• Korean Journal of Materials Research
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• 제8권12호
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• pp.1082-1089
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• 1998

To obtain fine dispersion of Ag particles in $YBa_2$$Cu_3$$O_{7-y}$ (123) superconductors, 123 samples were made by pyrophoric synthetic method using malic acid and the subsequent solid- state reaction. As the pyrophoric synthetic powder was used as a precursor material, fine 123 powder of submicron size was produced in a short reaction time. The added $Ag_2$O was converted to metallic Ag during Pyrophoric reaction and it accelerated both the formation of 123 phase and the grain growth via the enhanced mass transfer. The Ag particles of the sample sintered using the pyrephoric synthetic powder were more finely dispersed in the 123 matrix, compared to those of the sample sintered using the mechanically mixed powder, attributing to the improvement of the superconducting properties.

• Korean Journal of Materials Research
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• 제9권3호
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• pp.263-268
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• 1999

In this study, a new concept of aluminum-matrix composites and the possibility of in-situ processing are suggested, and preliminary results on AI- Ti system are presented. Fine powders of AI-lO% Ti were prepared by the gas atomization so that fine $Al_3Ti$ formed into flake shape. A 25v/o $Al_3Ti/Al$ composite sample was made by the pow­d er metallurgy process involving hot extrusion. Microstructure and mechanical behavior both at room temperature and high temperatures were analysed by OM, SEM, TEM and tension test. Microstructural characteristics and mechanical properties of the composites exhibited similar behavior to those of $SiC_w/2124$ composites. Merits and drawbacks of the $Al_3Ti/Al$ composites are discussed together with a possibility of further improvement.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.139-144
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• 2022

This study reports a microfluidic approach to produce monodisperse hydrogel microparticles in a simple and highly efficient manner. Specifically, we produce double emulsion drops with a thin oil shell surrounding an aqueous prepolymer solution, which is solidified via UV-induced free radical polymerization. When they are dispersed in an aqueous solution, the oil shell is dewetted due to the absence of surfactants, resulting in production of highly uniform hydrogel microparticles (C.V.=1%). Results show that production of monodisperse hydrogel microparticles with controllable size and composition can be achieved with minimal use of oil unlike water-in-oil (w/o) single emulsion-based approach. Furthermore, in-depth study of flow patterns in microfluidic device using a phase diagram exhibits a crucial relationship among relative flow rates while providing windows of readily controllable parameters for reliable manufacturing of hydrogel microparticles.

• Clean Technology
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• 제15권4호
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• pp.233-238
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• 2009

Supercritical fluid processes have gained great attention as a new and environmentally-benign method of preparing the microparticles of energetic materials like explosives and propellants. In this work, RDX (cyclotrimethylenetrinitramine) was selected as a target explosive. The microparticle formation of RDX using supercritical anti-solvent (SAS) recrystallization process was performed and the effect of operating variables on the size and morphology of prepared particles was observed. N,N-Dimethylformamide was used as organic solvent for dissolving the RDX. The size of the RDX particles decreased remarkably up to less than $10\;{\mu}m$ by SAS recrystallization. In the range of operating conditions of the SAS process studied in this work, the finest RDX particles were obtained at 313.15K, 150 bar, and 15wt% RDX concentration in feed solution.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• 제22권3호
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• pp.135-149
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• 2017

Microplastics are fractions of plastics less than 5 mm in size and can be divided into artificially manufactured primary microplastics and physically or chemically decomposed secondary microplastics. In this study, the emission source of microplastics made by the human activities is defined as the primary source of microplastics. And the primary sources of microplastics were summarized by using the literature and the emission potential of each source was estimated. As a result, this study showed that 63,000 to 216,000 ton/year of microplastics were discharged into the environment. Among primary sources, transport, tyre dust, and laundry were the major primary sources.

• Clean Technology
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• 제13권1호
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• pp.34-45
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• 2007

Phase behavior of the ternary systems of water-insoluble simvastatin drug, which is well known to be effective drugs for hypercholesterolemia therapy, in solvent mixtures of dichloromethane and supercritical carbon dioxide was investigated to present a guideline of establishing operating conditions in the particle formation of the drugs by a supercritical anti-solvent recrystallization process utilizing dichloromethane as a solvent and carbon dioxide as an anti-solvent. The solubilities of simvastatin in the mixtures of dichloromethane and carbon dioxide were determined as functions of temperature, pressure and solvent composition by measuring the cloud points of the ternary mixtures at various conditions using a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The solubility of the drug increased as the dichloromethane composition in solution and the system pressure increases at a fixed temperature. A lower solubility of the drug was obtained at a higher temperature. The second half of this work is focused on the particle formation of the simvastatin drug by a supercritical anti-solvent recrystallization process in a cylindrical high-pressure vessel equipped with an impeller. Microparticles of the simvastatin drug were prepared as functions of pressure (8 MPa to 12 MPa), temperature (303.15 K, 313,15 K), feed flow rate of carbon dioxide, and stirring speed (up to 3000 rpm), in order to observe the effect of those process parameters on the size and shape of the drug microparticles recrystallized.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권12호
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• pp.938-943
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• 2018

Thin nano-sized fibres were prepared by an electrospinning method. The spinning appratus consisted of pump for polymer injection, nozzle and nozzle rotus, and an aluminum plate collected the polymer fibers. Its surface was chemically modified for selective improved adsorption of carbon monoxide at indoor level. The chemical activation enabled to form the fibres 250-350 nm in thickness with pore sizes distributed between 0.6 and 0.7 nm and an average specific surface area of $569m^2/g$. The adsorption capacities of pure (100%) and indoor (0.3%) $CO_2$, of which level frequently appears, at the ambient condition were improved from 1.08 and 0.013 to 2.2 and 0.144 mmol/g, respectively. It was found that the adsorption amount of $CO_2$ adsorbed by the chemically activated carbon nanofiber prepared through chemical activation would vary depending on the ratio of specific surface area and micropores. In particular, chemical interaction between adsorbent surface and gas molecules could enhance the selective capture of weak acidic $CO_2$.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 한국안전학회 2003년도 춘계 학술논문발표회 논문집
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• pp.167-172
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• 2003

액정판넬(LCD) 및 반도체 제조공정에 있어서 정전기 발생으로 인하여 미세한 먼지가 LCD 및 반도체 웨이퍼에 부착되거나, 정전기 방전에 의해 반도체소자 및 LCD 유리기판상의 패헌의 파괴를 야기하여 제품의 수율을 저하시키고 제조원가를 상승시키는 주요한 요인이 된다. 현재 이러한 제조공정에서 정전기를 위한 대책으로 코로나방전에 의한 이온바(Ion Bar) 및 이온브로어(Ion Blower)를 제전설비로 사용하고 있으나, 이 장치는 코로나 방전에 의한 이온을 발생시키고 이온화된 공기를 불어 내기 위하여 팬을 사용하여 공기를 대류 시킨다.(중략)

• Proceedings of the Korean Fiber Society Conference
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• 한국섬유공학회 1998년도 가을 학술발표회논문집
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• pp.469-472
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• 1998

상업적으로 유용한 대부분의 합성고분자막들은 상전환법(phase inversion process)이라는 방법에 의해서 제조된다. 이 제조공정에서는 단일 고분자(homogeneous polymer)용액에 존재하는 용매를 비용매와 교환함으로써 액체로부터 고체로 상이 전환된다. 그리고 pore의 크기나 pore의 크기분포와 같은 막의 구조를 결정하는 요인은 일반적으로 용질의 입자크기 또는 분자크기 및 화학적 성질에 기인한다[1-3]. (중략)

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.263-263
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• 2014

자외선 영역에서 우수한 광촉매 반도체인 이산화티탄($TiO_2$)은 환경, 에너지와 같은 분야 등에 유용하게 이용된다. 용액상에서 고활성 광촉매의 제조가 가능한 수열합성법에 의해 균일한 결정상의 나노 크기의 미세한 이산화티탄($TiO_2$) 입자를 제조하고, XRD, TEM, UV-vis-DRS, 그리고 염료의 광촉매 흡착 반응을 통하여 그 특성과 광촉매 효율을 조사하였다.