• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.276-281
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• 2015

Nanostructured $TiO_2-SiO_2$ materials have widely been used as anti-reflecting coating, optical-chemical sensors and catalysts because of their superior optical and thermal properties as well as chemical durability. Web type $SiO_2$ microfibers with nano-crystalline $TiO_2$ were prepared by electrospinning of Ti-PCS mixed solution and oxidation controlled heat-treatment, rather simple than sol-gel process. Nano-crystalline anatase phase were formed for the heat-treatment up to $1200^{\circ}C$ and they were finely dispersed in the amorphous $SiO_2$ matrix.

• Applied Chemistry for Engineering
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• v.25 no.5
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• pp.526-530
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• 2014

Polystyrene-poly(etheramic acid) core-shell particles were prepared by dispersion polymerization of styrene using poly(etheramic acid) obtained by the reaction of 2,2'-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride and 3,5-diamniobenzoic acid as a stabilizer. 4-Vinylbenzyltrimethylammonium chloride was used as a comonomer to increase the binding efficiency of poly(etheramic acid). When the ethanol-water mixture (7 : 3) was used as a reaction medium, particles were stabilized well and the size distribution of particles was fairly narrow. The particle size increased with the amount of styrene. The particles polymerized in the dimethylformamide-water mixture had a broad size range. Polystyrene-poly(etheramic acid) core-shell particles were transformed to polystyrene-polyetherimide core-shell particles by the chemical imidization of shells.

• Journal of the Korean Ceramic Society
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• v.38 no.8
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• pp.749-754
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• 2001

마이크로파 추출 및 하소 공정을 통하여 카올린으로부터 베타 알루미나 전구체 및 베타 알루미나 분말을 합성하였다. 황산 알루미늄 및 가성소다의 혼합 용액을 교반되는 에탄올 용액 중에 적하시켜서 $Al_2$(SO$_4$)$_3$.17$H_2O$ 및 $Na_2$SO$_4$.10$H_2O$의 균일한 침전물을 얻었다. $\beta$- 및 $\beta$\"-Al$_2$O$_3$상으로 구성된 베타 알루미나를 얻기 위하여 재래식 및 마이크로파 하소법으로 주어진 온도에서 약 2h 동안 침전물 시료를 하소하였다. 재래식 하소된 시료에 비하여 마이크로파 하소된 시료는 $\beta$\"-Al$_2$O$_3$상이 상대적으로 많이 존재하였다. 또한, 재래식 하소된 시료와 마이크로파 하소된 시료의 미세구조는 매우 상이하였다. 매우 상이하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.8
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• pp.664-670
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• 1998

고순도의 Bi(Pb)-Sr-Ca-Gu-O 초전도 분말의 얻기 위하여 액상법의 하나인 이멀젼 건조방법이 응용되었다. 다양한 합성 변수 중 오일과 용액의 계면활설제의 혼합비율을 조정하여 고순도의 Bi(Pb)-Sr-Ca-Gu-O 초전도 분말을 성공적으로 얻을 수 있었다. 이 공정의 최적 혼합비율은 70:20:10이였다. 관측된 분말을 구형이었으며 마이크론 크기 이하의 균일한 크기를 보였다. 최적의 소결조건에 한에 $840^{\circ}C$ 50시간의 열처리를 통하여 거의 108K를 갖는 초전도 분말이 얻어졌다.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.316-320
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• 2009

UV curable hard and color coatings were formed on polycarbonate(PC) films. The coating materials were composed of a commercially available end-capped polyester(EB830), diacrylate monomer(HDDA), silicon acrylate, photoinitiator, and organic dye as a coloring agent. The surface properties of coating films were evaluated, and the influences of the compositions of coating materials were investigated. The coating films showed high transmission and good adhesion between coating layer and PC substrate. And the coating films exhibited higher hardness than bare PC film. The coating films with various colors were obtained by wet process, and the clear and color window lenses for mobile phone were prepared successfully.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.438-438
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• 2012

은(Ag) 또는 금(Au) 입자를 촉매로 이용하여 습식식각을 통해 선택적으로 짧은 시간동안 단결정 실리콘 웨이퍼의 표면을 텍스쳐링하여 반사방지막 특성을 효과적으로 얻을 수 있다. 일반적으로 금속입자는 주로 금속 이온이 포함된 용액이나, 전기증착법을 통해서 실리콘 웨이퍼 표면에 형성시켰지만, 금속입자의 크기와 분포를 조절하기 어려웠다. 하지만, 최근 진공장비를 이용하여 열증발증착법(thermal evaporation)과 급속열처리법(rapid thermal annealing)을 통해서 금속입자를 대면적으로 크기와 분포를 균일하게 조절할 수 있다. 이러한 현상은 열적 비젖음(thermal dewetting) 현상에 의해 실리콘 표면위에 증착된 금속 박막으로부터 나노입자로 형성할 수 있다. 본 연구에서는 실리콘 (100)기판위에 다양한 크기의 은 또는 금 나노입자를 형성시켜 식각용액에 짧은 시간동안 담그어 식각하여, 텍스쳐링 효과와 반사방지(antireflection) 특성을 분석하였다. 실험을 위해 각각 은 또는 금 박막을 열증발증착법을 이용하여 ~3-8 nm의 두께로 형성시켰으며, 급속가열장치를 이용하여 $500^{\circ}C$에서 5분 동안 열처리하였다. 그리고 탈이온수(de-ionized water)에 불화수소와 과산화수소가 혼합된 식각용액에 1-5분 동안 습식식각을 하였다. 각각의 텍스쳐링 된 샘플의 식각의 상태와 깊이를 관찰하기 위해 field emission scanning electron microscopy (FE-SEM)을 이용하여 측정하였으며, UV-vis-NIR spectrophotometer를 이용하여 300 nm에서 1,200 nm의 반사특성을 분석하였다. 또한 RCWA (rigorous coupled wave analysis) 시뮬레이션을 이용하여 텍스쳐링 된 기하학적구조에 대하여 반사방지막 특성을 이론적으로 분석하였다.

• Applied Chemistry for Engineering
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• v.24 no.2
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• pp.165-170
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• 2013

An external gelation method in place of an internal gelation method applied to the fabrication process of an intermediated compound of Uranium Oxy-Carbide (UCO) kernel spheres for Very High Temperature Reactor (VHTR) fuel preparation is under development in Korea. For the preliminary experiments of the UCO kernel sphere preparation using an external gelation method, the carbon black dispersion experiments were carried out using a simulated broth solution. From the selection experiments of various kinds of carbon black through dispersion experiments in a viscous metal salt solution, Cabot G carbon black was selected owing to its dispersion stability, and the homogeneous dispersing state of carbon black particles in our system. For the effective dispersion of nano-size aggregated carbon black particles in a high viscous liquid, the carbon black particles in a metal salt solution were first de-aggregated with ultrasonic force. The mixed solution was then dispersed secondly by the use of the extremely high-speed agitation with a mechanical mixer of 6000 rpm after feeding the Poly Vinyl Alcohol (PVA) in the solution. This results in the broth solution with good stability and homogeneity alongside no further changes in physical properties.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.416-422
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• 2013

In order to incorporate silver ions into the alginate, silver-alginate was prepared with aqueous solutions of silver nitrate. In the study, the silver-alginate was prepared by blending with poly vinylpyrrolidone solutions and the electrospinning was performed by using this blend solution. Antibacterial properties of silver-alginate/PVP solutions were estimated for Escherichia coli and Staphylococcus aureus by the colony counting test. Electrospinning conditions of silver-alginate/PVP solution were the tip-to-collector distance of 22 cm, the flow rate of the solution at 0.01 mL/min, and the voltage at 26 kV. The form and size of silver-alginate/PVP nanofibers were estimated by SEM and Image J. The average diameter of the electrospun SA5P15 fibers was 124 nm and showed a narrow diameter distribution. The reduction of bacteria for SA5P15 exhibited 99.9% after 24 h.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.785-789
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• 2005

$TiO_2$ powders with rutile and brookite phases were synthesized through homogeneous precipitation of the aqueous $TiOCl_2$ solution, prepared from $TiCl_4$ and HCl solution, and their properties were characterized. Based on the analytical results appropriate molar ratios of ${Cl^-}_{total}:Ti^{+4}$ in precipitating solution for synthesis of pure rutile phase and a mixture of rutile and brookite phases were proposed. The volumetric proportion of brookite increased with increasing HCl concentration under a typical condition obtaining mixed phase of rutile and brookite. The brookite phase in the mixture was transformed to anatase phase by heat treatment at about $800^{\circ}C{\sim}850^{\circ}C$, and finally converted to rutile phase at $1000^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.563-566
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• 1998

$BaTiO_3$ fine particles were prepared by hydrothermal process from titanium tetra-isoproproxide ($Ti(OiPr)_4$) and barium hexa-hydroxide ($Ba(OH)_2{cdot}8H_2O$) as raw materials. The fine particles were obtained at the temperature range of 160 to $185^{\circ}C$. The properties of $BaTiO_3$ particles were studied as a function of various parameters such as reaction temperature, reaction time and Ba/Ti ratio, etc. The average particle size of $BaTiO_3$ increased with increasing reaction temperature and time. After hydrothermal treatment at $170^{\circ}C$ for 8 h, the average particle size of $BaTiO_3$ was about 30 nm and the particle size distribution was narrow.