• 산업기술연구
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• 제26권B호
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• pp.173-181
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• 2006

We analyzed systematically particle growth in the pulsed $SiH_4$ plasmas by a numerical method and investigated the effects of pulse modulations (pulse frequencies, duty ratios) on the particle growth. We considered effects of particle charging on the particle growth by coagulation during plasma-on. During plasma-on ($t_{on}$), the particle size distribution in plasma reactor becomes bimodal (small sized and large sized particles groups). During plasma-off ($t_{off}$), there is a single mode of large sized particles which is widely dispersed in the particle size distribution. During plasma on, the large sized particles grows more quickly by fast coagulation between small and large sized particles than during plasma-off. As the pulse frequency decreases, or as the duty ratio increases, $t_{on}$ increases and the large sized particles grow faster. On the basis of these results, the pulsed plasma process can be a good method to suppress efficiently the generation and growth of particles in $SiH_4$ PCVD process. This systematical analysis can be applied to design a pulsed plasma process for the preparation of high quality thin films.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.168-173
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• 2000

Flame aerosol synthesis technology refers to the formation of fine particles from gases in flame and is widely used in practical materials processing. In this paper, an experimental investigation was performed on growth of the silica particles that were generated in $H_2/O_2$ Diffusion Flame by the direct injection or TEOS using Electro-spraying method. in this flame aerosol synthesis, four main parameters or nos interaction (flame temperature, residence time or particle in flame, TEOS flow rate, applied voltage) for particle generation and growth was investigated along the axial direction above the burner. A fairly monodisperse non-aggregated particles were successfully obtained.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1492-1494
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• 1996

We have studied the generation, growth and behavior of chemical species and particles in silane PCVD. We included the plasma chemistry of silane, particle nucleation by homogeneous formation, acrosol dynamics and transport phenomena of chemical species and particles. The concentration profile of chemical species and particles were shown as a function of reactor length. The effects of process variables such as reactor pressure, total gas flow rate and electrical field strength on the behavior of chemical species and particles were analyzed.

• 대한기계학회논문집B
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• 제23권5호
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• pp.670-677
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• 1999

An analysis of generation and growth of multicomponent particles has been carried out to predict the size and composition distributions of particles generated in the Modified Chemical Vapor Deposition(MCVD) process. In MCVD process. scale-up of sintering and micro-control of refractive index may need the Information about the size and composition distributions of $SiO_2-GeO_2$ particles that are generated and deposited. The present work solved coupled steady equations (axi-symmetric two dimensions) for mass conservation, momentum balance. energy and species(such as $SiCl_4$, $GeCl_4$, $O_2$, $Cl_2$) conservations describing fluid flow. heat and mass transfer in a tube. Sectional method has been applied to obtain multi-modal distributions of multicomponent aerosols which vary in both radial and axial directions. Chemical reactions of $SiCl_4$ and $GeCl_4$ were included and the effects of variable properties have also been considered.

• 한국입자에어로졸학회지
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• 제10권1호
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• pp.27-31
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• 2014

A simple bimodal model has been developed to analyze charged particle coagulation by modifying previously suggested bimdal model for evolution of particle generation and growth. In the present model, two monodisperse modes are used and 40 charge nodes are assigned to each mode to account both change of the particle size and charge distribution. In addition, we also implemented the effect of electrostatic dispersion loss in the present model. Based on the developed model, we analyzed coagulation of asymmetric bipolar charged particles by computing evolutions of particle number concentration, geometric mean diameter of particles, charge asymmetric ratio and geometric standard deviation of particle size distribution for various initial charge asymmetric ratios. The number concentration of asymmetric bipolar charged particles decreases faster than that of neutral particles but that does not give faster growth of particles since the electrostatic dispersion loss overwhelms particle growth by coagulation.

• 산업기술연구
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• 제30권A호
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• pp.127-132
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• 2010

We analyzed the effects of several process variables on the $SO_2$ removal and particle growth by the dielectric barrier discharge - photocatalysts hybrid process. In this process, $SO_2$ was converted into the ammonium sulfate ($(NH_4)_2SO_4$) particles. The size and crystallinity of ammonium sulfate particles were examined by using TEM and XRD analysis. The dielectric barrier discharge reactor consisted of two zones: the first is for plasma generation and the second is for ammonium sulfate particles formation and growth. The first zone of reactor was filled with glass beads as a dielectric material. To enhance $SO_2$ removal process, the $TiO_2$ photocatalysts were coated on glass beads by dip-coating method. As the voltage applied to the plasma reactor or the pulse frequency of applied voltage increases, the $SO_2$ removal efficiency increases. Also as the initial concentration of $SO_2$ decreases or as the residence time increases, the $SO_2$ removal efficiency increases. $(NH_4)_2SO_4$ particles continue to grow by particle coagulation and surface reaction, moving inside the reactor. Larger particles in site are produced according to the increase of residence time or $SO_2$ concentrations.

• 한국입자에어로졸학회지
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• 제5권3호
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• pp.95-109
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• 2009

A low temperature plasma process has been widely used for semiconductor fabrication and can also be applied for the preparation of solar cell, MEMS or NEMS, but they are notorious in the point of particle contamination. The nano-sized particles can be generated in the low temperature plasma process and they can induce several serious defects on the performance and quality of microelectronic devices and also on the cost of final products. For the preparation of high quality thin films of high efficiency by the low temperature plasma process, it is desirable to increase the deposition rate of thin films with reducing the particle contamination in the plasmas. In this paper, we introduced the studies on the generation and growth of nanoparticles in the low temperature plasmas and tried to introduce the recent interesting studies on nanoparticle generation in the plasma reactors.

• 한국진공학회지
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• 제10권2호
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• pp.275-281
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• 2001

플라즈마 반응기 내에서 입자 전하 분포가 Gaussian형태로 표현될 때 전하 분포를 가지는 입자들의 충돌에 의한 입자 성장을 discrete-sectional 모델을 사용하여 이론적으로 고찰하였다. 플라즈마 반응기 내에서 입자 성장을 분석하기 위해 monomer크기, monomer생성 속도 등의 공정 변수들을 변화시켰다. 입자 크기가 40 m이상인 큰 입자들은 플라즈마 반응기내에서 대부분이 음으로 존재하였으며 40 m이하인 작은 입자들은 음성, 중성 혹은 양으로 존재하였다 입자 충돌에 의해 입자 크기가 증가함에 따라 입자 표면적의 증가와 더불어 입자가 가지는 평균 음전하수도 증가하였다. 입자 충돌에 의해 큰 입자들이 생성됨에 따라 입자크기분포는 2개의 모드로 양분화 됐다. 본 연구의 이론 결과와 Shiratani 등 [3]의 실험결과가 비교적 잘 맞았으며 본 연구에서 사용한 모델식은 플라즈마 반응기 내에서 수 나노 크기의 입자 성장 연구에도 활용될 수 있을 것으로 기대된다.

• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1972-1979
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• 2006

This study was conducted in order to generate model particles which were similar to particles in diesel emission. Spark discharge was used for carbon agglomerates and hydrocarbon condensation for particles that consist of carbon agglomerates and hydrocarbon. The size of the carbon agglomerates, whose mean size were 30 and 70 nm, ranged between 15 and 200 nm, and the total number concentration of the particles ranged from 3 to $5{\times}10^7#/cm^3$ as the controllable variables in spark discharge generator changed. The result of the hydrocarbon condensation experiment showed that the final sizes of the particles enlarged by condensation did not depend on the initial sizes, but the maximum condensational growth of carbon agglomerates by dodecane ($C_{12}H_{26}$) condensation was 112 times the initial size of 40 nm, while the size of the agglomerates by benzene ($C_6H_6$) was 3.25 times its initial size.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1351-1358
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• 2000

Two dimensional aerosol dynamics considering the effects of particle generation, coagulation, thermophoresis, sintering and convection has been studied to obtain the growth of non-spherical silica particles in conjunction with determining flame temperature by performing combustion analysis of premixed flat flame. Heat and mass transfer analysis includes 16 species, 29 chemical reaction steps together with oxidation and hydrolysis of SiCl4. The effect of radiation heat loss has also been included. The predictions of flame temperatures and the evolution of particle size distributions were in a reasonable agreement with the existing experimental data.