• Composites Research
• /
• v.13 no.4
• /
• pp.42-53
• /
• 2000

A study has been made to establish an optimum condition in the surface treatment and curing method that is important for the fabrication of Al 7075/CFRP laminates. PAA(Phosphoric Acid Anodizing) provided a good adhesive strength and FPL(Sulfuric / Sodium Dichromate Acid Etching) had a similar adhesive strength with PAA. On the other hand, the poor adhesive strength was shown on vapor degrease and CAA(Chromic Acid Anodizing). By using the atomic force microscope(AFM), it was found that the PAA oxide surface obviously had a greater degree of microroughness as compared to vapor degrease, CAA and FPL treated surfaces. These results support the concept of a mechanical interlocking of the adhesive with-in the oxide pores as the predominant adhesion mechanism. In curing methods, the adhesive strength of co-curing method was higher than that of secondary curing method. With respect to stability of specimen shape, the secondary curing method was better than co-curing method. DMA(Dynamic Mechanical Analysis) test revealed $T_g$ in curing times over 60 min is nearly same, so it is estimated they will have similar degree of curing and joint durability in using FM300M adhesive film.

• Resources Recycling
• /
• v.16 no.4
• /
• pp.33-39
• /
• 2007

Titanium scrap was re-melted and refined by using a DC-ESR (Direct Current Electro Slag Remelting) apparatus. A graphite rod was used as an anode. The used slag was $CaF_2-TiO_2-CaO$ slag system. The effect of slag composition on the shape and oxygen content of re-melted ingot was studied. The titanium ingot was produced very well from the $CaF_2-TiO_2$ slag system, and the oxygen content of the ingot was less than that of titanium scrap. The addition of CaO into $CaF_2-TiO_2$ slag system made the bad shape of titanium ingot. The oxygen content of the ingot was also higher than that of titanium scrap.

• Journal of the Korean Electrochemical Society
• /
• v.6 no.1
• /
• pp.6-12
• /
• 2003

Plasma carbon black(PB) which prepared by plasma pyrolysis of methane was treated at 800, 1300 and $2100^{\circ}C$ under $2\times10^{-2}$ torr. Four different samples including raw PB were added to $LiCoO_2$, cathode active material of lithium secondary battery, to investigate effects of properties of plasma black as conductors on electrochemical characteristics. Based on our experimental results, PB conductors with low amount of surface functional groups and high electrical conductivity enhanced the cyclability and the initial discharge capacity. However, deterioration of rate capability and cyclability were observed (or the plasma black treated at $2100^{\circ}C$ For the plasma black conductor prepared from plasma pyrolysis, the effects of properties of carbon black on electrochemical characteristics were combined results of changes in electrical conductivity and structural properties such as agglomeration of plasma black. The conductivity of plasma black increased with treatment temperature, while dispersion of plasma black decreased. As a result, the high cyclability of cell was observed at $800^{\circ}C$ of heat treatment temperature.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.182-182
• /
• 2016

철강은 기본적으로 강도가 우수하고 그 매장량이 풍부할 뿐만 아니라 대량생산이 가능하다 또한 다른 금속과 합금을 구성하여 또 다른 특성을 부여할 수 있기 때문에 현재 전 세계 금속 생산량의 95%를 차지할 정도로 많이 사용되며, 각종 산업과 기술이 발달함에 따라 그 중요도는 점점 더 커져가고 있다. 하지만 철강은 사용 환경 중 부식에 의해 그 수명과 성능이 급격히 저하되기 때문에 내식성을 향상시키기 위하여 도장이나 도금 등의 표면처리를 포함한 다양한 방법이 적용되고 있다. 그 중 철강재의 도금 표면처리방법은 주로 아연을 이용한 용융도금이나 전기도금 등과 같은 습식 프로세스가 널리 사용되고 있다. 여기서 아연은 철보다 이온화 경향은 크나 대기 환경 중 산소와 물과 반응하여 Zn(OH)2와 같은 화합물을 형성함으로써 철강재 표면상 부식인자를 차단(Barrier)함은 물론 사용 중 철 모재가 노출되는 결함이 발생하는 경우에는 철을 대신하여 희생양극(Sacrificial Anode) 역할을 하기 때문에 철의 부식방식용 금속으로 가장 많이 사용되고 있다. 한편 최근에는 철강의 사용 환경이 다양해짐은 물론 가혹해지고 있어서 이에 따른 내식성 향상이 계속해서 요구되고 있는 추세이다. 따라서 본 연구에서는 철강재의 내식성을 향상시키기 위한 일환으로 현재 많이 사용되고 있는 용융아연도금 강판 상에 아연보다 활성이 높은 마그네슘(Mg)을 건식 프로세스 방법 중에 하나인 PVD(Physical Vapour Deposition)법에 의해 코팅하는 것을 시도하였다. 일반적으로 PVD법에 의해 진공증착하는 경우에는 그 도입가스로써 불활성가스인 아르곤(Ar)을 사용하는 경우가 대부분이나 여기서는 상대적으로 비활성이면서 그 크기가 작은 질소(N2)가스를 도입하여 그 증착 막의 몰포로지는 물론 결정구조도 제어하여 그 내식특성을 향상시키고자 하였다. 본 연구에서는 철강재의 내식성을 향상시키기 위한 방법으로 마그네슘(Mg)를 PVD(Physical Vapor Deposition)법 중 진공증착법(Vacuum Deposition)을 사용하여 용융아연도금 강판 상에 마그네슘 증착 막을 형성하였다. 즉, 여기서는 진공증착 중 질소(Nitrogen, N2)가스를 도입하여 진공챔버(Vacuum Chamber)내의 진공도를 $1{\times}10^{-1}$, $1{\times}10^{-2}$, $1{\times}10^{-3}$, $1{\times}10^{-4}$로 조절하며 제작하였다. 또한 제작된 시편에 대해서는 SEM(Scanning Electron Microscope) 및 XRD(X-Ray Diffraction)을 사용하여 형성된 아연도금상 마그네슘 막의 표면 몰포로지 및 결정구조의 변화를 분석함은 물론 침지시험, 염수분무시험, 분극시험을 통해 이 막들에 대한 내식특성을 분석 평가하였다. 상기 실험결과에 의하면, 진공 가스압이 증가됨에 따라 마그네슘 막의 두께는 감소하였으며, 그 몰포로지의 단면은 주상정(Columnar)에서 입상정(Granular) 구조로 변화하며 표면의 결정립은 점점 미세화 되는 경향을 나타냈다. 이때의 표면의 결정배향성(Crystal orientation)은 표면에너지가 상대적으로 큰 면이 우세하게 나타나는 경향이 있었다. 또한 본 실험에서 형성한 진공증착 막은 비교재인 용융아연도금강판보다 우수한 내식성을 나타냈고, 본 형성 막 중에는 마그네슘 막 두께가 작음에도 불구하고 질소 가스압이 가장 큰 조건일수록 내식성이 우수한 경향을 나타냈다. 이상의 결과는 철강재의 내식성 향상을 위한 응용표면처리설계에 기초적인 지침을 제공할 수 있을 것으로 기대된다.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.9
• /
• pp.42-47
• /
• 1998

We have fabricated electron-optical lens for micro E-beam system that can overcome the limitation of current E-beam lithography. Our electron-optical lens consists of multiple silicon electrodes which were fabricated by micromachining technology and assembled by anodic bonding. The assembled system was installed in UHV chamber to observe the emission characteristics of focused electrons by the electro-optical lens. We used STM(Scanning Tunneling Microscope) tip for electron source. By performing lithography with the focused electrons with PMMA(poly-methylmethacrylate) as E-beam resist. We could draw 0.13${\mu}{\textrm}{m}$ nano-scale lines.

• Journal of the Korean Institute of Gas
• /
• v.9 no.4 s.29
• /
• pp.6-10
• /
• 2005

This paper was studied on the damage behavior of stainless steel (STS 304) for gas boiler with specific resistance. The electrochemical polarization test of STS304 for gas boiler was carried out. And the anodic polarization and damage aspect, such as pitting corrosion, was considered. With being low specific resistance, the passive current density of STS 304 increases, passive region and pitting potential is low. Also, the patting aspect of STS304 In specific resistance $74{\Omega}{\cdot}m$ water little appears, the pitting number increases and the damage behavior, such as pitting aspect, gradually grow bigger with being low specific resistance.

• Journal of the Korean Ceramic Society
• /
• v.44 no.12
• /
• pp.715-719
• /
• 2007

STS444 with or without $La_{0.9}Sr_{0.1}MnO_3$ (LSM)-coating was contacted to $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ (LSCF) cathode on various electrolyte materials and the polarization resistance $(R_p)$ was measured by impedance spectroscopy. By making a symmetric half-cell and contacting only one side of the cathode with the interconnect, the effect of chromium (Cr) poisoning was separated from the aging effects. When the LSCF cathode was contacted with LSM-coated STS (stainless steel), $R_p$ of LSCF was lower than that contacted with the uncoated STS. Impedance patterns measured for the working electrode (W.E.), the counter electrode (C.E.) at $600^{\circ}C$ in air were analyzed. Normalized data of net Cr effect showed that $Ce_{0.9}Gd_{0.1}O_2$ (GDC) electrolyte is more tolerant to the chromium poisoning than $La_{0.9}Sr_{0.1}Ga_{0.8}Mg_{0.2}$ (LSGM) or 8 mol% $Y_2O_3-doped$ $ZrO_2$ (YSZ) electrolytes.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.19 no.6
• /
• pp.411-419
• /
• 1999

It has been well recognized that a long term service at elevated temperature of $350^{\circ}C{\sim}550^{\circ}C$ induces embrittlement damage due to carbide precipitation and/or P, Sb and Sn segregation at grain boundaries and thereby deteriorates the grain boundary strength of heat resisting components in the energy-related plants. Therefore, it is very important to assess quantitatively the extent of embrittlement damage of heat resisting components to secure the reliable and efficient service condition and to prevent brittle failure in service. However, because fracture tests are limited in size and number of specimen obtained from the structural components, nondestructive test method is required. In this study, the optimum electrochemical parameters are investigated and discussed to evaluate nondestructive embrittlement damage for aged 2.25Cr-1Mo steels by means of electrochemical polarization test method (ECPTM) in proper corrosive environment. In addition, the electrochemical test results are compared with embrittlement degree evaluated by semi-nondestructive SP test.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.2
• /
• pp.223-229
• /
• 2023

Seawater batteries are next-generation secondary batteries that use seawater as a cathode. They utilize marine resources to provide competitive prices, high eco-friendliness, and a structure suitable for marine applications. Based on these advantages, pouch types and prismatic types have been studied and developed assuming natural seawater exposure. However, because of the electrical characteristics of the secondary battery, its capacity and internal resistance vary depending on the use environment. These characteristics are not only utilized for predicting the life of a battery but also have a direct effect on the capacity and power suitable for a specific situation. Therefore, the internal resistance was analyzed in this study by measuring the capacity depending on the seawater battery use environment and the state-of-charge-open-circuit-voltage measurement method.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.12 no.1
• /
• pp.1-6
• /
• 2014

A large amount of acidic waste solution is generated from the practical electrokinetic decontamination equipments for the remediation of soil contaminated with uranium. After filtration of uranium hydroxides formed by adding CaO into the waste solution, the filtrate was recycled in order to reduce the volume of waste solution. However, when the filtrate was used in an electrokinetic equipment, the low permeability of the filtrate from anode cell to cathode cell due to a high concentration of calcium made several problems such as the weakening of a fabric tamis, the corrosion of electric wire and the adhension of metallic oxides to the surface of cathode electrode. To solve these problems, sulfuric acid was added into the filtrate and calcium in the solution was removed as $CaSO_4$ precipitate. A decontamination test using a small electrokinetic equipment for 20 days indicated that Ca-removed waste solution decreased uranium concentration of the waste soil to 0.35 Bq/g, which is a similar to a decontamination result obtained by distilled water.