This present study deals with the microstructure and tensile properties of 600 MPa-grade high strength and seismic resistant reinforcing steels. The high strength reinforcing steel (SD 600) was fabricated by Tempcore processing, while the seismic resistant reinforcing steel (SD 600S) was air-cooled after hot-rolling treatment. The microstructure analysis results showed that the SD 600 steel specimen consisted of a tempered martensite and ferrite-pearlite structure after Tempcore processing, while the SD 600S steel specimen had a fully ferrite-pearlite structure. The room-temperature tensile test results indicate that, because of the enhanced solid solution and precipitation strengthening caused by relatively higher contents of C, Mn, Si and V in the SD 600S steel specimen, this specimen, with fully ferrite-pearlite structure, had yield and tensile strengths higher than those of the SD 600 specimen. On the other hand, the hardness of the SD 600 and SD 600S steel specimens changed in different ways according to location, dependent on the microstructure, ferrite grain size, and volume fraction.

This present study deals with the effect of micro-alloying elements and transformation temperature on the correlation of microstructure and tensile properties of low-carbon steels with ferrite-pearlite microstructure. Six kinds of lowcarbon steel specimens were fabricated by adding micro-alloying elements of Nb, Ti and V, and by varying isothermal transformation temperature. Ferrite grain size of the specimens containing mirco-alloying elements was smaller than that of the Base specimens because of pinning effect by the precipitates of carbonitrides at austenite grain boundaries. The pearlite interlamellar spacing and cementite thickness decreased with decreasing transformation temperature, while the pearlite volume fraction was hardly affected by micro-alloying elements and transformation temperature. The room-temperature tensile test results showed that the yield strength increased mostly with decreasing ferrite grain size and elongation was slightly improved as the ferrite grain size and pearlite interlamellar spacing decreased. All the specimens exhibited a discontinuous yielding behavior and the yield point elongation of the Nb4 and TiNbV specimens containing micro-alloying elements was larger than that of the Base specimens, presumably due to repetitive pinning and release of dislocation by the fine precipitates of carbonitrides.

In this study, six kinds of low-carbon steel specimens with different ferrite-pearlite microstructures were fabricated by varying the Nb content and the transformation temperature. The microstructural factors of ferrite grain size, pearlite fraction, interlamellar spacing, and cementite thickness were quantitatively measured based on optical and scanning electron micrographs; then, Charpy impact tests were conducted in order to investigate the correlation of the microstructural factors with the impact toughness and the ductile-brittle transition temperature (DBTT). The microstructural analysis results showed that the Nb4 specimens had ferrite grain size smaller than that of the Nb0 specimens due to the pinning effect resulting from the formation of carbonitrides. The pearlite interlamellar spacing and the cementite thickness also decreased as the transformation temperature decreased. The Charpy impact test results indicated that the impact-absorbed energy increased and the ductile-brittle transition temperature decreased with addition of Nb content and decreasing transformation temperature, although all specimens showed ductile-brittle transition behaviour.

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.

This paper presents a study of the tensile properties of austenitic high-manganese steel specimens with different grain sizes. Although the stacking fault energy, calculated using a modified thermodynamic model, slightly decreased with increasing grain size, it was found to vary in a range of 23.4 mJ/m2 to 27.1 mJ/m2. Room-temperature tensile test results indicated that the yield and tensile strengths increased; the ductility also improved as the grain size decreased. The increase in the yield and tensile strengths was primarily attributed to the occurrence of mechanical twinning, as well as to the grain refinement effect. On the other hand, the improvement of the ductility is because the formation of deformation-induced martensite is suppressed in the high-manganese steel specimen with small grain size during tensile testing. The deformationinduced martensite transformation resulting from the increased grain size can be explained by the decrease in stacking fault energy or in shear stress required to generate deformation-induced martensite transformation.

The ductile-brittle transition behavior of two austenitic Fe-18Cr-10Mn-N-C alloys with different grain sizes was investigated in this study. The alloys exhibited a ductile-brittle transition behavior because of an unusual brittle fracture at low temperatures unlike conventional austenitic alloys. The alloy specimens with a smaller grain size had a higher yield and tensile strengths than those with a larger grain size due to grain refinement strengthening. However, a decrease in the grain size deteriorated the low-temperature toughness by increasing the ductile-brittle transition temperature because nitrogen or carbon could enhance the effectiveness of the grain boundaries to overcome the thermal energy. It could be explained by the temperature dependence of the yield stress based on low-temperature tensile tests. In order to improve both the strength and toughness of austenitic Fe-Cr-Mn-N-C alloys with different chemical compositions and grain sizes, more systematic studies are required to understand the effect of the grain size on the mechanical properties in relation to the temperature sensitivity of yield and fracture stresses.

In this study, low-carbon hypoeutectoid steels with different ferrite-pearlite microstructures were fabricated byvarying transformation temperature. The microstructural factors such as pearlite fraction and interlamellar spacing, and cementitethickness were quantitatively measured and then Charpy impact tests conducted on the specimens in order to investigate thecorrelation of the microstructural factors with impact toughness and ductile-brittle transition temperature. The microstructuralanalysis results showed that the pearlite interlamellar spacing and cementite thickness decreases while the pearlite fractionincreases as the transformation temperature decreases. Although the specimens with higher pearlite fractions have low absorbedenergy, on the other hand, the absorbed energy is higher in room temperature than in low temperature. The upper-shelf energyslightly increases with decreasing the pearlite interlamellar spacing. However, the ductile-brittle transition temperature is hardlyaffected by the pearlite interlamellar spacing because there is an optimum interlamellar spacing dependent on lamellar ferriteand cementite thickness and because the increase in pearlite fraction and the decrease in interlamellar spacing with decreasingtransformation temperature have a contradictory role on absorbed energy.

The present study deals with the effects of tempering treatment on the microstructure and mechanical properties of Cu-bearing high-strength steels. Three kinds of steel specimens with different levels of Cu content were fabricated by controlled rolling and accelerated cooling, ; some of these steel specimen were tempered at temperatures ranging from 350˚C to 650˚C for 30 min. Hardness, tensile, and Charpy impact tests were conducted in order to investigate the relationship of microstructure and mechanical properties. The hardness of the Cu-added specimens is much higher than that of Cu-free specimen, presumably due to the enhanced solid solution hardening and precipitation hardening, result from the formation of very-fine Cu precipitates. Tensile test results indicated that the yield strength increased and then slightly decreased, while the tensile strength gradually decreased with increasing tempering temperature. On the other hand, the energy absorbed at room and lower temperatures remarkably increased after tempering at 350˚C; and after this, the energy absorbed then did not change much. Suitable tempering treatment remarkably improved both the strength and the impact toughness. In the 1.5 Cu steel specimen tempered at 550˚C, the yield strength reached 1.2 GPa and the absorbed energy at -20˚C showed a level above 200 J, which was the best combination of high strength and good toughness.

Activated magnetite (Fe3O4-δ) has the capability of decomposing CO2 proportional to the δ-value at comparativelylow temperature of 300oC. To enhance the CO2 decomposition capability of Fe3O4-δ, (Fe1-xCox)3O4-δ and (Fe1-xMnx)3O4-δ weresynthesized and then reacted with CO2. Fe1-xCoxC2O4·2H2O powders having Fe to Co mixing ratios of 9:1, 8:2, 7:3, 6:4, and5:5 were synthesized by co-precipitation of FeSO4·7H2O and CoSO4·7H2O solutions with a (NH4)2C2O4·H2O solution. The samemethod was used to synthesize Fe1-xMnxC2O4·2H2O powders having Fe to Mn mixing ratios of 9:1, 8:2, 7:3, 6:4, 5:5 with aMnSO4·4H2O solution. The thermal decomposition of synthesized Fe1-xCoxC2O4·2H2O and Fe1-xMnxC2O4·2H2O was analyzedin an Ar atmosphere with TG/DTA. The synthesized powders were heat-treated for 3 hours in an Ar atmosphere at 450oCto produce activated powders of (Fe1-xCox)3O4-δ and (Fe1-xMnx)3O4-δ. The activated powders were reacted with a mixed gas(Ar:85%, CO2:15%) at 300oC for 12 hours. The exhaust gas was analyzed for CO2 with a CO2 gas analyzer. The decom-position of CO2 was estimated by measuring CO2 content in the exhaust gas after the reaction with CO2. For (Fe1-xMnx)3O4-δ,the amount of Mn2+ oxidized to Mn3+ increased as x increased. The δ value and CO2 decomposition efficiency decreased asx increased. When the δ value was below 0.641, CO2 was not decomposed. For (Fe1-xCox)3O4-δ, the δ value and CO2decomposition efficiency increased as x increased. At a δ value of 0.857, an active state was maintained even after 12 hoursof reaction and the amount of decomposed CO2 was 52.844cm3 per 1g of (Fe0.5Co0.5)3O4-δ.

A general synthetic method to make Fe3O4-δ (activated magnetite) is the reduction of Fe3O4 by H2 atmosphere. However, this process has an explosion risk. Therefore, we studied the process of synthesis of Fe3O4-δ depending on heat-treatment conditions using FeC2O4·2H2O in Ar atmosphere. The thermal decomposition characteristics of FeC2O4·2H2O and the δ-value of Fe3O4-δ were analyzed with TG/DTA in Ar atmosphere. β-FeC2O4·2H2O was synthesized by precipitation method using FeSO4·7H2O and (NH4)2C2O4·H2O. The concentration of the solution was 0.1 M and the equivalent ratio was 1.0. β-FeC2O4·2H2O was decomposed to H2O and FeC2O4 from 150˚C to 200˚C. FeC2O4 was decomposed to CO, CO2, and Fe3O4 from 200˚C to 250˚C. Single phase Fe3O4 was formed by the decomposition of β-FeC2O4·2H2O in Ar atmosphere. However, Fe3C, Fe and Fe4N were formed as minor phases when β-FeC2O4·2H2O was decomposed in N2 atmosphere. Then, Fe3O4 was reduced to Fe3O4-δ by decomposion of CO. The reduction of Fe3O4 to Fe3O4-δ progressed from 320˚C to 400˚C; the reaction was exothermic. The degree of exothermal reaction was varied with heat treatment temperature, heating rate, Ar flow rate, and holding time. The δ-value of Fe3O4-δ was greatly influenced by the heat treatment temperature and the heating rate. However, Ar flow rate and holding time had a minor effect on δ-value.

높은 선택도와 투과도를 가진 분리막이 요구되지만 선택도가 높은 막은 투과도가 낮은 것이 일반적이다. 본 연구에서는 적절한 선택도를 유지하면서 높은 투과도를 갖는 분리막을 제조하기 위하여 다공성 알루미나막을 실란커플링제로 코팅하였다. 코팅된막에 대한 물의 접촉각은 90º 이상이었으며, 큰 소수성을 가짐을 의미하기 때문에 에탄올, 이소프로판올, 부탄을 수용액의 농축을 위한 증기투과실험을 수행하였다. 공급액중의 알코을 농도가 증가함에 따라 투과도가 증가하였으며, 이는 물에 비하여 코팅된 막에 대한 에탄올, 이소프로판올, 부탄올의 친화도가 크기 때문으로 판단된다. 코팅된 알루미나막의 투과도는 고분자막의 투과도에 비하여 20~1000배로 크게 나타났다.

The objective of this study was to optimize the selection of sperm sources, optimal culture systems and vitrification method depends on sperm sources. The oocytes were inseminated with either KPN 105, 114, 191, SNU 101, 102, 103 or epididymis and then embryos inseminated were cultured in oviductal cell co-culture or HECM-6 as defined me dium. The blastocysts produced were pooled according to sperm sources as KPN, SNU or epididymis and then vitrified by OPP vitrification method. The results obtained were as follows: 1. The cleavage(86.2 or 84.7%) and development rates to blastocyst (30.6 or 32.0%) were not significantly different between oviductal cell co-culture or HECM-6 culture systems(P<0.05). 2. To determine the optimal sperm sources for using IVF in this system, cleavage rates in KPN 191 and SNU 101 (74.2, 55.8%) were significantly lower rather than those in KPN 105, 114, SNU 102, 103 or epididymis (86.7, 85.1, 89.8, 85.5 or 81.2%), but development rates to blastocyst in KPN 114, SNU 103 or epididymis sperm (30.0, 33.0 or 28.6%) were significantly higher rater than those in KPN 105, 191, SNU 101, 102(21.4, 15.4, 14.9 or 25.4%), respectively (P<0.05). 3. The blastocysts produced were pooled according to sperm sources as KPN, SNU or epididymis and then vitrified by OPP vitrification method. The survival rates were not significantly different among sperm sources (89.6%: 43/48 ; 90.1%: 46/51 ; 83.3% : 20/24). These results obtained indicate that the defined medium, HECM-6, could be use to produce of IVP bovine embryos. Since the frozen semen must be required to maintain of unvariation data in IVP embryo production system, KPN 114 and SNU 103 produced in our laboratory were useful for this purpose. The blastocysts produced by different sperm sources as KPN, SNU or epididymis were vitrified by OPP vitrification method and survived very high rates. The OPP vitrification method could be susceptibility to use of IVP bovine blastocyst embryos.

MOCVD(Metal-Organic Chemical Vapor Dposition) TiN 박막을 다양한 온도와 압력에서 tetrakis-dimethyl-amino-titanium(TDMAT (Ti[N(CH3)2]4))의 자체 열분해와 NH3와의 반응을 사용하여 형성하였다. 비저항은 박막내의 불순물 함량에 의존하였는데 특히 XPS curve fitting 결과 주요 불순물인 탄소와 산소 같은 불순물들이 박막내에서 다양한 침입형화합물을 만들어 박막의 물리적, 전기적 특성에 영향을 준다는 것을 알았다. Metal-organic source만을 사용하여 TiN을 형성할 경우 지름이 0.5μm이고 aspect ratio가 3:1인 구멍에서 step coverage가 매우 우수하였으나 NH3를 흘림에 따라 step coverage가 감소하는 것이 SEM으로 확인되었는데 이는 각각의 활성화에너지와 관련된 것으로 보인다.

Single-Si 기판과 poly-Si 기판에 각각 Ti을 sputter한 후 RTA 처리하여 안정한 TiSi2를 형성하였다. 그 위에 Si이 1% 첨가된 Al-1% Si을 600nm sputter한 후 후속 열처리로서 400-600˚C 에서 30분간 N2분위기로 furnace어닐링을 실시하였다. 이렇게 준비된 각 시편에 대하여 면저항 측정, Auger분석, SEM 사진으로 Al-1% Si/TiSi2이중층 구조에서 Ti-silicide의 열적 안정성을 살펴 보았고, EDS 분석과 X-ray 회절 peak 분석을 통하여 Al-1% Si 층과 TiSi2층의 반응으로 생긴 석출물의 성분과 상을 조사하였다. 이로 부터 다음과 같은 결과를 얻었다 Single-Si 기관에서 형성한 TiSi2층은 Al-1% Si 층과 550˚C에서 완전히 반응하여 석출물을 형성하였고, poly-Si 기판에서 형성한 TiSi2층은 Al-1% Si 층과 500˚C에서 완전히 반응하여 석출물을 형성하였는데 전반적으로 기판이 poly-Si인 경우가 반응이 더 잘 일어났고, 석출물의 크기도 비교적 컸다. 이는 poly-Si에 존재하는 grain boundary로 인해 poly-Si에서 형성된 Ti-silicide 층이single-Si 기관에서 형성된 Ti-silicide 층보다 불안정하기 때문으로 생각된다. EDS 분석에 의하여 석출물은 Ti, Al, 그리고 Si로 이루어진 3상 화합물이라고 추정되었고, X-ray회절 분석에 의해 석출물은 Ti, Al, 그리고 Si간의 3상 화합물인 Ti7Al5Si12로 확인되었다.

본 연구는 국내 특산식물이며 신 관상식물로 기대되는 산꼬리풀[Veronica rotunda var. subintegra (Nakai) T.Yamaz.]의 효과적인 재배법을 구명하고자 수행되었다. 플러그 육묘는 파종용기와 파종량을 달리하였다. 재배는 묘의 소질, 식재용기, 토양종류 및 차광정도를 달리하여 처리하였다. 묘의 소질은 162, 200 및 288구 트레이를 이용하여 육묘한 묘를 사용였으며, 파종량은 1, 2, 4 및 6립을 파종하여 생산된 묘를 사용하였다. 본 연구에서 산꼬리풀의 육묘 시 트레이 종류는 162구가 적절하였으며, 셀 당 1립씩 파종할 경우 각 개체의 생육이 증가하였으나 4립 파종 시에는 전체 식물의 생육에 유리하였다. 묘의 소질에 따른 실험은 162구 트레이에서 생산된 묘와 4립씩 파종하여 생산된 묘에서 각기 우수한 생육을 보였다. 산꼬리풀 재배 시 식재용기의 용적량이 커질수록 지상부 및 지하부의 생육이 증가 하는 경향이었으며, 용기의 재질에 따른 유의적인 차이는 나타나지 않았다. 토양조건별 생육은 원예상토에서 가장 왕성하였으며, 혼용토에서는 피트모스에 비해 마사토의 함량이 높은 조건에서 양호한 생육을 나타냈다.

본 연구는 진퍼리고사리의 전엽체 증식을 위한 배지를 선발하고, 포자체 증식을 위한 적정 배양토를 구명하여 대량생산 체계를 구축하고자 수행되었다. 전엽체 증식연구는 배지종류(1/4, 1/2, MS 배지, Knop 배지), sucrose (0, 1, 2, 3, 4%),의 농도를 달리한 배지에 전엽체 300 ㎎를 각각 접종하여 8주간 배양한 후 전엽체의 생육을 비교하였다. 포자체 형성 연구는 분쇄한 전엽체를 인공토양위에 접종하여 수행하였다. 인공토양은 원예상토, 펄라이트, 마사토의 비율을 다르게 조성하거나 원예상토단 용으로 사용했다. 그 후 접종한 전엽체를 12주간 배양한 다음 포자체 형성 및 생육을 조사하였다. 본 연구의 결과, 기내 전엽체는 2% sucrose를 첨가한 MS 배지에서 생체중과 생육이 가장 우수하였다. 포자체 형성을 위한 배양토 조성 실험에서는 원예상토:펄라이트 2:1(v:v)와 원예상토:마사토 2:1(v:v) 처리구에서 포자체의 형성이 가장 많았으며, 전반적인 생육은 원예상토:마사토 2:1(v:v)가 우수하였다.