• 열처리공학회지
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• 제8권1호
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• pp.53-64
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• 1995

A study was made to characterize the microstructures and mechanical properties of the base metal and the heat-affected zone(HAZ) in Cu-bearing HSLA-100 steel. The Gleeble thermal/mechanical simulator was used to simulated the weld HAZ. The relationship between microstructure and toughness of HAZ was studied by impact test, O. M, SEM, TEM, and DSC. The toughness requirement of military specification value was met in all test temperatures for the base metal. The decrease of HAZ toughness comparing to base plate is ascribed to the coarsed-grain and the formation of bainite. Obliquely sectioned Charpy specimens show that secondary crack propagate easily along bainite lath. Improved toughness(240J) at HAZ of $Tp_2=950^{\circ}C$ is due to the fine grain, and reasonable toughness(160~00J) in the intercritical reheated HZA is achieved by the addition of small amount of carbon which affects the formation of "M-A". Cu precipitated during ageing for increasing the strength of base metal is dissolved during single thermal cycle to $1,350^{\circ}C$ and is precipitated little on cooling and heating during subsequent weld thermal cycle. Thus, the decrease of toughness does not occur owing to the precipitation of Cu.

• Journal of Magnetics
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• 제10권3호
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• pp.89-92
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• 2005

The analytic possibility of mobile lead contained in soil has been studied using carboxylated magnetic beads. Extraction of heavy metal was performed to contaminated soil that has been collected and supplied for tests. As experiment materials, soil sample, distilled water and magnetic beads were only used. It means that the lead was extracted under neutral condition. In this condition, only the mobile fraction of lead could be extracted by magnetic beads. The mobile lead in the soil was quickly combined with magnetic beads in the mixture process. Then, the magnetic beads were dissolved into acids after collection by external magnetic force, and the lead combined with the beads was eluted and analyzed by Graphite Furnace Atomic Absorption Spectroscopy (GFAAS). In the results of extraction experiments for 3 sandy soils, the efficiency using beads was similar to or higher than that of EDTA (Ethylendiamintetraacetic acid), which is normally used for analyzing mobile heavy metal concentration in soil. With this, it was shown that this method is a more accurate and simple method to analyze mobile lead when analyzing mobile heavy metal concentration in sandy soil, rather than conventional method using EDTA.

• 한국해양환경ㆍ에너지학회지
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• 제5권1호
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• pp.51-67
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• 2002

경기도 서해안의 발달된 조간대 지역에 건설된 인공 호수인 시화호와 피 주변 하천 표층수 중의 중금속 거동을 이해하기 위하여 1996년부터 1998년까지 연구를 수행하였다. 반월 및 시화 공단, 도시 통의 다양한 인위적 오염원으로부터 극심한 오염물질 유입에 의해서 시화호와 주변 하천들은 중금속으로 오염되어 있었다. 하천과 공단 토구에서 유출수중의 용존성 중금속 농도와 입자성 중금속 농축계수는 매우 높게 나타났으며, 시ㆍ공간적인 변화 역시 크게 나타났다. 담수화 기간중 시화호 표층수의 중금속 공간분포는 산업 폐수 및 도시 하수의 유입 뿐 아니라 다양한 생지화학적 요인에 영향을 많이 밭으며, 유통의 제한으로 물리적인 혼합은 크게 작용하지는 않았다 또한 시화호는 담수화 중에 주변 환경에 의하여 중금속이 다량 축적되는 것으로 판단되며, 지속적인 환경 개선책이 마련되어야 할 것이다.

• 센서학회지
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• 제6권3호
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• pp.221-227
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• 1997

Pd/NiCr 게이트 MISFET 센서는 변압기 절연유중 용존수소를 감지하기 위해 제조되었다. 센서의 안정성과 고농도 감지성의 향상을 위해 Pd/NiCr 2중 촉매 금속 게이트가 사용되었다. 수소유입에 의한 게이트 전압의 드리프트를 줄이기 위해, 2개의 FET 게이트 절연층을 실리콘 산화막과 실리콘 질화막의 2중 구조로 하였다. Pd/NiCr 게이트 MISFET 센서의 수소 감응 감도는 Pd/Pt 게이트 MISFET 센서의 감도에 비해 약 0.5배이나, 안정성이 좋고, 1000 ppm까지의 고농도까지 측정할 수 있었다.

• 자원환경지질
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• 제32권1호
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• pp.101-111
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• 1999

Sedimentary organic matter, exposed to continental surficial environment, reacts with oxygen supplied from the atmosphee and forms carbon-containing oxidation products. Knowledge of the rate and mechanisms of sedimentary organic matter weathering is important because it is one of the major controls on atmospheric oxygen level through geologic time. Under the abiological conditions, the oxidation rate of coal organic matter by molecular oxygen is enhanced by the increase of oxygen concentration and temperature. At ambient temperature and pressure, aqueous coal oxidation results in the formation of dissolved $CO_2$ dissolved organic carbon and solid oxidation products which are all quantitatively significant reaction products. The effects of pH, ultraviolet light, and microbial activity on the weathering of sedimentary organic matter are poorly contrained. Based on the results of geochmical and environmental studies, it is believed that the photochemical reaction should play an important role in the decomposition and oxidation of sedimentary organic matter removed from the weathering profile. At higher pH conditions, the production rate of DOC can be accelerated due to base catalysis. These high molecular weight oranic matter can react with man-made pollutants such as heavy metal ions via adsorption/desorption or ion exchange reactions. The effect of microbial activity on the oxidative weathering of sedimentary organic matter is poorly understood and remains to be studied.

• Corrosion Science and Technology
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• 제20권6호
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• pp.325-334
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• 2021

In the open system (vessel and pipe), the maximum corrosion rate of carbon steel at ca. 80 ℃ was obtained due to the decrease of dissolved oxygen by increasing the solution temperature. Effect of temperature on the cavitation damage can be explained through several mechanisms. Moreover, when cavitation occurs on the surface of metal and alloys, whether cavitation is erosion or corrosion is still controversial. This work focused on the effect of solution temperature on the corrosion of carbon steel under cavitation in an open system, Tests were performed using an electrochemical cavitation corrosion tester in 3.5% NaCl solution and the effect of solution temperature of carbon steel was discussed. Cavitation corrosion rate can be increased by cavitation, but when the temperature increases, a dissolved oxygen content reduces at a very high speed and thus the maximum cavitation corrosion temperature changed from 80 ℃ to 45 ℃. Below the maximum cavitation temperature, the electrochemical effect was more dominant than the mechanical effect by increasing temperature, but over the maximum cavitation temperature, the mechanical effect was more dominant than the electrochemical effect by increasing temperature.

• 생태와환경
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• 제52권3호
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• pp.179-191
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• 2019

시화호 중금속 오염원을 추적하기 위하여 산업단지 5개 하천에서 하천수와 퇴적물을 채취하여 중금속 분포 특성과 오염도를 평가하였다. 용존 및 입자성 Ni과 Cu는 군자천에서, Zn과 Pb은 정왕천에서, Cd은 시흥천에서 상대적으로 높은 농도를 보이고 있어, 하천에 따라 유출되는 금속 오염원이 다른 것을 알 수 있었다. 하천 퇴적물 내 중금속의 평균농도는 Cu가 $2,549mg\;kg^{-1}$로 가장 높았으며 Cu>Zn>Pb>Cr>Ni>As>Cd>Hg의 농도순이었다. 시흥천에서 As를 제외한 금속원소의 평균농도가 다른 하천에 비해 매우 금속오염도가 큰 것으로 나타났다. 전체 하천 퇴적물 조사 정점 중 Cr (57%), Ni (62%), Cu (84%), Zn (60%), Cd (68%), Pb (81%)이 저서생물에 독성이 나타날 가능성이 있는 II 등급이상의 높은 농도였다. 농집지수를 통한 오염도 평가 결과, 하천 퇴적물 내 Cu와 Cd은 extremely polluted, Zn과 Pb은 heavily polluted의 오염상태로 구분되었다. 전체 퇴적물의 59%가 독성이 나타날 가능성이 높아 오염규모 확인이 필요한 "나쁨"의 등급이었으며, 35%의 조사 정점은 중장기적으로 배출시설 관리가 필요한 "매우 나쁨"에 해당되는 오염단계를 보이고 있었다. 하천수와 퇴적물 내 높은 금속 농도와 공간분포 특성을 고려하였을 때 금속오염은 금속의 제조와 사용과 관련된 산업폐수 즉 하천에 직접 유출되는 하수구를 통한 오염임을 알 수 있었다. 시화호의 주요한 금속 오염원은 산업활동에 기인한 높은 농도의 중금속을 포함한 폐수이며, 이 폐수가 지속적으로 하천을 통해 공급되고 있는 것으로 판단된다.

• Environmental Engineering Research
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• 제16권4호
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• pp.187-203
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• 2011

Chlorophenols (CPs) are widely used industrial chemicals that have been identified as being toxic to both humans and the environment. Zero valent iron (ZVI) and iron based bimetallic systems have the potential to efficiently dechlorinate CPs. This paper reviews the research conducted in this area over the past decade, with emphasis on the processes and mechanisms for the removal of CPs, as well as the characterization and role of the iron oxides formed on the ZVI surface. The removal of dissolved CPs in iron-water systems occurs via dechlorination, sorption and co-precipitation. Although ZVI has been commonly used for the dechlorination of CPs, its long term reactivity is limited due to surface passivation over time. However, iron based bimetallic systems are an effective alternative for overcoming this limitation. Bimetallic systems prepared by physically mixing ZVI and the catalyst or through reductive deposition of a catalyst onto ZVI have been shown to display superior performance over unmodified ZVI. Nonetheless, the efficiency and rate of hydrodechlorination of CPs by bimetals depend on the type of metal combinations used, properties of the metals and characteristics of the target CP. The presence and formation of various iron oxides can affect the reactivities of ZVI and bimetals. Oxides, such as green rust and magnetite, facilitate the dechlorination of CPs by ZVI and bimetals, while oxide films, such as hematite, maghemite, lepidocrocite and goethite, passivate the iron surface and hinder the dechlorination reaction. Key environmental parameters, such as solution pH, presence of dissolved oxygen and dissolved co-contaminants, exert significant impacts on the rate and extent of CP dechlorination by ZVI and bimetals.

• 한국광물학회지
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• 제24권3호
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• pp.217-224
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• 2011

철환원 박테리아인 미시가넨시스를 이용하여 용존 셀레늄을 제거할 때, 물 속의 다른 금속성분들인 철, 황산염, 그리 구리가 미칠 수 있 영향을 살펴보았다. 미시가넨시스 박테리아는 산화수가 4가인 산화 셀레나이트(2 mM)를 셀레나이드로 환원시키고 물속의 셀레늄 농도를 점차 감소시켰다. 환원된 셀레나이드는 용존 2가 철과 결합하여 나노입자 크기의 철-셀레나이드로 침전되었다. 용존 황산염과 구리는 미생물의 셀레나이트 환원작용에 부정적인 영향을 끼쳤는데, 특히 구리 성분은 미생물에 대해 독성으로 작용하여 셀레나이트 제거가 원활히 이뤄지지 못하게 하였다. 이러한 결과로부터 알 수 있는 것은 셀레늄으로 오염된 현장을 미생물로 정화할 때 황산염 혹은 구리의 농도 분포와 양을 충분히 고려해야 한다는 사실이다. 궁극적으로 미생물에 의한 철-셀레나이드 광물형성작용은 지하수를 따라 원거리로 이동할 수 있는 셀레늄의 확산을 억제하는 중요한 수단이라고 볼 수 있다.

• Nuclear Engineering and Technology
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• 제50권3호
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• pp.416-424
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• 2018

Microstructure of oxide formed on Zr-Nb-Sn tube sample was intensively examined by scanning transmission electron microscopy after exposure to simulated primary water chemistry conditions of various concentrations of Zn (0 or 30 ppb) and dissolved hydrogen ($H_2$) (30 or 50 cc/kg) for various durations without applying desirable heat flux. Microstructural analysis indicated that there was no noticeable change in the microstructure of the oxide corresponding to water chemistry changes within the test duration of 100 days (pretransition stage) and no significant difference in the overall thickness of the oxide layer. Equiaxed grains with nano-size pores along the grain boundaries and microcracks were dominant near the water/oxide interface, regardless of water chemistry conditions. As the metal/oxide interface was approached, the number of pores tended to decrease. However, there was no significant effect of $H_2$ concentration between 30 cc/kg and 50 cc/kg on the corrosion of the oxide after free immersion in water at $360^{\circ}C$. The adsorption of Zn on the cladding surface was observed by X-ray photoelectron spectroscopy and detected as ZnO on the outer oxide surface. From the perspective of $OH^-$ ion diffusion and porosity formation, the absence of noticeable effects was discussed further.