• 산업기술연구
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• 제21권B호
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• pp.149-153
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• 2001

A study on the particle growth in $TEOS/O_2$ plasma was performed, and particle size and its distribution was measured by the electrical aerosol analyzer (EAA), light scattering particle size analyzer and the particle size was also determined by SEM. The effects of process variables such as total gas flow rate, reactor pressure, supplied power and initial reactant concentration on the particle growth were investigated. From the EAA results, the particle size distribution is divided into three groups of the cluster size and the small and large size particles. The particle size distribution measured by the light scattering particle size analyzer becomes bimodal, because the cluster size particles smaller than 20 nm in diameter cannot be detected by the light scattering particle size analyzer. The size of particles measured by the light scattering particle size analyzer is in good agreements with those by the SEM. Also we could understand that the particle formation is very sensitive to the changes of reactor pressure and reactant concentration. As the total gas flow rate increases, the particle size decreases because of the shorter residence time. As the reactor pressure, or the reactant concentration increases, the particle concentration increases and the particles grow more quickly by the faster coagulation between particles.

• 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.

• 산업기술연구
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• 제23권A호
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• pp.175-179
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• 2003

A study on the particle growth in $TEOS/O_2$ plasma was performed by observing the particle size and its morphology by TEM. The qualitative chemical analysis of particles was also determined by the EDS (Energy Dispersive X-Ray Spectrometer). The effects of process variables such as the plasma on-time and bubbler temperature on the particle growth were investigated. The particle size becomes larger as the plasma on-time because of the longer coagulation, and also as the bubbler temperature increases because of the faster coagulation between particles.

• 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.

• KEPCO Journal on Electric Power and Energy
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• 제8권2호
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• pp.103-110
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• 2022

Ultrafine Particle number and size distributions were simultaneously measured at rural area around the power plant in Dangjin, South Korea. New Particle formation and growth events were frequently observed during January, 2021 and classified based on their strength and persistence as well as the variation in geometric mean diameter(GMD) on January 12, 21 and 17. In this study, we investigated mechanisms of new particle growth based on measurements using a high resolution time of flight aerosol mass spectrometer(HR-ToF-AMS) and a scanning mobility particle sizer(SMPS). On Event days(Jan 12 and 21), the total average growth rate was found to be 8.46 nm/h~24.76 nm/hr. These growth rate are comparable to those reported for other urban and rural sites in South Korea using different method. Comparing to the Non-Event day(Jan 17), New Particle Growth mostly occurred when solar radiation is peaked and relative humidity is low in daytime, moreover enhanced under the condition of higher precusors, NO₂ (39.9 vs 6.2ppb), VOCs(129.5 vs 84.6ppb), NH₃(11 vs 4.7ppb). The HR-ToF-AMS PM_1.0 composition shows Organic and Ammoniated nitrate were dominant species effected by emission source in domestic. On the other hand, The Fraction of Ammoniated sulfate was calculated to be approximately 16% and 31% when air quality is inflow from China. Longer term studies are needed to help resolve the relative contributions of each precusor species on new particle growth characteristics.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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• pp.13-19
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• 1997

From the formation of the monodispersed silica particle which is a valuable for the industry by Sol-Gel process, the effects of the parameters participated in the process, the growth mechanism and the characteristics of silica particles for each rection conditions are investigated. To investigate about the formation of final silica particles, the suspension which performs the polymerization is reacted with molybdic acid, and the evolutions of TEOS and silica particle size are investigated in the reaction time ？ 새 the characteristics of molybdic acid with the suspension. From the results, a constant number of silica particle is formed at early reaction stage. Silica particles grow through the aggregation of smaller particles and nucleation is rate-limiting step for the growth of particles. In the conditions of this study, spherical silica particles are formed, [NH$_3$] and [$H_2O$] concentration increase the particle size but particle size decrease with [$H_2O$] concentration which is a certain above region. Average particle sizes are 187.4~483.3 nm and standard deviations in the average particle size are 1.7~2.9% with each experimental condition. From the BET results, specific surface area is 5.5~23.4 $m^2$/g and these values decrease with increase size. The average pore size is 50~70$\AA$.

• Environmental Engineering Research
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• 제21권4호
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• pp.365-372
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• 2016

The effects of hydrodynamics and alum dose on particle growth were investigated by monitoring particle counts in a rapid mixing process. Experiments were performed to measure the particle growth and breakup under various conditions. The rapid mixing scheme consisted of the following operating parameters: Velocity gradient (G) ($200-300s^{-1}$), alum dose (10-50 mg/L) and mixing time (30-180 s). The Poisson regression model was applied to assess the effects of the doses and velocity gradient with mixing time. The mechanism for the growth and breakup of particles was elucidated. An increase in alum dose was found to accelerate the particle count reduction. The particle count at a G value of $200s^{-1}$ decreased more rapidly than those at $300s^{-1}$. The growth and breakup of larger particles were more clearly observed at higher alum doses. Variations of particles due to aggregation and breakup of micro-flocs in rapid mixing step were interactively affected by G, mixing time and alum dose. Micro-flocculation played an important role in a rapid mixing process.

• 한국세라믹학회지
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• 제32권2호
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• pp.147-154
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• 1995

Abnormal grain growth behavior of BaTiO3 ceramics with controlling of particle size distribution of calcined powder was investigated. The particle size distribution was controlled by changing the calcining temperature or by using of classification and regrinding process. With broadening of the normallized size distribution in calcined powder, it showeda normal grain growth behavior in sintered body due to an increase of volume fraction of seed grain in the calcined powder. It was supposed that the seed grains could easily contact each other for the rapid grain growth during sintering process and resulted in fast switching-over from abnormal to normal grain growth stage.

• 한국가시화정보학회지
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• 제20권2호
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• pp.63-69
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• 2022

In this study, we numerically simulate the condensational growth of micron-sized particles traveling through a pipe filled with humidified air. Using the finite volume method and Lagrangian particle tracking technique, the mixture of particle-laden flow with moist air in a T-juction pipe is simulated. The condensational growth of particles is calculated by considering the mass transfer of vapor in the air onto the particle surface. The results indicate that the growth rate of the particles increases as the relative humidity of air is higher. Furthermore, the placement of a porous media with low permeability in the pipe could enhance the degree of condensational growth.

• International Journal of Korean Welding Society
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• 제2권1호
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• pp.25-28
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• 2002

In the coarse grain HAZ adjacent to the fusion line, most of the TiN particles in conventional Ti added steel are dissolved and austenite grain growth is easily occurred during welding process. To avoid this difficulty, thermal stability of TiN particle is improved by increasing the nitrogen content in steel. In this study, the effect of hlgh nitrogen TiN particle on preventing austenite grain growth in HAZ was investigated. Increased thermal stability of TiN particle is helpful for preventing the austenite grain growth by pinning effect. High nitrogen TiN particle in simulated HAZ were not dissolved even at high temperature such as 1400'E and prevented the austenite grain growth in simulated HAZ. Owing to small austenite grain size in HAZ the width of coarse grain HAZ in high nitrogen TiN steel was decreased to 1/10 of conventional TiN steel. Even high heat input welding, the microstructure of coarse grain HAZ consisted of fine polygonal ferrite and pearlite and toughness of coarse grain HAZ was significantly improved.