• 대한금속재료학회지
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• 제49권9호
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• pp.699-707
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• 2011

P122 steel, with a composition of Fe-10.57%Cr-1.79%W-0.96Cu-0.59Mn was arc-welded and oxidized between $600^{\circ}C$ and $800^{\circ}C$ in air for up to 6 months. The oxidation rates increased in the order of the base metal, weld metal, and heat-affected zone (HAZ), depending on the microstructure. The scale morphologies of the base metal, weld metal, and HAZ were similar because it was determined mainly by the alloy chemistry. The scale consisted primarily of a thin $Fe_2O_3$ layer at $600^{\circ}C$ and $700^{\circ}C$ and an outer $Fe_2O_3$ layer and an inner ($Fe_2O_3$, $FeCr_2O_4$)-mixed layer at $800^{\circ}C$. The microstructural changes resulting from heating between $600^{\circ}C$ and $800^{\circ}C$ coarsened the carbide precipitates, secondary Laves phases, and subgrain boundaries in the matrix, resulting in softening of the base metal, weld metal, and HAZ.

• Corrosion Science and Technology
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• 제16권3호
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• pp.151-159
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• 2017

The MA8 alloy (formula Mg-Mn-Се) has been shown to have greater corrosion stability than the VMD10 magnesium alloy (formula Mg-Zn-Zr-Y) in chloride-containing solutions by Scanning Vibrating Electrode Technique (SVET) and by optical microscopy, gravimetry, and volumetry. It has been established that the crucial factor for the corrosion activity of these samples is the occurrence of microgalvanic coupling at the sample surface. The peculiarities of the kinetics and mechanism of the corrosion in the local heterogeneous regions of the magnesium alloy surface were investigated by localized electrochemical techniques. The stages of the corrosion process in artificial defects in the coating obtained by plasma electrolytic oxidation (PEO) at the surface of the MA8 magnesium alloy were also studied. The analysis of the experimental data enabled us to determine that the corrosion process in the defect zone develops predominantly at the magnesium/coating interface. Based on the measurements of the corrosion rate of the samples with PEO and composite polymer-containing coatings, the best anticorrosion properties were displayed by the composite polymer-containing coatings.

• 한국물환경학회지
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• 제18권3호
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• pp.271-282
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• 2002

The sonochemical process has been applied as a treatment method to investigate its effect on the decomposition of humic substances (HS). The reaction kinetics and mechanisms in the process of sonochemical treatment for humic substances in wastewater have also been discussed. It was observed that the metal ions such Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final step of the reaction is the conversion of organic acids to carbon dioxide.

• 자원환경지질
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• 제38권5호
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• pp.499-512
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• 2005

EPMA분석결과, 철망간-(산)수산화광물과 결정질 철-(산)수산화광물에서 각각 $0.3-11.0wt.\%$와 $2.1-7.4wt.\%$인 적은 양의 As가 검출되었다. 비정질 철-(산)수산화광물에는 $28-36wt.\%$ 범위의 다량의 As가 인지되었고 $As_2O_5-SO_3-Fe_2O_3$ 다이어그램에 도식한 결과 스코로다이트에 근접하였다. 용해된 As는 철망간-(산)수산화광물과 철-(산)수산화광물에 흡착되고 스코로다이트와 같은 2차광물로 침전되어 저감되고 있었다. 용출실험은 산성환경에서 As와 Fe의 용출특성을 알아보고자 실시하였다. 반응용액의 pH 3과 5에서 용출된 As의 함량은 청양광산의 광미의 경우, 7일 이후에 뚜렷이 증가하였으며(전체 함량의 최대 $2.4\%$), 이는 As를 함유한 2차 광물들의 용해에 인한 것으로 판단된다. 반면에 서보광산의 광미에 함유된 As는 거의 용출되지 않았다(전체 As함량의 $0.0-0.1\%$). pH 1의 용출실험결과, 서보광산과 청양광산의 광미는 각각 $1.1-4.2\%$와 $1.5-14.4\%$의 As가 용출되었으며 As와 Fe는 밀접한 상관관졔가 있는 것이 관찰되었다. 용출실험에서 kinetics 문제는 우기에 As 농도를 증가시킬 수 있는 중요한 요인이 된다. 청양광산의 광미에 함유된 As는 지표수와 지하수의 수질에 악영향을 미칠 수 있다. 반면에 서보광산의 광미의 경우, As의 이동은 2차 광물의 침전과 흡착을 통해서 제어되는 것으로 나타났다.