• Journal of the Korean Society for Heat Treatment
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• v.35 no.4
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• pp.203-210
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• 2022

In this study, hydrogen embrittlement in Inconel 718 fabricated by selective laser melting (SLM) was investigated. To focus on the effect of the SLM-induced solidification substructure, hydrogen embrittlement behavior of SLM as-built (SLM-AB) sample and that of conventionally produced (Con-S) sample were systematically compared. The detailed microstructural characterization showed that the SLM-AB sample exhibited a solidification substructure including a high density of dislocations and Laves phase, while the Con-S sample showed completely recrystallized grains without any substructure. Although the intrinsic strength in the SLM-AB sample was higher than the Con-S sample, the resistance to hydrogen embrittlement was higher in the SLM-AB sample. Nevertheless, a statistical analysis of the hydrogen-assisted cracks (HACs) revealed that the predominant HAC type of SLM-AB and Con-S samples was similar, i.e., intergranular HAC. The difference in the resistance to hydrogen embrittlement between the SLM-AB and Con-S samples were discussed in terms of the relation between the microstructural feature and its effect on hydrogen accumulation.

• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.331-343
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• 2005

Development of hydrogen station system is an important technology to commercialize fuel cells and fuel cell powered vehicles. Generally, hydrogen station consists of hydrogen production process including desulfurizer, reformer, water gas shift (WGS) reactor and pressure swing adsorption (PSA) apparatus, and post-treatment process including compressor, storage and distributer. In this review, we investigate the R&D trends and prospects of hydrogen station in domestic and foreign countries for opening the hydrogen economy society. Indeed, the reforming of fossil fuels for hydrogen production will be essential technology until the ultimate process that may be water hydrolysis using renewable energy source such as solar energy, wind force etc, will be commercialized in the future. Hence, we also review the research trends on unit technologies such as the desulfurization, reforming reaction of fossil fuels, water gas shift reaction and hydrogen separation for hydrogen station applications.

• Journal of Microbiology and Biotechnology
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• v.9 no.3
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• pp.265-270
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• 1999

A three phase fluidized bed bioreactor immobilized with Thiobacillus sp. IW was tested to remove hydrogen sulfide and methylmercaptan with high loading rate. In a single gas treatment, the bioreactor removed 92- 98％ of hydrogen sulfide with loading rate of 15- 66 g/l/h and removed 87-98％ of methylmercaptan with loading rate of 14-60 gl/sup -1/h/sup -1/. In the mixed gas treatment, the removal efficiencies of hydrogen sulfide and methylmercaptan maintained at 89-99％ for various inlet loading rates and were not affected by the inlet loading ratio of both gases in low loading rates. When the inlet concentration of methylmercaptan increased 3.8 times and was maintained for 30 h to observe the response of the bioreactor to sudden environmental change, the removal efficiency of methylmercaptan was maintained at an average of 91％.

• Corrosion Science and Technology
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• v.2 no.6
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• pp.283-288
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• 2003

The cathodic protection method is being widely used in marine structural steel, however a high tensile steel like RE 36 steel for marine structural steel is easy to get hydrogen embrittlement due to over protection during cathodic protection as well as preferential corrosion of HAZ(Heating Affected Zone) part. In this paper, corrosion resistance and mechanical properties such as elongation and hydrogen embrittlement were investigated with not only in terms of electrochemical view but also SSRT(Slow Strain Rate Test) method with applied constant cathodic potential, analysis of SEM fractography in case of both As-welded and PWHT(Post-Weld Heat Treatment) of $550^{\circ}C$. The best effect for corrosion resistance was apparently indicated at PWHT of $550^{\circ}C$ and elongation was increased with PWHT of $550^{\circ}C$ than that of As-welded condition. On the other hand. Elongation was decreased with applied potential shifting to low potential direction which may be caused by hydrogen embrittlement, however the susceptibility of hydrogen embrittlement was decreased with PWHT of $550^{\circ}C$ than that of As-welded condition and Q.C(quasi cleavage) fracture mode was also observed significantly according to increasing of susceptibility of hydrogen embrittlement. Eventually it is suggested that an optimum cathodic protection potential range not causing hydrogen embrittlernent is from -770 mV(SCE) to -850 mV(SCE) in As-welded condition while is from -770 mV(SCE) to -875 mV(SCE) in PWHT of $550^{\circ}C$.

• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.286-300
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• 2016

Pd-Ag alloy membranes have attracted a great deal of attention for their use in hydrogen purification and separation due to their high theoretical permeability, infinite selectivity and chemical compatibility with hydro-carbon containing gas streams. For commercial application, Pd-based membranes for hydrogen purification and separation need not only a high perm-selectivity but also a stable long-term durability. However, it has been difficult to fabricate thin, dense Pd-Ag alloy membranes on a porous stainless steel metal support with surface pores free and a stable diffusion barrier for preventing metallic diffusion from the porous stainless steel support. In this study, thin Pd-Ag alloy membranes were prepared by advanced Pd/Ag/Pd/Ag/Pd multi-layer sputter deposition on the modified porous stainless steel support using rough polishing/$ZrO_2$ powder filling and micro-polishing surface treatment, and following Ag up-filling heat treatment. Because the modified Pd-Ag alloy membranes using rough polishing/$ZrO_2$ powder filling method demonstrate high hydrogen permeability as well as diffusion barrier efficiency, it leads to the performance improvement in hydrogen perm-selectivity. Our membranes, therefore, are expected to be applicable to industrial fields for hydrogen purification and separation owing to enhanced functionality, durability and metal support/Pd alloy film integration.

• Toxicological Research
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• v.33 no.3
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• pp.219-224
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• 2017

Lipin1 was identified as a phosphatidate phosphatase enzyme, and it plays a key role in lipid metabolism. Since free radicals contribute to metabolic diseases in the liver, this study investigated the effects of free radicals on the regulation of Lipin1 expression in Huh7 and AML12 cells. Hydrogen peroxide induced mRNA and protein expression of Lipin1 in Huh7 cells, which was assayed by quantitative RT-PCR and immunoblotting, respectively. Induction of Lipin1 by hydrogen peroxide was confirmed in AML12 cells. Hydrogen peroxide treatment significantly increased expression of sterol regulatory element-binding protein (SREBP)-2, but not SREBP-1. Moreover, nuclear translocation of SREBP-2 was detected after hydrogen peroxide treatment. Hydrogen peroxide-induced Lipin1 or SREBP-2 expression was significantly reduced by N-acetyl-$\small{L}$-cysteine treatment, indicating that reactive oxygen species (ROS) were implicated in Lipin1 expression. Next, we investigated whether the hypoxic environments that cause endogenous ROS production in mitochondria in metabolic diseases affect the expression of Lipin1. Exposure to hypoxia also increased Lipin1 expression. In contrast, pretreatment with antioxidants attenuated hypoxia-induced Lipin1 expression. Collectively, our results show that ROS activate SREBP-2, which induces Lipin1 expression.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.164-165
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• 2007

The effect of hydrogen and oxygen plasma treatments on the structural properties of carbon nanotubes (CNTs) has been systematically investigated. The plasma treatment resulted in the removal of the amorphous carbon particles. As the plasma treatment time was longer, the CNT diameter was reduced, regardless of gas types. Especially, for the sample treated in hydrogen plasma, the catalyst metal on the tip of CNTs was eliminated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.943-947
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• 2007

The effect of hydrogen and oxygen plasma treatments on the structural properties of carbon nanotube(CNT) has been systematically investigated. As the plasma power was increased, nano particles were appeared at the surface of CNTs. At high plasma power(300 Watt), the structure of CNT was changed from nanotube type to nano particles. However, in case of hydrogen plasma treatment, there was no change in microstructure of CNT. From the Raman analysis, the crystallinity of CNT was deteriorated by the plasma treatment, regardless of gas types.

• Bulletin of the Korean Chemical Society
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• v.14 no.6
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• pp.700-704
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• 1993

The photocatalytic alanine and hydrogen production reaction were studied by using CdS as a semiconductor photocatalysts. The rate of alanine and hydrogen production depends strongly on the temperature in heat treatment of CdS powder. In particular, the rate of alanine production, which was observed using Pt/CdS(A)-(CdS from Mitsuwa), was increased about six times than that of using Pt/CdS(B)-(CdS from Furruchi) under the same heat treatment condition at 500$^{\circ}$C. And the photocatalytic activity for alanine production using bare CdS(A) or Pt/CdS(A) was almost same with increasing temperature in heat treatment in the range of 100-600$^{\circ}$C. From X-ray diffraction data and photoluminescence spectrum, we conclude that the crystal structure changes of CdS(A) or strong interaction at interface of Pt and CdS contribute to increasing the rate of alanine and hydrogen production reaction.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.6
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• pp.382-388
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• 2023

In this study, hydrogen embrittlement (HE) behavior of a SA-723 steel via controlling gaseous hydrogen pre-charging condition has been analyzed. The gaseous hydrogen charging of the SA-723 steel was performed under a constant pressure of 20 MPa of gaseous H₂ at 150℃ and 300℃ for 2 and 6h, and TDS, SSRT and Charpy tests were conducted to analyze the hydrogen embrittlement (HE) behavior of the SA-723 steel. Furthermore, prior to commencing the test, these specimens were coated with Zn to prevent hydrogen from diffusing out of a specimen during the tests. The TDS results showed that the 300℃-6h and 150℃-6h charged steels contain larger amounts of hydrogen than 300℃-2h and 150℃-2h charged steel. The SSRT and Charpy test results also showed the similar trends that the mechanical properties of the steels deteriorate as the amount of hydrogen charged in the steel increases. Therefore, this study suggests that, for SA-723 steel, the charging time parameter is more effective to charge more amount of hydrogen into SA-723 steel, rather than the charging temperature.