• Particle and aerosol research
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• v.5 no.4
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• pp.171-178
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• 2009

$PM_{2.5}$ is one of critical air pollutants due to its high absorbability of heavy metallic fumes, PAH and bacillary micro organisms. Such a fine particulate matter is often formed through various nucleation processes including condensation. This study attempts to find the nucleation behaviors of $PM_{2.5}$ arisen from coal power stations using a classical heterogeneous Fletcher's theory. The numerical simulation by C-language could approximate the nucleation process of $PM_{2.5}$ from water vapor, of which approach revealed the required energy for embryo formation and embryo size and nucleation rate. As a result of the calculation, it was found that wetting agents could affect the particle nucleation in vapor condensation. In particular, critical contact angle relates closely with the vapor saturation. Particle condensation could be reduced by lowering the angles. The wetting agents aid to decrease the contact angle and surface tensions, thereby may contribute to save the formation energy.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.392-397
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• 2000

Mono-disperse particles generated by a condensation particle generator are widely used to meet the experimental and industrial needs. The characteristics of particles generated by homogeneous nucleation have been studied experimentally using a laminar flow condensation particle generator. Dry nitrogen gas saturated with oleic acid vapor was cooled well below the saturation temperature causing the highly supersaturated vapor to nucleate. The dependence of GSD(Geometric Standard Deviation), GMD(Geometric Mean Diameter), and the mass concentration of particles on the temperature at the evaporator, flow rate and the temperature condition at condenser was studied. The experimental results show that the mass concentration of particles is affected by the radial temperature profile at condenser. Nucleation at the center of the condenser causes the mass concentration of particles to increase. The experimental results also show that the suppression of additional nucleation by a constant temperature condition at the condenser increases the mean diameter of particle.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.169-182
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• 2014

이 연구에서는 Lennard-Jones (LJ) particle을 이용하여 상분리 현상을 이해하기 위한 컴퓨터 시뮬레이션 연구를 수행하였다. 초기에 균일하게 분포되어 있는 LJ 입자들을 시뮬레이션 하면 상대적으로 dense phase와 dilute phase로 상분리 현상이 일어나게 된다. 상분리 현상의 첫 번째 단계를 핵 생성 (nucleation) 이라고 한다. 본 연구에서는 Brownian Dynamics (BD) Simulation과 Molecular Dynamics (MD) Simulation을 이용하여 상평형 그림을 구하고 초기에 일어나는 LJ 입자들의 nucleation rates를 구하였다.

• Journal of the Korean Chemical Society
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• v.56 no.4
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• pp.431-439
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• 2012

Dissipative particle dynamics (DPD) was carried out to study the nucleation and crystal growth process of $CeO_2$ nanoparticles in different alcohol aqueous solutions. The results showed that the nucleation and crystal growth process of $CeO_2$ can be classified into three stages: nuclei growth, crystal stabilization and crystal aggregation except the initial induction stage, which could be reproduced by collecting simulation results after different simulation time. Properly selecting the sizes of $CeO_2$ and water bead was crucial in the simulation system. The influence of alcohol type and content in solutions, and precipitation temperature on the particle dimension were investigated in detail and compared with the experimental results. The consistency between simulation results and experimental data verify that the simulation can reproduce the macroscopic particle aggregation process. The effect of solvent on the nucleation and crystal growth of $CeO_2$ nanoparticles are different at three stages and can not be simply described by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory or nucleation thermodynamics theory. Our work demonstrated that DPD methods can be applied to study nanoparticle forming process.

• Journal of Powder Materials
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• v.27 no.5
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• pp.394-400
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• 2020

Molybdenum trioxide (MoO₃) is used in various applications including sensors, photocatalysts, and batteries owing to its excellent ionic conductivity and thermal properties. It can also be used as a precursor in the hydrogen reduction process to obtain molybdenum metals. Control of the parameters governing the MoO₃ synthesis process is extremely important because the size and shape of MoO₃ in the reduction process affect the shape, size, and crystallization of Mo metal. In this study, we fabricated MoO₃ nanoparticles using a solution combustion synthesis (SCS) method that utilizes an organic additive, thereby controlling their morphology. The nucleation behavior and particle morphology were confirmed using ultraviolet-visible spectroscopy (UV-vis) and field emission scanning electron microscopy (FE-SEM). The concentration of the precursor (ammonium heptamolybdate tetrahydrate) was adjusted to be 0.1, 0.2, and 0.4 M. Depending on this concentration, different nucleation rates were obtained, thereby resulting in different particle morphologies.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.533-538
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• 2000

Ductile fracture of dual phase steel begins with void nucleation, at martensite-ferrite interface of deformed martensite particle. In this study, void nucleation, growth, and coalescence under various strain were studied in dual phase steel. Therefore, by means of the heat treatment of low carbon steel, the study deals with void nucleation and growth for ferrite grain size and martensite volume fraction of dual phase steel using statistical method. Void nucleation and growth with increasing strain are shown depend upon the ferrite grain size. Voids volume fraction generally increase as ferrite grain size decease.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.41-46
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• 2009

The rheological properties of highly concentrated Ag nano sol depending on particle size were studied. The Ag nano sol was prepared by reducing the Ag ion in aqueous solution. The size of Ag nano particle was controlled by two steps of nucleation and growth, and the thickness of adsorption layer was varied by molecular weight of polyelectrolytes. The polyelectrolytes acted as not only ionic complex agent in ionic state and but also dispersant after formation of Ag nano sol. The effective volume was controlled by combination of varying the molecular weight of polyelectrolytes and the size Ag nano sol. The particle size and the viscosity of nano sol were characterized by particle size analyzer, HR-TEM and cone & plate viscometer. It was found that the 10 nm and 40 nm-sized Ag nano sols were prepared by controlling the nucleation and growth steps, respectively. Finally, we could prepare highly concentrated Ag nano sol over 50 wt%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.239-244
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• 2019

Two hydrogenation surface modifications, namely hydrogen atmosphere heat treatment and hydrogen plasma treatment, were found to lead to improved dispersion of nanodiamond (ND) seed particles and enhanced nucleation density for deposition of smooth ultrananocrystalline diamond (UNCD) film. After hydrogenation, the C-O and O-H surface functionalities on the surface of nanodiamond particles were converted to the C-H surface functionalities, and the Zeta potential was increased. As the degree of dispersion was improved, the size of nanodiamond aggregates decreased significantly and nucleation density increased dramatically. After hydrogen heat treatment at 600℃, average size of ND particles was greatly reduced from 3.5 ㎛ to 34.5 nm and a very high nucleation of ~3.9 × 10¹¹ nuclei/㎠ was obtained for the seeded Si surface.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.4
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• pp.508-514
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• 2010

The objective of this work presented here was experimental study of steadystate and cold start exhaust nano-sized particle characteristics from common rail diesel engine. The effect of the diesel oxidation catalyst (DOC) on the particle number reduction was insignificant, however, particle number concentration levels were reduced by 3 orders of magnitude into the downstream of diesel particulate filter (DPF). In high speed and load conditions, natural regeneration of trapped particle occurred inside DPF and it was referable to increase particle number concentration. As fuel injection timing was shifted BTDC $6^{\circ}CA$ to ATDC $4^{\circ}CA$, particle number concentration level was slightly reduced, however particle number and size was increased at ATDC $9^{\circ}CA$. Nucleation type particle reduced and accumulation type particle was increased on EGR condition.

• Atmosphere
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• v.21 no.1
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• pp.35-44
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• 2011

We investigated characteristics of new particle formation and growth events observed at Gosan climate observatory using Scanning Mobility Particle Sizer (SMPS) measurements of particle number size distribution with 54 size ranges from 10 to 487 nm in October 2009. Four days (17~20 October) and five days (22~26 October) were classified into strong new particle formation and growth event ($N_S$) and weak particle formation and growth event ($N_W$), respectively. $N_S$ and $N_W$ divided by increase of aerosol number concentration in nucleation mode and continuity of growth from nucleation to Aitken mode. Particle growth rates of $N_S$ (5.34~$9.19nm\;h^{-1}$) were greater than that of $N_W$ (2.15~$3.53nm\;h^{-1}$). $N_S$ and $N_W$ were analyzed with synoptic pattern over East Asia, meteorological elements, and sulfur dioxide ($SO_2$) measured at Gosan. We found that $N_S$ was characterized by a fast and northwesterly wind accompanied cold and dry airmass, but $N_W$ was affected airmass originated from South China and come through the Korea Peninsula. The events ($N_S$ and $N_W$) occurred at conditions of high solar flux ($&gt;700W\;m^{-2}$) and low relative humidity (< 60%). The $SO_2$ concentration on $N_S$ and $N_W$ was higher than that on case of non observed new particle formation.