• 연구논문집
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• s.29
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• pp.141-149
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• 1999

Brazing of Fe-Cr-Al alloy was carried out at $1200^{\circ}C$ in vacuum furnace using nickel-based filler metals : BNi-5 powder(Ni-Cr-Si-Fe base alloy} and MBF-50 foil (Ni-Cr-Si-B). The effect of boron content on the stability of oxide scale on the brazed joint was investigated by means of cyclic oxidation test performed at $1050^{\circ}C$ and $1200^{\circ}C$. Apparently, the joints brazed with MBF-50 containing boron showed relatively stable oxidation rates compared to boron-free BNi-5 at both temperatures. However, it was considered that the slower weight loss of MBF-50 brazed specimen wasn’t resulted from the low oxidation rate but from the spallation of oxide layer. The oxide layer consisted of thick spinel oxide on the surface and $Al_2 O_3$ internal oxide layer along the interface between mother alloy and braze, the mother alloy was also eroded seriously by the formation of spinel oxides such as $FeCr_2 O_4$ and $NiCr_2 O_4$ on the surface, likely to be induced by the change of oxide forming mechanism due to diffusion of boron from the braze. On the contrary, the joint brazed with BNi-5 showed the good oxidation resistance during the cyclic oxidation test. It seems that the oxidation can be retarded by the formation of stable $Al_2 O_3$ layer at the surface.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.4
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• pp.43-49
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• 2003

This research work has been carried out for finding J-integral in mode II of CFRP(carbon fiber reinforced plastics) laminate plates based on the classical bar theory in dynamic conditions with consideration of the effect of inertia forces, eventually to lead to finding the dynamic inter-layer fracture toughness. Dynamic inter-layer fracture toughness was found by a self-made ENF(End Notched Flexure) experimental apparatus using Split Hopkinson's Bar(SHPB), and also observed the variation of the fracture toughness haying different resin contents and fiber arrangements of CFRP specimen([$0_3^{\circ}/90_3^{\circ}/0_6^{\circ}/90_3^{\circ}/0_3^{\circ}$], [$0_{20}^{\circ}$], [$0_5^{\circ}/90_{10}^{\circ}/0_5^{\circ}$]). As an experimental result, in either cases of quasi-static or dynamic load condition, the critical load and the inter-layer fracture toughness increased sharply depending on the increase of resin contents. Therefore, it could, be concluded that the effect by resin contents is the major factor determining the inter-layer fracture toughness in the CFRP laminate plates.

• Ocean Science Journal
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• v.42 no.3
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• pp.165-170
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• 2007

The structure of the nematodes communities has been studied in the sediments on two sites located outside and under the layer of Ahnfeltia tobuchiensis (Kanno and Matsubara 1932; Makijenko 1970). Bottom sediments at the stations were represented by sands with a different degree of silting. Specific structure of nematodes at the stations was significantly different under the similar environmental conditions (water depth, dissolved oxygen saturation, salinity, temperature of the bottom layer and organic carbon content inside of the sediment). Nematodes dominated (75.7 %) in meiobenthos community under the layer of A. tobuchiensis where concentration of silt particles was 12 %. Representatives of the family Comesomatidae were dominant. Low index of species diversity and high Simpson domination index were detected in this community. Under a layer of A. tobuchiensis with the thickness of 30 cm concentration of the silt particles was 5.39 %; nematodes density was low and made 32.1 % of the general density of meiobenthos. Species of the families Xyalidae and Monoposthiidae were dominant. Outside of A. tobuchiensis, field percentage of silt particles was minimal (3.1 %) and representatives of families Cyatholaimidae and Axonolaimidae dominated. The specific structure of nematodes in this type of the ground is characterized by high index of species diversity and low level of domination.

• Korean journal of food and cookery science
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• v.26 no.6
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• pp.860-865
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• 2010

This study was conducted to evaluate the baking characteristics of yellow layer cake containing chlorella powder. Chlorella at concentrations of 0, 4, 8, 12, and 16%(w/w) wheat powder were added, after which we evaluated the baking characteristics, physical properties, and sensory properties of the resulting cakes. Regarding the weight and volume of the cakes, the treatment groups were similar. However, control showed a high hardness value while 16% chlorella added cake showed a significantly low value. The 4% and 8% chlorella added groups maintained their structural condition while the 12% and 16% chlorella added groups were softer depending on the protein content of the flour, Lightness(L value) and yellowness(b value) of the cake crumbs became lower depending on the concentration of chlorella, whereas redness(a value) decreased. In the sensory test, the acceptability scores of the 12% and 16% chlorella added groups were lower compared to control while the 4% and 8% chlorella added groups had higher scores. Therefore, chlorella powder added yellow layer cake exhibited more functionality as well as higher quality.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.218-223
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• 2012

Fe-(8.5, 18.5, 28.3, 36.9) wt% Cr alloys were corroded between 600 and $800^{\circ}C$ for up to 70 h in a 1 atm gas mixture that consisted of 0.0242 atm of $H_2S$, 0.031 atm of water vapor, and 0.9448 atm of nitrogen gas. Their corrosion resistance increased with an increment in the Cr content. The Fe-8.5%Cr alloy corroded fast, forming thick, fragile, nonadherent scales that consisted primarily of an outer FeS layer and an inner (Fe, Cr, O, S)-mixed layer. The outer FeS layer grew into the air by the outward diffusion of $Fe^{2+}$ ions, whereas the inner mixed layer grew by the inward diffusion of oxygen and sulfur ions. At the interface of the outer and inner scales, voids developed and cracking occurred. The Fe-(18.5, 28.3, 36.9)% Cr alloys displayed much better corrosion resistance than the Fe-8.5Cr alloy, because thin $Cr_2O_3$ or $Cr_2S_3$ scales formed.

• Journal of Korea Foundry Society
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• v.40 no.6
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• pp.135-145
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• 2020

Aluminum cast iron has excellent oxidation resistance, sulfurization resistance, and corrosion resistance. However, the ductility at room temperature is insufficient, and at temperatures above 600?, the strength drops sharply and practicality is limited. In the case of heat-resistant cast iron, high-temperature materials containing Cr and Ni account for 30 to 50% or more. However, these high-temperature materials are expensive. Aluminum heat-resistant cast iron is considered as a substitute for expensive heat-resistant materials. Oxidation due to the aging temperature and holding time conditions increases more in 0 wt.% Al-cast iron than in 2 and 4 wt.% Al-cast iron according to oxidized weight and gravimetric oxide layer thickness measurements. As a result of observing the cross-section of the oxide layer, it was found to contain 0 wt.% of Al-cast iron silicon oxide-containing SiO₂ or Fe₂SiO₄ oxide film. In cast iron containing aluminum, the thickness of the internal oxide layer due to aluminum increases as the aging temperature and retention time increase, and the amount of the iron oxide layer generated on the surface decreases.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.660-665
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• 2020

Silicon heterojunction solar cells can achieve high conversion efficiency with a simple structure. In this study, we investigate the passivation characteristics of VOx thin films as a hole-selective contact layer using ALD (atomic layer deposition). Passivation characteristics improve with iVoc (implied open-circuit voltage) of 662 mV and minority carrier lifetime of 73.9 µs after post-deposition annealing (PDA) at 100 ℃. The improved values are mainly attributed to a decrease in carbon during the VOx thin film process after PDA. However, once it is annealed at temperatures above 250 ℃ the properties are rapidly degraded. X-ray photoelectron spectroscopy is used to analyze the chemical states of the VOx thin film. As the annealing temperature increases, it shows more formation of SiOx at the interface increases. The ratio of V5+ to V4+, which is the oxidation states of vanadium oxide thin films, are 6:4 for both as-deposition and annealing at 100 ℃, and 5:5 for annealing at 300 ℃. The lower the carbon content of the ALD VOx film and the higher the V5+ ratio, the better the passivation characteristics.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.69-69
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• 2001

We report a study of the nitriding of the martensitic grade of stainless steel AKSK 420 in a low-pressure rl discharge using pure nitrogen. Much studied samples of the austenitic grade AISI 304 were treated at the same time to provide a comparison. With a treatment time of 4.0 h at $400^{\circ}C$, the nitrogen-rich layer on MSK 420 is 20pm thick and has a hardness about 4.3 times higher than that of the untreated material. The layer thickness is much greater than that obtained on AISI 304 under identical treatment conditions, reflecting the different Cr content of the two alloys. The alloy AlISI 420 is more susceptible than AISI 304 to the formation of CrN and ferrite, and this has a deleterious effect on the hardnes, gain. Below the temperature at which CrN forms, the treated layer retains its martensitic structure, but with a larger lattice parameter than the bulk, a phase that we term expanded martensite, by analogy with the situation with austenitic stainless steel. The fact that the treated layer retains a martensitic structure is interesting in view of previous evidence that nitrogen is an austenite stabilizer.

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.12
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• pp.1903-1907
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• 2010

Drying curves for raw Alaska pollack seemed to follow typical food dehydration process with a very short initial settling down period. It was evident that there are some differences in drying rates between each part of fish body showing the highest drying rate for fish head followed by that for fish skin and that for flesh, presumably because of differences in water holding capacity of the components of each part. Specifically, the drying curve of fish flesh revealed that a boundary layer, thereby, a time period, existed which showed a big difference in moisture content and/or water activity as drying proceeds. The boundary layer in fish flesh with high moisture content between the layer contributes to reduce drying rate mainly as a consequence of protein aggregation resulting in hardening of fish flesh. The first boundary layer in this work appeared to show within several hours after initiation of drying. For Hwangtae, a naturally cyclic freeze-thaw dried and aged Alaska pollack which was popular in Korea, manufacturing process, it is clear that periodic moistening of boundary layer in fish flesh prohibits hardening fish flesh in boundary layer and enables steady moisture diffusion from inside of the fish flesh to surface of the fish body.

• Journal of the Korean Society of Food Culture
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• v.8 no.3
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• pp.249-255
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• 1993

To minimize the waste amount of surface layer kochujang during aging, the effects of the three finishing methods(nothing, salt scatering and Polyethylene film on the kochujang surface) and sunning(conventional aging method) or nonsunning aging(cap covering) on water content, redness and spreadability, film forming yeast occurance and salinity of surface layer kochujang during 120 days aging were investigated. In the case of sunning aging, film forming yeast was not visually found on the surface. The surface layer kochujang was so low spreadability(zero) and very high salinity(18-30%) that could not eat. However, the aging method after PE-film covering on the kochujang surface, and then cap covering(nonsunning) was very effective in keeping of soundness of surface layer kochujang without film forming yeast growth on the surface kochujang, especially was greatly effective in keeping of redness, moderate moisture content and spreadability. The PE-film and cap covering aging were effective in prevention of water evaporation and $CO_2$ release, and in accumulation of ethanol and organic acids between the PE-film and surface layer of kochujang.