• 한국분말재료학회지
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• 제21권2호
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• pp.114-118
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• 2014

In this study, an aluminum oxide layer for sealing treatment of nano-diamond powder was synthesized by anodizing under constant current. The produced pore size and oxide thickness were investigated using scanning electron microscopy. The pore size increased as the treatment time increased, current density increased, sulfuric acid concentration decreased, which is different from the results under constant voltage, due to a dissolution of the oxide layers. The oxide layer thickness by the anodizing increased as temperature, time, and current density increased. The results of this study can be applied to optimize the sealing treatment process of nano-diamond particles of 4-10 nm to enhance the resistances of corrosion and wear of the matrix.

• Current Photovoltaic Research
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• 제8권1호
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• pp.12-16
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• 2020

This study investigates the degradation characteristics of different material types of ethyl vinyl acetate (EVA) and polyolefin (POE) with combining transparent backsheet. To this end, we fabricated samples with structure of glass/encapsulant/transparent backsheet for each type of encapsulants, and shingled Si modules with the same structure. The samples were then subjected to accelerated test by storing under damp heat condition of 85℃ and 85% RH. As a result, encaplsulant discoloration was observed, which the transmittance of the samples with EVA decreased in a rapid rate than the samples with POE. The discoloration also affected a power degradation of the shingled modules with a reduction of current density, resulting that the module with EVA showed more drop on the efficiency than the modules with POE. Furthermore, corrosion of the soldered ribbon caused by acetic acid produced from the degraded EVA also contributed in fill factor reduction.

• Tribology and Lubricants
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• 제29권6호
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• pp.392-396
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• 2013

Biodiesel fuels contain unsaturated fatty acid ester, which can easily oxidize, especially when exposed to ultraviolet light. The products formed by this oxidation give rise to sediment or gum formation. As a result, the fuel can contribute to the corrosion and plugging of the filter pump. Antioxidants have been used in an effort to stabilize biodiesels, but there is still a need for a biodiesel composition with improved oxidation stability. In general, good fuel compositions should provide synergistic combinations of a biodiesel and antioxidants. Our work involved the synthesis of antioxidants to improve the oxidative stability of biodiesel fuel.

• 한국정밀공학회지
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• 제23권4호
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• pp.146-152
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• 2006

In micro electrochemical machining (ECM), electrodes should be prevented from unfavorable oxide and Passive layer formation on the machined surface or overall corrosion of the entire surface. Generally, metal electrodes corrode, passivate or dissolve in the electrochemical cell according to the electrode potential. Therefore, each electrode must maintain its stable potential. Tn this paper, the stable electrode potentials of tool and workpiece were determined using the potentiodynamic polarization test and verified experimentally considering machining stability and surface quality. Stable workpiece electrode potentials of two different passive materials of 304 stainless steel and nickel were determined in the 0.1 M sulfuric acid. Experimental results show good machined surface and fast machining rate using the determined electrode potentials.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.197-203
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• 1999

Stainless steels in general has passive film having strong corrosion resistance on surface. Therefore it must be necessarily removed by etching in mixing solution of sulfuric and chloric acid before Nitriding treatment. But in the ion nitriding, nitride layer was easily formed because passive film was removed without difficult by sputtering effect. The removal extent of these passive films was greatly effected by gas mixing ratios and pressure and holding times of pre sputtering factors in pre sputtering stage. As a results of experiment it has been known that pre sputtering pressure and holding time was not nearly effective on the formation behavior of nitride layer. But when A/H2 gas mixing ratios was 1/2 (vol%) was the most effective of the all pre sputtering conditions. It was resulted from the combination of mechanical reaction byArgon bombardment and chemical reaction by reduction of hydrogen on the passive film.

• 한국표면공학회지
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• 제21권4호
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• pp.176-182
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• 1988

Effects of Cr, Ni and W on the anodic polarization behavior were investigated for Fe-Cr-Ni-W alloys in deaerated 1N HCI solution. Surface films formed on the polarization were analysed using AES, SEM and EDAX. A higerconcentration of tungten was found in the surface oxide film compared to the matrix. It played an importanet role on incresing the stability of the passive film. The presence of an adequate amount of Cr was essential to increase the pitting resistance of the alloys in acid chloride media. Under 12 wt%cr,alloys containing 6wt%W did not exhidit any passivity at all. The main role of Ni was to control the microstructure rather than to modify the corrosion resistance. In 23 cr-14Ni-^W alloy, the duplex microstructure of ferrite($\delta$-phase) in an austenic matrix was developed. The reson why proferred pitting appeared in austenite and ferrite/austenite interface was that ferrite had more amount of Cr and W than austenite.

• 한국안전학회지
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• 제19권3호
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• pp.40-44
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• 2004

To the removal of hardness materials, we've test the absorptive capacity of main material $Mg^{2+},\;Ca^{2+}$ on the using the activated carbon powder saturated in 0.1M Nitrilotriacetic acid by experimental methods. The absorptive properties of $Ca^{2+}\;and\;Mg^{2+}$ were measured with absorbent quantity and contact time., and investigated the physical properties of overall rate constant and adsorption constant adsorption isotherm, and Langmuir and Freundlich constant. In case of k' adsorption rate constants of $Ca^{2+},\;Mg^{2+}$, was 0.00299, 0.00529 by Bhattahary and Venkobachar equation. $k_{aa}$ was 0.00373, 0.00640 according with adsorption rate constants of Lagergren.

• 한국표면공학회지
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• 제43권1호
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• pp.12-16
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• 2010

The morphology of the passivated surface of stainless steel (SS) was quantitatively characterized based on fractal geometry. In particular, the surface irregularities of the passivated 304 and 439 SSs were comparatively analyzed in terms of their self-similar fractal dimensions. The passivated surface of 439 SS in an acid-based electrolyte proved to have a higher fractal dimension, as compared to that of 304 SS, esp. at a scale of several tens of nanometers, strongly indicating the higher irregularity of the passivated surface. It is anticipated that the fractal approach suggested herein might be effectively utilized to analyze the irregularity of the steel surface and/or the compactness of the oxide film.

• Nuclear Engineering and Technology
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• 제50권3호
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• pp.411-415
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• 2018

Nuclear fusion may be among the strongest sustainable ways to replace fossil fuels because it does not contribute to acid rain or global warming. In this context, activated cobalt materials in corrosion products for fusion energy are significant in determination of dose levels during maintenance after a coolant leak in a nuclear fusion reactor. Therefore, cross-section studies on cobalt material are very important for fusion reactor design. In this article, the excitation functions of some nuclear reaction channels induced by proton particles on $^{59}Co$ structural material were predicted using different models. The nuclear level densities were calculated using different choices of available level density models in ALICE/ASH code. Finally, the newly calculated cross sections for the investigated nuclear reactions are compared with the experimental values and TENDL data based on TALYS nuclear code.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1541-1558
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• 2023

The new Modified-690Gd alloy, namely as Ni-30Cr-(10-x) Fe-xGd (x = 0.5, 1.0, 1.5,2.0, 3.0 wt%) for function structure integrated thermal neutron shielding has been prepared and characterized. The Modified-690Gd alloy was mainly composed of γ austenite matrix and (Ni, Cr, Fe)₅Gd precipitated along grain boundaries. The new Modified-690Gd alloy had great mechanical properties, which had the tensile strength exceeding 620 MPa and the elongation being above 50%. Meanwhile, this alloy had excellent weldability and good corrosion resistance in boric acid. The new Modified-690Gd alloy is expected to be a kind of high efficiency thermal neutron shielding materials.