• Journal of the Korean institute of surface engineering
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• v.38 no.1
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• pp.37-43
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• 2005

Nanosized titanium-colloid particles were prepared by sol-gel method. The physical properties, such as thermal stability, crystallite size and crystallinity according to synthesis condition have been investigated by TEM, XRD, SEM, TGA and DTA. In addition, Zinc phosphating has been studied in order to compare the phosphating characterization of prepared nanosized titanium-colloid particles. The major phase of all the prepared titanium-colloid particles was an amorphous structure regardless of synthesis temperature and the structure was composed of phoshate complex and titanium. The micrographs of HR- TEM showed that nanosized titanium-colloid particles possessed a spherical morphology with a narrow size distribution. The crystallite size of the titanium-colloid particles synthesized at 80℃ was 4-5 nm and increased to 8-10 nm with an increase of synthesis temperature (150℃). In addition, the coating weight increased with an increase of temperature of phosphating solution and when the concentration of titanium-colloid was 2.0 g/l, the coating weight was 1.0 g/㎡.

• Analytical Science and Technology
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• v.25 no.6
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• pp.476-482
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• 2012

Asian dust particles are known to have sizes ranging from a few nanometers up to about a few micrometers. The environmental and health effects depend on the size of the dust particles. The smaller, the farther they are transported, and the deeper they penetrate into the human respiratory system. Sedimentation field-flow fractionation (SdFFF) provides separation of nano to microparticles using a combination of centrifugal force and parabolic laminar flow in a channel. In this study, the steric mode of SdFFF (Sd/StFFF) was tested for size-based separation and characterization of Asian dust particles. Various SdFFF experimental parameters including flow rate, stop-flow time and field strength of the centrifugal field were optimized for the size analysis of Asian dust. The Sd/StFFF calibration curve showed a good linearity with $R^2$ value of 0.9983, and results showed an excellent capability of Sd/StFFF for a size-based separation of micron-sized particles.The optical microscopy (OM) was also used to study the size and the shape of the dust particles. The size distributions of the samples collected during a thick dust period were shifted towards larger sizes than those of the samples collected during thin dust periods. It was also observed that size distribution of the sample collected during dry period shifts further towards larger sizes than that of the samples collected during raining period, suggesting the sizes of the dust particle decrease during raining periods as the components adsorbed on the surface of the dust particles were removed by the rain water. Results show Sd/StFFFis a useful tool for size characterization of environmental particles such as the Asian dust.

• Particle and aerosol research
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• v.7 no.3
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• pp.79-85
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• 2011

Porous $TiO_2-SiO_2$ particles were synthesized by co-assembly of nanoparticles of $TiO_2$ and $SiO_2$ in evaporating aerosol droplets. Poly styrene latex (PSL) particles were employed as a template of porous particles. Flowrate of dispersion gas, weight ratio of $TiO_2/SiO_2$ and $SiO_2$ concentration in the precursor, and PSL size were chosen as process variables. The morphology, crystal structure, chemical bonding, and pore size distribution were analyzed by FE-SEM, XRD, FT-IR, BET. The morphology of porous $TiO_2-SiO_2$ particles was spherical and the average particle size range were from 1 to $10{\mu}m$. The particles were composed of meso and macro pores. The average particle diameter and pore volume of the as prepared particles were dependant on process variables. It was found that UV-Vis absorption of the porous particles was comparable with pure $TiO_2$ nanoparticles even though $TiO_2/SiO_2$ ratio is low in the porous particles.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.96-96
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• 2010

Monodispersed spherical silica-coated ceria nanoparticles were prepared through a sol-gel process using tetraethylorthosilicate (TEOS) and ceria fine particles. In this process, ceria fine particles were also prepared from cerium nitrate. The mean size of ceria particles was 300nm. Silica nanoparticles with narrow particle size distribution were prepared by controlled hydrolysis of TEOS solution. The silica sols were obtained by peptization, the process of redispersing a coagulated colloid, and were coated on ceria particles by the control of the weight ratio of silica/ceria and the pH of the mixture in aqueous solution. The morphologies of particles were characterized with scaning electron microscopy(SEM), transmission electron microscopy(TEM) and atomic force microscopy(AFM). The coating thickness of silica particles obtained by using this method was controlled in the range of 30 - 70nm.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.62-68
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• 2019

The optoelectronic display units such as TFT-LCD or OLED require many thin optical plastic films and their mass manufacturing processes employ CO2 laser cutting of those thin films in a large quantity. However, laser film cutting could generate fume particles through melt shearing, vaporization, and chemical degradation and those particles could be of great concern for film surface contamination. In order to appreciate the fume particle dispersion behaviors in laser film cutting, this study relies on random particle simulations by probabilistic distributions of particle size, ejection velocity and angles coupled with Basset-Boussinesq-Oseen model of particle trajectory in low Reynolds number flows. Here, up to one million particles of random sampling have been tested to effectively show fume particles dispersed on the film surface. The computational results could show that particular range of fume particle size could easily disperse into the pixel region of processed optical films.

• Journal of the Optical Society of Korea
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• v.11 no.1
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• pp.34-39
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• 2007

Laser-induced breakdown of colloidal suspensions, such as polystyrene, $ZrO_2$, and $SiO_2$ particles in diameters of 100-400 nm in water is investigated by nanosecond flash-pumped Nd:YAG laser pulses operating at a wavelength ${\lambda}$= 532 nm. The breakdown threshold intensity is examined in terms of breakdown probability as a function of laser pulse energy. The threshold intensity for $SiO_2$ particles ($1.27{\times}10^{11}\;W/cm^2$) with a size of 100 nm is higher than those for polystyrene and $ZrO_2$ particles with the same size, namely $5.7{\times}10^{10}$ and $5.5{\times}10^{10}\;W/cm^2$, respectively. Results indicate that the absorption of five photons is required to induce ionization of $SiO_2$ particles, whereas the other particles necessitate four-photon absorption. These breakdown thresholds are compared with those measured by nanosecond pulses from a diode-pumped Nd:YAG laser having a different focusing geometry.

• Korean Journal of Materials Research
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• v.16 no.8
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• pp.485-489
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• 2006

The preparation conditions of $YBO_3$:Eu phosphor particles having the maximum photoluminescence intensity under vacuum ultraviolet in the spray pyrolysis were optimized. The $YBO_3$:Eu phosphor particles prepared from spray solution with stoichiometric amount of boric acid had the maximum photoluminescence intensity. The $YBO_3$:Eu phosphor particles with pure phases were formed at low post-treatment temperatures because of fast reaction of yttrium and boron components without volatilization of boron component. The prepared $YBO_3$:Eu phosphor particles by spray pyrolysis had fine size, narrow size distribution and regular morphology. The photoluminescence intensity of the prepared $YBO_3$:Eu phosphor particles under vacuum ultraviolet was 103% of the commercial $(Y,Gd)BO_3$:Eu phosphor particles.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.174-179
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• 2000

Ultrafine particles have been used widely in many high technology industrial areas. The spherical nonagglomerated and uniform nanometer-size $SiO_2$ particles are synthesized by the direct injection of TEOS(Tetraethyorthosilicate) using electro-hydrodynamic spray ins method. Electro-hydrodynamic spray can generate in the range of submicron-size TEOS particles with high electric charge by applying a high electric field between the liquid injection nozzle and the reaction tube. This TEOS particles are thermally decomposed or oxidized to produce nanometresized $SiO_2$ particles in the reaction tube. Spherical, nonagglomerated and ultrafine particle generated and examined at furnaced temperature, $800^{\circ}C$ and TEOS flowrate of 0.49 or $1.00cm^3/hr$ using SEM and SMPS. As the total gas flowrate changes from 1.51pm to 5.01pm, the mean diameter of $SiO_2$ particle decreases from 120 nm to 68nm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1542-1547
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• 2003

Although dielectric barrier discharge (DBD) in air has been applied to a wider range of aftertreatment processes for HAPs (Hazardous Air Pollutants), due to its high electron density and energy, its potential use as precharging dust particles is not well known. In this work, we measured size distributions of bimodal aerosol particles and estimated collection efficiency of the particles by an electrostatic precipitator (ESP) using DBD as particle charger. To examine the particle collection with DBD charger, nano size particles of NaCl(20∼100nm) and DOS (50∼500nm) were generated by a tube furnace and an atomizer, respectively. For experimental conditions of 60㎐, 11㎸ and 60 lpm, the particle collection efficiency for the hybrid system was over 85%, based on the number of particles captured.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.69-75
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• 2014

Accurate analysis of fly ash particles is not trivial because of complex nature in physical and chemical properties. SPLITT fractionation (SF) was employed to fractionate the fly ash particles into subpopulations in large quantities. Then the SF-fractions were analyzed by the steric mode of sedimentation field-flow fractionation (Sd/StFFF) for size analysis. The SF-fractions were also analyzed by ICP-OES. The results showed that the fly ash is mainly composed of Fe, Ca, Mg and Mn. No particular trends were observed between the particle size and the concentrations of Fe, Ca, Mg, while Mn, Cu and Zn were in higher concentrations in smaller particles. Sample preparation procedures were established, where the fly ash particles were sieved to remove large contaminants, and then washed with acetone to remove organics on the surface of particles. The sample preparation and analysis methods developed in this study could be applied to other environmental particles.