• Journal of the Korean Ceramic Society
• /
• v.26 no.4
• /
• pp.539-549
• /
• 1989

Polycrystalline TiO2 thin films were deposited on Si and Al2O3 substrates by CVD method. Ethyl titanate, Ti(OC2H5)4, was used as a source material for Ti and O, and Ar was used for carrier gas. In the surface chemical reaction controlled deposition condition, the apparent activation energy of 6.74 Kcal/mole was obtained, and the atomic adsorption on substrate surface was proved to be governed by Rideal-Elley mechanism. In the mass transfer controlled deposition condition, the deposition rate was in a good agreement with the result which was calculated by the simple boundary layer theory. It was also observed that TiO2 thin films show different surface morphology according to the different deposition mechanism, which was fixed by deposition conditions. This phenomenon could be well explained by the surface perturbation theory.

• Carbon letters
• /
• v.15 no.1
• /
• pp.71-76
• /
• 2014

Activated carbon nanofibers (ACNF) were prepared from polyacrylonitrile (PAN)-based nanofibers using $CO_2$ activation methods with varying activation process times. The surface and structural characteristics of the ACNF were observed by scanning electron microscopy and X-ray diffraction, respectively. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller and Dubinin-Radushkevich equations. As experimental results, many holes or cavernous structures were found on the fiber surfaces after the $CO_2$ activation as confirmed by scanning electron microscopy analysis. Specific surface areas and pore volumes of the prepared ACNFs were enhanced within a range of 10 to 30 min of activation times. Performance of the porous PAN-based nanofibers as an electrode for electrical double layer capacitors was evaluated in terms of the activation conditions.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2013.12a
• /
• pp.32-32
• /
• 2013

Using the Vienna ab initio simulation package (VASP) incorporating van der Waals interaction, we have explored structural, adsorption, and magnetic properties of Ni(111)/BN/Co(111) systems. We have found that both Ni(111) and Co(111) layers shows half metallic state, while the spacer BN layer becomes weak metal for one monolayer (ML) thickness and an insulating barrier for two ML thickness. The half metallic states in both Ni(111) and Co(111) layers are robust because it is unchanged independently on the magnetic coupling of Ni(111) and Co(111). This finding suggests that the Ni(111)/BN/Co(111) systems can be utilized for perfect tunneling magnetoresistance system. Moreover, it can be applied for potential spin injecting into semiconductor in FM/semiconductor system due to the fact that the half metallic state in FM layers at the interface will be unchanged.

• Computers and Concrete
• /
• v.16 no.5
• /
• pp.775-793
• /
• 2015

Moisture transport in concrete in atmospheric environment was studied in this paper. Based on the simplified formula of the thickness of the adsorbed layer, the pore-size distribution function of cement paste was calculated utilizing the water adsorption isotherms. Taking into consideration of the hysteresis effect in cement paste, the moisture diffusivity of cement paste was obtained by the integration of the pore-size distribution. Concrete is regarded as a two-phase composite with cement paste and aggregate, neglecting the moisture diffusivity of aggregate, then moisture diffusivity of concrete was evaluated using the composite theory. Finally, numerical simulation of humidity response during both wetting and drying process was carried out by the finite difference method of partial differential equation for moisture transport, and the numerical results well capture the trend of the measured data.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.1
• /
• pp.45-50
• /
• 2014

A fully packed capillary electrochromatographic (CEC) microchip with an on-column micro-solid phase extraction (SPE) bed for the preconcentration and separation of organic analytes was prepared. A linear microchannel with monodisperse colloidal silica packing was formed on a cyclic olefinic copolymer microchip with two reservoirs on both ends. Silver-cemented silica packing frit structure was formed at the entrance of the microchannel by electroless plating treatment as a base layer. A gold coating was formed on it by reducing $Au^{3+}$ to gold with hydroxylamine. Finally micro-SPE bed was formed by self-assembly adsorption of 1-dodecanethiol on it. Micro-SPE beds were about 100-150 ${\mu}m$ long. Approximately $10^3$ fold sensitivity enhancements for Sulforhodamine B, and Fluorescein in nM concentration levels were possible with 80 s preconcentration. Basic extraction characteristics were studied.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.609-609
• /
• 2013

나노선은 대표적인 일차원 나노구조로 높은 부피-표면적 비율과, 조절 가능한 밴드갭 에너지, 뛰어난 광학적/전기적 특성으로 인해 다양한 잠재적 응용처를 가지며, 많이 연구되고 있다. 특히 ZnO 나노선은 대표적인 광촉매로, 높은 감광성과 높은 부피-표면적 비율 등의 특징을 가지지만, 상대적으로 넓은 밴드갭 에너지 때문에 가시광선 영역을 사용하지 못하는 단점이 있다. 본 연구에서는 CuS 나노입자/ZnO 나노선 이종구조를 간단한 두 가지의 방법으로 합성하였다. ZnO 나노선은 간단한 수열합성 방법으로 합성하였고, 그 위에 CuS 나노입자를 successive ionic layer adsorption and reaction (SILAR) 방법으로 증착하였다. 합성된 나노 구조는 기존의 ZnO 구조와는 달리 가시광 영역에서도 향상된 광촉매 특성을 보였으며, 이는 ZnO와 CuS사이의 interfacial charge transfer (IFCT)에서 기인한 것이다. SEM, TEM, XRD를 통해 CuS/ZnO 이종구조의 형태와 결정구조, 구성성분을 분석할 수 있었고, Acid Orange 7의 광분해 실험을 통해 향상된 광촉매 특성을 확인 할 수 있었다.

• Journal of the Korean institute of surface engineering
• /
• v.39 no.3
• /
• pp.115-120
• /
• 2006

The codeposition behavior of WC particles from an additive-free nickel sulfate and sulfamate solution has been investigated. Electroplating of Ni/WC composites was carried out at different current density with variation of WC particle size. The Guglielmi adsorption mechanism is applied to the electroplating of the fine WC in Ni matrix. The contents of WC in Ni composite coating were increased both by increasing current density and WC concentration in the bath. The hardness of Ni/WC composite coating at low current density is higher than that at high current density since finer WC particles dispersed through the coating. The codeposition behaviors of Co coated WC particles were also investigated. Conducting layer of particles promoted the codeposition behavior of Ni/WC-Co composite coatings.

• Journal of the Korean institute of surface engineering
• /
• v.37 no.4
• /
• pp.215-219
• /
• 2004

We fabricated protein chip plates coated with silane carboxylate. The silane compound was immobilized by hydrogen bond and/or other chemical bonds on the surface of the plate. The plates were then prepared by binding $Ni^{2+}$ to surfaces terminated with silane carboxylate groups. The carboxylic acid surface was generated by chemical oxidation of the terminal double-bond functions of the silane-deposited layer. The $Ni^{2+}$ ions on the surface reacted readily to His-tagged proteins. A significant increase in His-tagged protein adsorption was achieved on the surface terminated with silane carboxylate with longer alkyl chain, suggesting better availability of these protein chip plates for proteomic studies.

• Journal of the Korean Ceramic Society
• /
• v.52 no.3
• /
• pp.221-223
• /
• 2015

In this work, we report on the preparation of the anodically-grown $TiO_2$ nanotube arrays sensitized with $In_2S_3$ nanoparticles by using the SILAR (successive ionic layer adsorption and reaction) process. We evaluate the photo-catalytic properties of the prepared hetero-structures under visible-light illumination. The results reveal that the $TiO_2/In_2S_3$ system has enhanced photo-catalytic characteristics including higher chopping height. Improved performance of the heterojunction is attributed to the narrower band gap of $In_2S_3$ and its favorable position within the conduction band relative to that of $TiO_2$.

• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.3
• /
• pp.220-226
• /
• 2010

The heat transfer performance improvement in closed cooling water system of an electric power generation can be achieved by a corrosion control using corrosion inhibitors. The effect of trisodium phosphate and sodium nitrite upon carbon steel at various $Cl^{-1}$ ion containing water concentrations was examined by an integrated corrosion monitoring system. Nitrite was found to be the most effective inhibitor among tested inhibitors for carbon steel. The inhibiting process is considered as adsorption of nitrite ions in oxide layer which form a passive film on the carbon steel surface.