• The Korean Journal of Rheology
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• v.9 no.4
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• pp.183-189
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• 1997

본 연구에서는 고분자용액을 분산매로한 현탁액 내에서 입자의 수력학적확산에 관 한 실험적인 연구를 수행하여다. 입자로는 평균직경 275마이크론의 polymethlmethacrylate (PMMA)구형입자를 사용하였고, 분산매로는 PMMA 입자와 밀도르 맞춘 글리세린과 에틸 렌글리콜의 혼합용액에 고분자를 첨가하여 사용하였다. 고분자로는 분자량 6백만의 시약용 폴리아크릴아마이드를 사용하였다. 입자농도는 50%이었다. 용액의 농도는 0∼700ppm이었으 며 이러한 용액은 전단박화현상을 나타내지 않았다. 확산계수는 쿠엣장치 내에서 입자가 두 원통사이에서 아래쪽의 빈 공간으로 확산할 때 시간에 따른 점도측정결과로부터 예측하여 다. 본 연구의 결과 뉴튼성유체의 경우와는 달리 무차원확산계수(D/2)가 일정하지 않으며 전단율이 증가될수록 점점 감소하는 현상을 나타내었다. 고분자의 농도가 증가하는 경우에 는 무차원 확산계수가 감솨는 것을 볼수있었다. 이러한 무차원 확산계수의 감소는 유동하는 현탁액 내에서 입자간의 상호작용이 뉴튼성유체에 비하여 가역적인 것에 기인하는 것으로 판단된다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.161-161
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• 2013

본 연구에서는 백금 나노입자의 크기, 형상, 분포도에 따른 전기 화학적 효율을 평가하기 위해 계면활성제 농도를 달리하여 백금 나노입자를 합성하였다. 계면활성제로는 CTAB(cetyltrimethylammonium bromide)이 사용되었으며, 0.5 mM의 $H_2PtCl_6$의 백금 염을 환원시키기 위하여 유체 플라즈마 공정을 이용하였다. 공정 시간은 UV-vis 스펙트럼 결과를 토대로, 262 nm의 파장대에서 관찰된 LMCT(ligand-to-metal charge transfer) peak이 사라지는 시간을 기준으로 하여 공정을 진행하였다. 합성된 나노입자는 순환 전류-전압곡선(CV), TEM이미지와 XRD 분석을 이용하여 전기화학적 특성, 입자의 평균 크기 및 형상 변화를 비교 분석 하였다. 그 결과 CTAB을 넣지 않은 백금나노입자의 경우, CTAB을 넣고 제조한 백금 나노입자와는 달리 구의 형태로 뭉쳐있음을 관찰하였고, 이러한 백금 나노입자의 구조는 보다 높은 전기화학적 활성 특성을 가짐을 보였다.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.597-602
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• 2015

Characteristics of continuous preparation of ZnO powder were investigated in a micro drop/bubble fluidized reactor of which diameter and height were 0.03 m and 1.5 m, respectively. The flow rate of carrier gas for transportation of precursors to the reactor was 6.0 L/min and the concentration of Zn ion in the precursor solutions was 0.4 mol/L, respectively. Effects of reaction temperature (973 K~1,273 K) and flow rate of micro bubbles (0~0.4 L/min) on the pore characteristics of prepared ZnO powder were examined. The optimum reaction temperature for the maximum porosity in the ZnO powder was 1,073 K within this experimental condition. The mean size of ZnO powder prepared continuously in the reactor decreased but the surface of the powder became smooth, with increasing reaction temperature. The injection of micro bubbles into the reactor could enhance the formation of pores in the powder effectively, and thus the mean BET surface area could be increased by up to 58%. The mean size of prepared ZnO powder was in the range of $1.25{\sim}1.75{\mu}m$ depending on the reaction temperature.

• Journal of Conservation Science
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• v.28 no.2
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• pp.165-173
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• 2012

In this work, scientific and systematic analysis was conducted for finding out the methods and techniques of ancient ink stick making. Analysis the ancient ink stick on ancient documents and wooden writing as letter or painting, we concluded as followings. From the analysis of ancient wood by dendrochronology, wood was cut at 1899, which provided the information on the year of ink stick's made on writing on ancient wood. Single particle size for soot of ancient ink stick was 107 nm for ink on the roof-filling timber in Sinsunwonjeon of Changdeok Palace, compared to 38 to 86 nm on the letter on ancient 12 paper document. Aggregate particle size was 370 nm for ink on the roof-filling timber in Sinsunwonjeon of Changdeok Palace, but 206 to 318 nm for aggregate particle size on 12 paper documents. There was similar pattern between single particle size and aggregate particle size of soot, which might provide the information of raw material for ancient ink. From infra-red and Raman spectroscopic analysis of sheet of writing on paper or wood, there was severe interference from background material (paper or wood). From Raman spectroscopic analysis of ancient ink carefully separated from ancient wood, spectrum pattern was closer to ink stick made by the soot from pine burning.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.191-196
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• 1999

Effects of agitation and heating rate on crystallinity, size distribution and mean size of $\alpha$-$SiO_2$powder prepared hydrothermally were investigated. $\alpha$-$SiO_2$crystalline powder, in mean particle size of 1~3.2 $\mu\textrm{m}$, was obtained at $350^{\circ}C$ using KOH as a mineralized for a 3 h reaction. Experimental results showed that particle size became smaller as the rate of agitation increased if it was introduced from the beginning of reaction, however, crystallinity was reduced at the low rate of agitation and it was became enhanced at above 150 r/min. Particle size became larger if agitation was introduced at any time during the reaction rather than introduced from the beginning of reaction. It was also found that particle size became smaller if heating rate was reduced, while the rate of agitation kept constant.

• Korean Journal of Food Science and Technology
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• v.22 no.4
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• pp.369-372
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• 1990

Although the measurement of oil globule size distribution is necessary to detect the process of demulsification, the reasonable methodology for its measurement has not been suggested because the solution of soymilk contains insoluble soybean particle and the protein to interfere with the detection of oil globule or oil content. The oil globule size distribution was measured by the homogeneous suspension and cumulative method under gravitational force or centrifugal force, which were modified with Stokes' low. The geometric mean diameter of oil globules in this soymilk was $033{\mu}m\;and\;031{\mu}m$ under gravitational method and centrifugal method, respectively. The differences of oil globule size distribution in the solutions emulsified by different pressures were detected by this method. The mean diameter of the solutions treated at higher pressure was shifted to smaller size and the distribution pattern of the solutions at higher pressure became more compact around the mean diameter.

• Clean Technology
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• v.19 no.3
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• pp.249-256
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• 2013

The experiments have been performed to obtain zinc complex compound with smaller particle sizes, which is used as a charge control agent in manufacturing toner. Metallic salts and polyhydric alcohols have been studied to investigate their effects on the formation and the triboelectric charge of zinc complex-compound particle with different sizes. Reactants such as zinc chloride and 3,5-di-tert.-butyl salicylic acid have been used to form the complex compound. Polyethylene glycol (PEG-300), glycerin and ethylene glycol have been added into the zinc chloride solution beforehand to lower the reaction rate in the formation of zinc complex-compound. Aluminium(III) chloride has been mixed in the zinc chloride solution beforehand to restrain the particle size from growing. When PEG-300 and aluminium(III) chloride are used to lower the reaction rate and to restrain the particle size from growing, the average particle size of zinc complex compound decreases from $5.28{\mu}m$ to $2.33{\mu}m$, which was 44.1% of $5.28{\mu}m$.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.8-13
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• 2012

The experiments have been performed to obtain zinc complex compound with smaller particle size, which is used as a charge control agent in manufacturing toner. Metallic salts and polyhydric alcohols have been studied to investigate their effects on the formation of different sizes of zinc complex-compound particle. Reactants such as zinc chloride and 3,5-di-tert-butyl salicylic acid have been used to form the complex compound. Polyethylene glycol (PEG-300), glycerin and ethylene glycol have been added into the zinc chloride solution beforehand to lower the reaction rate in the formation of zinc complex-compound. Zirconium (IV) oxychloride octahydrate has been mixed in the zinc chloride solution beforehand to restrain crystals from growing. When PEG-300 and zirconium (IV) oxychloride octahydrate are used to lower the reaction rate and to restrain the particle size from growing, the average particle size of zinc complex compound decreases from 5.28 to 1.84 ${\mu}m$, which is 34.9% of 5.28 ${\mu}m$.

• Composites Research
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• v.24 no.6
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• pp.18-24
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• 2011

The effect of surface treatments with the atmospheric pressure flame plasma (APFP) and epoxy silane (ES) is experimentally investigated to yield the best mechanical properties of silica ($V_f=40%$) reinforced elastomeric composites. The tensile strength of the composites is increased significantly with decrease the mean diameter. When the diameter is $2.2{\mu}m$, that of the composite is increased about 1.4 times compared to the matrix (2.52 MPa). Also, the tensile strength of silica reinforced composites with APFP and ES treated is increased 8.8~13.3%, 9.9~12.5%, respectively. When the diameter is $26.6{\mu}m$, the tensile modulus of the composite is increased about 2 times compared to the matrix (0.88MPa), and the tensile modulus of silica reinforced composites with APFP and ES treated is increased 15.6~22.8%, 21.1~5.8%, respectively. Conventional silane coupling agent treatment have a few disadvantages because of using organic solvents. However APFP treatment is a fast, economic and eco-friendly method to improve the mechanical properties.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.9-15
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• 2012

As a propellant of a high speed underwater vehicle, the hydro-reactive solid metal particles using seawater as a oxidizer maximizes its specific impulse when the solid metal particles and the seawater are uniformly mixed in the combustion chamber. The purpose of this study is to investigate the effects of injector geometry on the particle distribution of similarity point of view. For the purpose of this similarity of the mean velocity and particle number density along the radial direction was measured by Particle Image Velocimetry(PIV).