• Korean Journal of Materials Research
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• v.13 no.2
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• pp.126-132
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• 2003

In order to evaluate the corrosion resistance at the anode side separator for molten carbonate fuel cell, STS316 and SACC-STS316 (chromium and aluminum were simultaneously deposited by diffusion into STS316 authentic stainless steel substrate by pack-cementation process) were applied as the separator material. In case of STS316, corrosion proceeded via three steps ; a formation step of corrosion product until stable corrosion product, a protection step against corrosion until breakaway occurs, a advance step of corrosion after breakaway. Especially, STS316 would be impossible to use the separator without suitable surface modification because of rapid corrosion rate after formation of corrosion product, occurs the severe problem on stability of cell during long-time operation. Whereas, SACC-STS316 was showed more effective corrosion resistance than the present separator, STS316 due to the intermetallic compound layer such as NiAl, Ni3Al formed on the surface of STS316 specimen. And it is anticipated that, in order to use SACC-STS316 alternative separator at the anode side, coating process, which can lead to dense coating layer, has to be developed, and by suitable pre-treatment before using it, very effective corrosion resistance will be achieved.

• Journal of the Korean Electrochemical Society
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• v.24 no.2
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• pp.13-27
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• 2021

Stainless steel, which includes Ni and Cr with Fe balance, is most often applied for a wide range of applications such as structure and equipment material. It is not only suitable for use in these applications due to its good corrosion resistance, but also can be applied to catalyst, supporting material, and current collector due to intrinsic properties of Ni and Fe contained in stainless steel. Therefore, in recent years, a lots of surface treatment methods have been studied to activate stainless steel, developing application of water splitting system. In this review paper, the research on the surface treatment technology of stainless steel for water splitting is summarized. It is expected to be able to propose the diverse surface treatment approaches of stainless steel for application to low-cost and highly efficient water splitting electrode.

• Nuclear Engineering and Technology
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• v.45 no.5
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• pp.689-694
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• 2013

A duplex stainless steel sheet with 1 wt.% gadolinium was fabricated for a neutron absorbing material with high strength, excellent corrosion resistance, and low cost as well as high neutron absorption capability. The microstructure of the as-cast specimen has typical duplex phases including 31% ferrite and 69% austenite. Main alloy elements like chromium (Cr), nickel (Ni), and gadolinium (Gd) are relatively uniformly distributed in the matrix. Gadolinium rich precipitates were present in the grains and at the grain boundaries. The solution treatment at $1070^{\circ}$ for 50 minutes followed by the hot-rolling above $950^{\circ}$ after keeping the sheet at $1200^{\circ}$ for 1.5 hours are important points of the optimum condition to produce a 6 mm-thick plate without cracking.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.861-863
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• 1998

As-casted high nitrogen alloys (Fe-25%Mn-12%Cr-1%Ni) have been investigated to study core material. Nitrogen concentration in molten alloys was increased with increasing the square root of nitrogen gas pressure in melting chamber. This result can be explained by Sievert's law. Nitrogen that dissolved as a interstital solid solution element in austenite stainless steel increased lattice parameter and hardness. Electric resistivity($\rho$) was increased with increasing nitrogen concentration and was about $80{\mu}{\Omega}cm$ at room temperature. Coefficient of linear thermal expansion of the nitrogen steel was about $22{\times}10^{-6}/^{\circ}C$.

• Korean Journal of Materials Research
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• v.8 no.6
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• pp.571-576
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• 1998

This study was carried out for investigating the corrosion behaviors, corrosion mechanisms, and behaviors of elements on a separator for a molten carbonate fuel cell under both the electrolyte and anode side environment. A 310S austenitic stainless steel was used as the separator material. Corrosion proceeded via three steps; the formation step of corrosion product in which rapid corrosion takes place until stable corrosion product is formed after the beginning of corrosion, the protection step against corrosion until breakaway occurs after the formation step of stable corrosion product and the advancing step of corrosion after the breakaway. From the standpoint of the behavior of the elements in the specimen, Fe and Cr, Ni were enriched in the region of corrosion product, in the region of corrosion protection, and at the Cr-deplete zone, respectively. With respect to corrosion mechanism, ionization of electrolyte at the anode side was the main corrosion mechanism, and the final corrosion products were $LiFeO_2$ and $LiCrO_2$ at the anode side.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.7
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• pp.522-527
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• 2013

In this paper, We studied the change of surface and variation of elements on both electrodes of hydrogen generator of alkaline electrolysis in use of FE-SEM and SIMS. We used the stainless steel 316(600 ${\mu}m$) as electrode in condition of 25%KOH, $60^{\circ}C$ Temperature. The results show that the intensity of elements (C, Si, P, S, Ti, Cr, Mn, Fe, Ni, Mo) of Positive Electrode are decreased as much as about $10^1{\sim}10^3 $than the original electrode. Thickness of Positive Electrode is decreased about 40 ${\mu}m$ after chemical reaction. The negative electrode, however, shows a slight variation in the intensity of elements (C, Si, P, Fe, Ni, Mn, Mo) but Change of thickness and surface' shape of electrode show nothing after chemical reaction. The change in thickness and variation of Stainless Steel 316 cause the lifetime of electrode to be shorted. We also observed hydrogen, oxygen, potassium in both electrodes. Especially, The potassium is increased in proportional with depth of positive electrode. this means the concentration of alkali solutions is changed. and so we have to supply alkaline solution to generator in order to produce same quantity of hydrogen gas continuously. we hope that this study gives a foundation to develop the electrode for hydrogen generator of alkaline electrolysis.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.647-653
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• 2020

Stainless steel is used commonly in nuclear applications for shielding radiation, so in this study, three different types of new stainless steel samples were designed and developed. New stainless steel compound ratios were determined by using Monte Carlo Simulation program Geant 4 code. In the sample production, iron (Fe), nickel (Ni), chromium (Cr), silicium (Si), sulphur (S), carbon (C), molybdenum (Mo), manganese (Mn), wolfram (W), rhenium (Re), titanium (Ti) and vanadium (V), powder materials were used with powder metallurgy method. Total macroscopic cross sections, mean free path and transmission number were calculated for the fast neutron radiation shielding by using (Geant 4) code. In addition to neutron shielding, the gamma absorption parameters such as mass attenuation coefficients (MACs) and half value layer (HVL) were calculated using Win-XCOM software. Sulfuric acid abrasion and compressive strength tests were carried out and all samples showed good resistance to acid wear and pressure force. The neutron equivalent dose was measured using an average 4.5 MeV energy fast neutron source. Results were compared to 316LN type stainless steel, which commonly used in shielding radiation. New stainless steel samples were found to absorb neutron better than 316LN stainless steel at both low and high temperatures.

• Plant Journal
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• v.4 no.2
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• pp.60-65
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• 2008

As the operating conditions in a supercritical oxidation reactor are set in high temperature with high pressure causing a reactor suffering from the harsh circumstances. It means the reactor adopts itself with Fe-Cr alloy in acidic atmosphere with low pH value and Ni alloy in basic atmosphere with high pH value due to its superior corrosion resistance. The study, whose target waster water is pertinent to the latter part, has selected Ni alloy such as ostenite type stainless steel 304 and 316, superstainless steel AL6XN, Inconel 625, MAT 21, and titanium Gr. 5 in order to measure corrosion resistance against those samples under the same conditions of temperature and pressure applied for a supercritical oxidation reactor. The result shows the identifiable difference in corrosion resistance by observing the surface states through a scanning probe microscope as well as measuring the weight loss through making the samples above deposited in wastewater for two-week and four-week stay. The purpose of this corrosion experiment is to identify the most corrosion-resistant material among sample species pre-selected according to pH concentration of wastewater in pursue of applying for a reactor exposed to the extreme corrosion environment. It is because such a reactor made of a verified material enables to safeguard a stable operation under the supercritical wastewater processing facility.

• Journal of Ocean Engineering and Technology
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• v.5 no.1
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• pp.88-96
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• 1991

Fatigue life and retardtion behavior after through-thickness were examined experimentally by using a CT specimen and surface-cracked specimen. The material used was 3% Ni-Cr-Mo steel. The fatigue crack shape before through-thickness is almost semicircular, and the measured aspect ratio is larger than the value obtained by calculation using the K value proposed by Newman-Raju. It is found that the crack growth behavior on the back side after through-ghickness is unique and can be divided into three stages a, b and c. A retardation parameter has been used successfully to predict the growth of cracks in specimen, and in this time, retardation factor is 4.3. By using the crack propagation rule considering on retardation state and the K value proposed by the authors, the remarkable crack growth behavior and the change in crack shape can be evaluated quantitatively.

• Corrosion Science and Technology
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• v.20 no.4
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• pp.210-229
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• 2021

To safely operate domestic nuclear power plants approaching the end of their design life, the material degradation management strategy of the components is important. Among studies conducted to improve the soundness of nuclear reactor components, research methods for understanding the degradation of reactor internals and preparing management strategies were surveyed. Since the IGSCC (Intergranular Stress Corrosion Cracking) initiation and propagation process is associated with metal dissolution at the crack tip, crack initiation sensitivity was decreased in the hydrogenated water with decreased crack sensitivity but occurrence of small surface cracks increased. A stress of 50 to 55% of the yield strength of the irradiated materials was required to cause IASCC (Irradiation Assisted Stress Corrosion Cracking) failure at the end of the reactor operating life. In the threshold-stress analysis, IASCC cracks were not expected to occur until the end of life at a stress of less than 62% of the investigated yield strength, and the IASCC critical dose was determined to be 4 dpa (Displacement Per Atom). The stainless steel surface oxide was composed of an internal Cr-rich spinel oxide and an external Fe and Ni-rich oxide, regardless of the dose and applied strain level.