• 동력기계공학회지
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• 제18권6호
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• pp.7-12
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• 2014

The effect of various synthesis conditions in the fabrication of graphene using the exfoliation methods has been investigated. Graphite oxide and graphene fabricated by various synthesis conditions were identified by SEM and XRD. Graphite oxide was made from graphite by the chemical oxidation, and graphene was manufactured from graphite oxide by thermal exfoliation method. As a result, it is confirmed that graphite oxide was well formed from graphite, and the graphene could be obtained from graphite oxide. And it was found that the interlayer spacing between the graphene layers depended on the reaction time and particle size, regardless of the reaction temperature from $5^{\circ}C$ to $25^{\circ}C$.

• 공업화학
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• 제30권2호
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• pp.133-140
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• 2019

Two-dimensional (2D) ultrathin molybdenum dichalcogenides $MoS_2$ has gained a great deal of attention in energy conversion and storage applications because of its unique morphology and property. The 2D $MoS_2$ nanosheets provide a high specific surface area, 2D charge channel, sub-nanometer thickness, and high conductivity, which lead to high electrochemical performances for energy storage devices. In this paper, an overview of properties and synthetic methods of $MoS_2$ nanosheets for applications of supercapacitors and rechargeable batteries is introduced. Different phases triangle prismatic 2H and metallic octahedral 1T structured $MoS_2$ were characterized using various analytical techniques. Preparation methods were focused on top-down and bottom-up approaches, including mechanical exfoliation, chemical intercalation and exfoliation, liquid phase exfoliation by the direct sonication, electrochemical intercalation exfoliation, microwave-assisted exfoliation, mechanical ball-milling, and hydrothermal synthesis. In addition, recent applications of supercapacitors and rechargeable batteries using $MoS_2$ electrode materials are discussed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.290.1-290.1
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• 2016

Grapehen, a single atomic layer of graphite, has been in the spotlight and researched in vaious fields, because its fine mechanical, electrical properties, flexibility and transparence. Synthesis methods for large-area graphene such as chemical vaper deposition (CVD) and mechanical, chemical exfoliation have been reported. In particular, chemical exfoliation method receive attention due to low cost process. Chemical exfoliation method require reduction of graphene oxide in the process of exfoliation such as chemical reduction by strong reductant, thermal reduction on high temperature, and optical reduction via ultraviolet light exposure. Among these reduction methods, optical reduction is free from damage by strong reductant and high temperature. However, optical reduction is economically infeasible because the high cost of short-wavelength ultraviolet light sorce. In this paper, we make graphene-oxide and lanthanoid ion mixture aqueous solution which has highly optical absorbency in selective wevelength region. Sequentially, we synthesize reduced graphene oxide (RGO) using the solution and visible laser beam. Concretely, graphene oxide is made by modified hummer's method and mix with 1 ml each ultraviolet ray absorbent Gd3+ ion, Green laser absorbent Tb3+ ion, Red laser absorbent Eu3+ ion. After that, we revivify graphene oxide by laser exposure of 300 ~ 800 nm layser 1mW/cm2 +. We demonstrate reproducibility and repeatability of RGO through FT-IR, UV-VIS, Low temperature PL, SEM, XPS and electrical measurement.

• Elastomers and Composites
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• 제39권1호
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• pp.51-60
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• 2004

본 연구에서는 organoclay를 혼합한 NR/BR blend의 가황특성, 동적점탄성 및 기계적 물성을 carbon black 및 silica를 함유한 배합고무와 비교 평가하였다. Solution 혼합법을 이용함으로써 광범위한 나노 복합체를 제조할 수 있었으며, 충전제의 함량은 10phr로 고정하였다. XRD 실험으로 clay의 삽입 및 박리정도를 측정하였다. 통상적인 혼합법을 이용할 경우 clay의 박리 또는 삽입정도가 미약한 반면 solution 혼합법을 이용할 경우 광범위한 박리형태의 clay 배합고무를 얻을 수 있음을 확인하였다. Clay 배합고무는 carbon black 및 silica를 함유한 배합고무에 비해 높은 tan ${\delta}$값을 나타내며, solution 혼합법을 이용할 경우 통상적인 혼합법에 의해 제조된 clay 배합고무에 비해 우수한 기계적 물성을 가짐을 확인할 수 있었다.

• 산업기술연구
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• 제35권
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• pp.59-65
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• 2015

As the fossil fuels are depleted nowadays, development of alternative energies is absolutely required in the world. Efficient production of hydrogen by water-splitting using solar energy can be one of the methods to solve the global energy and environmental problems. But this method has a problem of low conversion efficiency. The application of graphene can be one method to help increase the conversion efficiency. For this reason, mass production of high quality graphene is required. In this study, we prepared graphene using the chemical exfoliation method. We applied the Hummer's method and Tour's method to oxidize the graphite and could get the different Graphene Oxide(GO) from different process conditions. We also tried to convert the GO to graphene by thermal reduction and could remove functional group of GO effectively. The control of oxidation conditions was quite important to obtain the high quality graphene.

• 한국양식학회지
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• 제16권4호
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• pp.223-228
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• 2003

전복 치패를 부착기질로부터 분리시키는 박리는 전복양식에 있어서 치패의 선별과 밀도 조절을 위해 필수적인 작업이다. 현재 물리적인 방법과 마취제를 이용한 방법이 개발되어 있으나 치패의 손상이 없는 마취제에 의한 박리가 보다 효과적인 것으로 판단되고 있다. 따라서 본 연구는 요소비료($Co(NH_2)_2$)를 마취제로 이용하여 요소비료의 농도와 수온 등 물리적 요인이 까막전복 Haliotis discus의 박리율과 회복률에 미치는 영향을 조사함으로써 경제적이며 효과적인 박리 기술을 개발하고자 하였다. 실험 결과 9∼15%의 요소비료를 해수에 용해시키고 이를 자연 해수와 동일한 수온으로 상승시킨 후 박리를 실시하였더니 3분 이내에 97% 이상이 박리되었으며 치패의 회복률도 역시 높았다. 또한 요소비료 농도와 수온은 높을수록 박리율도 높았으나 치패의 회복률은 낮았다. 결론적으로 본 연구를 통하여 농업용 요소비료를 전복의 박리에 사용할 수 있음을 확인하였으며, 다른 종류의 전복에서도 본 기술의 적용이 가능할 것으로 생각되며, 본 기술은 현재 사용되고 있는 모든 전복 박리방법이나 전복 마취제로 쓰이는 화학약품을 대체할 수 있는 방법으로 판단된다.

• Fibers and Polymers
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• 제3권3호
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• pp.103-108
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• 2002

The viscosity effect of matrix polymer on melt exfoliation behavior of an organoclay in poly($\varepsilon$-caprolactone) (PCL) was investigated. The viscosity of matrix polymer was controlled by changing the molecular weight of poly($\varepsilon$-eaprolactone), the processing temperature, and the rotor speed of a mini-molder. Applied shear stress facilitates the diffusion of polymer chains into the gallery of silicate layers by breaking silicate agglomerates down into smaller primary particles. When the viscosity of PCL is lower, silicate agglomerates are not perfectly broken into smaller primary particles. At higher viscosity, all of silicate agglomerates are broken down into primary particles, and finally into smaller nano-scale building blocks. It was also found that the degree of exfoliation of silicate layers is dependent upon not only the viscosity of matrix but thermodynamic variables.

• 통합자연과학논문집
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• 제2권4호
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• pp.280-284
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• 2009

The unique electronic property of graphene sheets provides potential applications in nanocomposites and fabricating various nicroelectrical devices, such as field-effect transistors, ultrasensitive sensors, and electromechanical resonators. Several effective techniques have been developed for preparing graphene sheets. Among these technique, mechanical exfoliation can produce pure graphene and epitaxial graphene sheets have been prepared by treatment of silicon carbide wafers at high temperature. Recently, graphene sheets have been developed by chemical reduction method from graphene oxide. In this work, we have synthesized graphene sheets based on mechanical exfoliation and chemical reduction methods. Graphene sheets were characterized by field-effect scanning electron microscope (FE-SEM). The size of graphene sheets was from few hundreds nanometer to decades micrometer.

• 한국분말재료학회지
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• 제29권5호
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• pp.376-381
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• 2022

Tungsten disulfide (WS₂) nanosheets have attracted considerable attention because of their unique optical and electrical properties. Several methods for fabrication of WS₂ nanosheets have been developed. However, methods for mass production of high-quality WS₂ nanosheets remain challenging. In this study, WS₂ nanosheets were fabricated using mechano-chemical ball milling based on the synergetic effects of chemical intercalation and mechanical exfoliation. The ball-milling time was set as a variable for the optimized fabricating process of WS₂ nanosheets. Under the optimized conditions, the WS₂ nanosheets had lateral sizes of 500-600 nm with either a monolayer or bilayer. They also exhibited high crystallinity in the 2H semiconducting phase. Thus, the proposed method can be applied to the exfoliation of other transition metal dichalcogenides using suitable chemical intercalants. It can also be used with high-performance WS₂-based photodiodes and transistors used in practical semiconductor applications.

• 한국재료학회지
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• 제31권9호
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• pp.496-501
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• 2021

Metal halide perovskite nanocrystals, due to their high absorption coefficient, high diffusion length, and photoluminescence quantum yield, have received significant attention in the fields of optoelectronic applications such as highly efficient photovoltaic cells and narrow-line-width light emitting diodes. Their energy band structure can be controlled via chemical exchange of the halide anion or monovalent cations in the perovskite nanocrystals. Recently, it has been demonstrated that chemical exfoliation of the halide perovskite crystal structure can be achieved by addition of organic ligands such as n-octylamine during the synthetic process. In this study, we systematically investigated the quantum confinement effect of methylammonium lead bromide (CH₃NH₃PbBr₃, MAPbBr₃) nanocrystals by precise control of the crystal thickness via chemical exfoliation using n-octylammonium bromide (OABr). We found that the crystalline thickness consistently decreases with increasing amounts of OABr, which has a larger ionic radius than that of CH₃NH₃⁺ ions. In particular, a significant quantum confinement effect is observed when the amounts of OABr are higher than 60 %, which exhibited a blue-shifted PL emission (~ 100 nm) as well as an increase of energy bandgap (~ 1.53 eV).