• Carbon letters
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• 제13권2호
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• pp.109-114
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• 2012

A nuclear, biological, chemical (NBC) canister was indigenously developed using active carbon impregnated with ammoniacal salts of copper (II), chromium (VI) and silver (I), and high efficiency particulate aerosol filter media. The NBC canister was evaluated against carbon tetra chloride ($CCl_4$) vapours, which were used as a simulant for persistent chemical warfare agents under dynamic conditions for testing breakthrough times of canisters of gas masks in the National Approval Test of Respirators. The effects of $CCl_4$ concentration, test flow rate, temperature, and relative humidity (RH) on the breakthrough time of the NBC canister against $CCl_4$ vapour were also studied. The impregnated carbon that filled the NBC canister was characterized for surface area and pore volume by $N_2$ adsorption-desorption isotherm at liquid nitrogen temperature. The study clearly indicated that the NBC canister provides adequate protection against $CCl_4$ vapours. The breakthrough time decreased with the increase of the $CCl_4$ concentration and flow rate. The variation in temperature and RH did not significantly affect the breakthrough behaviour of the NBC canister at high vapour concentration of $CCl_4$, whereas the breakthrough time of the NBC canister was reduced by an increase of RH at low $CCl_4$ vapour concentration.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.490-490
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• 2011

Graphene, hexagonal network of carbon atoms forming a one-atom thick planar sheet, has been emerged as a fascinating material for future nanoelectronics. Huge attention has been captured by its extraordinary electronic properties, such as bipolar conductance, half integer quantum Hall effect at room temperature, ballistic transport over ${\sim}0.4{\mu}m$ length and extremely high carrier mobility at room temperature. Several approaches have been developed to produce graphene, such as micromechanical cleavage of highly ordered pyrolytic graphite using adhesive tape, chemical reduction of exfoliated graphite oxide, epitaxial growth of graphene on SiC and single crystalline metal substrate, and chemical vapor deposition (CVD) synthesis. In particular, direct synthesis of graphene using metal catalytic substrate in CVD process provides a new way to large-scale production of graphene film for realization of graphene-based electronics. In this method, metal catalytic substrates including Ni and Cu have been used for CVD synthesis of graphene. There are two proposed mechanism of graphene synthesis: carbon diffusion and precipitation for graphene synthesized on Ni, and surface adsorption for graphene synthesized on Cu, namely, self-limiting growth mechanism, which can be divided by difference of carbon solubility of the metals. Here we present that large area, uniform, and layer controllable graphene synthesized on Cu catalytic substrate is achieved by acetylene-assisted CVD. The number of graphene layer can be simply controlled by adjusting acetylene injection time, verified by Raman spectroscopy. Structural features and full details of mechanism for the growth of layer controllable graphene on Cu were systematically explored by transmission electron microscopy, atomic force microscopy, and secondary ion mass spectroscopy.

• Restorative Dentistry and Endodontics
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• 제18권2호
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• pp.431-445
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• 1993

The purpose of this study was to observe corrosion characteristics of six dental amalgams and was to analyse corrosion products electrochemically. After each amalgam alloy and Hg was triturated as the direction of the manufacturer by using mechanical amalgamator, the triturated mass was inserted into the cylinderical metal mold ($12{\times}10mm$) and was condensed with 160kg/$cm^2$ by using the hydrolic press. The specimen was removed from the mold and was stored at room temperature for 1 week, and was polished with amalgam polishing kit. The anodic and cathodic polarization curve was obtained by using cyclic voltammetric method with 3-electrode potentiostat in saline for each amalgam and Ag, Sn, Cu plate specimen at $37{\pm}0.5^{\circ}C$. The potential sweep range was -1.7V~0. 4V(vs SCE) in working electrode and scan rate was 50mV/s and the exposed surface area of each specimen to the electrolytic solution was $0.79cm^2$. The results were as follows. 1. In anodic-cathodic polarization curve of amalgam specimens, two anodic current rising areas and two cathodic current peaks were obtained at the low Cu amalgam(CF, CS) specimen and three anodic current rising areas and three cathodic current peaks were obtained at the high Cu amalgam (TY, DS, HV) specimen. 2. As this compared with the anodic and cathodic current peak potentials of Sn, Cu and Ag specimen, the first cathodic current peak I c was caused by the reduction of divalent tin salt, second cathodic current peak IIIc results from the reduction of quadravalent tin salt, and third cathodic current peak me results from the reduction of copper salt. 3. As reverse potential sweeping was done repeatedly, anodic current was decreased slightly in all amalgam specimens.

• 공업화학
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• 제33권5호
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• pp.466-470
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• 2022

최근 촉매 소각 공정은 휘발성 유기 화합물을 저온(< 450 ℃)에서 고효율(> 95%)로 산화 및 분해하기 위해 상당한 주목을 받고 있다. 많은 귀금속 촉매 물질이 잘 연구되어 사용되고 있으나 단가가 비싸고 위험하다. 본연구에서는 Cu와 Mn 전구체의 공침법을 활용하여 간단하고 손쉬운 합성 방법을 개발함으로써 고활성 및 저비용의 Cu-Mn 바이메탈 촉매를 제조하였다. 촉매 합성은 Cu와 Mn의 조성비를 조절하여 최적화하였다. 최적화된 촉매는 메조포러스 구조로 230.8 m²/g의 넓은 표면적을 나타냈다. 촉매 성능을 입증하기 위해 에틸 아세테이트의 산화 반응에 대해 Cu-Mn 촉매를 테스트했으며, 250 ℃의 저온에서 100%의 높은 전환 효율을 나타내었다.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2184-2194
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• 2021

The Free-Piston Stirling engine (FPSE) is of interest for many research in aerospace due to its advantages of long operating life, higher efficiency, and zero maintenance. In this study, a 1-kW FPSE was proposed by analyzing the requirements of Space Reactor Power Systems (SRPS), of which performance was evaluated by developing a code through the Simple Analysis Method. The results of SAM showed that the critical parameters of FPSE could satisfy the designed requirements. The heater of the FPSE was designed with the copper rectangular fins to enhance heat transfer, and the parametric study of the heater was performed with Computational Fluid Dynamics (CFD) software STAR-CCM⁺. The Performance Evaluation Criteria (PEC) was used to evaluate the heat transfer enhancement of the fins in the heater. The numerical results of the CFD program showed that pressure drop and Nusselt number ratio had a linear growth with the height of fins, and PEC number decreased as the height of fins increased, and the optimum height of the fin was set as 4 mm according to the minimum heat exchange surface area. This paper can provide theoretical supports for the design and numerical analysis of an FPSE for SRPSs.

• 자원환경지질
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• 제33권2호
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• pp.91-100
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• 2000

It has been more than ten years since Dukun mine was abandoned. Tailings of waste deposits and slime dumps in the abandoned Dukum mine have been left to be deserted for fifty years. The results of fifty years of neglecting are nothing short of major environmental problems. Slime dumps have been exposed to air and water in the mine over ten years and then soil profile has been formed well. Soil in the upper layer (A horizon) is the light gray color due to the leaching of cations. Soil in the lower layer (A2 horizon, 0.2∼0.3m)is tinted with reddish brown and yellowish brown color due to the development of iron oxides and iron hydroxides. Soil in the lower part of B horizon of (1.0∼3.0m) with the growth of copper and zinc oxides exposes to the bluish green, light blue, and dark gray. Ranging from 3m to 8m in depth, 85 samples were taken from 22 sampling sites with 50m intervals located on the slime dump area with hand auger and trench (open cut). As tailings was distributed, heavy metal elements extracted by the process of surface water and ground water move and disperse in to the hydrosphere. Waste dumps were distributed in and around the mine and water draining from those dumps be a potential source of contamination. Soils, thus, can be dispersed into downslope and downstream through wind and water by clastic movement. These materials may be deposited in another horizon if the water is withdrawn, or if the materials are precipitated as a result of differences in pH, or other conditions in deeper horizons. These were primarily associated with acid mine drainage. The characteristics and rate of release of acid mine drainage are influenced by various chemical and biological reactions at the source of acid generations. Prolonged extration of heavy metal elements has a detrimental effect on the agricultural land and residental area. Twenty soil samples were collected from the agricultural land in the area (0∼30 cm). Seventeen samples were also taken from the sediment in the stream running alongside the dumps. The dispersion patterns of heavy metal elements are as follows: The content of As ranged 2∼6 ppm in a horizon, 20∼125 ppm in B horizon with large amount of clay mineral is concentrated and the content of Cd ranged 1∼2 ppm in A horizon, 4∼22 ppm in B horizon. Like Cd, the content of As, Cu, Zn, Pb in B horizon is higher than that in A horizon (approximately 5∼100 times). When soil formation proceeds in stages, it is necessary to investicate the B horizon with the concentration of heavy metal and preventive measures will have to established.

• 한국환경농학회지
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• 제13권1호
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• pp.10-17
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• 1994

수질오염에 따른 Cu의 함량변화 차이를 구명하기 위하여 도시하수 및 공단배출수의 영향을 받는 만경강 유역의 논 토양을 중심으로 1982년도에 표 심토로 구분 채취한 것과 1990년도에 채취한 토양시료를, 그리고 1990년의 토양 시료채취 지역에서 재배된 수도체시료 중 Cu 함량을 분석하였다. 만경강 유역의 토양 중 Cu함량은 5.20-71.70mg $kg^{-1}$였다. 평균함량은 1990년도 토양 중의 것이 1982년도 토양에서 보다 높았다. 도시하수 유입지역으로 부터 거리 별 함량변화가 1982년보다 1990년도 토양이 보다 규칙적으로 감소되는 변화를 나타냈다. 수도체의 엽신부위의 Cu함량과 토양중의 Cu, Zn 및 Pb의 함량간에 유의성이 인정되었다. 토양 중 Cu 함량과 토양 중 Zn 및 Pb 함량간에 유의한 상관관계를 나타내고 있어서 Cu가 이들 금속들과 함께 유입되는 오염물질 임을 나타냈다. 이 지역에서 재배된 현미중 Cu함량의 범위는 0.4-10.1 mg $kg^{-1}$이었고, 수도체 부위중 최고 Cu함량은 화서축으로 현미에 비하여 2.3배 높았으며, 엽초 중의 Cu함량은 토양 중 Zn 및 Pb 함량과 상관관계를 나타냈다.

• 한국해양학회지:바다
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• 제5권4호
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• pp.276-284
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• 2000

시화호 표층과 주상시료 퇴적물의 유기탄소(Co$_{org}$), 유기질소(N$_{org}$), 중금속(Zn, Pb, Cr, Cu, Mn)의 함량과 분포를 규명하기 위하여 '97년 4월, 9월 그리고 '98년 3월에 총 30개의 퇴적물 시료가 채취하였다. 분석결과 표층 및 주상시료 퇴적물의 유기탄소${\cdot}$질소 그리고 중금속들의 함량과 분포는 조사시기와 정점별 차이에 따른 변화를 나타냈다. 표층 퇴적물의 유기탄소와 유기질소 함량은 시화호 안쪽의 육지에 인접할 수록 높은값을 나타냈다. 이러한 분포는 주변 하천 및 공단으로부터의 영향인 것으로 사료된다. 표층 퇴적물의 중금속 함량은 유기탄소 함량과 일차적인 관계가 있다고 해석된다. 주상시료 퇴적물의 C/N비의 변화폭은 3${\sim}$32이고 평균은 13.9를 나타냈다. 주상시료의 중금속함량분포 경향은 유기탄소와 유기질소의 함량분포 경향과 유사하였다. 표층 퇴적물의 중금속 함량을 방조제 축조 이전과 이후로 비교했을 때 축조 후 증가한 중금속은 Cu이고, 반대로 낮은 함량을 보이는 중금속은 Zn와 Mn으로 조사되었다. 이와는 달리 Pb의 함량은 일정하였다. 시화호 배수갑문 내측 주변과 방조제 외측 연안 퇴적물의 중금속함량은 유사하였다.

• 공업화학
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• 제24권5호
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• pp.513-517
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• 2013

본 연구에서는 화재나 화생방전 시 비상대피에 사용되는 상용 방독면의 흡착소재인 첨착활성탄의 특성을 분석하고 일산화탄소(CO)의 흡착성능 및 산화반응을 조사하고자 하였다. 대표 제품 4개를 선정하여 BET/BJH 측정을 통해 각 활성탄소의 비표면적, 기공부피 및 기공크기를 비교분석하고 SEM/EDS와 XPS를 이용한 표면 성분분석을 수행하여 일산화탄소 제거 효율간의 관계를 연구하였다. 불순물 제거를 위한 전처리(heat-treatment) 후 망간(Mn)과 구리(Cu)가 주 금속으로 첨착되어 있는 화재용 시료에서는 업체에 관계없이 반응 초기에 일산화탄소의 흡착을 보였고 이후 활성 탄소 내에 첨착된 금속 촉매에 의해 최대 99%의 이산화탄소($CO_2$) 변환율로 높은 촉매활성을 보이며 산화반응이 진행되었다. 망간(Mn)을 함유하지 않은 화생방용 시료의 경우 이산화탄소로의 변환율은 최대 60%로서 화재용 시료에 비해 떨어짐을 관찰하였다. 화재용 시료의 전처리 유무에 따른 일산화탄소 반응성 조사에서는 전처리 후 기공 내 불순물 제거 효과로 상온에서 이산화탄소의 검출시간이 약 30 min간 지연되어 일산화탄소와 이산화탄소에 대해 모두 더 높은 제거율을 보임을 확인하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.81.2-81.2
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• 2012

To fabricate a metal mold for injection molding, hot-embossing and imprinting process, mechanical machining, electro discharge machining (EDM), electrochemical machining (ECM), laser process and wet etching ($FeCl_3$ process) have been widely used. However it is hard to get precise structure with these processes. Electrochemical etching has been also employed to fabricate a micro structure in metal mold. A through mask electrochemical micro machining (TMEMM) is one of the electrochemical etching processes which can obtain finely precise structure. In this process, many parameters such as current density, process time, temperature of electrolyte and distance between electrodes should be controlled. Therefore, it is difficult to predict the result because it has low reliability and reproducibility. To improve it, we investigated this process numerically and experimentally. To search the relation between processing parameters and the results, we used finite element simulation and the commercial finite element method (FEM) software ANSYS was used to analyze the electric field. In this study, it was supposed that the anodic dissolution process is predicted depending on the current density which is one of major parameters with finite element method. In experiment, we used stainless steel (SS304) substrate with various sized square and circular array patterns as an anode and copper (Cu) plate as a cathode. A mixture of $H_2SO_4$, $H_3PO_4$ and DIW was used as an electrolyte. After electrochemical etching process, we compared the results of experiment and simulation. As a result, we got the current distribution in the electrolyte and line profile of current density of the patterns from simulation. And etching profile and surface morphologies were characterized by 3D-profiler(${\mu}$-surf, Nanofocus, Germany) and FE-SEM(S-4800, Hitachi, Japan) measurement. From comparison of these data, it was confirmed that current distribution and line profile of the patterns from simulation are similar to surface morphology and etching profile of the sample from the process, respectively. Then we concluded that current density is more concentrated at the edge of pattern and the depth of etched area is proportional to current density.