• 한국재료학회지
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• 제18권3호
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• pp.153-158
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• 2008

Fe-aluminides have the potential to replace many types of stainless steels that are currently used in structural applications. Once commercialized, it is expected that they will be twice as strong as stainless steels with higher corrosion resistance at high temperatures, while their average production cost will be approximately 10% of that of stainless steels. Self-propagating, high-temperature Synthesis (SHS) has been used to produce intermetallic and ceramic compounds from reactions between elemental constituents. The driving force for the SHS is the high thermodynamic stability during the formation of the intermetallic compound. Therefore, the advantages of the SHS method include a higher purity of the products, low energy requirements and the relative simplicity of the process. In this work, a Fe-aluminide intermetallic compound was formed from high-purity elemental Fe and Al foils via a SHS reaction in a hot press. The formation of iron aluminides at the interface between the Fe and Al foil was observed to be controlled by the temperature, pressure and heating rate. Particularly, the heating rate plays the most important role in the formation of the intermetallic compound during the SHS reaction. According to a DSC analysis, a SHS reaction appeared at two different temperatures below and above the metaling point of Al. It was also observed that the SHS reaction temperatures increased as the heating rate increased. A fully dense, well-bonded intermetallic composite sheet with a thickness of $700\;{\mu}m$ was formed by a heat treatment at $665^{\circ}C$ for 15 hours after a SHS reaction of alternatively layered 10 Fe and 9 Al foils. The phases and microstructures of the intermetallic composite sheets were confirmed by EPMA and XRD analyses.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 제17회 워크샵 및 추계학술대회
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• pp.631-633
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• 2005

For biohydrogen production, hydrogenase is a key enzyme. In the present work we performed search of [NiFe]-hydrogenases from hydrogen producing microorganisms using degenerate polymerase chain reaction (PCR) strategy. Degenerate primers were designed from the conserved region of [NiFe]-hydrogenase group I especially on structural genes encoding for catalytic subunit of [NiFe]-hydrogenase from bacteria producing hydrogen. Most of [NiFe]-hydrogenase (group I) are expressed via complex mechanism with aid of auxiliary protein and localized through twin-arginine translocation pathway. [NiFe]-hydrogenase is composed of large and small subunits for catalytic activity. It is known that only small subunit has signal peptide for periplasmic localization and large & small subunitscome together before localization. During this process, large subunit is treated by endopeptidase for maturation. Based on these information we used signal peptide sequence and C-terminal of large subunit by recognized by endopeptidase as templates for degenerate primers. About 2,900 bp of PCR products were successfully amplified using the designed degenerate primers from genomic DNAs of several microorganisms. The amplified PCR products were inserted into T-vector and then sequenced to confirm.

• 한국실내디자인학회논문집
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• 제19권6호
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• pp.197-205
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• 2010

For the spatial experience of spectators visiting a museum, the route search of trying to follow the spatial structure or production of exhibition and the information search of trying to see are accomplished at the same time. In such process, the spectator's reaction of visual perception produces the result of emotional reaction and action exchanged between human and space by going through the recognition and perception on the target of environment factor. For the spatial experience of a spectator, the reaction of visual perception which interacts according to the exhibit and exhibition environment within space according to viewing purpose, interest and concern of spectator comes out as visual activity which is an activity to understand the spatial information shown as various activities according to spatial structure and unfolding characteristics of the display. The purpose of this study is to identify The Correlation of Spectator Movement Created According to Structural Form of Exhibition Area Based on Interaction between Exhibition Area Structure and Spectator to utilize as basic material while designing museum exhibition using isovist field which is a quantitative analysis tool of spectator's visual behavior and spatial structure at each exhibition area.

• 한국잠사곤충학회지
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• 제39권1호
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• pp.73-78
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• 1997

분자량 약 7000의 Fcp는 효소분해역반응을 이용하는 것에 의해 분자량 약 17000과 약 24000까지 고분자량화된 PIFcp가 얻어졌다. 또, 효소분해의 역반응에 의해 고분자량화되는 것은 일부의 Fcp이며 Silk II형결정으로부터 Silk I형결정으로 전이하는 것은 대부분의 Fcp에서 나타났다. 이 PIFcp는 X선회절과 시차열분석(DTA)의 결과로부터 어느정도 안정한 Silk I형의 결정구조를 가지는 것이 확인되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.316-319
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• 2006

There is a worldwide interest in the development and commercialization of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) for vehicular and stationary applications. One of the major objectives is the reduction of loaded electrode materials, which is comprise of the Pt-based noble metals. In this paper, a novel chemical strategy is described for the preparation and characterization of carbon-supported and surface-alloys, which were prepared by using a successive reduction process. After preparing Au colloid nanoparticles, the deposition of Au colloid nanoparticles occurred spontaneously in the carbon black-dispersed aqueous solution. Then nano-scaled active materials were formed on the surface of carbon-supported Au nanoparticles. The structural and electrochemical analyses indicate that the active materials were deposited on the surface of Au nanoparticles selectively and that an at toying process occurred during the successive reducing process The carbon-supported & surface-alloys showed the higher electrocatalytic activity than those of the particle-alloys and commercial one (Johnson-Matthey) for the reaction of methanol and formic acid oxidation. The increased electrocatalytic activity might be attributed to the effective surface structure of surface-alloys, which have a high utilization of active materials for the surface reaction of electrode.

• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.149-152
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• 2002

The effect of pressure on the catalytic properties of glutamate racemase from Aquifex pyrophilus, an extremophilic bacterium, was investigated. The activation volume for the overall reaction $({\Delta}V^{\neq})$ and catalysis $({{Delta}V_{cat}}^{\neq})$ was -96.97 ml/mol and 4.97 ml/mol, respectively, while the reaction volume for the substrate binding (${\Delta}V_{K_m^-1}$) was -101.94 ml/mol. The large negative ${\Delta}V^{\neq}$ for the overall reaction indicated that the pressurization of glutamate racemase resulted in enhanced catalytic efficiencies. In addition, this value was also due to the large negative ${Delta}V_{K_m^-1}$ for the substrate binding. The negative value of ${Delta}V_{K_m^-1}$ implied that the conformational changes in the enzyme molecule occurred during the substrate binding process, thereby increasing the degree of hydration. The small value of ${{Delta}V_{cat}}^{\neq}$suggested that the pressure did not affect the glutamate racemase catalysis after the substrate binding.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1920-1926
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• 2008

We investigated the C-H bond activation mechanism of aldimine by the [RhCl$(PPH_3)_3$] model catalyst using DFT B3LYP//SBKJC/6-31G*/6-31G on GAMESS. Due to their potential utility in organic synthesis, C-H bond activation is one of the most active research fields in organic and organometallic chemistry. C-H bond activation by a transition metal catalyst can be classified into two types of mechanisms: direct C-H bond cleavage by the metal catalyst or a multi-step mechanism via a tetrahedral transition state. There are three structural isomers of [RhCl$(PH_3)_2$] coordinated aldimine that differ in the position of chloride with respect to the molecular plane. By comparing activation energies of the overall reaction pathways that the three isomeric structures follow in each mechanism, we found that the C-H bond activation of aldimine by the [RhCl$(PH_3)_3$] catalyst occurs through the tetrahedral intermediate.

• Corrosion Science and Technology
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• 제16권5호
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• pp.247-256
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• 2017

The feasibility of using hydrazine for inhibiting pitting corrosion in copper sprinkler tubes was investigated by examining microscopical and structural evolution of corrosion by-products with SEM, EDS, and XRD. Hydrazine removed dissolved oxygen and reduced CuO and $Cu_2O$ as well. The stable phase was changed from CuO to $Cu_2O$ or Cu depending on hydrazine concentration. Hydrazine concentration of 500 ppm could convert all CuO corrosion by-products to $Cu_2O$. In a tightly sealed acryl tube filled with aqueous solution of 500 ppm hydrazine, octahedral $Cu_2O$ particles were formed while plate-like structures with high concentration of Cu, O, N and C were formed near a corrosion pit. The inside structure of a corrosion pit was not altered by hydrazine aqueous solution. Uniform corrosion of copper was almost completely stopped in aqueous solution of 500 ppm hydrazine. Corrosion potential of a copper plate was linearly dependent on log (hydrazine concentration). The concept of stopping pitting corrosion reaction by suppressing oxygen reduction reaction could be verified by applying this method to a reasonable number of real sprinkler systems before full-scale application.

• 한국수소및신에너지학회논문집
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• 제14권4호
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• pp.298-304
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• 2003

The thermal behavior of $NiFe_2O_4$ prepared by a solid-state reaction was investigated for $H_2$ generation by the thermochemical cycle. The reduction of $NiFe_2O_4$ started from $800^{\circ}C$, and the weight loss was 0.2-0.3 wt% up to $1000^{\circ}C$. In the $H_2O$ decomposition reaction, $H_2$ was generated by oxidation of reduced $NiFe_2O_4$. The crystal structure of $NiFe_2O_4$ maintained during the redox reaction of 5 cycles. From this observation, the lattice oxygen in $NiFe_2O_4$ is released without the structural change during the thermal reduction and oxygen deficient $NiFe_2O_4$ can be restored to the spinel structure of $NiFe_2O_4$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권4호
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• pp.139-143
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• 2005

For application of carbon nano-tube (CNT) as a counter electrode materials of dye-sensitized solar cell (DSSC), the electrochemical behavior of CNT electrode was studied, employing cyclic-voltammetry (C-V) and impedance spectroscopy. Fabrication of CNT-paste and formation of CNT-counter electrode for characteristic measurement have been carried out using ball-milling and doctor blade process, respectively. Unit cell for measurements was assembled using Pt electrode, CNT electrode, and iodine-embedded electrolyte. Field emission-scanning electron microscopy (FE-SEM) was used for structural investigation of CNT powder and electrode. Sheet resistance of electrode was measured with 4-point probe method. Electrochemical properties of electrode, C-V and impedance spectrum, were studied, employing potentiogalvanostat (EG&G 273A) and lock in amplifier (EG&G 5210). As a results, the sheet resistance of CNT electrode is almost similar to that of F-doped SnO2 (FTO) coated glass substrate as approximately 10 ohm/sq. From C-V and impedance spectroscopy measurements, it was found that CNT electrode has high reaction rate and low interface reaction resistance between CNT surface and electrolyte. These results provides that CNT electrode were superior to that of conventional Pt electrode. Particularly, the reaction rate in the CNT electrode is about thrice high than Pt electrode. Therefore. CNT electrode is to be good candidate material for counter electrode in DSSC.