Analysis of Particle Contamination in Plasma Reactor by 2-Sized Particle Growth Model

Kim, Dong-Joo,Lyoo, Pil Jo,Kim, Kyo-Seon 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.2

Rapid particle growth in the silane plasma reactor by coagulaton between 2-sized particles was analyzed for various process conditions. The particle coagulation rate was calculated considering the effects of particle charge distribution based on the Gaussian distribution function. The large size particles are charged more negatively than the small size particles. Some fractions of small size particles are in neutral state or charged positively, depending on the plasma conditions. The small size particle concentration increase at first and decreases later and reaches the steady state by the balance of generation rate and coagulation rate. The large size particles grow with discharge time by coagulation with small size particles and their size reaches the steady state, while the large size particle concentration increase with discharge time by faster generation rate and reaches the steady state by the balance of generation and disappearance rates. As the diameter of small size particles decreases, the diameter of large size particles increases more quickly by the faster coagulation with small size particles of higher concentration. As the residence time increases, the concentration and size of large size particles increase more quickly and the average charges per small size and large size particle decrease.

Aerosol size distributions observed at the Seoul National University campus in Korea during the Asian dust and non-Asian dust periods

Park, Soon-Ung,Kim, Jong-Won Elsevier 2006 Atmospheric environment Vol.40 No.9

<P><B>Abstract</B></P><P>Aerosol size distributions of observed mass concentration and number concentration at the Seoul National University (SNU) campus site in Korea during the non-Asian dust and the Asian dust (Hwangsa) periods have been examined using the 8-stage cascade impactor and the 8-channel airborne particle counting system, respectively. The particle size distribution of the observed mass concentration during the Asian dust period at the SNU site is compared with that observed at the Asian dust source site of Duolun in Inner Mongolia, China. The results indicate that the size distribution of both the mass concentration and the number concentration shows a bi-modal distribution that can be regressed optimally with two log-normal distribution functions. It is found that the optimally regressed probability density function of the mass concentration distribution during the non-Asian dust period at the SNU site shows two log-normal distributions with the particle mean diameters of 0.66 and 8.51μm and the standard deviations of 1.78 and 2.14μm, respectively. The probability density of the small size mode is slightly smaller than that of the large size mode. During the Asian dust period at the SNU site the estimated probability density function of the mass concentration also composes of two log-normal distributions with the particle mean diameters of 0.89 and 9.12μm and the standard deviations of 2.40 and 2.14μm, respectively. However, the high probability density is greatly shifted to the large size mode. The probability density of the small size mode is only 6% of that of the large size mode. A quite similar size distribution pattern is found in the Asian dust source region of Duolun, suggesting the high probability density at the large particle-size mode during the Asian dust period being mainly attributed to long-range transport of particles from the Asian dust source region. It is also found that the estimated probability density function of the number concentration distribution observed at the SNU site during the non-Asian dust period has a bi-modal distribution with the particle mean diameters of 0.36 and 1.12μm and the mean standard deviations of 1.48 and 1.91μm, respectively. Much higher probability density is found in the small size mode in contrast to that of the mass concentration distribution where the probability density of both modes is almost the same.</P>

TEOS/O₂플라즈마 반응기에서 미립자 성장에 대한 실험적 분석

김동주,김교선 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.B

A study on the particle growth in TEOS/O2 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 20nm 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 deceases 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.

Two dimensional size-mass distribution function inversion from differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) measurements

Rawat, V.K.,Buckley, D.T.,Kimoto, S.,Lee, M.H.,Fukushima, N.,Hogan, C.J. Pergamon Press ; Elsevier Science Ltd 2016 Journal of aerosol science Vol.92 No.-

<P>We developed and applied a data inversion routine to determine the number based size-mass distribution function (the two dimensional distribution function) from tandem differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) measurements. The two dimensional distribution function is expressed in units of particle number concentration per unit mobility diameter per unit particle mass. It can be used to directly calculate the number based size distribution (commonly determined using DMA measurements) or the mass based size distribution (commonly inferred from impactor measurements). The inversion routine utilizes the Twomey-Markowski algorithm and is applied in this study to DMA-APM measurements of sodium chloride, cesium iodide, and ammonium sulfate particles in the 30-200 nm mobility diameter range, as well as acetylene flame generated soot aggregates in the 40-350 nm range. To utilize the inversion routine, the APM transfer function must be known a priori. Here it is computed using a modified version of the Ehara (uniform flow) model, with a transmission correction factor inferred from measurements. For the three examined salt particle types, visual representation of the two dimensional distribution function reveals that at a given mobility diameter, particles have very narrow mass distributions, with the peak masses in good agreement with predictions based on bulk salt densities. However, for soot particles, extremely broad distributions are observed. Soot measurements are compared to predictions for quasifractal aggregates in the transition regime; this comparison suggests that aggregates with fractal dimensions ranging from 1.4 to 2.5 are all generated in the same system. Finally, we determine the two-dimensional distribution function for a mixture of ammonium sulfate and soot particles, demonstrating that these two particle populations are separable from one another via mobility-mass analysis. (C) 2015 Elsevier Ltd. All rights reserved.</P>

Comparisons of particle size measurement method for colloidal silica

Dong-Hyun Lee 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.2

Several methods have been used to measure the particle size and distribution of colloidal silica. It is an important parameter governing the proper function of many industrial products, for example, organic-inorganic hybrid coatings, ceramic coatings, paints, and inks, etc. Particle size distribution of commercial colloidal silica of eight was measured by TEM (transmission electron microscopy) or DLS (dynamic light scattering). The accuracy of the particle distribution is decreased when the colloidal silica is a mixture of approximately 50 nm particles and 100 nm particles. The particles less than ~50 nm may not be detected by DLS analyzer in the case of mixture sample. In order to investigate the difference in particle size distribution among measurement methods, we have compared and discussed particle size results measured from DLS, TEM, and BET (Brunauer-Emmett-Teller) analysis. In the TEM observation, 16 TEM images from one grid were compared and found out that the particle size distribution may vary based on the positions from which the particles are observed either scattered or agglomerated. We suggest combination of DLS, TEM and BET method to obtain the particle size distribution reflecting the dispersion, which represents the surface properties and aggregation state.

이차원 개별요소 수치해석을 통한 화강풍화토의 평균입자크기와 전단강도의 관계 규명

김선욱,임희대 한국지반공학회 2012 한국지반공학회논문집 Vol.28 No.12

We have carried out a series of numerical experiments to study the effect of average particle size on the mechanical properties of granite-derived weathered soils. A distinct-element method was adopted to study the changes in macro-scale mechanical properties with particle size and maximum-to-minimum particle size ratio. The numerical soil specimen with cohesion values of 0.25 MPa and internal friction angle of 29 degrees was prepared for reference. While keeping the porosity values constant, we varied particle size and size distribution to study how cohesion and internal friction angle changes. The experimental results show that the values of cohesion apparently decrease with increasing particle size. Changes in the values of internal friction angles are small, but there is a trend of increase in internal friction angle as the average particle size increases. This study demonstrates a possibility that the results of numerical experiments of this type may be used for rapid estimation of mechanical properties of granite-derived weathered soils. For example,when mechanical properties obtained through in situ tests and particle size data obtained through lab analysis are available for a site, it is expected that the mechanical properties of weathered granite soils with varying degrees of weathering (thus, varying particle size) may be estimated rapidly only with particle size data for that site.

골재의 입도분포 변화에 따른 PE 섬유보강 고연성 시멘트 복합체의 인장성능

이방연,강수태 한국구조물진단유지관리공학회 2020 한국구조물진단유지관리공학회 논문집 Vol.24 No.5

For the purpose of developing a PE fiber-reinforced highly ductile cementitious composite having high tensile strain capacity more than 2% under the condition of containing aggregates with large particle size, this study investigated the tensile behavior of composites according to the particle size and distribution of aggregates in the composite. Compared with the mixture containing silica sand of which particle size is less than 0.6 mm, mixtures containing river sand and/or gravel with the maximum particle size of 2.36mm, 4.75mm, 5.6mm, 6.7mm were considered in the experimental design. The particle size distributions of aggregates were adjusted for the optimized distribution curves obtained from modified A&A model by blending different sizes of aggregates. All the mixtures presented clear strain-hardening behavior in the direct tensile tests. The mixtures with the blended aggregates to meet the optimum curves of aggregate size distributions showed higher tensile strain capacity than the mixture with silica sand. It was also found that the tensile strain capacity was improved as the maximum size of aggregate increased which resulted in wider particle size distribution. The mixtures with the maximum size of 5.6mm and 6.7 mm presented very high tensile strain capacities of 4.83% and 5.89%, respectively. This study demonstrated that it was possible to use coarse aggregates in manufacturing highly ductile fiber-reinforced cementitous composite by adjusting the particle size distribution. 이 연구에서는 입경이 큰 골재를 사용하면서 2% 이상의 인장변형률 성능을 나타내는 고연성 PE 섬유보강 시멘트 복합체 개발을 목적으로 골재의 크기와 입도분포에 따른 고연성 섬유보강 시멘트 복합체의 인장거동 특성을 살펴보고자 하였다. 0.6mm 이하의 입경들로 구성된 규사를 사용한 배합을 기준으로 최대입경 2.36mm, 4.75mm, 5.6mm, 6.7mm의 강모래 및 강자갈을 사용한 배합을 비교하여 성능평가를 실시하였다. 골재의 입도분포는 수정 A&A 모델에 기반한 최적입도분포곡선에 가깝도록 세분화된 입경별 혼합비율을 조절하였다. 직접인장실험을 통해 구한 인장거동은 모든 배합에서 뚜렷한 인장변형률 경화 거동을 보였다. 골재 입경별 혼합비율을 조절하여 입도분포가 최적곡선에 가깝도록 한 경우에는 모든 배합에서 규사를 사용한 경우보다 높은 인장변형률 성능을 나타내었다. 또한 골재의 최대입경이 커서 입도분포가 넓을수록 높은 인장변형률 성능을 보였으며, 최대입경 5.6mm, 6.7mm의 굵은 골재를 포함하는 경우 각각 4.83%와 5.89%의 매우 높은 인장변형률 성능을 나타내었다. 이 연구를 통해 적절한 입도분포 조절을 통해 굵은 골재를 사용하면서도 고연성 섬유보강 시멘트 복합체의 제조가 가능함을 보였다.

펄 안료의 입도분포에 미치는 분쇄시간 및 바인더의 영향

소태섭 ( Tae-sup So ),고두진 ( Du-jin Go ),노희수 ( Hee-su Ro ),김상범 ( Sang-bum Kim ),김태원 ( Tae-won Kim ),김중회 ( Joong-hoi Kim ) 대한화장품학회 2004 대한화장품학회지 Vol.30 No.4

메이크업 제품에 있어서 특히 아이섀도나 블러셔와 같은 포인트 메이크업 제품의 제조시 화사함이나 광택을 부여하기 위하여 사용되는 펄 안료에 대하여 분쇄시간에 따른 입도분포 변화와 결합제로 사용되는 바인더의 영향에 따른 입도분포의 변화에 대하여 검토하였다. 고속 회전형 믹서기를 사용하였으며 레이져 회절·산란법을 이용하여 입도분포를 측정하였다. 평균경 5 ㎛의 펄 안료인 경우 120 s간 분쇄하였을시 4.5 ㎛로 입자경의 변화 폭이 작지만, 45 ㎛인 경우 27 ㎛로 현저히 작아지며 그에 따라 본래의 광택감도 떨어지는 것을 확인할 수 있었다. 바인더의 경우, raw material의 입자사이즈에 따라 분쇄시간과의 상관성을 확인하였으며, 바인더 함량에 따라 입자간의 응집에 의하여 발생하는 분립체의 입도분포의 변화에 대해서도 고찰하였다. For pearl pigments used for splendor or gloss effect of make-up products, especially point make-up products like eye-shadow and blusher, we studied the variation of particle size distribution by the grinding time and by the binder used as a binding agent. In this study, high speed mixer was used and the particle sire distribution was measured by using the light scattering method. In case of pearl pigments, its median diameter of 5 ㎛, the particle size was reduced to 4.6 um when it was ground for 120 s. When it was applied for the pearl pigment of 45 ㎛, the particle size was reduced to 27 ㎛. We confirmed that the latter was reduced more largely and the original gloss was reduced too. For the binder, we studied the correlation between particle size of raw material and grinding time. We also investigated the effects of the binder contents on the variation of particle size distribution of products by aggregation of particles.

Size Monitoring in the Synthesis of Silica Nanoparticles Using Asymmetrical Flow Field-Flow Fractionation (AF4)

한수정,최재영,Yeongsuk Yoo,정의창,이승호 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.3

Particle size is one of the important parameters that determine the characteristics (and applicability) of silica nanoparticles. An accurate sizing technique is therefore required for quality control during the synthesis of silica nanoparticles. Unlike other sizing techniques, the field-flow fractionation (FFF) provides size-based separation of colloidal particles, and allows an FFF elution profile, which can be converted to a size distribution directly. Synthesis of silica nanoparticles having narrow size distributions is not trivial, as there are many parameters affecting the characteristics of the synthesized particles. In this study, silica nanoparticles were synthesized by emulsion polymerization, where ethanol, ammonium hydroxide, and tetraethyl orthosilicate (TEOS) were mixed at room temperature. First, silica nanoparticles were synthesized in a smaller scale with a total reaction volume of 175 mL. Then the effect of various reaction parameters on the particle size distribution (PSD) was systematically investigated using asymmetrical flow FFF (AF4), a member of FFF family. The synthesis scale was then increased to the total reaction volume of 3 L. It was observed that, as the concentrations of TEOS and ethanol increased, the size of the silica nanoparticles tended to decrease, while as the concentration of ammonium hydroxide increased, the size tended to increase. Silica nanoparticles of about 100 nm having a relatively narrow size distribution could be obtained in a large scale with the concentrations of TEOS, ethanol, and ammonia solution of 95, 95, and 15%, respectively. The results suggest that AF4 is a useful tool for fast and accurate size monitoring of silica nanoparticles.

겨울철 도시지역 대기 수용성 에어로졸 입자의 크기 분포를 결정하는 주요 인자

박승식,Park, Seungshik 한국입자에어로졸학회 2021 Particle and Aerosol Research Vol.17 No.3

Size distributions of atmospheric particulate matter (PM) and its water-soluble organic and inorganic components were measured between January and February 2021 at an urban site in Gwangju in order to identify the major factors that determine their size distributions. Their size distributions during the study period were mainly divided into two groups. In the first group, PM, NO₃^-, SO₄^2-, NH₄⁺ and water-soluble organic carbon (WSOC) exhibited bi-modal size distributions with a dominant condensation mode at a particle size of 0.32 ㎛. This group was dominated by local production of secondary water-soluble components under atmospheric stagnation and low relative humidity (RH) conditions, rather than long-range transportation of aerosol particles from China. On the other hand, in the second group, they showed tri-modal size distributions with a very pronounced droplet mode at a diameter of 1.0 ㎛. These size distributions were attributable to the local generation and accumulation of secondary aerosol particles under atmospheric conditions such as atmospheric stagnation and high RH, and an increase in the influx of atmospheric aerosol particles by long-distance transportation abroad. Contributions of droplet mode NO₃^-, SO₄^2-, NH₄⁺ and WSOC to fine particles in the second group were significantly higher than those in the first group period. However, their condensation mode contributions were about two-fold higher in the first group than in the second group. The significant difference in the size distribution of the accumulation mode of the WSOC and secondary ionic components between the two groups was due to the influx of aerosol particles with a long residence time by long-distance transport from China and local weather conditions (e.g., RH).