• 연구논문집
• /
• 통권29호
• /
• pp.141-149
• /
• 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.

• 한국공작기계학회논문집
• /
• 제12권4호
• /
• pp.43-49
• /
• 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
• /
• 제42권3호
• /
• pp.165-170
• /
• 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.

• 한국식품조리과학회지
• /
• 제26권6호
• /
• pp.860-865
• /
• 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.

• 대한금속재료학회지
• /
• 제50권3호
• /
• pp.218-223
• /
• 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.

• 한국주조공학회지
• /
• 제40권6호
• /
• pp.135-145
• /
• 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.

• 한국재료학회지
• /
• 제30권12호
• /
• pp.660-665
• /
• 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.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2001년도 추계학술발표회 초록집
• /
• pp.69-69
• /
• 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.

• 한국식품영양과학회지
• /
• 제39권12호
• /
• pp.1903-1907
• /
• 2010

명태의 건조경향은 초기의 평형상태가 뚜렷하지 않은 과정을 제외하면, 일반적인 식품건조형태를 따르는 것으로 보인다. 따라서 시간이 지날수록 건조속도는 어육과 외기의 수분농도차이가 줄어듦에 따른 결과뿐만 아니라, 표면 건조에 의한 고화현상에 의해 수분이동이 억제됨에 따라 느려지게 된다. 명태의 부위별 건조속도는 잘 알려진 바와 같이 머리 부분이 몸통부분보다 빨랐다. 건조가 진행될수록 어육표면과 중심부의 수분함량과 그에 따른 수분활성도의 차이는 증가함으로써 어육내부의 수분이동이 잘 일어나지 않아 전체적인 건조속도의 저하를 나타내었다. 주어진 외기의 건조조건(온도, 습도, 풍속)에서 초기의 높은 건조속도에 의한 어육 표면응고로 인해 건조개시 수 시간 이내에 어피(피부)와 어피 바로밑부분의 어육과 어체 내부 어육의 수분함량 차이가 급격히 일어나는 것을 알 수 있었다. 황태 제조과정의 전단계인 건조과정에서 건조가 시작된 뒤 주기적으로 수분활성도의 차이가 급격히 일어나는 시간(지점)은 황태 특유의 조직감을 형성하기 위해 건조과정에서 조직의 고화를 방지함으로써 일정한 건조속도를 유지하기 위해 주기적으로 수분을 공급해 주어야 하는 시점임을 제시해 준다.

• 한국식생활문화학회지
• /
• 제8권3호
• /
• pp.249-255
• /
• 1993

고추장을 직립성 용기에 담아 숙성보관시 곱이 발생하는 것을 방지하기 위하여 햇빛을 쪼여 표면을 관리하는 것이 일반적이나 이 경우 표면층 고추장이 건조되고, 적색이 흑변되고, 유동성이 상실되며, 과염도 및 이물질 오염 등으로 인하여 많은 양이 비가식화되는 문제가 있어 왔다. 숙성 보관중 표층 고추장의 악변에 의한 손실을 최소화할 수 있는 숙성 조건을 조사하기 위하여 표면을 3가지 방법(무처리, 소금뿌림, PE-film덮기)으로 처리한 후 각각 햇빛을 쪼이면서 숙성한 경우(A, B, C)와 A, B, C와 같이 처리한 후 뚜껑을 덮어 숙성(A', B', C')시키면서 15일 간격으로 수분, 염도, pH, 점도, 퍼짐성(찍음성), 색도, 곱의 발생유무를 조사 비교하였다. 2일에 1회 햇빛을 쪼이면서 120일간 숙성시킨 경우(A, B, C)곱은 발생되지 않았으나 수분함량 감소$(59%{\rightarrow}21-29%)$, 적색도 감소 내지는 흑색화$(21{\rightarrow}0-1)$, 퍼짐성 감소, 굳기 증가$(20{\;}g{\rightarrow}380{\;}g)$ 및 과염도화$(8-18%{\rightarrow}18-30%)$ 등으로 많은 양이 비가식화되는 문제가 발생하였다. 반면 뚜껑을 덮어 숙성시킨 경우 적색도, 염도, 퍼짐성, 굳기는 양호하게 유지되었으나 PE-film을 사용한 경우를 제외하고 곱이 많이 발생되어 PE-film을 덮어 숙성시키는 것이 고추장 표면을 건전하게 관리하는데 효과적인 방법으로 확인되었다.