• Journal of Magnetics
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• 제8권3호
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• pp.118-120
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• 2003

As an alternative promising way of producing high coercivity Sr-ferrite for a permanent magnet application, intensive mechanical milling process was applied to the raw materials of the Sr-ferrite with different composition. Synthesising reactivity for the Sr-ferrite of the mechanically milled raw material containing $SrCO_3$, $La_2O_3$, $Fe_2O_3$, $Co_3O_4$, and $SiO_2$ was inferior to that of the raw material containing $SrCO_3$ and $Fe_2O_3$, The Sr-ferrite prepared from mechanically milled raw materials had profoundly improved magnetic properties compared to the Sr-ferrite prepared by conventional method. Beneficial effect of the substituting ($La_2O_3$, $Co_3O_4$) and additive ($SiO_2$) oxides for improving the magnetic properties was not exploited in the Sr-ferrite prepared from the mechanically milled raw material. The Sr-ferrite powder prepared from the mechanically milled raw materials was magnetically isotropic in nature.

• 한국분말재료학회지
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• 제12권5호
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• pp.345-350
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• 2005

In this study the nanostructured ${\alpha}-Al_{2}O_3$ ceramics have been fabricated by the combined application of magnetic pulsed compaction (MPC) and subsequent spark plasma sintering (SPS), and their density and hardness properties were investigated. The ${\alpha}-Al_{2}O_3$ prepared by the combined processes showed an increase by $8.4\%$ in density, approaching the value close to the true density, and an enhancement by $210\~400\;Hv$ in hardness, compared to those fabricated by MPC or static compaction method followed by sintering treatment.

• 한국분말재료학회지
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• 제27권4호
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• pp.305-310
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• 2020

In this study, partially dry transfer is investigated to solve the problem of fully dry transfer. Partially dry transfer is a method in which multiple layers of graphene are dry-transferred over a wet-transferred graphene layer. At a wavelength of 550 nm, the transmittance of the partially dry-transferred graphene is seen to be about 3% higher for each layer than that of the fully dry-transferred graphene. Furthermore, the sheet resistance of the partially dry-transferred graphene is relatively lower than that of the fully dry-transferred graphene, with the minimum sheet resistance being 179 Ω/sq. In addition, the fully dry-transferred graphene is easily damaged during the solution process, so that the performance of the organic photovoltaics (OPV) does not occur. In contrast, the best efficiency achievable for OPV using the partially dry-transferred graphene is 2.37% for 4 layers.

• 한국재료학회지
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• 제20권3호
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• pp.148-154
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• 2010

It is necessary to develop new methods to prevent catastrophic failure of structural material in order to avoid accidents and conserve natural and energy resources. Design of intelligent materials with a self-diagnosing function to prevent fatal fracture of structural materials was achieved by smart composites consisting of carbon fiber tows or carbon powders with a small value of ultimate elongation and glass fiber tows with a large value of ultimate elongation. The changes in electrical resistance of CF-GFRP/GFRP (carbon fiber and glass fiber-reinforced plastics/glass fiber-reinforced plastics) composites increased abruptly with increasing strain, and a tremendous change was seen at the transition point where carbon fiber tows were broken. Therefore, the composites were not to monitor damage from the early stage. On the other hand, the change in electrical resistance of CP-GFRP/GFRP (carbon powder dispersed in glass fiber-reinforced plastics/glass fiber-reinforced plastics) composites increased almost linearly in proportion to strain. CP-GFRP/GFRP composites are superior to CF-GFRP/GFRP composites in terms of their capability to monitor damage by measuring change in electrical resistance from the early stage of damage. However, the former was inferior to the latter as an application because of the difficulties of mass production and high cost. A method based on monitoring damage by measuring changes in the electrical resistance of structural materials is promising for improved reliability of the material.

• 한국분말재료학회지
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• 제27권6호
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• pp.458-463
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• 2020

Hispidin is a secondary metabolite found in numerous medicinal mushrooms that has attracted significant attention, owing to its distinct biological effects, including antioxidant, anti-inflammatory, antitumor, and cytoprotective properties. Experiments are being carried out to study the interaction of detonation nanodiamonds (DNDs) with synthetic and natural hispidin sourced from extracts of Pholiota sp. fungus. The bioluminescence method is used to determine the adsorption/desorption properties of DNDs toward hispidin. It is found that hispidin forms strong conjugates with DNDs, and the use of various eluents does not result in a significant release of the adsorbed hispidin molecules. DND-bovine serum albumin (BSA) complex, where DNDs serve as a carrier for the protein and the latter acts as a hispidin sorbent, has been developed and applied in hispidin adsorption/desorption tests. The results support the use of the DNDs as a carrier for hispidin in medical applications. They also advocate the application of the DND-BSA complex for isolating the substance from fungal extracts.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.456-461
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• 2022

Heavy metal pollution is caused due to anthropogenic activities and is considered as a serious environmental problem which endangers human health and environment. The present study deals with biosorption, an eco-friendly technique for the removal of heavy metal Zn(II) from aqueous medium. Various natural materials have been explored for the uptake of metal ions, where most of them are physically or chemically enhanced. Dry cowdung powder (DCP) has been utilized as a low-cost, environmentally friendly humiresin without any pre-treatment, thus demonstrating the concept of Green Chemistry. Batch biosorption studies using ⁶⁵Zn(II) tracer were performed and the impact of different experimental parameters was studied. Results revealed that at pH 6, 94 ± 2% of Zn(II) was effectively biosorbed in 5 min, at 303 K. The process was spontaneous and exothermic, following pseudo-second-order reaction. The mechanism of heavy metal biosorption employing green adsorbent was therefore elucidated in order to determine the optimal method for removing Zn(II) ions. DCP has a lot of potential in the wastewater treatment industry, as seen by its ability to meet 3A's affordability, adaptability, and acceptability criteria. As a result, DCP emerges as one of the most promising challengers for green chemistry and the zero-waste idea.

• 한국분말재료학회지
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• 제30권5호
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• pp.436-441
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• 2023

Molybdenum-tungsten (Mo-W) alloy sputtering targets are widely utilized in fields like electronics, nanotechnology, sensors, and as gate electrodes for TFT-LCDs, owing to their superior properties such as high-temperature stability, low thermal expansion coefficient, electrical conductivity, and corrosion resistance. To achieve optimal performance in application, these targets' purity, relative density, and grain size of these targets must becarefully controlled. We utilized nanopowders, prepared via the Pechini method, to obtain uniform and fine powders, then carried out spark plasma sintering (SPS) to densify these powders. Our studies revealed that the sintered compacts made from these nanopowders exhibited outstanding features, such as a high relative density of more than 99%, consistent grain size of 3.43 ㎛, and shape, absence of preferred orientation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.93.2-93.2
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• 2010

Recently, printing and coating technologies application fields have been expanded to the energy field such as solar cell. One of the main reasons, why many researchers have been interested in printing technology as a manufacturing method, is the reduction of manufacturing cost. In this paper, We fabricated CIGS solar cell thin film layer by doctor blade methods using synthesis of CIS precursor nanoparticles ink on molybdenum (Mo) coated soda-lime glass substrate. Synthesis CIS precursor nanoparticles ink fabrication was mixed Cu, In, Se powder and Ethylenediamine, using microwave and centrifuging. Using multi coating process as we could easily fabrication a fine flatness CIS thin-film layer ($0.7{\sim}1.35{\mu}m$), and reduce a manufacture cost and process steps. Also if we use printing and coating method and solution process in each layer of CIGS solar cell (electrode, buffer), it is possible to fabricate all printed thin-film solar cell.

• 한국식품과학회지
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• 제35권6호
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• pp.1129-1134
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• 2003

양념창란젓갈 제조시 감마선의 산업적 적용을 위하여 상업적 제조방법과 동일하게 제조된 양념창란젓갈을 0, 2.5, 5.0 및 10 kGy로 감마선 조사하여 이화학적 특성을 관찰하였다. 또한, 고춧가루를 10 kGy의 감마선 조사로 살균한 후 같은 방법으로 양념창란젓갈을 제조하여 비교하였다. 휘발성 염기태질소(VBN) 함량은 10 kGy로 조사된 고춧가루를 첨가하여 제조한 양념창란젓갈이 37.5 mg%로 낮은 함량을 나타내었으며, 아미노태 질소의 함량은 모든 시료구에서 꾸준히 증가하다 저장 12주 후에는 0, 2.5, 5.0, 10 kGy 및 10 kGy로 조사한 고춧가루를 첨가하여 제조한 젓갈(HP-10 kGy)의 경우 각각 98.9, 98.5, 92.4, 88.0 및 93.1 mg%를 나타내었다. Biogenic amine의 함량을 조사한 결과 조사된 젓갈은 비조사된 젓갈에 비해 그 함량이 현저히 감소하는 것으로 나타났다. 따라서 감마선 조사는 양념창란젓갈의 저장기간을 연장시키는데 효과적이며, 위해물질 감소를 통해 화학적 안전성을 개선시키는 것으로 나타났다. 또한, 10kGy로 조사하여 미생물학적 안전성을 높인 고춧가루를 첨가하여 제조한 양념젓갈의 이화학적 특성은 대조구에 비해 우수한 결과를 나타내었으며, 일반적으로 양념젓갈제조 후 $2.5{\sim}5\;kGy$로 감마선 조사한 시료와 동일한 품질수준을 나타내어 상업적 적용이 추천된다.

• 한국재료학회지
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• 제24권9호
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• pp.502-507
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• 2014

Recently, improvement in the conversion efficiency of silicon-based solar cells has been achieved by decreasing emitter doping concentration, because the lightly doped emitter can effectively prevent the recombination of electrons and holes generated by solar light irradiation. This type of emitter is very thin due to the low doping concentration, thus conductive materials (i.e., silver) used for front electrodes can easily penetrate the emitter during a firing process because of their large diffusivity in silicon. This results in junction leakage currents which might reduce cell efficiencies. In this study, $Al_2O_3$-coated Ag powders were synthesized by an ultrasonic spray pyrolysis method and applied to the conductive materials of the front electrode to control the junction leakage current. The $Al_2O_3$ shell obstructs the Ag diffusion into the emitter during the firing process. The powder is spherical with a core-shell structure and the thickness of the $Al_2O_3$ shell is tens of nanometers. Solar cells were fabricated using pure Ag powders or the $Al_2O_3$-coated Ag powder as front electrode materials, and the conversion efficiency and junction leakage current were compared to investigate the role of the $Al_2O_3$ shell during the firing processes.