• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.1-2
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• 1999

시간과 공간의 구애를 받지 않는 양질의 음성, 화상, 문자정보의 교환을 위한 노력으로 디지털 휴대폰과 휴대용 컴퓨터가 등장하면서 음성과 문자정보의 교환분야에 커다란 진보를 이룩하였다. 그러나 현재는 휴대폰이 음성정보에 문자정보교환이 추가된 상황이기 때문에, 아직도 관련 정보교환기술 및 기기개발이 진행되고 있다. 앞으로 휴대폰과 휴대용 컴퓨터의 기능을 통합하고 화상정보까지 결합된 휴대용 정보기기를 위해서는 전자회로의 집적화 및 통신속도 증대가 필수적이다. 또한 이들 휴대용 정보기기를 구동시키기 위한 전력도 증가될 것으로 예측되기 때문에, 현재 전원으로 사용되는 2차전지보다 에너지 밀도가 더욱 증패된 전지가 요구될 것으로 예상된다. 그리고 내연기관의 배기에 의해 발생되는 환정오염문제를 해결하기 위한 방법중의 일환으로 전기자동차 개발이 진행되고 있으며, 이들 전기자동차에 2차전지를 장착하기 위해서 경제성이 있고, 고속충전이 가능하고, 안전성이 높은 고에너지 밀도의 2차 전지 개발이 요구되고 있다. 현재 2차전지는 음극재료나 양극재료에 따라 낚축전지, 니켈/카드륨(Ni/Cd) 전지, 니켈/수소(Ni/MH) 전지, 라륨 2 차전지등이 있으며, 전극재료의 고유특성에 의해 전위와 애너지 밀도가 결정된다. 특히 리튬 2차전지는 리튬의 낮은 산화환원전위와 분자량으로 인해 에너지 밀도가 높기 때문에 앞에서 언급한 휴대용 전자기기의 구동전원으로 많이 사용되고 있다. 리튬 2차전지는 음극 재료가 금속리튬인 경우는 리튬금속으로, 탄소재료인 경우는 리튬이온이라 하며, 한편으로 전해질이 고체 고분자이거나 혹은 역체 유기용매와 리튬염을 고분자와 혼성시킨 겔(gel)인 경우는 고분자로, 전해짙이 리튬염이 전리되어 있는 유동성 액체일 경우는 고분자를 생략하여 구분하고 있다. 즉 리튬금속 2 차전지(LB), 리튬이온 2 차전지(LIB), 리튬금속 고분자 2차전지(LPB), 리튬 이온 고분자 2차전지(LIPB)로 크게 구분된다. 금속리듐을 음극으로 사용하고 전해질로는 리튬염이 전리되어 있는 액체유기용매 를 사용한 리튬금속 2차전지는, 금속리튬전극이 충방전 과정을 반복하면서, 전리된 리튬이 균일하게 산화환원되지 못하고 표변에서 양극방향으로 성장하는 수지상 (dendrite) 현상으로 인해 안전성 확보에 문게가 있었다. 리튬과 알루미늄 합금형태로 음극에 사용한 동전형 전지는 상용화 되었지만, 이러한 단점을 개선하기 위해 리튬이온이 금속으로 석활되는 환원반응전위보다 높은 전위에서 전극재료가 충전되면서 리튬이온이 저장되고, 방전되면서 배출되는 탄소를 음극재료로, 그리고 리튬이온이 충방 전시 가역적으로 삼입 탈리되는 층상의 리튬금속산화물을 양극으로 구성하고, 엑체 전해질과 다공성 고분자 분리막을 사용한 것이 LIB이다. LIB에서 리튬이온의 이동이 가능한 액체전해질의 가능을 고분자 전해질이 대신함으로서 보다 높은 안정성을 확보 한 전지가 LIPB 이다. 또한 고분자 전해질을 사용한 경우 금속리튬상에서의 수지상 성장이 저하되는 현상이 관찰됨으로서, 이론용량이 3,860mAh/g 에 달하는 리튬금속 혹은 합금을 고분자 전지에서 음극으로 사용하고자 하는 2 차전지가 LPB 이다. 리튬 2차전지는 비록 1989년 액체전해질을 사용한 금속리튬 2차전지의 실패전력을 안고있지만 궁극적으로는 이론적으로 최대의 에너지밀도를 가지고 있는 LPB를 지 향할 것으로 예상되지만 가까운 장래에 실현되기는 어려울 것이다. 따라서 향후의 라튬 2차전지의 전개방향은 현재의 LIB를 고분자 전해질을 채용하는 LIPB로 진행시커면서 저가의 전극재료개발을 지속적으로 추진할 것으로 예상된다. 현재 리튬 2차전지는 소형전지에 국한되고 있지만 전기자동차나 전력저장용으로 이를 대형화시커기 위해서는 열적특성이 우수하고 저가인 전극재료개발이 선행되야하기 때문에, 저가의 탄소재료와 코발트산화물을 대신할 수 있는 철, 망칸 또는 니켈산 화물의 개발이 필요하다.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.25-31
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• 1994

The magnetic properties of aluminum anodized film in which Co-Fe alloy electrodeposited are investigated with regard to the alloy composition of magnetic films. The electrodeposited Co-Fe particles are confirmed to be single phase Co-Fe alloys by X-ray diffractions. At 34 at% Co, the sample with small pore diameter(particle diameter $150\;{\AA}$) has a large magnetic energy product($B_{max}$) of about 1.44 MGOe due to the large saturation magnetization, the high coercive force and good squareness of the M-H curve. However, for the samples with particle diameter larger than $450\;{\AA}$, the bottom of each particle forms abnormal particle claaed branch-shaped unlike the sample of the particle diameter $150\;{\AA}$. In this case, the magnetic anisotropy energy was about zero at the compositions of 45 and 75 at% Co. Moreover, at the compositions from 50 to 70 at% Co, the anisotropy became negative value. This means that an easy axis of magnetization of the film is in plane in plane in spite of the perpendicular shape anisotropy of the particle. It was found that the bottom extremity of the particle contains FeC from the X-ray diffraction. Thus the effect of the bottom extremity, that is, an unusal magnetic property was removed by electrodepositing Cu at the bottom extremity of the particle. Itis clear that the magnetic properties of the ilms are influenced by he branch-shaped bottom extremity filled with FeC.

• Journal of the Korean institute of surface engineering
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• v.42 no.6
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• pp.260-266
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• 2009

The anodic oxidation behaviour of a cast component of AC2A Al alloy with machined surface and ascast surface was investigated in sulfuric acid solution. The anodized specimen showed relatively uniform and thick anodic oxide films on the as-cast surface, while non-uniform and very thin oxide films were formed on the machined surface. Non-anodized as-cast surface was observed to be covered with thick oxide scales and showed a number of second-phase particles containing Si, while non-anodized machined surface showed no oxide scales and relatively very small number of Si particles. Thus, the very limited growth of anodic oxide films on the as-cast surface was attributed to the presence of thick oxide scales and Si-containing second-phase particles on its surface.

• Journal of the Korean institute of surface engineering
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• v.48 no.2
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• pp.68-72
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• 2015

The corrosion behavior of metals and alloys for the safety of offshore structures in seawater was investigated for the application of sacrificial anodes. The experiments were focused on the polarization behaviors and the surface morphology of each metal after experiments. Pure Zn, pure Al (Al1050), Al alloys (Al5052, Al6061), Mg alloys (AZ31, AZ91D) and steel (SCM440) were assessed in 3.5% sodium chloride solution by means of potentiodynamic polarization to verify the galvanic corrosion potential ($E_{couple}$). Potentiostat plots were plotted to compare the surface and corrosion current density ($i_{couple}$) of metals as sacrificial anodes in seawater to protect steel alloy as a cathode. Al alloys showed the best performance as a sacrificial anode, on the other hand, Mg alloys showed overprotection behavior. The surface morphologies of sacrificial anodes were observed by FESEM and compared.

• Corrosion Science and Technology
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• v.14 no.3
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• pp.140-146
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• 2015

The commercialization of aluminum had been delayed than other metals because of its high oxygen affinity. Anodizing is a process in which oxide film is formed on the surface of a valve metal in an electrolyte solution by anodic oxidation reaction. Aluminum has thin oxide film on surface but the oxide film is inhomogeneous having a thickness only in the range of several nanometers. Anodizing process increases the thickness of the oxide film significantly. In this study, porous type oxide film was produced on the surface of aluminum in sulfuric acid as a function of electrolyte temperature, and the optimum condition were determined for anodizing film to exhibit excellent cavitation resistance in seawater environment. The result revealed that the oxide film formed at $10^{\circ}C$ represented the highest cavitation resistance, while the oxide film formed at $15^{\circ}C$ showed the lowest resistance to cavitation in spite of its high hardness.

• Tribology and Lubricants
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• v.26 no.1
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• pp.68-72
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• 2010

A ceramic coating is a surface treatment method that is being used widely in the industrial field, recently. Ni-P plating is also being used widely because of its corrosion resistance and low cost. An anodizing method is applicable to aluminum alloy. An anodizing method generates a thick oxide layer on the surface and then, that heightens hardness and protects the surface. These surface treatments are applied to various mechanical components and treated surfaces relatively move one another. In this study, tribological characteristics of Ni-P plating and TiAlN coating on anodized Al alloy are compared. The counterpart, anodized Al alloy, is worn out abrasively by Ni-P plating and TiAlN coating that have higher hardness. Abrasively worn debris accumulated on the surfaces of Ni-P plating and TiAlN coating, and then transferred layer is formed. This transferred layer affects the amplitude of variation of friction coefficient, which is related to noise and vibration. The amplitude of variation of friction coefficient of Ni-P plating is lower than those of TiAlN coating during the tests.

• Journal of the Korean institute of surface engineering
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• v.53 no.5
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• pp.219-226
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• 2020

This paper investigated the characteristics of anodized aluminum 6061-T6 alloy for corrosion and stress corrosion cracking(SCC) under natural seawater. The hard anodizing oxide film formed on the 6061-T6 was a uniform thickness of about 25 ㎛. The corrosion characteristics were performed with a potentiodynamic polarization test. SCC was characterized by a slow strain rate tensile test under 0.005mm/min rate. As a result, the anodizing film showed no significant effect on SCC in the slow strain rate test. However, the corrosion current density of base metal was measured to be approximately 13 times higher than that of the anodized specimen. Therefore, the anodizing film significantly improved the corrosion resistance of 6061-T6 alloy in natural seawater.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.639-646
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• 2006

Over the last two decades, microbiologically influenced corrosion (MIC) of metallic materials has received considerable attention due to its serious effects on industrial field. In this context, it is important to devise control methods which inhibit biofilm formation on various metallic compounds and are compatible with environment. It was change of various conditions (duty cycle, current density, $AgNO_3$ concentration and pH) for injection of Ag particles in anodized Aluminum alloy pore using pulsed current. Optimal condition was obtained by means of FE-SEM, ICP analysis etc. The antibacterial metal's specimen were manufactured under optimal condition and this specimen were tested the antibacterial characterization and anticorrosion characterization. In result of test, we can confirmed that the antibacterial characterization and anticorrosion characterization of the specimens of injected Ag particles in anodized Aluminum alloy pore using pulsed current were better than the anodized Aluminum alloy specimens.

• Journal of the Korean institute of surface engineering
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• v.49 no.4
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• pp.349-356
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• 2016

In this study, electrochemical damage behaviors with flow rate were investigated for anodized 5083 aluminum alloy in seawater. As the results of anodic polarization experiments and potentiostatic experiments at +1.0 V (vs. SSCE), the non-flow condition presented largely damaged surface resulting from a tendency of local pitting damage. Under various flow rate conditions, however, less surface damages under the application of anodic potential was obtained which is attributed to no accumulation of $H^+$ and $Cl^-$ ions on the surface. On the other hand, the results of the potentiostatic experiments at -1.0 V (vs. SSCE) with flow rate showed that anodized 5083 aluminum alloys could achieve the effective cathodic protection by low cathodic protection current density less than $2.61{\times}10^{-7}A/cm^2$ even under high flow rate of 1 m/s.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.381-386
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• 2018

In this study, plasma electrolytic oxidation (PEO) method was used to from anodic oxide films on Al alloy and their resistance and morphological characteristics were investigated as a function of film formation voltage and treatment time. Cross-sectional morphology and composition of the PEO films were analyzed by SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive Spectroscopy). The PEO films showed increased surface roughness and thickness with of film formation voltage and treatment time. The wear resistance was found to be the best for the PEO film formed for 5 min at 500V which is attributed to be denser structure relatively and lower surface roughness.