• Transactions of the Korean hydrogen and new energy society
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• v.5 no.2
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• pp.81-90
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• 1994

The hydrogen fuel tanks having hydrogen storing capacity of about 300g and 1200g are manufactured using $MmNi_{4.7}Al_{0.25}V_{0.05}Fe_{0.001}$ alloy. They are composed of several unit reactor made of Cu-tube(outer diameter = 50.1mm, thickness = 2mm). In order to increase the heat and mass transfer property of the hydride bed, Al-plates are inserted perpendicular to axial direction at intervals of 5mm and three arteries of diameter 8mm are installed symmetrically in each unit reactor. Hydrogen absorption is proceeded about 80% within 30 minute and is completed within 60 minute at the conditions of charging hydrogen pressure of 25atm and temperature of $22^{\circ}C$. On desorbing hydrogen at a constant rate of 30 slm at $20^{\circ}C$, discharging hydrogen pressure is sustained at 3~5atm for 120 minutes. The discharging pressure is increased upto 5~8atm as the increase of the reactor temperature to $30^{\circ}C$. From the experimental results and the brief discussions about the hydrogen absorption and disorption behaviors of the hydrogen storage tank, it is suggested that the behaviors of hydrogen charging and discharging could be controlled by adjusting the operating parameters and the reactor design parameters.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.83-88
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• 2010

The composite electroplating is accomplished by adding inert materials during the electroplating. Permalloy is the term for Ni-Fe alloy and it is used for industrial applications due to its high magnetic permeability. Microhardness for microdevices is enhanced after composite coating and it increases the life cycle. However, the hydroxyl group on the silica makes their surface susceptible to moisture and it causes the silica nanoparticles to be agglomerated in the aqueous solution. The agglomeration problem causes poor dispersion which eventually interrupts uniform deposition of silica nanoparticles. In this study, the dispersion of silica nanoparticles in the permalloy electroplated layer is reported with variation of additives and sonication time. Longer sonication period guaranteed better silica nanopowder dispersion and sonication period also influenced on composition of deposits. The amount of silica nanopowder codeposition and surface morphologies were influenced with variation of additives. In alkaline bath, smooth surface morphology and relatively high contents of silica nanopowder codeposition were obtained with addition of sodium lauryl sulfate.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.1
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• pp.31-40
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• 2005

High temperature - high pressure apparatus was developed to simulate nickel fewite corrosion products which were main compositions of the radioactive crud in the nuclear power plant. Corrosion product similar to the crud was obtained by a tube accumulator system. Nickel alloy (Inconel 690) and carbon steel (SA106 Gr. C) were corroded at 270 $\^{circ}C$ in the corrosion product generator. Ni ions and Fe ions dissolved by corrosion reaction were able to be transported to the accumulator because the crud generation mechanism was the solubility change with temperature. To evaluate the properties of simulated corrosion products, scanning electron microscope (SEM) observation and EDAX analysis were performed. SEM observation of corrosion product showed the needlelike or crystal structure of oxide depending on precipitating location. The crystal oxide was the nickel ferrite, which was similar to the crud in nuclear power plants.

• Journal of Powder Materials
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• v.22 no.3
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• pp.197-202
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• 2015

In this study, porous stainless steel (STS316L) sintered body was fabricated by powder metallurgy method and its properties such as porosity, compressive yield strength, hardness, and permeability were evaluated. 67.5Fe-17Cr- 13Ni-2.5Mo (wt%) powder was produced by a water atomization. The atomized powder was classified into size with under $45{\mu}m$ and over $180{\mu}m$, and then they were compacted with various pressures and sintered at $1210^{\circ}C$ for 1 h in a vacuum atmosphere. The porosities of sintered bodies could be obtained in range of 20~53% by controlling the compaction pressure. Compressive yield strength and hardness were achieved up to 268 MPa and 94 Shore D, respectively. Air permeability was obtained up to $79l/min{\cdot}cm^2$. As a result, mechanical properties and air permeability of the optimized porous body having a porosity of 25~40% were very superior to that of Al alloy.

• Korean Journal of Materials Research
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• v.15 no.3
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• pp.155-160
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• 2005

The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which results in a chemically aggressive environment that is very corrosive fir typical structural materials. So, it is essential to choose the optimum material f3r the process equipment handling molten salt. In this study, the corrosion behavior of Al-Y coated Haynes 263 in a molten salt of $LiCl-Li_2O$ under oxidation atmosphere was investigated at $650^{\circ}C$ for $72\~168$ hours. The corrosion rate of Al-Y coated Haynes 263 was low while that of bare Haynes 263 was high in a molten salt of $LiCl-Li_2O$. Al-Y coated Haynes 263 improved the corrosion resistance better than bare Haynes 263 alloy. An Al oxide layer acts as a protective film which Prohibits Penetration of oxygen. Corrosion Products were formed $Li(Ni,Co)O_2$ and $LiTiO_2$ on bare Haynes 263, but $LiAlO_2,\;Li_5Fe_5O_8\;and\;LiTiO_2$ on Al-Y coated Haynes 263.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.419-428
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• 2020

The kinetics of direct methanation over activated charcoal-supported molybdenum catalyst at 30 bar was studied in a cylindrical fixed-bed reactor. When the temperature was not higher than 400℃, the CO conversion increased with increasing temperature according to the Arrhenius law of reaction kinetics. While XRD and Raman analysis showed that Mo was present as Mo oxides after reduction or methanation, TEM and XPS analysis showed that Mo₂C was formed after methanation depending on the loading of Mo precursor. When the temperature was as high as 500℃, the CO conversion was dependent not only on the Arrhenius law but also on the catalyzed reaction by nanoparticles, which came off from the reactor and thermocouple by metal dusting. These nanoparticles were made of Ni, Fe, Cr and alloy, and attributed to the formation of carbon deposit on the wall of the reactor and on the surface of the thermocouple. The carbon deposit consisted of amorphous and disordered carbon filaments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.342-349
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• 2009

This study investigated the growth characteristics of carbon nanotubes (CNTs) by changing a period of annealing time and a $C_{2}H_{2}/H_2$ flow ratio at temperature as low as $450^{\circ}C$ with inductively coupled plasma chemical vapor deposition. The 1-nm-thick Fe-Ni-Co alloy thin film served as a catalyst layer for the growth of CNTs, which was thermally evaporated on the 15-nm-thick Al underlayer deposited on the 50-nm-thick Ti diffusion barrier. The annealing at low temperature of $450^{\circ}C$ brought about almost no granulation of the catalyst layer, and the CNT growth was not affected by a period of annealing time. A study of changing the flow rate of $C_{2}H_{2}$ and $H_2$ showed that as the ratio of the $C_{2}H_{2}$ flow rate to the $H_2$ flow rate was lowered, the CNTs were grown to be longer With further decreasing the flow ratio, the length of CNTs reached the maximum and then became shorter. Under the optimized gas flow rates, we successfully synthesized CNTs with a uniform length over a 4-inch Si wafer at $450^{\circ}C$.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.131-137
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• 2017

In order to safely protect high over current flowing into the main circuit at short-circuit without any explosion or fire, the enclosed cartridge fuse with a high interrupting capacity should be applied. But this fuse is impossible to be applied to an inner electronic circuit because of a limited space problem result from the miniaturization trend of products. Therefore, it is necessary to apply a sub-miniature fuse with a relatively small size. However the semi-enclosed fuse which is more free for an influx of air than the enclosed cartridge fuse and is possible to protect fuse elements with chemical and physical combination can be adoptable. But it has a limit of implementing the characteristic of a high breaking capacity. For these reasons, the Fe-42wt％Ni fuse elements alloy and fuse-link with less space were designed to increase a breaking capacity of sub-miniature fuse and its safety for fire and explosion was confirmed in this paper.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1083-1091
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• 1988

Vacuum brazing is the most modern brazing process and is at present, far from being completely understood. By brazing under high vacuum, in an atmosphere free of oxidizing gases, a superior product with greater strength, ductility and uniformity can be obtained. In this study, the influence of brazing parameters such as base metal characteristics, joint clearance and brazing time were described in relation to the metallurgical phenomena and shear strength of vacuum-brazed joints between carbon steels and 304 stainless steel (SUS 304) brazed by copper filler metal. In copper brazing of SUS 304 to a medium carbon steel(M.C.S) the columnar Fe-Cr-Ni-Cu-C alloy structure was formed and grew from the M.C.S side and at the same time, the surface of M.C.S. was decarbonized. The driving force for the formation and growth of columnar structure was the difference of carbon content between base metals. As the joint clearance is narrower and brazing time is longer, the formation and growth of columnar phase and decarburization of carbon steels were more noticeable. Because of decarburization of carbon steels, the shear strength of brazed joints were reduced as the formation of columnar structure was increased.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.448-459
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• 2022

Generally, steel is the most commonly used in the industry because of good strength, processability and cost-effectiveness. Steel can be surface-treated such as coating or used as an alloy by adding elements such as Cr, Ni, Zr, and Al to increase corrosion resistance. However, even if steel is used in same environment corrosion resistance is sharply lowered when it is exposed to a high temperature for a fixed or extended period of time due to an overload or other factors. In particular, the use of hot-dip aluminized plated steel, which is used in high-temperature atmospheres, is increasing due to the surface Al₂O₃ oxide film. This steel necessitates an urgent solution as issues of corrosion resistance limitations often appear. It is an important issue that not only cause analysis but also the research for the surface treatment method that can be solved. Thus, in this study, Cr in which it is expected to be effective in corrosion resistance and heat resistance attempted to deposit on hot dip aluminized plated steel with PVD sputtering. And it was possible to present the surface treatment application of various types of industrial equipment exposed to high temperature and basic design guidelines for use by confirming the corrosion resistance of hot dip Al-Si plated steel with Cr film deposited at high temperature.