• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.3046-3054
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• 2013

Synthesis of Carbon Nanotube bundles has been achieved by simple and economical solvothermal procedure at very low temperature of $180^{\circ}C$. The product yield obtained was about 70-75%. The optimization of reaction conditions for an efficient synthesis of CNTs has been presented. The CNTs are obtained by reduction of hexachlorobenzene in the presence of Na/Ni in cyclohexane. The X-ray diffraction, Fourier transform infrared and Raman spectral studies have inferred us the graphene structure of the products. The CNTs formed as the bundles were viewed on scanning electron microscope, transmission electron microscope and high-resolution transmission electron microscope. These are the multiwalled CNTs with outer diameter of 5-10 nm, the inner diameter 2-4 nm and cross sectional diameter up to 5 nm. Brunauer-Emmett-Teller (BET) based $N_2$ gas adsorption studies have been made to obtain BET surface area and $H_2$ storage capacity. Effect of the experimental variables such as reaction temperature, amount of catalyst and the amount of carbon source were investigated. It is found that they affect significantly on the product nature and yield.

• 한국세라믹학회지
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• 제52권3호
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• pp.204-208
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• 2015

Synthesis of hydroxyapatite (HA) was attempted through a room-temperature reaction of calcined eggshell with phosphoric acid. Ball-milled, calcined eggshell powder, which has a specific surface area of $31.6m^2/g$, was mixed with various concentrations of phosphoric acid at room temperature. The mixtures showed high reactivity and a vigorous exothermic reaction ; the reacted samples showed both $Ca(OH)_2$ and $CaHPO_4$ crystal phases. After heating at temperatures above $400^{\circ}C$, an HA crystal phase was observed in all samples. The calcined eggshell showed a pure CaO single phase, while the $Ca(OH)_2$ phase was only observed in the wet, ball-milled calcined powder. The degree of formation of the HA crystal phase increased as the phosphoric acid concentration and the heating temperature were increased. A mixture with 50 wt% phosphoric acid concentration showed a well-developed HA crystal phase after heat treatment at $800^{\circ}C$, while the formation of a more intensive amorphous phase was observed in the products of the room-temperature reaction.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1355-1360
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• 2004

The oxidative decomposition of trichloroethylene (TCE) was investigated using palladium catalysts supported on pure and sulfated zirconia. The reactions were performed under dry and wet conditions in the temperature between 200 and $550^{\circ}C$ keeping GHSV of 14,000 $h^{-1}.$ The products such as $C_2Cl_4,\;C_2HCl_5,\;CO\;and\;CO_2$ were observed in the reaction. The addition of water in the feed affected the distribution of reaction product with dramatically improved catalytic activity. The spectroscopic investigations gave an evidence that the strong acid sites play an important role on controlling the catalytic activity. Among the catalysts investigated, the Pd-loaded sulfated zirconia catalyst with 1 wt% Pd was found to exhibit the highest catalytic activity in the presence of water vapor having the stability for 30 h of the reaction at $500^{\circ}C$. The successful performance of the catalyst might be attributed to promotional effect of Pd active sites and strong acid sites induced from surface sulfate species on zirconia.

• Bulletin of the Korean Chemical Society
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• 제1권1호
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• pp.10-17
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• 1980

Penicillin amidohydrolase was partially purified from the fermented broth of Bacillus megaterium, and was immobilized on nylon fiber. The surface area of nylon fiber was increased by roughening it with fine sand and activated by acid treatment. The free amino groups on the nylon fiber exposed by such treatment were then utilized to immobilize the penicillin amidase. Enzymatic properties of penicillin amidohydrolase immobilized on the nylon fiber by covalent bonding and cross linking with glutaraldehyde were studied and compared with those of soluble enzyme. The optimal pH and temperature profile of immobilized enzyme showed only slightly broader peaks, and the values of kinetic constants, $K_m$, $K_{ia}$, and $K_{ip}$, of the immobilized enzyme are only slightly greater than those of the soluble enzyme. These results suggest that the mass transfer effect on the reaction rate for the penicillin amidase immobilized on nylon fiber is not so significant as the enzyme immobilized on some other support material like bentonite. The experimental results of batch reaction agreed well with the results of computer simulation for both the immobilized and soluble enzyme systems, confirming the validity of the rate equation derived which was based on the combined double inhibition by two reaction products.

• 방사성폐기물학회지
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• 제11권1호
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• pp.55-61
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• 2013

본 논문에서는 염소화 반응을 통해 Zircaloy-4 (Zry-4) 피복관으로부터 Zr의 회수 연구를 수행하였다. 피복관의 Zr을 전부 $ZrCl_4$로 전환시키기 위해, Zry-4 피복관을 380도에서 70 cc/min $Cl_2$ + 70 cc/min Ar 기체를 이용하여 8시간 동안 반응시켰다. 피복관의 초기 무게는 51.7 g이었으나, 8 시간 반응 후에는 0.49 g만이 잔류물로 남아있는 것을 확인하였는데 이는 초기 무게의 0.95wt%에 해당하는 값이다. 반응 생성물의 무게는 121.7 g 이었으며, Zr의 순도는 99.80wt%였다. 주요 불순물로는 Fe (0.18wt%)와 Sn (0.02wt%)를 확인할 수 있었다. 실험 결과를 통해 확인한 Zr의 회수율은 96.95wt%였으며, 실험상 손실은 2.34wt%로 확인되었다. 반응 잔류물의 관찰을 통해 염소화 반응이 길이 방향으로 주로 일어나며, 표면의 산화층이 반응 잔류물로 남는다는 것을 확인할 수 있었다. 본 연구를 통해 확인된 Zr의 높은 순도와 회수율은 염소화 공정이 폐 피복관 처리 방법으로 매우 유망한 기술임을 의미한다고 볼 수 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.147-147
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• 2000

Chemisorption of oxygen molecules on the Si(111)-(7x7) surface has been studied extensively as a model for the initial-stage oxidation of the surface. The basic step to the surface oxidation is the dissociation of the adsorbed O2 molecules, but the dissociation procedure and the atomic structure of the reaction products still remains as a subject of debates. We present here density-functional theory calculations on the initial-stage oxidation states of the Si adatom site for all possible dissociation configurations that can be generated by multiple O2 reactions. We determine the equilibrium structures and analyze their electronic and vibrational properties in comparison with measured UPS, XPS, and EELS spectra. The O(ad) atom bonded on top of the Si adatom is always less stable than the O(ins) atom inserted into one of the adatom backbonds. Our electronic and vibrational analysis demonstrates further that the O(ad) and O(ins) atoms account well for the metastable and stable features in previous experiments, respectively. Moreover, the calculated decay pathways of the metastable structures and the comparison of the calculated O ls core-level shifts with XPS data provides a convincing argument in unambiguously identifying the experimental metastable and stable structures, thereby making it possible to build a correct atomic-scale picture of the initial-stage oxidation process on this surface.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 1999년도 Proceedings of Pre-symposium of the 10th ISWPC
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• pp.115-119
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• 1999

During mechanical pulp production and blcaching wood components, such as extractives, carbohydrates and lignin are dissolved and dispersed into the process waters. These components are called dissolved and colloidal substances(DCS). DCS can accumulate during water circulation and can in turn affect paper machine runnability and also the strength and optical properties of the paper. In this work DCS fraction origination from TMP process were treated with enzymes acting on triglycerides. glucomannans, and lignin and the effect of enzymatic treatments on the water composition as well as sheet properies were evaluated. Lipases were found to modify the chemical structure of the extractives resulting in more hydrophilic fibre surface and subsequent improvement in the sheet strength properties. Mannanase treatment, on the other hand, destabilized pitch. As a result, aggregation of pitch to the fibres was observed which in turn resulted in impaired strength properties. Laccase could effectively polymerize lignans and the reaction products seemed to be sorbed onto the fibres.

• Environmental Engineering Research
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• 제13권3호
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• pp.136-140
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• 2008

$TiO_2$ photocatalyst has been known to exhibit a notable disinfecting activity against a broad spectrum of microorganisms. A lot of commercial $TiO_2$ photocatalyst products have been developed for antimicrobial purposes. However, a standard method has not yet been proposed for use in testing antimicrobial activity. In this study, we developed a $TiO_2$ photocatalytic adhesion test method with film as the standard testing method for the evaluation of antimicrobial activity. This method was devised by modifying the previous antimicrobial products test method, which has been widely used, and considering the characteristics of $TiO_2$ photocatalytic reaction. The apparatus for testing the antimicrobial activity was composed of a Black Light Blue (BLB) lamp as UV-A light source, a Petri dish as the cover material, and a polypropylene film as the adhesion film. The standard $TiO_2$ photocatalyst sample, Degussa P25 $TiO_2$ - coated glass, could only be used once. The optimal initial concentration of the microorganism, proper light intensity, and light irradiation time were determined to be $10^6$ CFU/mL, 1.0 mW/$cm^2$, and 3 hr, respectively, for testing and evaluating antimicrobial activity on the $TiO_2$ surface.

• 한국결정성장학회지
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• 제13권3호
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• pp.139-144
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• 2003

유기용매로서 에탄올을 함유한 염화니켈 수용액으로부터 니켈 미분말을 제조하고 이들의 산화특성을 검토하였다. 에탄올을 함유한 염화니켈 수용액에서 히드라진의 환원반응은 반응온도에 크게 의존하였다. 히드라진에 의한 환원반응시간은 반응온도가 증가함에 따라 감소하였다. 반응온도를 제어함으로써 입경이 0.1 $\mu\textrm{m}$-1.0 $\mu\textrm{m}$ 범위를 갖는 구형 분말을 얻을 수 있었다. 또한, 반응온도가 증가함에 따라 입경은 다소 증가하였고 조대한 입자들의 존재로 인하여 넓은 입도 분포를 나타내었다. $60^{\circ}C$에서 합성된 니켈 분말의 평균 입경과 비표면적은 각각 0.3 $\mu\textrm{m}$와 31.8 $m^2$/g이었다. $300^{\circ}C$에서 니켈 분말의 중량감소는 $Ni(OH)_2$의 분해반응에 기인한 것이다. $200^{\circ}C$ 공기중에서 가열처리한 경우 내산화성은 합성 분말보다 현저하였다

• BMB Reports
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• 제42권2호
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• pp.106-112
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• 2009

The bio-complex "reaction pattern in vertebrate cells"(RiV) is mainly represented by characteristic exosome-like particles - probably as reaction products of cells to specific stress. The transcription factor NF-kappaB plays a central role in inflammation. We tested the hypothesis that RiV particle preparations (RiV-PP) reduce cellular adhesion molecule (CAM) expression (ICAM-1, VCAM-1, E-selectin) by the attenuation of NF-kappaB translocation in human umbilical vein endothelial cells (HUVEC). After 4 hours, pre-incubation of HUVEC with RiV-PP before stimulation with TNF-alpha significantly reduced ICAM-1 (65.5${\pm}$10.3%) and VCAM-1 (71.1${\pm}$12.3%) mRNA expression compared to TNF-alpha-treated cells (100%, n=7). ICAM-1 surface expression was significantly albeit marginally reduced in RiV/TNF-alpha- treated cells (92.0${\pm}$5.6%, n=4). No significant effect was observed on VCAM-1 surface expression. In RiV/TNF-alpha-treated cells (n=4), NF-kappaB subunits p50 (85.7${\pm}$4.1%) and p65 (85.0${\pm}$1.8%) nuclear translocation was significantly reduced. RiV-PP may exert an anti-inflammatory effect in HUVEC by reducing CAM mRNA expression via attenuation of p50 and p65 translocation.