• Journal of the Korean Electrochemical Society
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• v.12 no.4
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• pp.342-348
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• 2009

Zn/Air secondary batteries are high energy density type and environment-friendly. Also, they have safer properties than batteries of other type by low manufacturing cost and using the electrolyte solution. But, they have a weak concerning large output discharge. Oxygen evolution reaction(OER) and oxgen reduction reaction(ORR) in aqueous solution make a result of a decrease of cell efficiency and life span. Therefore, to minimize the voltage drop from between OCV and charge/discharge voltage is key point. The problem should be solved through developing catalysts of high efficiency. In this study, we synthesized $Pr_{1-x}(Sr,\;Ca)_x\;CoO_3$ powders by citric method and then measured physical characteristics of each powder by XRD, SEM, TGA etc. We examined its electrochemical properties by the cathodic polarization, anodic polarization and cyclic voltammogram. We achieved results that new catalysts showed better performances than existing $La_{1-x}Sr_xCoO_3$, $La_{1-x}Ca_xCoO_3$, ect. catalysts prepared in our lab.

• Nuclear Engineering and Technology
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• v.27 no.4
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• pp.453-462
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• 1995

In connection with the safe storage of high level nuclear waste, effect of $H_2O$$_2$ on the corrosion behavior of 304L stainless steel was examined. Open circuit potentials and polarization curves were measured with and without $H_2O$$_2$. The experimental results show that $H_2O$$_2$ increased corrosion potential and decreased pitting potential. The passive range, therefore, decreased as $H_2O$$_2$ concentration increased, indicating that pitting resistance was decreased by the existence of $H_2O$$_2$ in the electrolyte. These effect of $H_2O$$_2$ on corrosion of 304L stainless steel are considered to be similar to those of ${\gamma}$-irradiation. To compare the effects of $H_2O$$_2$ with those of $O_2$, cathodic and anodic polarization curves ore made in three types of electrolyte such as aerated, deaerated, and stirred electrolyte. The experimental results show that the effects of $H_2O$$_2$ on the corrosion behavior were tory similar to those of $O_2$ such as increase of corrosion potential, decrease of pitting resistance, and increase of repassivation potential. In acid and alkaline media, the corrosion potential shifts by $H_2O$$_2$ were restricted by the large current density of proton reduction and by the le Chatelier's principle respectively.y.

• Journal of the Korean Institute of Gas
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• v.9 no.4 s.29
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• pp.11-16
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• 2005

In this paper, the hydrogen osmosis test and the mechanical tensile test were carried out to examine hydrogen cracking behavior of STS444 with welding conditions. In $0.5MH_2SO_4+0.001M \;As_2O_3$ solution, the hydrogen embrittlement characteristics of weld zone of STS444 added to load of $1,400 kg/cm^2$ together with hydrogen osmosis by current of $30mA/cm^2$ for 60 min. was considered. As a result of study on the hydrogen embrittlement and mechanical characteristics of STS444외와 with welding conditions the tensile stress and elongation of STS444 get lower by the absorption of oil or water before welding. Also, the reduction rate of tensile stress and elongation of STS444 is larger because of hydrogen embrittlement by the absorption of oil or water. STS444 by the absorption of water before welding is more sensitive to hydrogen embrittlement than oil.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.352-355
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• 2006

As the stainless steel has good corrosion resistance, mechanical property and ease of manufacture, it has been studied as the candidate material of metallic bipolar plate for automotive PIMFC. But, metal is dissolved under fuel cell operating conditions Dissolved ions contaminate a membrane electrode assembly (MEA) and, decrease the fuel cell performance. In addition, metal oxide formation on the surface of stainless steel increases the contact resistance in the fuel cell. These problems have been acted as an obstacle in the application of stainless steel to bipolar plate. Therefore, many kinds of coating technologies have been examined in order to solve these problems. In this study, stainless steel was coated in order to achieve high conductivity and corrosion resistance by several methods. Contact resistance was measured by using a tensile tester and impedance analyzer Corrosion characteristics of coated stainless steel were examined by Tafel-extrapolation method from the polarization curves in a solution simulating the anodic and cathodic environment of PEMFC. Fuel cell performance was also evaluated by single cell test. We tested various coated metal bipolar plate and conventional and graphite were also tested as comparative samples. In the result, coated stainless steel bipolar plate exhibited better cell performance than graphite to bipolar plate.

• Journal of Applied Reliability
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• v.18 no.3
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• pp.271-279
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• 2018

Purpose: Probabilistic safety analysis was performed to enhance the safety and reliability of nuclear power plants because traditional deterministic approach has limitations in predicting the risk of failure by crack growth. The study introduces a probabilistic approach to establish a basis for probabilistic safety assessment of passive components. Methods: For probabilistic modeling of fatigue crack growth rate (FCGR), various FCGR tests were performed either under constant load amplitude or constant ${\Delta}K$ conditions by using heat treated X-750 at low temperature with adequate cathodic polarization. Bayesian inference was employed to update uncertainties of the FCGR model using additional information obtained from constant ${\Delta}K$ tests. Results: Four steps of Bayesian parameter updating were performed using constant ${\Delta}K$ test results. The standard deviation of the final posterior distribution was decreased by a factor of 10 comparing with that of the prior distribution. Conclusion: The method for developing a probabilistic crack growth model has been designed and demonstrated, in the paper. Alloy X-750 has been used for corrosion fatigue crack growth experiments and modeling. The uncertainties of parameters in the FCGR model were successfully reduced using the Bayesian inference whenever the updating was performed.

• Journal of the Korean Chemical Society
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• v.25 no.5
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• pp.325-330
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• 1981

The electrochemical behavior of cadmium electrode for the nickel-cadmium battery system has been studied by cyclic voltammetry, controlled potential electrolysis and X-ray diffraction method. Cathodic polarization curve for cadmium hydroxide electrode prepared by electrochemical pretreatment of metallic cadmium showed two peaks. It has been found that cadmium hydroxide was reduced to cadmium metal at the first peak potential, whereas very activated metal of cadmium which was strongly oriented (002) rather than (101) was formed at the second peak potential. It was also found that the cadmium formed at the second peak potential reacted rapidly with oxygen. Therefore, it could be presumed that the cadmium recombination reaction with the oxygen was chemical, and could be represented as $2Cd + O_2 + 2H_2O\;{\longrightarrow}\;2Cd(OH)_2$.

• Journal of the Korean Chemical Society
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• v.23 no.3
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• pp.180-185
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• 1979

Electrochemical reduction behavior from 2-butyne-1, 4-diol (BID) to 2-butene-1,4-diol (BED) by the use of various cathodes, such as Ti, Zr, Ni, Pt, Cu, Ag, Au, Zn, Hg, Pb and graphite has been studied. It has been found that cathodic polarization curve with metal of IB subgroup such as Cu, Ag and Au consisted of one wave in BID-alkaline solution, whereas it was not formed any wave in BED solution. Therefore, it was found that the cathode which was the most suitable in order to proceed in this reaction was Cu, Ag and Au. At cyclic voltammetry using a silver cathode in BID-alkaline solution, the current of the peak was proportional to square root of the sweep rate of potential and also proportional to concentration of BID. Activation energy was calculated for 3.75 kcal/mole from the plot of log $I_l$ vs. 1/T. Consequently, the reduction current of BID with a silver cathode in alkaline solution was found the diffusion current.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.1
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• pp.19-25
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• 2010

Composites of LSCF($La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$) and CGO (gadolinium doped ceria)-based ceramics are logical candidate cathode materials with CGO electrolytes. LSCF with perovskite structure was synthesized and investigated by Solid State Reaction (SSR) method used as cathode materials for SOFC (solid oxide fuel cell). The optimized temperature was $1100^{\circ}C$ to synthesize $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ with rhombohedral structure. The polarization resistance of the LSCF/CGO (50:50 wt.%) was smaller than that of other composite cathodes. The analysis of the EIS data of LSCF/CGO suggests that the diffusion and adsorption-desorption of oxygen can be the key process in the cathodic reaction.

• Journal of Electrochemical Science and Technology
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• v.8 no.2
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• pp.133-145
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• 2017

Palm oil production is among the highest worldwide, and it has been mainly used in the food industry and other commodities. Currently, a lot of palm oil production has been destined for the synthesis of biodiesel; however, its use in applications other than the food industry has been questioned. Thereby for a sustainable development, in this paper the use of palm oil of low quality for corrosion inhibitors synthesis is proposed. The performance of the synthesized inhibitors was evaluated by using electrochemical techniques such as open circuit potential measurements, linear polarization resistance and electrochemical impedance spectroscopy. The results indicate that the fatty amides from palm oil are excellent corrosion inhibitors with protection efficiencies greater than 98%. Fatty amides molecules act as cathodic inhibitors decreasing the anodic dissolution of iron. When fatty amides are added, a rapid decrease in the corrosion rate occurs due to the rapid formation of a molecular film onto carbon steel surface. During the adsorption process of the inhibitor a self-organization of the hydrocarbon chains takes place forming a tightly packed hydrophobic film. These results demonstrate that the use of palm oil for the production of green inhibitors promises to be an excellent alternative for a sustainable use of the palm oil production.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.315-318
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• 2008

The atmospheric corrosion performance of Al-alloying, Si-alloying and Al-Si-alloying steel were studied by wet/dry cyclic corrosion tests (CCT) at $30^{\circ}C$ and 60% relative humidity (RH). The corrosion electrolyte used for CCT was 0.052 wt% $NaHSO_{3}$ (pH~4) solution. The result of gravimetry demonstrated that Al-Si-bearing steels showed lower corrosion resistance than other rusted steels. But the rusted 0.7%Si-alloying steel showed a better corrosion resistance than rusted mild steel. Polarization curves demonstrated that Al-/Si-alloying and Al-Si-alloying improved the rest potential of steel at the initial stage; and accelerated the cathodic reduction and anodic dissolution after a rust layer formed on the surfaces of steels. XRD results showed that Al-Si-alloying decreased the volume fraction of $Fe_{3}O_{4}$ and $\alpha-FeOOH$. The recycle of acid accelerated the corrosion of steel at the initial stage. After the rust layer formed on the steel, the leak of rust destabilized the rust layer due to the dissolution of compound containing Al (such as $FeAl_{2}O_{4}$, $(Fe,\;Si)_{2}(Fe,\;Al)O_{4}$). Al-Si-alloying is hence not suitable for improving the anti-corrosion resistance of steel in industrial atmosphere.