• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3227-3232
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• 2013

A novel Cu-Co-O composite nanocatalyst was designed and prepared for the ozonation of phenol. A synergistic effect of copper and cobalt was observed over the Cu-Co-O composite nanocatalyst, which showed higher activity than either copper or cobalt oxide alone. In addition, the Cu-Co-O composite revealed good activity in a wide initial pH range (4.11-8.05) of water. The fine dispersion of cobalt on the surface of copper oxide boosted the interaction between catalyst and ozone, and the surface Lewis acid sites on the Cu-Co-O composite were determined as the active sites. The Raman spectroscopy also proved that the Cu-Co-O composite was quite sensitive to the ozone. The trivalent cobalt in the Cu-Co-O composite was proposed as the valid state.

• 한국표면공학회지
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• 제47권2호
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• pp.68-74
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• 2014

The seed step-coverage enhancement process (SSEP) using Pd/Cu/PVP colloids was investigated for the filling of through silicon via (TSV) without void. TEM analysis showed that the Pd/Cu nano-particles were well dispersed in aqueous solution with the average diameter of 6.18 nm. This Pd/Cu nano-particles were uniformly deposited on the substrate of Si/$SiO_2$/Ti wafer using electrophoresis with the high frequency Alternating Current (AC). After electroless Cu deposition on the substrate treated with Pd/Cu/PVP colloids, the adhesive property between deposited Cu layer and substrate was evaluated. The Cu deposit obtained by SSEP with Pd/Cu/PVP colloids showed superior adhesion property to that on Pd ion catalyst-treated substrate. Finally, by implementing the SSEP using Pd/Cu/PVP colloids, we achieved 700% improvement of step coverage of Cu seed layer compared to PVD process, resulting in void-free filling in high aspect ratio TSV.

• 한국지하수토양환경학회지:지하수토양환경
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• 제11권3호
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• pp.12-19
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• 2006

본 연구에서는 우리나라의 경주에서 산출된 칼슘벤토나이트 콜로이드의 안정성에 대한 연구를 동적광산란 방법을 이 용하여 이온강도 및 pH 등의 지화학적 조건 변화에 따른 크기 변화를 관측함으로써 수행하였다. 속도론적 및 평형상태에서 pH 및 이온강도의 변화에 따른 칼슘벤토나이트 콜로이드의 크기변화를 관측하였다. 실험결과 칼슘벤토나이트 콜로이드의 안정성은 접촉시간, 매질의 이온강도와 pH 에 매우 크게 의존함을 보였으며 0.01 M $NaClO_4$ 이상의 이온강도에서는 고려된 대부분의 pH 에서 콜로이드가 불안정함을 보였다. 아울러 칼슘벤토나이트 콜로이드의 안정비 W와 CCC(Critical Coagulation Concentration) 등을 속도론적 응집 실험 자료들을 이용하여 계산하였다. 안정비 W는 이온강도가 증가함에 따라 감소하는 경향을 뚜렷하게 나타내었으며 pH 변화에 따른 W 값의 변화는 이온강도에 따라 다른 양상을 보였다. 또 pH 7 근처에서 칼슘벤토나이트 콜로이드의 CCC 는 약 0.05 M $NaClO_4$ 임을 알 수 있었다.

• 한국세라믹학회지
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• 제46권3호
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• pp.288-294
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• 2009

The platelet AlO(OH) nano colloids were prepared by hydrothermal reaction of the $\gamma-Al_2O_3$ obtained with dehydration of $\gamma$-AlO(OH) and dilute $CH_3COOH$ solution. In hydrothermal reaction process, reversible reaction was accompanied between $\gamma-Al_2O_3$ and AlO(OH), and hydrothermal reaction temperature, hydrothermal reaction time and $CH_3COOH$ concentration had an effect on the crystal structure, surface chemical property, surface area, pore characteristics and crystal morphology of the AlO(OH) nano colloid particles. In this study, it was investigated to the hydrothermal reaction condition of the AlO(OH) nano colloid for using catalyst support, heat resisting agent, adsorbents, binder, polishing agent and coating agent. The crystal structure, surface area, pore volume and pore size of the platelet AlO(OH) nano colloids were investigated by XRD, TEM, TG/DTA, FT-IR and $N_2$ BET method in liquid nitrogen temperature.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1891-1896
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• 2010

Submicron-sized polymeric colloidal particles can self assemble into 3-dimensional (3D) opal structure which is a useful template for photonic crystal. Narrowly dispersed polymer microspheres can be synthesized by emulsion polymerization in water using water-soluble radical initiator. In this report, we demonstrate a facile and reproducible emulsion polymerization method to prepare various polymeric microspheres within 200 - 400 nm size ranges which can be utilized as colloidal photonic crystal template. By controlling the amount of monomer and surfactant, monodisperse polymer colloids of polystyrene (PS) and acrylates with various sizes were successfully prepared without complicated synthetic procedures. Such polymer colloids self-assembled into 3D opal structure exhibiting bright colors by reflection of visible light. The colloidal particles and the resulting opal structures were rigorously characterized, and the wavelength of the structural color from the colloidal crystal was confirmed to have quantitative relationship with the size of constituting colloidal particles as predicted by Bragg equation. The tunability of the structural color was achieved not only by varying the particle size but also by infiltration of the colloidal crystal with liquids having different refractive indices.

• 대한화장품학회지
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• 제28권1호
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• pp.214-224
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• 2002

High concentrated $TiO_2$ nano colloids were synthesized by sol-gel method. Reactions were performed in $TiCl_4$/HCl/$H_2O$ aqueous solution and the conditions of particles such as shape, size and aggregation, etc. were controlled by polymerization and adsorption of acrylamide in surface of $TiO_2$ nano particles. And also, aminopropyltriethoxysilane was added instead of acrylamide and compared each other. The prepared colloids were well dispersed and showed the strong absorption peaks at 350nm-370nm which is blue shifted to 20-30nm, compared to macro particles. The obtained techniques from $TiO_2$ nato colloids synthesis were utilized in coating on boron nitride powders which are nonpolar and isoelectronic materials of carbon. Their surface morphology, structure, thermal stability and U. V absorption chracteristics were examined by SEM(Scanning Electron Microscopy), XRD(X-ray diffraction), TG/DTA(Thermogravimetric and Differential Thermal Analysis), UV-VIS(Ultraviolet-Visible Spectroscopy).

• 한국세라믹학회지
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• 제27권1호
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• pp.67-73
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• 1990

The behavior of optical properties of ion exchanged glasses was investigated inthis study. The used glasses were soda-lime-silica glasses that were produced by float process. The coloring effect by Ag colloids is measrued by spectral transmittance, color coordinates, dominant wavelength and excitation purity resulting from silver ions exchange of glasses immersed into the mixed molten salt with AgNO3. Ion exchange coloring of glasses made it possible to obtain glasses with a range from yellow to brown, and transmittance was decreased with increasing the amount of Ag colloids which reduced from Ag+ions. Also, obtain from yellow to reddish brown with increasing purity by reheating treatment in air for ion exchanged glasses. The size of Ag colloids are 0.02~0.1${\mu}{\textrm}{m}$ with ion exchange conditions.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 추계학술발표회
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• pp.115-119
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• 2001

Contaminant retardation factor is derived from the colloidal and contaminant transport equations for a four-phase porous medium: an aqueous phase, two mobile colloidal phases, and a solid matrix. It is assumed that the contaminant sorption to solid matrix and colloidal particles and the colloidal deposition on solid matrix follow the linear isotherms. The behavior of the contaminant retardation factor in response to the change of model parameters is examined employing the experimental data of Magee et al. (1991) and Jenkins and Lion (1993). In the four-phase system, the contaminant retardation factor is determined by both the contaminant association with solid matrix and colloidal particles and the colloidal deposition on solid matrix. The contaminant mobility is enhanced when the affinity of contaminants to mobile colloids increases. In addition, as the affinity of colloids to solid matrix decreases, the contaminant mobility increases.

• Applied Microscopy
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• 제44권1호
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• pp.30-33
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• 2014

Colloidal systems or colloids consist of microparticles or nanoparticles (solute) uniformly suspended in a liquid (solvent), also called colloidal suspensions. They can mimic and exhibit microscopic or atomic aspects of molecular and atomic systems. They have been increasingly studied because of their similarity with atomic systems. They can be microscopically observed by optical microscopes because they are large enough in size and slow in motion to be monitored; microscopic methods are very useful and powerful in research on colloidal systems. Recently, confocal laser microscopy has been known as a powerful tool to obtain information of real-space and real-time behaviors of colloidal suspensions. In particular, it is possible to exactly track individual colloids in three dimensions with confocal microscopy. In this article, we briefly discuss the usefulness of confocal microscopy in colloidal systems that are currently used as model systems to resolve important questions in materials science.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2669-2674
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• 2009

Controlled reduction of silver alkylcarbamate complexes with hydrogen gas was investigated as a facile synthetic method for high concentrations of silver nanocolloids in organic solvent. Polyvinylpyrrolidone (PVP) was used to stabilize the silver colloids obtained from the chemical reduction. To determine optimum conditions for preparation of the stable and controlled silver colloids with the narrowest particle size and distribution, a large number of experiments were carried out involving variations in the concentrations of the silver 2-ethylhexylcarbamate (Ag-EHCB) complex, PVP, and 2-propanol. The initial colloid had a mean particle diameter between 5$\sim$50 nm, as measured by transmission electron microscopy, and exhibited a sharp absorption band in the UV region with a maximum size near 420 nm. After treatment with a reducing agent, the colloids were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy.