A spin coating process for RRAM, which is a TiN/TiO2/FTO structure based on a PTC sol solution, was developed in this laboratory, a method which enables low-temperature and eco-friendly manufacturing. The RRAM corresponds to an OxRAM that operates through the formation and extinction of conductive filaments. Heat treatment was selected as a method of controlling oxygen vacancy (VO), a major factor of the conductive filament. It was carried out at 100 oC under moisture removal conditions and at 300 oC and 500 oC for excellent phase stability. XRD analysis confirmed the anatase phase in the thin film increased as the heat treatment increased, and the Ti3+ and OH- groups were observed to decrease in the XPS analysis. In the I-V analysis, the device at 100 oC showed a low primary SET voltage of 5.1 V and a high ON/OFF ratio of 104. The double-logarithmic plot of the I-V curve confirmed the device at 100 oC required a low operating voltage. As a result, the 100 oC heat treatment conditions were suitable for the low voltage driving and high ON/OFF ratio of TiN/TiO2/FTO RRAM devices and these results suggest that the operating voltage and ON/OFF ratio required for OxRAM devices used in various fields under specific heat treatment conditions can be compromised.

The ZnO–Na2Ti6O13 composites were synthesized by facile solution combustion method with different molar concentrations of sodium titanate which is prepared by hydrothermal route. The formation of the composites was confirmed by the X-ray diffraction (XRD) analysis. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) results revealed that the synthesized composites exhibit porous morphology, whereas the pristine Na2Ti6O13 nanoparticles have whisker like morphology. Diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) studies were utilized to compute the bandgap and the presence of defects in the composites respectively. The photocatalytic activity of ZnO–Na2Ti6O13 catalyst was investigated through the degradation of 4-nitrophenol under solar light over a period of 180 min and the composite with 0.05 M of Na2Ti6O13 showed higher degradation efficiency (96%) than the other concentrations of Na2Ti6O13 and pristine ZnO. The reduced bandgap, high charge transfer, more oxygen vacancies and the production of high superoxide anion radicals have profound effect on the higher photocatalytic efficiency of the composite with 0.05 of M Na2Ti6O13.

This study explored the possibility of forming a coating layer containing alginic acid on the surface of a magnesium alloy to be used as a biomaterial. We formed a coating layer on the surface of a magnesium alloy using a plasma electrolytic oxidation process in an electrolytic solution with different amounts of alginic acid (0 g/L ~ 8 g/L). The surface morphology of all samples was observed, and craters and nodules typical of the PEO process were formed. The cross-sectional shape of the samples confirmed that the thickness of the coating layer became thicker as the alginic acid concentration increased. It was confirmed that the thickness and hardness of the sample significantly increase with increasing alginic acid concentration. The porosity of the surface and cross section tended to decrease as the alginic acid concentration increased. The XRD patterns of all samples revealed the formation of MgO, Mg2SiO4, and MgF2 complex phases. Polarization tests were conducted in a Stimulate Body Fluid solution similar to the body's plasma. We found that a high amount of alginic acid concentration in the electrolyte improved the degree of corrosion resistance of the coating layer.

이번 연구는 효과적으로 2화방 개화묘를 생산하여 조기에 토마토를 수확하고 수확 기간을 연장하기 위하여 적절한 양액 농도 관리방법을 구명하기 위해 실시되었다. 처리는 양액 농도 로 1줄기 2화방 개화묘 연구에서는 양액 EC를 1.5, 2.0, 2.5dS·m-1, 동적 관리(3.0 → 3.5 → 4.5dS·m-1)로 공급하였다. 육묘기간은 65일로 관행묘에 비해 20－40일, 1화방 개화묘 (큐브 육묘)보다는 10일 정도 길었다. 초장은 EC 2.5dS·m-1와 동적 관리는 각각 78, 77cm로 EC 1.5dS·m-1처리 88cm보다 짧았다. 정식 전 큐브 내 EC는 동적 관리가 EC 5.5dS·m-1로 가 장 높았으며, EC 1.5dS·m-1로 공급한 큐브는 3.0dS/m으로 가 장 낮았다. 2화방 개화묘에서 EC 처리 간 생산량 차이는 나타 나지 않았으나 1화방 개화묘는 2화방 개화묘보다 생산성이 떨 어졌다. 2화방 개화묘는 첫 수확일이 6월 4일로 정식 후 35일 만에 수확하였으며 1화방 개화묘는 6월 11일로 42일만에 수 확하였다. 절곡에 의한 초장 및 뿌리 생육의 차이는 나타나지 않았다. 2줄기 2화방 개화묘 생산 연구에서는 공급 양액 EC를 2.0, 2.5, 3.0dS·m-1, 동적 관리(3.0 → 3.5 → 4.5dS·m-1)로 하 여 공급하였다. 육묘 기간은 90일로 관행묘에 비해 40－50일, 1화방 2줄기 개화묘(큐브 육묘)보다는 10일 정도 길었다. 초장 은 공급 양액 EC 2.0dS·m-1에서 80cm, 2.5dS·m-1에서는 81cm였으며 3.0dS·m-1 처리에서는 75cm, 동적 관리에서는 73cm로 가장 짧았다. 배지 내 EC는 모든 처리에서 육묘 기간 이 길어질수록 높아졌으며 특히 공급 EC가 가장 높았던 동적 관리 처리에서 EC 5.1dS·m-1로 가장 높았다. EC 처리 간 생산 량 차이는 나타나지 않았으나 육묘 기간이 10일 정도 길었던 2 화방 개화묘가 1화방 개화묘보다 15% 정도 생산량이 많았다. 2화방 개화묘의 초장을 짧게 만들기 위해서는 가식 후 공급 양 액 농도를 높이는 방법이 가장 효율적인 방법으로 판단된다.

Spent nuclear fuel is a very complex material because various elements such as fission products, transuranium elements and activation products are produced from initial fresh UO2 fuel after irradiation. These elements exist in UO2 with various forms and can change the structure and of physicochemical properties of UO2. These changes could provide the surface activation site that could enhance chemical reactions and corrosion processes, and would significantly affect the storage environment for long-term disposal of spent nuclear fuel. Therefore, it can be important to understand the characteristics of spent nuclear fuel to design reliable and safe geological repositories. However, it is too hard to study the characteristics of spent nuclear fuel, because it is a very complex material by itself and not easy to handle due to its radioactivity, and it is also difficult to independently understand the effects of each element. Therefore, a simulated spent nuclear fuel containing an element that forms a solid solution and epsilon particle was manufactured to understand the change in characteristics of each element. Most of the elements that form solid solutions are lanthanides or actinides and can change the structure of the UO2 lattice itself. The epsilon particles exist as metals at the grain boundaries of UO2. In this study, structural changes were measured using XRD, SEM, and Raman spectroscopy, and physical and chemical properties were also identified by measuring electrical conductivity and electrochemical properties. The results were summarized, and the effects of solid solution elements and epsilon particles on the structure and properties of UO2 matrix were compared and discussed.

Strontium-90 is a high heat-generating nuclide in spent nuclear fuel. The removal of the nuclide separation is indispensable to reduce the burden of storage and disposal of high-level radioactive waste. Korea Atomic Energy Research Institute has developed the molten salt immersion technique to separate the strontium by the chlorination of the strontium oxide in molten salt. It is needed to separate the salt for the recovery of strontium from the salt solution after the chlorination reaction. In this study, it was investigated on the recovery of the strontium from the salt. Vacuum distillation was used for the separation of strontium from the molten salt. The vapor pressures of the candidate salts were calculated by HSC chemistry and the apparent evaporation rates (AER) were measured at 830°C to evaluate the salts for strontium recovery. The candidate salts were LiCl, KCl, MgCl2, NaCl and CaCl2. The AERs of MgCl2 and NaCl were 1.9 and 1.3 g/cm2-h, respectively. Those two salts can be separated from the strontium compound even though the AER values are much lower than those of LiCl-KCl (~ 8 g/cm2-h). CaCl2 salt was rarely evaporated (AER < 0.03 g/cm2-h) and it is not suitable to use as a strontium recovery salt. Therefore, MgCl2, NaCl, LiCl and KCl can be regarded as candidates for a strontium recovery salt.

The formation behavior of a passive state film on the surface of STS304 in electrolytic solution was analyzed to determine its metallic ion composition. The properties of passive state films vary depending on the Fe and Cr ions in the electrolytic solution. It was observed that the passive state film surface became flat and glossy as the concentration of Fe and Cr ions in the electrolytic solution increased. The corrosion resistance property of the passive state film was proportional to the amount of Fe and Cr in the electrolytic solution. An initial passive state film with high Fe concentration was formed on the surface of STS304 during early electrolytic polishing. Osmotic pressure of Fe ions occurs between the passive state film and electrolytic solution due to the Fe ion concentration gradient. The Fe in the passive state film is dissolved into the electrolyte, and Cr fills up the Fe ion vacancies. As a result, a good corrosion-resistant floating film was formed. The more Fe ions in the electrolytic solution, the faster the film is formed, and as a result, a flat passive state film containing a large amount of Cr can be formed.

최근 농지 및 수자원의 염류화로 인해 염생식물에 대한 작물화와 생육 조건 구명을 위한 연구 필요성이 높아지고 있다. 그러나 재배 조건 변화에 따른 작물의 생육 및 기능성 성분 변화 분석을 위해서는 양액 및 작물 생육부 시료를 채취하여 이를 전처리 및 분석해야 하여 시간적, 인적 자원의 소모가 높다. 본 연구에서는 염생식물의 최적 생육 조건 구명을 효율적으로 수행하기 위해 비파괴적으로 재배 현장에서 실시간으로 작물 생육부와 수경재배 근권부의 염분 농도를 모니터링할 수 있는 시스템을 개발하였다. 개발 시스템을 통해 NaCl 0 mM, 50 mM, 150 mM, 300 mM의 4가지 농도 조건에서 갯방풍을 대상으로 재배실험을 수행한 결과, 재배 중 염분 농도 수치의 변화 및 염분 농도가 높을수록 생체중이 감소하는 것을 확인하였다. 실제 생육 분석 결과에 따르면 개발 시스템을 통한 모니터링 결과에 상응하는 생체중 결과를 확인하여 염생식물의 생육 모니터링 적용이 가능할 것으로 평가되었다. 그러나 단위 생체중 당 기능성물질 함량의 경우, NaCl 농도가 증가할수록 증가하는 것으로 나타나 갯방풍의 상업적 재배 조건의 구명을 위해서는 생체중 외에 기능성 성분의 모니터링을 위한 시스템 보완이 필요하다고 판단되었다.

In order to extend the business viability of carbon nanotubes (CNTs), research on CNT dispersion in a solvent as well as in polymer matrix should be established. Herein, three kinds of dispersing agents, sodium deoxycholate (DOC), sodium dodecylbenzene sulfonate (NaDDBS), polyvinyl pyrrolidone (PVP), are selected and applied to quantify the dispersibility and dispersion stability of CNT aqueous dispersion. The dispersibility of CNT dispersion with the PVP, evaluated via viscosity and particle size analyses, are superior to those with the DOC and NaDDBS dispersing agents. CNT aqueous solution dispersed with PVP showed slightly higher viscosity and narrower particle size distribution than those with DOC and NaDDBS dispersing agents. In addition, the dispersion stability of CNT dispersion with the PVP, measured via lumisizer analyses, are superior to those with the DOC and NaDDBS dispersing agents. HR-TEM analysis verifies that the outstanding dispersibility and dispersion stability of CNTs in aqueous solution are due to the effect of the robust polymer wrapping of the PVP dispersing agent on the CNT surface. From the results of this study, the guidelines for the selection of the suitable dispersing agents and the systematic evaluation of dispersibility and dispersion stability of CNT dispersions can be suggested.

NbC, HfC, TaC, and their solid solution ceramics have been identified as the best materials for ultrahigh-temperature ceramics. However, their structural stability and elastic properties are mostly unclear. Thus, we investigated structure and elastic properties of (Nb1-xTax)C and (Nb1-xHfx)C solid solutions via ab initio calculations. Our calculated results show that the stability of (Nb1-xTax)C and (Nb1-xHfx)C increases with the increase of Hf and Ta content, and (Nb1-xHfx)C is more stable than (Nb1-xTax)C at the same content of Hf and Ta. The lattice constants decrease with increasing of Hf and Ta content. (Nb1-xTax)C and (Nb1-xHfx)C carbides are mechanically stable and brittle. Bulk modulus of (Nb1-xTax)C increases with increasing Ta content. In contrast, bulk modulus of (Nb1-xHfx)C decreases with increasing Hf content. Hardness of solid solutions shows the highest values at the (Nb0.25Ta0.75)C and (Nb0.75Hf0.25)C. In particular, (Nb0.75Hf0.25)C shows the highest hardness for the current system. The results indicate that the overall mechanical properties of (Nb1-xHfx)C solid solutions are superior to those of (Nb1-xTax)C solid solutions. Therefore, controlling the Hf and Ta element and content of the (Nb1-xTax)C and (Nb1-xHfx)C Solid solution is crucial for optimizing the material properties.

전자 및 화학 산업의 초순수 생산 및 원자력 발전소의 부식 제어를 위해 이온교환 수지탑의 성능 파악이 필수적이다. 따라서 본 연구에서는 4종의 H 및 ETAH 형 양이온 교환수지가 채워진 양이온 및 혼상 이온교환수지탑에 미량의 NaCl를 포함하는 에탄올아민(ETA) 및 암모니아(NH3) 용액을 주입하여 양이온 파과특성을 조사하였다. 조사 결과, 주성분인 ETAH+ 및 NH4 +와 달리, 미량성분인 Na+는 (이론적교환용량의 3배 이상) 시험기간 동안 수지탑 출구에서 파과 및 오버슈팅 현상이 나타나지 않았다. H형 수지탑의 파과현상은 ETAH+ 및 NH4 +가 순서대로 일어났고, 오버슈팅은 NH4 +가 파과할때 ETAH+에 대해서 발생했다. 파과영역의 너비로 결정되는 상대적 선택도는 NH4 +가 ETAH+보다 최대 51.5 % 더 높았다. 유입수 Na+ 농도가 높을수록, 선택도는 감소하고 오버슈팅 현상은 증가하였다. 이온교환 수지의 고유 특성을 개선하여 감소시킬 수 있는 Na+ 누출은, ETAH형에서 높았고 4종의 양이온수지에 대해 동일하지 않은 것으로 조사되었다.

Cymbidium is one of the most popular and economically important species cultivated as a commercial ornamental crop. The objectives of this study were to determine the appropriate electrical conductivity (EC) treatments of nutrient solution, which gives the highest spike production and quality. Three-year-old Cymbidium ‘Lovely Smile’ plants were grown in the environmentally controlled Information and Communication Technology (ICT) smart greenhouse at Seoul Women’s University. The EC of the nutrient solution was changed in three distinct stages: vegetative, flower initiation, and flower development. The EC treatments were 1-0-1 (dS·m-1, EC101), 1-1-1 (dS·m-1, EC111), 2-1-2 (dS·m-1, EC212), 2-2-2 (dS·m-1, EC222), 3-2-3 (dS·m-1, EC323), 3-3-3 (dS·m-1, EC333) and the pH was adjusted to 6.0–6.5. Pseudobulb diameter increased in the plants treated with EC 101 and EC111 compared to the plants treated with EC 2.0–3.0 dS·m-1 at the reproductive stage 28 weeks after nutrient solution treatment. Flower spike production per pot and pseudobulb showed the highest values in the plants treated with EC111 of 3.3 and 1.4, respectively. Flower spikes length was the highest in the plants treated with EC 1.0 dS·m-1 and stem thickness, number of flowers, and fresh weight were the largest in the plants with EC 1.0 dS·m-1 among the EC treatments. Flower spikes had the worst quality (e.g., plant growth and flowering quality) in the plants treated with EC 3.0 dS·m-1 among the EC treatments. Floral bud and flower development took place 1–2 weeks earlier in the plants treated with EC 101, 111, and 212 than the other treatments. Flower diameter showed the highest values in the plants treated with EC 1.0 dS·m-1 among the EC treatments and flower color showed higher L* and b* values and lower a* values in the plants treated with EC 3.0 dS·m-1 compared to EC 1.0 and 2.0 dS･m-1. Nutrient solution of EC 1.0 dS·m-1 (EC111) can be recommended to improve flower spike quality and advanced flower development of Cymbidium.

The efficient nutrient solution cooling system consisting of buffer tank, three-way valve, and heat pump et al. was developed for hydroponics of leafy vegetables at high temperatures period. It was designed in such a way that the buffer tank was first cooled to enable precise temperature control of the nutrient solution with small capacity heat pump. Developed system was installed in the NFT hydroponics farm cultivating leafy vegetables and performance evaluation was carried out. For cultivation of Lalique lettuce(Lactuca sativa var.), the temperature of nutrient solution tank, buffer tank, and the root zone, the performance of cooling system, and the environment of greenhouse were analyzed. Also, by measuring the growth and yield of lettuce, the effect of cooling nutrient solution on the growth of lettuce NFT hydroponics was analyzed.

Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.