• Journal of Power System Engineering
• /
• v.18 no.6
• /
• pp.7-12
• /
• 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 $25^{\circ}C$.

• Journal of the Korean Ceramic Society
• /
• v.47 no.2
• /
• pp.132-135
• /
• 2010

Thermal properties of layered metal chalcogenides such as $WT_2$ (T=S,Se) with two-dimensionally disordered structure were evaluated. Thermal conductivity shows a marked decrease after exfoliation and subsequent restacking because of random stacking of two-dimensional crystalline sheet, which circumvents thermal conduction pathways along longitudinal direction in anisotropic materials.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.11
• /
• pp.3225-3227
• /
• 2010

The thermal conductivity of layered metal chalcogenides such as $MT_2$ (M = Mo, W; T = S, Se) shows a marked decrease after exfoliation and subsequent restacking process. Random stacking of two-dimensional crystalline sheets circumvents thermal conduction pathways along a longitudinal direction, which results in a reduction in thermal conductivity. $WS_2$ and $WSe_2$ compounds retain p-type conducting behavior after exfoliation and restacking with decreased electrical conductivity due to the change in carrier concentration. $MoSe_2$ compound exhibits metallic behavior < $130^{\circ}C$ with a small Seebeck coefficient, which results from metastable 1T-$MoSe_2$ structure of the restacked phase.

• Transactions on Electrical and Electronic Materials
• /
• v.13 no.4
• /
• pp.204-207
• /
• 2012

Epoxy nanocomposite was synthesized through the exfoliation of organoclay in an epoxy matrix, which was composed of diglycidyl ether of bisphenol A (DGEBA), 4,4'-methylene dianiline (MDA) and malononitrile (MN). Organoclay was prepared by treating the montmorillonite with octadecyl trimethyl ammonium bromide (ODTMA). The exfoliation of the organoclay was estimated by wide angle X-ray diffraction (WAXD) analysis. In order to measure the cure rate of DGEBA/MDA (30 phr)/MN (5 phr)/organoclay (3 phr), differential scanning calorimetry (DSC) analysis was performed at various heating rates, and the data were interpreted by Kissinger equation. Thermal degradation kinetics of the epoxy nanocomposite were studied by thermogravimetric analysis (TGA), and the data were introduced to the Ozawa equation. The activation energy for cure reaction was 45.8 kJ/mol, and the activation energy for thermal degradation was 143 kJ/mol.

• Journal of Industrial Technology
• /
• v.35
• /
• pp.59-65
• /
• 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.

• Nuclear Engineering and Technology
• /
• v.52 no.4
• /
• pp.797-801
• /
• 2020

Most of irradiated graphite that should be disposed comes from moderators and reflectors of nuclear power plants. The quantity of irradiated graphite could be higher in the future if high-temperature reactors (HTRs) will be deployed. In this case noteworthy quantities of fuel pebbles containing semi-graphitic carbonaceous material should be added to the already existing 250,000 tons of irradiated graphite. Industry graphite is largely used in industrial applications for its high thermal and electrical conductivity and thermal and chemical resistance, making it a valuable material. Irradiated graphite constitutes a waste management challenge owing to the presence of long-lived radionuclides, such as ¹⁴C and ³⁶Cl. In the ENEA Nuclear Material Characterization Laboratory it has been successfully designed a procedure based on the exfoliation process organic solvent assisted, with the purpose of investigate the possibility of achieving graphite significantly less toxic that could be recycled for other purpose [1]. The objective of this paper is to evaluate the possibility of the scalability from laboratory to industrial dimensions of the exfoliation process and provide the prototype of a chemical plant for the treatment of irradiated graphite.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.29 no.1
• /
• pp.19-23
• /
• 2019

The PMMA (polymethyl methacrylate)/clay nanocomposites were synthesized by in situ radical polymerizations with different clay contents (3 and 7 wt%) using microwave heating. The nanostructure, optical, and thermal properties of the synthesized PMMA/clay nanocomposites were measured by XRD, TEM, AFM, UV-vis, and TGA. It was found that the intercalated- or exfoliated structure of PMMA/clay nanocomposites was strongly dependent on the content of clay. Thus, the imposition of microwave-assisted polymerization facilitated a delamination process of layered silicates to achieve exfoliation state of interlayer distance. The PMMA/3 wt% C10A nanocomposite with well-dispersed and exfoliated clay nano-layers showed the good optical transparency similar to pure PMMA in this study. The thermal decomposition rates of the PMMA/clay nanocomposites become to be lower compared to that of the pure PMMA, indicating the intercalated- or exfoliated inorganic silicate has high thermal stability. A possible reason is that the thermally segmental motion of PMMA polymer into inorganic silicate interlayer spacing has increased the thermal stability of the PMMA/clay nanocomposites.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.290.1-290.1
• /
• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.6
• /
• pp.538-543
• /
• 2008

Nanostructured materials are attracting increased interest and application. Exciting perspectives may be offered by electrical insulation. Epoxy/Organoclay nanocomposites may find new and upgraded applications in the electrical industry, replacing conventional insulation to provide improved performances in electric power apparatus, e.g, high voltage motor/generator stator winding insulation, dry mold transformer, etc. In the paper work, the electrical and thermal properties of epoxy/organoclay nanocomposites materials were studied. The electrical insulation characteristics were analyzed through the permittivity characteristics. by analyzing the permittivity spectra, it was found that dielectric constant becomes smaller with increase frequency and becomes larger with increase temperature. This indicates restriction of molecular motion and strong bonds at the epoxy/organoclay nanocomposites. The morphology of nanocomposites obtained was examined using TEM and X-ray diffraction. It has been shown that the presence of polar groups leads to an increased gallery distance and partial exfoliation. Nevertheless, full exfoliation of clay platelets has not been achieved.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.9
• /
• pp.2679-2682
• /
• 2010