• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.3
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• pp.273-282
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• 2018

Objectives: Dustiness of nanomaterials is considered as exposure index of essential material. Research on dustiness of nanomaterial is needed to control exposure in workplaces. Method: Dustiness measurement using vortex shaker were installed in the laboratory. Nanomaterials, 1 g, was put in the glass test tube and shaked using vortex shaker. Aerosol dispersed was measured using scanning mobility particle sizer(SMPS) and optical particle counter(OPC). Mass concentration using PVC filter and cassette was measured and TEM grid sampling was conducted. Total particle concentration and size distribution were calculated. Image and chemical composition of particles in the air were observed using transmission electron microscopy and energy dispersive X-ray spectrometer. Eleven different test nanomaterials were used in the study. Results: Rank of mass concentration and particle number concentration were coincided in most cases. Rank of nanomateirals with low concentration were not coincided. Two types of fumed silica had the highest mass concentration and particle number concentration. Indium tin oxide, a mixture of indium oxide and tin oxide, had high mass concentration and particle number concentration. Indium oxide had very low mass concentration and particle number concentration. Agglomeration of nanoparticles in the air were observed in TEM analysis and size distribution. In this study, mass concentration and particle number concentration were coincided and two index can be used together. The range of dustiness in particle number concentration were too wide to measure in one method. Conclusion: Particle number concentration ranged from low concentration to high concentration depend on type of nanomaterial, and varied by preparation and amount of nanomaterial used. Further study is needed to measure dustiness of all nanomaterial as one reference method.

• Particle and aerosol research
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• v.4 no.2
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• pp.69-75
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• 2008

Nanosize ZnO particles were prepared by oxidation of zinc vapor and the particle growth was modeled by a coagulation model by assuming that the characteristic time for reaction was much shorter than coagulation time and residence time (${\tau}_{reaction}{\ll}{\tau}_{coagulation}{\ll}{\tau}_{residence}$). Experimental measurement of zinc oxide particles diameter was consistent with the predicted result from the coagulation model. For practical purpose of predicting zinc oxide size in areosol reactor, the constant kernel solution is concluded to be sufficient, Uniqueness of nano-scale property of zinc oxide was confirmed by the higher photocatalytic activity of zinc oxide than nanosize titania particles.

• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.857-862
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• 2014

Mechanical alloying under various gas atmospheres such as Ar, an Ar-$H_2$ mixture, and He gases were carried out, and its effects on the powder properties, microstructure and mechanical properties of ODS ferritic steels were investigated. Hot isostatic pressing and hot rolling processes were employed to consolidate the ODS steel plates. While the mechanical alloyed powder in He had a high oxygen concentration, a milling in Ar showed fine particle diameters with comparably low oxygen concentration. The microstructural observation revealed that low oxygen concentration contributed to the formation of fine grains and homogeneous oxide particle distribution by the Y-Ti-O complex oxides. A milling in Ar was sufficient to lower the oxygen concentration, and this led a high tensile strength and fracture elongation at a high temperature. It is concluded that the mechanical alloying atmosphere affects oxygen concentration as well as powder particle properties. This leads to a homogeneous grain and oxide particle distribution with excellent creep strength at high temperature.

• Transactions on Electrical and Electronic Materials
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• v.4 no.1
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• pp.29-33
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• 2003

Europium doped yttrium oxide submicron-sized particles were prepared by ultrasonic aerosol pyrolysis. To examine the size effect of submicron-sized-particle, the photoluminescence of the particles was investigated. The particle size was controlled by pH, reaction temperature, molar concentration of yttrium in precursor solution. The PL intensity of submicron-sized particles was decreased with particles size. When the particle size is above about 150 times of Bohr radius of Y$_2$O$_3$, the optical property of the particles shows the bulk characteristics.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.25-32
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• 2014

In this study, nano-sized cobalt oxide powder with an average particle size below 50 nm was prepared from a cobalt chloride solution by the spray pyrolysis process. The influences of reaction temperature on the properties of the generated powder were examined. The average particle size of the particles formed based on the spray pyrolysis process at a reaction temperature of $700^{\circ}C$ is roughly 20 nm. Moreover, most of these particles cannot appear with an independent type, thereby coexisting in a droplet type. When the reaction temperature increases to $800^{\circ}C$, the average particle size not only increases to roughly 40 nm but also shows a more dense structure while the ratio of particles which shows a polygonal form significantly increases. As the reaction temperature increases to $900^{\circ}C$, the distribution of the particles is from roughly 70 nm to 100 nm, while most of the particle surface is more intricately close and forms a polygonal shape. When the reaction temperature increases to $1000^{\circ}C$, the particle size distribution of the powder shows an existing form from 80 nm to at least 150 nm in an uneven form. As the reaction temperature increases, the XRD peak intensity gradually increases, yet the specific surface area gradually decreases.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.654-655
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• 2006

This is about the effects deoxidization, carbonization and alloying preparation on fine grain W, WC, and grade YG8 powder reduced by "yellow tungsten oxide" and "blue tungsten oxide". The result indicates that yellow tungsten has single composition and blue tungsten oxide has complex composition. With this feature, yellow tungsten oxide got better uniformity and concentration distribution on fine particle size W and WC powder than blue tungsten oxide's. The grade alloy YG8 that made of this W or WC powder has uniform alloy construction, concentrated WC grain distribution and better alloy properties.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.173-176
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• 1999

The production of fine metal oxide particles in supercritical water has been studied. Cobalt nitrate solution and manganese nitrate solution have been selected as model solutions for metal salt aqueous solution and the particles of cobalt oxide and manganese oxide have been produced. It was observed that the production of fine metal oxide particles in supercritical water was feasible and the dehydration rate was remarkably high in supercritical water. In spite of a short residence time (3~100 seconds), fine particles ($0.5{\sim}2{\mu}m$) have been produced. In the supercritical water process, the temperature of mixer had a significant effect on particle size and size distribution. It was observed that a change in reaction temperature resulted in the control of particle size.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.426-432
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• 2012

This study involves using nickel chloride solution as a raw material to produce nano-sized nickel oxide powder with average particle size below 50 nm by the spray pyrolysis reaction. The influence of the inflow speed of raw material solution on the properties of the produced powder is examined. When the inflow speed of the raw material solution is at 2 ml/min., the average particle size of the powder is 15~25 nm and the particle size distribution is relatively uniform. When the inflow speed of the solution increases to 10 ml/min., the average particle size of the powder increases to about 25 nm and the particle size distribution becomes much more uneven. When the inflow speed of the solution increases to 20 ml/min., the average particle size of the powder increases in comparison to the case in which the inflow speed of the solution was 10 ml/min. However, the particle size distribution is very uneven, showing various particle size distributions ranging from 10 nm to 70 nm. When the inflow speed of solution increases to 50 ml/min., the average particle size of the powder decreases in comparison to the case in which the inflow speed was 20 ml/min., and the particle size distribution shows more evenness. As the inflow speed of the solution increases from 2 ml/min. to 20 ml/min., the XRD peak intensities gradually increase, while the specific surface area decreases. When the inflow speed of solution increases to 50 ml/min., the XRD peak intensities rather decrease, while the specific surface area increases.

• Journal of Powder Materials
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• v.9 no.2
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• pp.89-95
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• 2002

Spherical fine powders of tungsten oxide powders were prepared by the emulsion evaporation method. The characteristics of the powders prepared were examined by means of TGA, X-ray diffraction, SEM and image analysis. The emulsions were prepared by fast mixing of aqueous phase containing tugsten and the organic phase which composed of kerosene, surfactant, and paraffin oil. Precursors were made by evaporating the emulsionin the kerosene bath at $160^{\circ}C$, and then calcined at $650^{\circ}C$ in order to produce tungsten oxide powders. The average particle size of the tungsten oxide powders was $0.5\mutextrm{m}$ and their shapes were spherical at the both case of w/o and o/w type emulsions. As the HLB value of the surfactant increased and the concentration of tungsten ions decreased the mean particle siqe of tungsten oxide powders decreased whereas agglomerationsize increased. The optimum concentration of Span 80 was 8 percent by volume, and the optimum stirring speed in the emulsion formation was 5000 rpm in order to obtain fine and well dispersed $WO_3$ powders.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.251-251
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• 2009

The generation of energy and the cooling of system using thermoelectric semiconductor material have been in spotlight. Thermoelectric effect increases with the decrease of the thermal conductivity. In the thermoelectric devices, thermal conductivity is related to phonon scattering. Therefore, few studies have been conducted in the thermoelectric materials dispersed nano oxide particle for increasing the phonon scattering. However, core-shell structure which nano particle disperses in solvents and then which thermoelectric materials coated on the nano oxide particles has not been reported. In this study, we selected commercial nano powder such as $Al_2O_3$. This nano particle was about 20nm and was crushed aggregate by mechanical treatment. We have developed the effect of the dispersant and the solvent. The properties of particles were evaluated by SEM, TEM, particle size analysis, and BET. Dispersion and dispersion stability were evaluated by electronic microscope and turbidity.