• 한국재료학회지
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• 제21권12호
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• pp.690-696
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• 2011

In this study, nano-sized tin oxide powder with an average particle size of below 50 nm is prepared by the spray pyrolysis process. The influence of air pressure on the properties of the generated powder is examined. Along with the rise of air pressure from $0.1kg/cm^2$ to $3kg/cm^2$, the average size of the droplet-shaped particles decreases, while the particle size distribution becomes more regular. When the air pressure increases from $0.1kg/cm^2$ to $1kg/cm^2$, the average size of the dropletshaped particles, which is around 30-50 nm, shows hardly any change. When the air pressure increases up to $3kg/cm^2$, the average size of the droplet-shaped particles decreases to 30 nm. For the independent generated particles, when the air pressure is at $0.1kg/cm^2$, the average particle size is approximately 100 nm; when the air pressure increases up to $0.5kg/m^2$, the average particle size becomes more than 100 nm, and the surface structure becomes more compact; when the air pressure increases up to $1kg/cm^2$, the surface structure is almost the same as in the case of $0.5kg/cm^2$, and the average particle size is around 80- 100 nm; when the air pressure increases up to $3kg/cm^2$, the surface structure becomes incompact compared to the cases of other air pressures, and the average particle size is around 80-100 nm. Along with the rise of air pressure from $0.1kg/cm^2$ to $0.5kg/cm^2$, the XRD peak intensity slightly decreases, and the specific surface area increases. When the air pressure increases up to $1kg/cm^2$ and $3kg/cm^2$, the XRD peak intensity increases, while the specific surface area also increases.

• 환경위생공학
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• 제9권2호
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• pp.24-31
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• 1994

Aerosol size distribution were determined in Seoul by Anderson sampler from October 1989 to September 1991 for the major ionic species(SO$_{4}$$^{2-}$, NO$_{3}$$^{-}$, Cl$^{-}$, Na$^{+}$, Na$^{+}$, K$^{+}$, Ca$^{2+}$ and Mg$^{2+}$) and TSP( Total Suspended Particles ). The seasonal variations in concentrations and size distribution have been investigated. The size distributions of TSP and each of ionic species were bimodal throughout the year. The size distribution of these ions were divided as follows; (1) fine- mode dominant for SO$_{4}$$^{2-}$ and N%'. (2) coarse- mode dominant for NO$_{3}$$^{-}$, Cl$^{-}$, Ca$^{2+}$ and Mg$^{2+}$. (3) both- mode dominant for TSP.

• Asian Journal of Atmospheric Environment
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• 제6권1호
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• pp.14-22
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• 2012

This paper is focused on the comprehensive and detailed interpretation for the chemical transformation of individual Asian dust (hereafter called "AD") particles during long-range transport from source regions to receptor area. A multi-stage particle sampler was operated at a ground-based site in Taean, Korea directly exposed to the outflow of air masses from China during AD period in April 2003. Both quantitative and qualitative analyses for size-classified individual particles were carried out by a microbeam X-ray fluorescence (XRF) method and a microbeam Particle Induced X-ray Emission (micro-PIXE), respectively. Among major characteristic elements, the elemental masses of soil derived components, sulfur, and chloride varied as a function of particle size showing the monomodal maximum with a steeply increasing at 3.3-4.7 ${\mu}m$ particle size. Although the details on chemical composition of AD particle collected on a straight line from source area to our ground-based site are needed, a large amount of Cl coexisted in and/or on AD particles suggests that AD particles collected in the present study might be actively engaged in chemical transformation by sea-salt and other Cl containing pollutants emitted from the China's domestic sources. Through the statistical analyses it was possible to classify individual AD particles into six distinct groups. The internally mixed AD particles with Cl, which has various sources (e.g., sea-salt, coal combustion origin HCl, gaseous HCl derived from the adsorption of acids to sea-salt, and Cl containing man-made particles) were thoroughly fractionated by the elemental spectra drivened by the double detector system of micro-PIXE.

• 공업화학
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• 제22권6호
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• pp.631-635
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• 2011

직접산화법으로 제조한 구형 실리카졸과 비구형 실리카졸의 입자크기와 형상에 따른 산화막의 기계화학적 연마율에 미치는 영향을 연구하였다. 구형 실리카졸은 금속 실리콘 분말로부터 직접산화법에 의해 10~100 nm까지 크기별로 제조하였다. 직접산화법으로 제조한 10 nm 크기의 실리카졸에 산, 알콜, 실란과 같은 응집유도제에 의한 첨가하여 입자간 응집을 유도한 시드 졸을 제조하고, 여기에 실리콘 분말과 알칼리 촉매를 투입하여 직접산화법으로 입자를 성장하여, 두 개 이상의 입자가 응집되어 있는 실리카 시드의 형상이 유지된 상태에서 성장한 응집 비구형 실리카졸을 제조하였다. 이를 산화막 CMP에 적용하여 구형 및 비구형 실리카졸의 입자형상 및 크기에 따른 연마율을 비교하였다. 구형 실리카의 경우, 입자크기가 증가할수록 연마율은 높아졌고, 비구형 실리카졸은 평균입경이 유사한 크기의 구형 실리카 보다 더욱 높은 연마율을 나타내었다.

• 한국재료학회지
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• 제22권6호
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• pp.298-302
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• 2012

Fe/$SiO_2$ core-shell type composite nanoparticles have been synthesized using a reverse micelle process combined with metal alkoxide hydrolysis and condensation. Nano-sized $SiO_2$ composite particles with a core-shell structure were prepared by arrested precipitation of Fe clusters in reverse micelles, followed by hydrolysis and condensation of organometallic precursors in micro-emulsion matrices. Microstructural and chemical analyses of Fe/$SiO_2$ core-shell type composite nanoparticles were carried out by TEM and EDS. The size of the particles and the thickness of the coating could be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of TEOS within the micro-emulsion. The water/surfactant molar ratio influenced the Fe particle distribution of the core-shell composite particles, and the distribution of Fe particles was broadened as R increased. The particle size of Fe increased linearly with increasing $FeNO_3$ solution concentration. The average size of the cluster was found to depend on the micelle size, the nature of the solvent, and the concentration of the reagent. The average size of synthesized Fe/$SiO_2$ core-shell type composite nanoparticles was in a range of 10-30 nm and Fe particles were 1.5-7 nm in size. The effects of synthesis parameters, such as the molar ratio of water to TEOS and the molar ratio of water to surfactant, are discussed.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.17-17
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• 2002

The magnetic effects connected to finite-size of the particles become dominant at transition of particles in region several nanometers and less [1]. At reduction of atom numbers in magnetic cluster (tens or hundreds atoms), along the classical features, essential appear the quantum phenomena resulting in spin transformation of magnetic structure, both with reduction of the size and at applying of an external magnetic field. (omitted)

• 공업화학
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• 제10권6호
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• pp.889-894
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• 1999

유화중합법으로 마이크론 크기의 고분자 라텍스 입자 제조시, 라텍스 입자의 응집, 2세대 입자의 생성 등의 문제 때문에 원하는 형태, 크기, 구조를 지니는 입자를 제조하기가 매우 어려운 것으로 알려져 있지만 구조적, 기능적 고분자 미립자를 합성할 수 있는 장점이 있다. 따라서, 본 연구에서는 마이크론 크기의 라텍스 입자를 제조하는데 있어서, 미립자 성분으로 n-butyl acrylate(BA)를 선정하고, 개시제의 농도, 유화제의 양, 반응 온도, 가교제의 양 및 교반기의 속도 등의 반응 변수 조건에 따른 seed 유화 중합을 실시하여 각 반응 변수들이 입자의 크기 및 분산도에 미치는 영향에 대하여 조사하였다. 실험 결과를 바탕으로 반응 변수의 최적 조건들을 규명하여 연속적 seed 유화중합법으로 $0.14{\sim}3.67{\mu}m$의 평균 입자경을 갖는 poly(n-butyl acrylate)(PBA) 라텍스 입자를 제조할 수 있었다.

• 한국염색가공학회지
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• 제27권4호
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• pp.245-260
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• 2015

The effect of salt milling process on the crystal size, morphology, and color characteristics of C.I. Pigment Red 57:1 was studied. The primitive morphology and color properties of the pigment after synthesis were studied in the former series work. The size and morphology of primary particles and the second aggregation features should be considered because they are very important to determine pigment quality. We compared the primary morphology of pigment particles before drying with the secondary aggregated morphology of pigment particles after drying and salt milling process. Morphological properties were investigated by particle size analysis, X-ray diffraction, and scanning electron microscopy and color measurement was carried out. Significant reduction in particle size as well as enhanced crystallite size after salt milling process was observed. This result might give a difference in color of the pigment, turning into brighter and more blue-toned red color. It was revealed that synthesis condition affect the morphology and color of the pigment even after milling. Increase in HCl concentration in the synthesis process enhanced crystal size and quality forming bluer-red pigments but an increase in $CaCl_2$ concentration resulted in more amorphous crystals forming darker-red pigments after salt milling.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2003년도 추계학술대회 논문집
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• pp.199-199
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• 2003

During the cleanup of US Department of energy facilities, contaminated materials, toxic and hazardous radionuclides (e.g., Th, Cs, and U) and heavy metals (e.g., Cr, Hg, Pb, and Ni)-laden ultrafine particles are generated. The size of the particles is up to about 200 nm. Understanding of the production of these nanometer size particles is critical in determining the surface cleaning efficiently. (omitted)

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.111-114
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• 2012

The ignition behavior of single coal particles of five kindes of coal with different ranks (low volatile bituminous, low volatile sub-bituminous, high volatile bituminous, lignite) with particle size of $150-200{\mu}m$ was investigated at high heating rate condition. Particles were injected into a laminar flow reactor and the ignition behavior was observed with high speed cinematography. Sub-bituminous were observed to ignite homogeneously; however, low volatile bituminous coal and lignite undergo fragmentation prior to igntion. The observation was analyzed with previous work.