozzle exit were also predicted. The liquid sheet thickness at nozzle exit, as well as the discharge coefficient, turned out to be a sole function of the swirl Reynolds number. However, the axial and tangential velocities at nozzle exit and the spray angle could not be expressed only with the swirl Reynolds number. The predicted outline shape and spray angle of the liquid sheet agreed reasonably with the measured data.

• 한국진공학회지
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• 제8권3A호
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• pp.231-237
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• 1999

$SrBi_{22.4}Ta_2O_9$ (SBT) thin films of 70~150 nm thickness were prepared on platinized silicon substrates by Liquid Source Misted Chemical Deposition (LSMCD) process, and their microstructure, feroelectric and leakage current characteristics were investigated. By annealing at $800^{\circ}C$ for 1 hour in oxygen ambient, SBT films were fully crystallized to the Bi layered perovskite structure without preferred orientation. The grain size of the LSMCD- derived SBT films was about 100nm, and was not varied with the film thickness. $2P_r$ and $E_c$ of the SBT films increased with decreasing the film thickness, and the 70nm-thick SBT film exhibited $2P_r$ of 17.8 $\mu$C/$\textrm{cm}^2$ and $E_c$ of 74kV/cm at applied voltage of 5V. Within the film thickness range of 70~150nm, the relative dielectric permittivity of the LSMCD-derived SBT film decreased with decreasing the film thickness. Leakage current densities lower than $10^{-7}\textrm{A/cm}^2$ at 5V were observed in the SBT films thicker than 125nm.

• 반도체디스플레이기술학회지
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• 제2권1호
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• pp.25-29
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• 2003

The fluid flow, mass transfer, heat transfer and film thickness variation during the spin coating process are numerically studied. The model is said to be I-dimensional because radial variations in film thickness, concentration and temperature are ignored. The finite difference method is employed to solve the equations that are simplified using the similarity transformation. In early time, the film thinning is due to the radial convective outflow. However that slows during the first seconds of spinning so the film thinning due to evaporation of solvent becomes sole. The time varing film thickness is analyzed according to the wafer spin speed, the various solvent fraction in the coating liquid, and the various solvent vapor fraction in the bulk of the overlying gas during the spin coating is estimated.

• 한국인쇄학회지
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• 제23권2호
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• pp.129-141
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• 2005

The liquid film behavior between two rotating rollers has been analyzed for many years. Their contributions were, however, limited almost within the areas of polymer laminar flow in there. When the slip contact of two rotating rollers is used as a role of vehicle to distribute the liquid discharged on to each roller after splitting from the nip, there was few available relationship to control the roller speed and to design system. On this work it was possible to get out a certain relationship between the discharged film thickness ratio and the roller surface seeds without any help of pressure limit at the splitting point. The hydrodynamic analyzation of Newtonian liquid behavior around the point was well proved on some manipulative experiment. The thickness ratio increases along with the roll surface speed ratio increases. And the discharged volume flow rate ratio on each roller surface varies with square of the speed ratio. Both of these relationship have a decision factor also made up by the speed ratio.

• 대한기계학회논문집B
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• 제35권11호
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• pp.1169-1176
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• 2011

액막류는 레이놀즈수 및 유동 안정성에 의해 파동이 없는 층류액막류, 파동을 동반한 층류 액막류 및 난류액막류로 구분된다. 파동액막류는 강한 비선형성에 의해 매우 복잡하여 기존에는 주로 실험적 연구가 진행되었다. 수치적 해석은 주로 파동이 없는 경우에 국한되었으며 여러 가지 자유표면 해석기법을 이용하여 평균액막두께를 예측하였다. 이 연구에서는 층류액막류의 파동현상을 레이놀즈수 20~1000 범위에서 수치해석하였다. 이 때, VOF 자유표면 해석기법에 기반한 여러 가지 수치방법을 비교 연구하였으며 평균액막두께, 파동속도 및 진폭을 실험결과와 비교하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.251-253
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• 2017

Prefilming air blast 연료노즐의 다상유동 해석을 수행하였다. 연료가 미립화되는 과정을 관찰하였으며 liquid film의 두께와 속도를 계산하였다. Slot에서 분사된 연료는 prefilmer surface에서 얇은 액막을 형성한 후 연료노즐 lip에서 액적으로 분열되었다. 또한 계산된 liquid film의 두께와 속도를 경계조건으로 하여 반응유동장 해석을 수행하였다. 분사된 액적은 venturi throat를 지나면서 기화되었고 연료노즐 하류에 반응영역이 형성되어 안정적으로 보염이 이루어졌다.