• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.236-240
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• 2007

In order to control the microstructure of amorphous/crystalline composites, gas atomized $Cu_{54}Ni_{6}Zr_{22}Ti_{18}$ metallic glass powders wrapped in a crystalline brass were extruded repeatedly. The size of microstructure in the resultant composites was varied depending on the pass of extrusion as well as on the area reduction ratio. The microstructure could be estimated using an equation of $r_n=r_{n-1}/R^{1/2}$, where R is reduction ratio and $r_n$ is the resultant radius of the extruded bar after n pass. Theory of microstructural refinement as well as the relationship between the resultant microstructures and mechanical properties was discussed.

• 소성∙가공
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• 제16권5호통권95호
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• pp.386-390
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• 2007

In order to, simultaneously, synthesize and control the size of microstructure of amorphous/crystalline composites, a repeated extrusion process was performed using the gas atomized $Cu_{54}Ni_6Zr_{22}Ti_{18}$ metallic glass powders and the crystalline brasses. The size of microstructure in the resultant composites was varied depending on the pass of extrusion as well as on the area reduction ratio. The microstructure could be estimated using an equation of $r_n=r_{n-1}/R^{1/2}$, where R is reduction ratio and $r_n$ is the resultant radius of the extruded bar after n pass. Theory of microstructural refinement as well as the relationship between the resultant microstructures and mechanical properties was discussed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.142-142
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• 2007

• 한국식품영양과학회지
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• 제25권3호
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• pp.470-477
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• 1996

This study was intended to observe the changes of pectic substances and enzyme activities, texture, microstructure of anchovy added kimchi during fermentation for 4 weeks at 4$^{\circ}C$. Content of alcohol insoluble solid(AIS) and HCl soluble pectin(HClSP) were decreased, whereas content of hot water soluble pectin(HWSP) was increased during fermentation. Content of HClSP was higher and HWSP was lower in anchovy added kimchi than control. Activity of pectinesterase(PE) was decreased, whereas activity of polygalacturonase(PG) was increased during fermentation. In anchovy added kimchi, PG activity was lower than control. Changes in microstructure of Chinese cabbage and kimchi during fermentation was lower than control. Changes in microstructure of Chinese cabbage and kimchi during fermentation was observed ; in the raw cabbage, parenchyma cells, intercellular space and middle lamella were clearly shown. But in salted cabbage, middle lamella became separated. In the late stage of fermentation, parenchyma cell walls were wrinkled and collapsed. Puncture forces of kimchi were decreased, whereas cutting forces of kimchi were increased as fermentation proceeded. The firmness was slightly higher in anchovy added kimchi than control at the late stage fermentation, which may be explained by the PG activity.

• 한국세라믹학회지
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• 제42권8호
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• pp.542-547
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• 2005

Keys to the attainment of tailored properties in SiC ceramics are microstructure control and judicious selection of the sintering additives. In this study, three different strategies for controlling microstructure of liquid-phase-sintered SiC ceramics (LPS-SiC) have been suggested: control of the initial $\alpha-SiC$ content in the starting powder, a seeding technique, and a post-sintering heat treatment. The strategies suggested offer substantial flexibility for producing toughened SiC ceramics whereby grain size, grain size distribution, and aspect ratio can be effectively controlled. The present results suggest that the proposed strategies are suitable for the manufacture of toughened SiC ceramics with improved toughness.

• Korean Membrane Journal
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• 제7권1호
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• pp.42-50
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• 2005

Among ceramic membranes developed to date, amorphous silica membranes are attractive for gas separation at elevated temperatures. Most of the silica membranes can be formed on a porous support by sol-gel or chemical vapor deposition (CVD) process. To improve gas permselectivity of the membrane, well-controlled pores having desired size and chemical affinity between permeates and membrane become important factors in the preparation of membranes. In this article, we review the literature and introduce our technologies on the microstructure to be solved and pore size control of silica membranes using sol-gel and CVD methods.

• 소성∙가공
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• 제18권6호
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• pp.458-464
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• 2009

Thermal energy control is a important factor to control properties of large sized product in ingot-forging. Good control of thermal energy helps to increase characteristics and eliminate defects of large cast-forged part, such as large sized forged shell. We have studied about not only large size ring forging process and after heat treatment process by FEM simulation. Changes of temperature and microstructure for forged shell were predicted according to different heat treatment conditions. Therefore, we can choose the proper heat treatment condition by FEA. The sectional properties confirmed by practical experiment and evaluation have presented possibilities of process design by computational analysis.

• Archives of Metallurgy and Materials
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• 제64권3호
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• pp.949-952
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• 2019

The effects of different types of process control agents (PCA) on the microstructure evolution of Ni-based oxide dispersion-strengthened superalloy have been investigated. Alloy synthesis was performed on elemental powders having a nominal composition of Ni-15Cr-4.5Al-4W-2.5Ti-2Mo-2Ta-0.15Zr-1.1Y₂O₃ in wt % using high energy ball milling for 5 h. The prepared powders are consolidated by spark plasma sintering at 1000℃. Results indicated that the powder ball-milled with ethanol as PCA showed large particle size, low carbon content and homogeneous distribution of elemental powders compared with the powder by stearic acid. The sintered alloy prepared by ethanol as PCA exhibited a homogeneous microstructure with fine precipitates at the grain boundaries. The microstructural characteristics have been discussed on the basis of function of the PCA.

• 한국분말재료학회지
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• 제22권1호
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• pp.21-26
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• 2015

In this study, the control of microstructure for increasing surface roughness of Al with an electro-chemical reaction and a post treatment is systematically investigated. The Al specimen is electro-chemically treated in an electrolyte. In condition of the post treatment at $100^{\circ}C$ for 10 min, a change of the surface microstructure occur at 50V (5 min), and a oxidized layer is at 400V, to which lead a decreasing surface roughness. The minimum temperature of the post treatment for a change of microstructure is $80^{\circ}C$. Moreover, in the condition of 300V (5 min), the electro-chemical reaction is followed by the post treatment at $100^{\circ}C$, the critical enduring time for the change of microstructure is 3 min. The longer post treatment time leads to the rougher surface. The treated Al specimen demonstrate better heat release ability owing to the higher surface roughness than the non-treated Al.

• 한국세라믹학회지
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• 제34권12호
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• pp.1240-1246
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• 1997

Silicon carbides with self-reinforced microstructure which hore a small grain matrix and dispersed large grains with rod-like type were prepared by the liquid-phase sintering and the control of starting phases of raw materials. The specimens with self-reinforced microstructure could be obtained from the compacts with mixed compositions of $\alpha$-SiC and 10-50 % $\beta$-SiC powders and by the pressureless sintering at 185$0^{\circ}C$ for 5h. Large grains with rod or plate-like types were 4H-SiC and small grains with equi-axed type were 6H-SiC. Fracture grains with rod or plate-like types were 4h-SiC and small grains with equi-axed type were 6H-SiC. Fracture toughness of specimens with self-reinforced microstructure was increased by the crack deflection and formation of microcracking due to the existence of rod-like large grains during crack propagation.