• 한국산학기술학회논문지
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• 제18권10호
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• pp.603-610
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• 2017

탄약을 포함한 다양한 산업 분야에서 사용되는 철강 재료는 부식에 취약하므로, 표면 그대로 사용하는 것은 바람직하지 않다. 따라서 도금, 도장, 화성처리와 같은 표면 처리 이후 사용하여야 하는데, 탄약 제조 과정에서는 주로 아연계 인산염 피막 처리가 사용되고 있다. 표면 처리 기법 중 하나인 아연계 인산염 피막은 금속 표면을 화학적으로 처리하여 안정성이 높은 화합물 층을 표면에 고착시키는 방법으로, 크게 도장 하지용 경인산염 피막과 부식 방지용 중인산염 피막으로 나뉘어지는데, 아연계 인산염 피막은 전산도, 철 함량과 같은 여러 가지 인자에 의해 피막의 품질과 내식성이 결정된다. 본 연구에서는 전산도 및 철 함량이 탄약 부식 방지 목적으로 사용되는 아연계 중인산염 피막의 중량 및 내식성에 미치는 영향에 대하여 알아보았다. 철 함량에 따라 피막의 구조가 치밀해지며, 내식성이 향상되는 결과를 확인할 수 있었으나, 전산도는 피막의 두께와 중량에만 영향을 주고 내식성에는 큰 영향을 주지 못하였다. 위 결과를 토대로 탄약 제조 과정에서 사용되는 인산염 피막 처리 공정의 최적 제어 수준을 제시하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1083-1089
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• 2006

Acid drainage occurs when sulfide minerals are exposed to an oxidizing environment. The objective of this study was to examine the optimum condition for creating a phosphate coating on standard pyrite surfaces for reduction of pyrite oxidation. The solution of $10^{-2}M\;KH_2PO_4\;10^{-2}M\;H_2O_2$ pH 6 was identified as the best phosphate coating agent for the reduction of pyrite oxidation. The formation of an iron phosphate coating on pyrite surfaces was confirmed with ore microscope and scanning electron microscope equipped with energy dispersive spectroscopy. The temperature did not significantly affect on the formation of phosphate coating on the surface of pyrite. However, the phosphate coating was less stable at higher temperature than at lower temperature. The phosphate coating was quitely stable at wide range of pH and $H_2O_2$ concentration. The less than 3.4% of phosphate was dissolved at pH 2.79 and 10.64 and less than 1.0% of phosphate was dissolved at 0.1M $H_2O_2$. On the basis of these results, the phosphate coating can effectively reduce the negative environmental of acid rock drainage.

• 자원환경지질
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• 제39권1호
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• pp.75-82
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• 2006

암석 또는 광미시료에 포함되어 있는 황철석의 산화에 의해 발생하는 산성배수를 저감하기 위하여 황철석 표면에 철인산염 피막을 형성시킬 수 있다. 첫 단계로 표준황철석을 이용한 실내실험을 통하여 최적의 피막형성 조건을 도출하였다. 피막형성제와 황철석을 24시간 반응시킬 때 최적조건은 $10^{-2}M\;KH_2PO_4,\;10^{-2}M\;H_2O_2$, PH 6으로 결정되었으며, 이 조건으로 황철석을 피막처리한 후 반사현미경, 주사전자현미경, 에너지분산분광기로 피막의 형성을 확인하였다. 피막의 내구성을 검증하기 위하여 온도 pH, 산화제의 농도변화에 따른 인산염의 용출을 조사한 결과, $4^{\circ}C$와 $70^{\circ}C$에서 온도의 영향은 거의 없었으며, 강산 또는 강알칼리 환경에서 $3.4\%$미만, 산화제의 농도별 조건하에서 $1.0\%$미만의 인산염이 피막으로부터 용출되었다. 실험 결과는 암석 또는 광미시료의 철인산염 피막형성 연구의 기초자료로 활용될 수 있을 것이다.

• Corrosion Science and Technology
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• 제22권6호
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• pp.429-434
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• 2023

This study investigated the localized corrosion behavior of a UNS G41400 steel surface treated with manganese phosphate. The phosphate coating, primarily composed of oxygen (O), phosphorus (P), and manganese (Mn) elements, had an approximate thickness of 6 ㎛. The particles comprising the coating varied in size by several micrometers; smaller particles were mainly composed of O, P, Mn, and iron (Fe) elements, indicating incomplete formation of the manganese phosphate film. Potentiodynamic polarization curves revealed a decrease in anodic current after surface treatment and a shift in corrosion potential toward the noble direction after treatment. After immersion in a 3.5 wt% NaCl solution for 96 hours, localized corrosion was observed, with some regions retaining residual phosphate film. Even though localized corrosion occurred on the treated surface, it was less severe than that on the untreated UNS G41400 steel surface. These findings suggest that manganese phosphate coating improved resistance to localized corrosion.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.160-161
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• 2006

Seasonal changes have been recognized in particle characteristics and forming characteristics of iron powder with insulated coating for a compacted magnetic core because of its high hygroscopicity, due to its phosphate coating and resin binder additives. For this reason, particle characteristics and molding characteristics of the powder with diverse water absorbtivity have been studied. The result shows that the higher the volume of absorbed water, the worse the fluidity becomes, resulting in the reduction in both springback during the molding process and expansion reduction after the heat treatment. The requirement on dimension accuracy for the finished product can be satisfied with an additional drying process on the material powder, which contributes to maintain its water volume constant.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2698-2700
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• 2010

• Corrosion Science and Technology
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• 제4권1호
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• pp.15-18
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• 2005

Hydroxyapatite(HAp) was synthesized using the waste sludge from semiconductor process and used as an anticorrosive pigment. The water absorption of coating pigmented with anticorrosive pigment and the corrosion at interface between coating and substrate were monitored using AC impedance techniques. The anticorrosive performance of HAp was compared with those of red lead(RL) and zinc potassium chromate(ZPC), which have been known as representative anticorrosive pigments. The amount of absorbed water in ZPC- and HAp- pigmented coatings was much higher compared to that in RL-pigmented and unpigmented film. However, it seems that the water absorbed into HAp- or ZPC-pigmented film is beneficial to anticorrosive function. The anticorrosive performance of HAp is superior or at least comparable to those of ZPC and RL. The excellent anticorrosive properties of HAp can be explained by its passivating ability, caused by the reaction of the soluble component of HAp with Fe to form iron phosphate in the presence of water.

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.536-540
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• 2011

This study reports the origin of the electrochemical improvement of $LiFePO_4$ when synthesized by wet milling using acetone without conventional carbon coating. The wet milled $LiFePO_4$ delivers 149 $mAhg^{-1}$ at 0.1 C, which is comparable to carbon coated $LiFePO_4$ and approximately 74% higher than that of dry milled $LiFePO_4$, suggesting that the wet milling process can increase the capacity in addition to conventional carbon coating methods. UV spectroscopy, elemental microanalysis, and evolved gas analysis are used to find the root cause of the capacity improvement during the mechanochemical reaction in acetone. The analytical results show that the improvement is attributed to the conductive residual carbon on the surface of the wet milled $LiFePO_4$ particles, which is produced by the reaction of $FeC_2O_4{\cdot}2H_2O$ with acetone during wet milling through oxygen deficiency in the precursor.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.836-840
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• 2011

This study examines the effects of a carbon coating on the electrochemical performances of $LiFePO_4$. The results show that the capacity of bare $LiFePO_4$ decreased sharply, whereas the $LiFePO_4$/C shows a well maintained initial capacity. The Li ion diffusivity of the bare and carbon coated $LiFePO_4$ is calculated using cyclic voltammetry (CV) to determine the correlation between the electrochemical performance of $LiFePO_4$ and Li diffusion. The diffusion constants for $LiFePO_4$ and $LiFePO_4$/C measured from CV are $6.56{\times}10^{-16}$ and $2.48{\times}10^{-15}\;cm^2\;s^{-1}$, respectively, indicating considerable increases in diffusivity after modifications. The Li ion diffusivity (DLi) values as a function of the lithium content in the cathode are estimated by electrochemical impedance spectroscopy (EIS). The effects of the carbon coating as well as the mechanisms for the improved electrochemical performances after modification are discussed based on the diffusivity data.

• 열처리공학회지
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• 제10권3호
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• pp.165-171
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• 1997

Laser hardening for the piston ring groove of ductile cast iron was tried. Mechanical and microstructural investigation for the hardened area indicated that the laser heating technique could replace conventional induction hardening process completely and further showed that post grinding process would be eliminated by minimizing bulging of heat treated area. In laser hardening, the volume increase caused by martensitic phase transformation proved to be less than $10{\mu}m$, which insures no post machining on the hardened surface. As expected, the depth of hardening was inversely proportional to the beam scanning velocity and the highest surface hardness was obtained at the beam velocity of 0.75m/min. Heat treatment using phosphate coating demonstrated quite comparable result to the case of graphite suscepter.