• 한국전자통신학회논문지
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• 제8권4호
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• pp.549-554
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• 2013

CVD를 이용하여 Cu 시편에 그래핀의 합성을 보이고, Cu 시편의 grain 크기와 방향성에 따른 그래핀의 성장거동을 보이고자 한다. 동일한 온도 및 압력 하에서도 사용하는 분위기 가스의 종류에 따라서 Cu의 확산에 영향을 주게 되고, 그래핀 합성 시 사용되는 $H_2$와 $CH_4$ 가스 분위기 하에서 Cu grain의 성장에도 영향을 미치는 것을 알 수 있었으며, 결과적으로 Cu grain의 성장이 그래핀의 합성과 성장에 직접적인 관련이 있음을 보이고자 하였다. 부식 저항성은 상온에서 동전위 분극실험를 통하여 분석하였으며, 부식속도 비교에서 그래핀 코팅된 Cu 시편의 경우가 그래핀의 화학적 안정성에 기인하여 순수 Cu 시편의 경우보다 동일한 부식 환경에서 약 10배 정도 안정적인 것으로 관찰이 되었다. 또한, grain boundary를 포함, 결함이 없는 그래핀의 균일한 성장의 가능성을 보이고, 이의 합성을 통한 공학적인 활용이 그 최종적인 목적이 될 것이다.

• 농업과학연구
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• 제42권3호
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• pp.151-158
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• 2015

This study was conducted to know the variation and relationship of rice grain quality and starch pasting properties by transplanting times. Two early maturing rice cultivars which accounted for the most area of early maturing rice cultivar in Chungnam province were used. The experiment was laid out in a split-plot design with 3 replications. The main plot consisted of three transplanting times viz. early (April 25), ordinary (May 25) and late (June 25) with sub-plots containing two cultivars. According to the transplanting times, most of rice grain quality and starch pasting properties showed significant difference and Joami showed higher grain quality than Unkwang in all transplanting times. Especially, rice grain quality was improved when transplanted late, showing high head rice and glossiness of cooked rice due to the lower mean temperature during grain filling stage. Glossiness of cooked rice was positively correlated with head rice ratio, amylose content and setback value, and negatively correlated with chalky rice ratio and protein content. The highest positive and negative correlation were observed between breakdown value and peak viscosity ($r=0.98^{**}$), and breakdown and setback ($r=-0.94^{**}$), respectively. These results provide some information for rice researchers and producers producing cultivars with an improved quality, suggesting that rice quality is highly influenced by temperature at grain filling stage, and transplanting times is crucial in improving rice quality. In addition, starch pasting properties are useful for determining rice quality because rice grain quality and starch pasting properties are dependent on each other.

• 한국작물학회지
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• 제30권1호
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• pp.39-46
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• 1985

추파 대·소맥의 조숙품종의 조기출수에 따른 개화등숙 및 수량성 변화를 구명하고자 대맥품종 조강보리, 밀양6호, 올보리, 동보리 1호 및 부농과 소맥품종 수원210호, 올밀, 조광 및 농림16호 등을 공시포장조건에서 파종기 차이와 장일처리로써 조기출수 및 출수기 차이를 유도하여 본 실험을 수행하여 얻은 결과를 요약하면 다음과 같다. 1. 파종기 및 장일처리에 의해 대·소맥에서 15일 출수기 차이가 유도되었으나, 성숙기는 불과 2∼6밖에 촉진되지 않았다. 2. 조기출수한 경우 출수∼개화 일수 및 등숙일수가 연장되었으며, 출수∼개화 일수 연장이 더 큰 것으로 나타났고, 이들 기간과 평균기온 간에는 각각 고도의 부상관이 있었다. 3. 조기출수만 것일수록 등숙초기의 엽면적은 좁았고, 엽면적유지기간(Leaf area duration)은 컸으며, 순동화율(NAR)은 낮았다. 4. 조기출수한 것에서 천립중은 증가하였으나 종실수량은 현저히 감소하였는데 이는 주로 수수 및 일수입수의 감소에 기인하는 것으로 나타났다.

• 한국재료학회지
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• 제22권6호
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• pp.280-284
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• 2012

Bismuth antimony telluride (BiSbTe) thermoelectric materials were successfully prepared by a spark plasma sintering process. Crystalline BiSbTe ingots were crushed into small pieces and then attrition milled into fine powders of about 300 nm ~ 2${\mu}m$ size under argon gas. Spark plasma sintering was applied on the BiSbTe powders at 240, 320, and $380^{\circ}C$, respectively, under a pressure of 40 MPa in vacuum. The heating rate was $50^{\circ}C$/min and the holding time at the sintering temperature was 10 min. At all sintering temperatures, high density bulk BiSbTe was successfully obtained. The XRD patterns verify that all samples were well matched with the $Bi_{0.5}Sb_{1.5}Te_{3}$. Seebeck coefficient (S), electric conductivity (${\sigma}$) and thermal conductivity (k) were evaluated in a temperature range of $25{\sim}300^{\circ}C$. The thermoelectric properties of BiSbTe were evaluated by the thermoelectric figure of merit, ZT (ZT = $S^2{\sigma}T$/k). The grain size and electric conductivity of sintered BiSbTe increased as the sintering temperature increased but the thermal conductivity was similar at all sintering temperatures. Grain growth reduced the carrier concentration, because grain growth reduced the grain boundaries, which serve as acceptors. Meanwhile, the carrier mobility was greatly increased and the electric conductivity was also improved. Consequentially, the grains grew with increasing sintering temperature and the figure of merit was improved.

• 한국작물학회지
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• 제35권3호
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• pp.195-200
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• 1990

수도주요생육시기별 고온처리(주간 : 37$\pm$2$^{\circ}C$, 야간 : 27$\pm$2$^{\circ}C$) 및 고온시 물관리방법이 생육 및 수량에 미치는 영향을 구명하여 고온장해대책을 위한 기초자료로 활용코자 본 시험을 실시하여 다음과 같은 결과를 얻었다. 1. 주요생육시기별 고온처리의 영향은 생육시기에 관계없이 공시품종 모두 무처리에 비해 지상부 건물중이 감소하고 부근량이 증가하며 식물체내 전 질소함량이 감소하고 규산함량이 증가하였다. 2. 수량 및 수량구성요소에 미치는 고온의 영향은 수당발화수는 감수분열기에, 임실비율 및 등숙율은 출수기에 그리고 천립중은 등숙기에 가장 저하되었으며 고온에 의한 수량감소정도는 출수기에 가장 컸으며 그 다음은 등숙기 >감수분열기 >유수형성기 >최고분염기 >분염기 순이었다. 3. 물관리방법에 따른 답면수온의 변화는 상시담수는 최적수온 보다 주간 1.1$^{\circ}C$, 야간 3.7$^{\circ}C$ 높았으며 흘러대기 물관리방법에 의하여 최적수온(주간 : 31$^{\circ}C$, 야간 : 21$^{\circ}C$)으로의 조절이 가능하였으며 이에따라 초장이 단축되고 건물중 및 신근발생율이 증가하였다. 4. 주간흘러대기 야간담수 및 화야간흘러대기 물관리 방법은 상시담수구보다 수당발화수, 등숙율 및 천립중 등의 수량구성형질의 향상을 도모하여 4-8%의 증수효과가 있었다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.217-221
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• 2002

In the coarse grain HAZ adjacent to the fusion line, most of the TiN particles in conventional Ti added steel are dissolved and austenite grain growth is easily occupied during welding process. To avoid this difficulty, thermal stability of TiN particle is improved by increasing the nitrogen content in steel. In this study, the effect of high nitrogen TiN particle on preventing austenite grain growth in HAZ was investigated. Increased thermal stability of TiN particle is helpful for preventing the austenite grain growth by pinning effect. High nitrogen TiN particle in simulated HAZ were not dissolved even at high temperature such as 1400 C and prevented the austenite grain growth in simulated HAZ. Owing to small austenite grain size in HAZ the width of coarse grain HAZ in high nitrogen TiN steel was decreased to 1/10 of conventional TiN steel. Even high heat input welding, the microstructure of coarse grain HAZ consisted of fine polygonal ferrite and pearlite and toughness of coarse grain HAZ was significantly improved.

• 한국재료학회지
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• 제25권9호
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• pp.497-502
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• 2015

The hardenability of boron steel specimens with different molybdenum and chromium contents was investigated using dilatometry and microstructural observations, and then was quantitatively measured at a critical cooling rate corresponding to 90 % martensite hardness obtained from a hardness distribution plotted as a function of cooling rate. Based on the results, the effect of an austenitizing temperature on the hardenability and tensile properties was discussed in terms of segregation and precipitation behavior of boron atoms at austenite grain boundaries. The molybdenum addition completely suppressed the formation of pro-eutectoid ferrite even at the slowest cooling rate of $0.2^{\circ}C/s$, while the chromium addition did at the cooling rates above $3^{\circ}C/s$. On the other hand, the hardenability of the molybdenum-added boron steel specimens decreased with an increasing austenitizing temperature. This is associated with the preferred precipitation of boron atoms since a considerable number of boron atoms could be concentrated along austenite grain boundaries by a non-equilibrium segregation mechanism. The secondary ion mass spectroscopy results showed that boron atoms were mostly segregated at austenite grain boundaries without noticeable precipitation at higher austenitization temperatures, while they formed as precipitates at lower austenitization temperatures, particularly in the molybdenum-added boron steel specimens.

• 열처리공학회지
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• 제3권4호
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• pp.23-40
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• 1990

This study has been carried out to investigate into some effects of Mn content with varying amounts and austenite grain size on hardenability in boron-added Fe-C-Cr-Mo alloy systems. (1) Austenite grains have been found to hardly grow in the temperature range of $900^{\circ}C$ to $950^{\circ}C$, whereas they grow rapidly in the temperature range of $975^{\circ}C$ to $1100^{\circ}C$. (2) Austenite grain growth is considerably small with increasing holding time at a given austenitizing temperature and is, in particular, hardly found to occur at a temperature of $900^{\circ}C$. (3) The hardenability improves ramarkably as Mn content is increased at three different austenitizing temperatures $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. (4) The maximum hardenability is obtained from steels A, B and C austenitized at the $900^{\circ}C$, although Mn content is varied in each specimen.

• 한국재료학회지
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• 제26권10호
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• pp.535-541
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• 2016

The present study deals with the effects of micro-alloying elements such as Ni, V, and Ti on the recrystallization behavior of carbon steels at different strain rates. Eight steel specimens were fabricated by varying the chemical composition and reheating temperature; then, a high-temperature compressive deformation test was conducted in order to investigate the relationship of the microstructure and the recrystallization behavior. The specimens containing micro-alloying elements had smaller prior austenite grain sizes than those of the other specimens, presumably due to the pinning effect of the formation of carbonitrides and AlN precipitates at the austenite grain boundaries. The high-temperature compressive deformation test results indicate that dynamic recrystallization behavior was suppressed in the specimens with micro-alloying elements, particularly at increased strain rate, because of the pinning effect of precipitates, grain boundary dragging and lattice misfit effects of solute atoms, although the strength increased with increasing strain rate.

• Nuclear Engineering and Technology
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• 제45권6호
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• pp.821-826
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• 2013

In the present study, the effects of various heat treatments on the microstructure and mechanical properties of dual phase ODS steels were investigated to enhance the high strength at elevated temperature. Dual phase ODS steels have been designed by the control of ferrite and austenite formers, i.e., Cr, W and Ni, C in Fe-based alloys. The ODS steels were fabricated by mechanical alloying and a hot isostatic pressing process. Heat treatments, including hot rolling-tempering and normalizing-tempering with air- and furnace-cooling, were carefully carried out. It was revealed that the grain size and oxide distributions of the ODS steels can be changed by heat treatment, which significantly affected the strengths at elevated temperature. Therefore, the high temperature strength of dual phase ODS steel can be enhanced by a proper heat treatment process with a good combination of ferrite grains, nano-oxide particles, and grain boundary sliding.