• Journal of Advanced Marine Engineering and Technology
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• 제39권8호
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• pp.838-842
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• 2015

The Li-air battery is a promising candidate for the most energy-dense electrochemical power source because it has 5 to 10 times greater energy storage capacity than that of Li-ion batteries. However, the Li-air cell performance falls short of the theoretical estimate, primarily because the discharge terminates well before the pore volume of the air electrode is completely filled with lithium oxides. Therefore, the structure of carbon used in the air electrode is a critical factor that affects the performance of Li-air batteries. In a previous study, we reported a new class of carbon nanomaterial, named carbon nanoballs (CNBs), consisting of highly mesoporous spheres. Structural characterization revealed that the synthesized CNBs have excellent a meso-macro hierarchical pore structure, with an average diameter greater than 10 nm and a total pore volume more than $1.00cm^3g^{-1}$. In this study, CNBs are applied in an actual Li-air battery to evaluate the electrochemical performance. The formation mechanism and electrochemical performance of the CNBs are discussed in detail.

• Journal of Electrochemical Science and Technology
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• 제6권2호
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• pp.50-58
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• 2015

There is a great deal of current interest in the development of rechargeable batteries with high energy storage capability due to an increasing demand for electric vehicles (EVs) with driving ranges comparable to those of gasoline-powered vehicles. Among various types of batteries under development, a Li-O₂ battery delivers the highest theoretical energy density; thus, it is considered a promising energy storage technology for EV applications. Despite the fact that extensive research efforts have been made in the field of Li-O₂ batteries in recent years, there are still many technical challenges to be addressed, such as low round-trip efficiency, poor reversibility, and poor power capability. In this article, we provide a short review on the fundamental electrochemistry of Li-O₂ batteries with non-aqueous electrolytes and on electrode materials that have been employed in cathodes (oxygen electrodes). The major aim of this mini-review is to highlight the physical and electrochemical origins of scientific challenges facing Li-O₂ battery technology and to overview the strategies proposed to overcome them.

• Current Research on Agriculture and Life Sciences
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• 제31권4호
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• pp.250-255
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• 2013

As a renewable nanomaterial, cellulose nanocrystal (CNC) isolated from wood grants excellent mechanical properties in developing high performance nanocomposites. This study was undertaken to compare the reinforcing efficiency of two different CNCs, i.e., cellulose nanowhiskers (CNWs) and cellulose nanofibrils (CNFs) from hardwood bleached kraft pulp (HW-BKP) as reinforcing agent in polyvinyl alcohol (PVA)-based nanocomposite. The CNWs were isolated by sulfuric acid hydrolysis while the CNFs were isolated by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. Based on measurements using transmission electron microscopy, the individual CNWs were about $6.96{\pm}0.87nm$ wide and $178{\pm}55nm$ long, while CNFs were $7.07{\pm}0.99nm$ wide. The incorporation of CNWs and CNFs into the PVA matrix at 5% and 1% levels, respectively, resulted in the maximum tensile strength, indicating different efficiencies of these CNCs in the nanocomposites. Therefore, these results suggest a relationship between the reinforcing potential of CNCs and their physical characteristics, such as their morphology, dimensions, and aspect ratio.

• 열처리공학회지
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• 제22권3호
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• pp.149-154
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• 2009

Dense $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ composite was consolidated from mechanically synthesized powders by pulsed current activated sintering method within 1 min. $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ powder was synthesized from 3CuO and 2FeAI using the high energy ball milling. Dense $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ with relative density of up to 95% was produced under simultaneous application of a 80 MPa pressure and the pulsed current. Mechanical properties and grain size of the composite were investigated.

• 한국산업융합학회 논문집
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• 제16권2호
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• pp.41-46
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• 2013

On the purpose of helping the inhabitants living in farming, fishing villages, and islands for more safe and hygienic water from simple waterworks, experimental investigations were performed concerning the development of a water purifier with silver nanomaterial packed, having a function of the auto-disinfection. The results show as follows through such filteration and auto-disinfection processes. It is possible to get hygienic and safe water, for example, more than 95% of general bacteria, total coliforms, and fecal coliforms were removed. It is also possible to get good-quality water, for 49.4% of spent potassium permanganate and 85% and 63% of turbidity and conductivity were removed respectively. It is a very effective equipment, for 100% cost reduction of used chemicals was achieved by no-chemical disinfection process and THM was not generated.

• 생태와환경
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• 제44권4호
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• pp.317-326
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• 2011

With its recent advances, nanotechnology is now being applied to various areas. Despite the benefits of nanoparticles, their risk in the environment has caused controversy, which is now becoming an international issue. Nanoparticles can easily infiltrate into cells, accumulate in biota, and may cause adverse effects in the levels of molecules, cells and organisms, and in the community. If nanoparticles are released into the environment, they can be transferred to organisms in the ecosystem, and eventually to the human body through the food chain. In this study, the research trend of the trophic transfer of nanoparticles in the food chain was investigated. Although a few investigations have been conducted regarding this topic, the trophic transfer of nanoparticles is becoming a significant issue in the area of nanotoxicology due to the potential risk to humans via the biomagnification process. While previous studies have demonstrated evidence of the trophic transfer of nanoparticles intensive future studies are needed to provide further information on the properties of nanomaterials, the exposure media, and the in vivo mechanisms such as uptake, accumulation, and depuration.

• 대한기계학회논문집 C: 기술과 교육
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• 제5권1호
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• pp.69-77
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• 2017

나노기술은 IT, BT 기술과 함께 21세기에 기술혁명을 주도해 나갈 핵심 기술이기에 현재 우리나라를 비롯한 전 세계의 선진국들이 이 분야에 많은 연구 역량을 집중시키고 있고, 그 중에서도 나노소재 산업은 이 경쟁의 중심에 있다고 볼 수 있다. 본 연구에서는 기계공학 측면에서 나노소재 산업에 대하여 살펴보았다. 나노소재는 나노크기의 재료라는 점에서 기존의 마이크론 혹은 서브마이크론 재료에 서 발견할 수 없는 특별한 효과를 나타내거나 전혀 새로운 응용분야를 만들어낼 가능성이 크다. 특히 환경, 바이오, 에너지, 촉매 등 다양한 분야에서 그 응용이 기대된다.

• 방사성폐기물학회지
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• 제18권3호
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• pp.363-372
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• 2020

Anionic radionuclides pose one of the highest risks to the long-term safety assessments of disposal repositories. Therefore, techniques to immobilize and separate such anionic radionuclides are of crucial importance from the viewpoints of safety and waste volume reduction. The main objective of this study is to design a separator with minimum pressure disturbance, based on the concept of a conventional cyclone separator. We hypothesize that the anionic radionuclides can be immobilized onto a nanomaterial-based substrate and that the particles generated in the process can flow via water. These particles are denser than water; hence, they can be trapped within the cyclone-type separator because of its design. We conducted particle tracking analysis using computational fluid dynamics (CFD) for the conventional cyclone separator and studied the effects due to the morphology of the separator. The proposed sandglass-like design of the separator shows promising results (i.e., only one out of 10,000 particles escaped to the outlet from the separation zone). To validate the design, we manufactured a laboratory-scale prototype separator and tested it for iron particles; the efficiency was ca. 99%. Furthermore, using an additional magnetic effect with the separator, we could effectively separate particles with ~100% efficiency. The proposed sandglass-like separator can thus be used for effective separation and recovery of immobilized anionic radionuclides.

• 세라미스트
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• 제22권1호
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• pp.36-55
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• 2019

Atomically thin two-dimensional (2D) nanomaterials, including transition metal dichalcogenides (TMDs), graphene, boron nitride, and black phosphorus, have opened up new opportunities for the next generation optoelectronics owing to their unique properties such as high absorbance coefficient, high carrier mobility, tunable band gap, strong light-matter interaction, and flexibility. In this review, photodetectors based on 2D nanomaterials are classified with respect to critical element technology (e.g., active channel, contact, interface, and passivation). We discuss key ideas for improving the performance of the 2D photodetectors. In addition, figure-of-merits (responsivity, detectivity, response speed, and wavelength spectrum range) are compared to evaluate the performance of diverse 2D photodetectors. In order to achieve highly reliable 2D photodetectors, in-depth studies on material synthesis, device structure, and integration process are still essential. We hope that this review article is able to render the inspiration for the breakthrough of the 2D photodetector research field.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.47-50
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• 2002

ZnO nanowires were coated conformally with aluminum oxide ($Al_{2}O_{3}$) material by atomic layer deposition (ALD). The ZnO nanowires were first synthesized on a Si (100) substrate at $1380^{\circ}C$ from ball-milled ZnO powders by a thermal evaporation procedure with an argon carrier gas without any catalysts; the length and diameter of these ZnO nanowires are $20\sim30{\mu}m$ and $50{\sim}200$ nm, respectively. $Al_{2}O_{3}$ films were then deposited on these ZnO nanowires by ALD at a substrate temperature of $300^{\circ}C$ using trimethylaluminum (TMA) and distilled water ($H_{2}O$). Transmission electron microscopy (TEM) images of the deposited ZnO nanowires revealed that 40nm-thick $Al_{2}O_{3}$ cylindrical shells surround the ZnO nanowires.