• 한국표면공학회지
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• 제51권1호
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• pp.47-53
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• 2018

Sn-based lithium-ion batteries have low cost and high theoretical specific capacity. However, one of major problem is the capacity fading caused by volume expansion during lithiation/delithiation. In this study, 3-dimensional foam structure of Cu-Sn alloy is prepared by co-electrodeposition including large free space to accommodate the volume expansion of Sn. The Cu-Sn foam structure exhibits highly porous and numerous small grains. The result of EDX mapping and XPS spectrum analysis confirm that Cu-Sn foam consists of $SnO_2$ with a small quantity of CuO. The Cu-Sn foam structure electrode shows high reversible redox peaks in cyclic voltammograms. The galvanostatic cell cycling performances show that Cu-Sn foam electrode has high specific capacity of 687 mAh/g at a current rate of 50 mA/g. Through SEM observation after the charge/discharge processes, the morphology of Cu-Sn foam structure is mostly maintained despite large volume expansion during the repeated lithiation/delithiation reactions.

• 대한금속재료학회지
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• 제48권12호
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• pp.1056-1063
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• 2010

We present a new joining method for Pd-Cu membrane foils used as permeation tubes to collect $CO_2$. Since foils have poor mechanical strength, joining should be done at low temperatures to reduce residual stresses and without joining pressure. This contradicts the well known conditions for good contact between base materials that determines joint qualities. We selected Sn-Ag-Cu alloys that are highly reactive with Pd and Cu as a filler metal. As the filler melts at joining temperatures as low as $220{\sim}280^{\circ}C$, Pd and Cu are dissolved into the melt and react with the filler elements, which raises the melting temperature of the filler based on eutectic structures among the elements. Then, isothermal solidification progresses for the rest of the joining time. Intermetallic compounds (IMC) in the joints, one of the main factors for brittle joints, are inevitably formed. However, by optimizing both joining time and temperature, we balanced the wettability with IMC. Sealing test results confirmed that the joints are mechanically reliable during operation.

• 한국환경과학회지
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• 제27권2호
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• pp.109-122
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• 2018

This study was conducted to investigate the removal characteristics of heavy metals and sulfate ion from acid mine drainage by porous zeolite-slag ceramics (ZS ceramics) that was prepared by adding wood flour as pore-foaming agent while calcining the mixtures of natural zeolite and converter slag. The batch test showed that the removal efficiency of heavy metals by pellet-type porous ZS ceramics increased as the particle size of wood flour was decreased and as the weight mixing ratio of wood flour to ZS ceramics was increased. The optimal particle size and weight mixing ratio of wood flour were measured to be $75{\mu}m$ and 7~10%, respectively. The removal test with the porous ZS ceramics prepared in these optimal condition showed very high removal efficiencies: more than 98.4% for all heavy metals and 73.9% for sulfate ion. Relative to nonporous ZS ceramics, the increment of removal efficiency of heavy metals by porous ZS ceramics with $75{\mu}m$ and 10% wood flour was 5.8%, 60.5%, 36.9%, 87.7%, 10.3%, and 57.4% for Al, Cd, Cu, Mn, Pb, and Zn, respectively. The mechanism analysis of removal by the porous ZS ceramics suggested that the heavy metals and sulfate ion from acid mine drainage are eliminated by multiple reactions such as adsorption and/or ion exchange as well as precipitation and/or co-precipitation.

• 분석과학
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• 제28권3호
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• pp.182-186
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• 2015

본 연구는 상온에서 과망간산칼륨 (KMnO₄)과 망간아세테이트 (Mn(CH₃COO)₂·4H₂O) 수용액을 반응시켜 초산구리 (Cu(CH₃COO)₂·H₂O) 수용액을 공침한 다공성 CuO/MnO₂ 촉매에 대한 물리화학적 특성에 대해 분석하였다. 합성방법은 KMnO₄과 Mn(CH₃COO)₂·4H₂O의 반응 몰비율을 0.3:1, 0.6:1, 1:1로 반응시켜 초산구리 수용액을 망간아세테이트 투입량 대비 10~75 wt%로 공침시켜 구리이온을 담지시켰다. 제조된 촉매는 TGA/DTA, XRD, SEM 및 BET를 통해 촉매에 대한 물리화학적 특성을 분석하였고, 그 결과 반응 몰비율 변화에 따라 γ-MnO₂, α-MnO₂로 상변이가 이루어 졌으며, 반응 몰비율이 0.6:1 일 때 비표면적이 253 m²/g을 갖는 다공성 CuO/γ-MnO₂ 촉매가 제조되었다.

• 공업화학
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• 제5권6호
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• pp.1009-1015
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• 1994

분산중합으로 합성한 폴리스티렌 seed를 사용하여 seed 중합방법으로 단분산성인 다공성 스티렌-디비닐벤젠(St-DVB) 겔과 아크릴로니트릴-에틸렌 디메타크릴레이트(AN-EDMA) 겔을 제조하였다. 합성한 St-DVB 겔과 AN-EDMA 겔은 HPLC용 충진제로 적합한 좁은 입도분포와 다공성을 갖고 있으며, 이들 겔을 충진한 GPC 또는 HPLC용 column은 비교적 높은 효율을 나타내었다, 또한 AN-EDMA 겔을 아미드옥심화한 AAN-EDMA 겔에 대한 $Cu^{2+}$, $Cd^{2+}$ 및 ${UO_2}^{2+}$ 이온의 흡착특성을 시험하였다.

• 한국재료학회지
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• 제34권9호
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• pp.409-421
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• 2024

Among the products of the electrocatalytic reduction of carbon dioxide (CO₂RR), CO is currently the most valuable product for industrial applications. However, poor stability is a significant obstacle to CO₂RR. Therefore, we synthesized a series of bimetallic organic framework materials containing different ratios of tungsten to copper using a hydrothermal method and used them as precursors. The precursors were then subjected to pyrolysis at 800 ℃ under argon gas, and the M-N bimetallic sites were formed after 2 h. Loose porous structures favorable for electrocatalytic reactions were finally obtained. The material could operate at lower reduction potentials than existing catalysts and obtained higher Faraday efficiencies than comparable catalysts. Of these, the current density of WCu-C/N (W:Cu = 3:1) could be stabilized at 7.9 mA·cm^-2 and the FE of CO reached 94 % at a hydrogen electrode potential of -0.6 V (V vs. RHE). The novel materials made with a two-step process helped to improve the stability and selectivity of the electrocatalytic reduction of CO₂ to CO, which will help to promote the commercial application of this technology.

• 한국해양학회지:바다
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• 제6권1호
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• pp.13-26
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• 2001

망간각의 조직 및 지화학적 특성과 코발트 연대측정법(Co-chronometry)을 이용하여, 망간각 형성 이후의 서태평양 지역 고해양환경 변화를 파악하기 위하여 마샬제도 배타적 경제수역 내 Lomilik과 Litakpooki 해저산에서 채취된 6개의 망간각을 분석하였다. 망간각은 조직과 지화학적 성분 차이에 의해, 치밀한 조직(층 1), 퇴적물이나 철산화물이 충진되어 있는 다공성 조직(층 2),그리고 탄산염불화 인회석(Carbonate Fluoapatite)이 충진 또는 치환하고 있는 흑색의 균질한 조직(층 3)의 3개 층으로 구분된다. 층 1은 층 2에 비해 Mn, Co, Ni, Mg의 함량이 높고, 층 2는 Fe, Al, Ti, Ba, Cu, Zn의 함량이 높다. 층 3은 Ca, p의 함량이 층 1과 층 2에 비해 현저히 높으며, Mn, Fe, Co, Ni등의 함량은 층 1과 층 2에 비해 낮다. 코발트 연대측정법 결과에 근거할 때, 연구지역의 망간각은 최소 56~31 Ma(초기 에오세${\sim}$올리고세)전에 형성되기 시작한 것으로 추정된다. 층 1과 층 2, 층 2와 층 3의 경계면은 7${\sim}$3 Ma, 26${\sim}$14 Ma정도이다. 층 3은 층 2가 형성되기 이전의 인산화 작용으로 Ca와 P의 함량이 높으며, 미세조직들이 잘 보존되어 있는 것으로 보아 층 3의 철${\cdot}$망간산화물들이 아산화(suboxic)환경에서 재결정되었다고 보기는 힘들다. 또한 층 3에서 Mn에 비해 상대적으로 더 낮은 Co 함량 등을 고려할 때 과거 지질시대동안 Co 공급량이 일정치 않았을 가능성도 있다. 다공성 조직의 층 2는 약 26${\sim}$9 Ma 동안 형성되었다. 공극사이에 유공충을 포함한 생물기원퇴적물이 포함되어 있으며, Ba, Cu, Zn 등 수층 생물과 관련된 원소의 함량이 높은 것으로 보아 층 2는 고에너지환경에서 형성되었음을 시사한다. 또한 층 2에서 Al의 증가는 쇄설기원 물질의 유입에 의한 것으로 추정된다. 플라이오세 이후에 형성된 층 1은 치밀한 조직을 보이며, 형성 이후 속성작용을 받지 않았다.

• 분석과학
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• 제15권3호
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• pp.263-269
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• 2002

평균입경이 200 ${\mu}m$인 코디어라이트 분말로 다공성 필터를 제조한 후, 진공함침법으로 Pt, Pd, Cu, Co, La, $V_2O_5$ 촉매를 담지시켰다. VOC의 일종인 톨루엔을 촉매담지 세라믹필터에 통과시키며 촉매산화시킴으로서 톨루엔에 대한 촉매들의 활성에 대하여 고찰하였다. 제조된 다공성 필터의 겉보기 기공률은 62%였고, 압축강도는 약 10 MPa이었으며, 5 cm/sec 유속에서의 차압은 15 mmHg였다. 촉매를 필터에 담지시키면 기공률은 감소하고, 차압과 압축강도는 증가하였다. 필터에 담지된 촉매들 중에서 Pt 촉매의 활성이 가장 높았고, 250 $^{\circ}C$의 온도에서 90% 이상의 톨루엔을 제거시킬 수 있었다. 250 $^{\circ}C$ 이하의 온도에서는 Pt 촉매 담지량이 톨루엔의 전환율에 영향을 미쳤지만, 그 이상의 온도에서는 Pt 촉매 담지량의 차이에 의한 영향은 나타나지 않았다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2000년도 춘계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.11-11
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• 2000

Large-size ceramic/metal bulk FGMs have been fabricated on a recently developed and the world's largest Spark Plasma Sintering(SPS) systems, As a part of the development program for practical production processes and machines for FGMs by SPS, the processes, mechanical properties, dimensional size and shape effects, and production machine systems were investigated. In the past, $ZrO_{2}$/TiAI, $ZrO_{2}$/Ni, $Al_{2}O_{3}$/Ti, WC/Co, WC/Co/Steel, A1/P, Polymide, Cu/Polymide, nano-composites, porous and other combinations of bulk FGMs have already been processed using SPS. However, most of the specimen sizes were small, in a range of 20 to 30mm in diameter. Recently disk-shape sintered compacts with diameters of 100 and 150 mm, and thickness of approximately 15 and 17 mm, $ZrO_{2}$(3Y)/ stainless steel FGMs were homogenous consolidated in a shorter sintering time, while maintaining high quality and repeatability by utilizing a temperature gradient sintering method. The SPS heating up and holding time totaled less than one hour. Therefore, the SPS process in expected to find increased use in the fabrication of large-size FGMs as a new industrial processing technology. This paper introduces SPS systems, the processing principles, features and the characteristies of ceramic/metal bulk FGM.

• 상하수도학회지
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• 제19권2호
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• pp.228-237
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• 2005

The main purpose of this study was to investigate the red water reducing effects of phosphate based inhibitor when it was applied to water distribution system. The effects of pH, alkalinity, calcium concentration in the reduction of the red water also studied. The most finished water in Korea showed relatively high corrosiveness and was required to introduce some types of corrosion reducing methods such as addition of alkalinity. The precipitation of $CaCO_3$ by addition of $Ca(OH)_2$ formed porous film on the surface of the carbon steel pipes and was displaced easily from the surface of the pipes; on the other hand, addition of zinc phosphate (ZOP) formed reliable film on the surface and reduced iron release and color. Although the main function of ZOP was to suppress the release of Pb and Cu, it also reduced iron concentration released from water distribution pipes.