• Carbon letters
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• 제2권1호
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• pp.1-8
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• 2001

Exfoliated graphite was found to sorb selectively a large amount of heavy oil, about 80 g of heavy oil floating on water per 1 g of exfoliated graphite, which is highly possible to be applied to recovering spilled heavy oil. Sorption capacity, selectivity and kinetics of exfoliated graphite were reviewed. The possibility of recovery of heavy oil from exfoliated graphite and recycling of both recovered heavy oil and exfoliated graphite was also discussed. Its sorption performance was compared with other materials which were reported to show sorption of heavy oil.

• Bulletin of the Korean Chemical Society
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• 제23권12호
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• pp.1801-1805
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• 2002

The graphite intercalation compounds(GIC) were prepared by a dry process that led to the intercalation from the direct reaction of gaseous $SO_3$ with flake type graphite. The basal spacing of the GIC was increased from 8.3 ${\AA}$ to 12 in the gallery height. The ejection of interlayer $SO_3$ molecules by the heating for 1 minute at $950^{\circ}C$ resulted in an exfoliated graphite (EG) with surprisingly high expansion in the direction of c-axis. The expansion ratios of the exfoliated graphites were increased greatly between 220 times and 400 times compared to the original graphite particles, and the bulk density was range of 0.0053 to 0.01 $g/cm^3$, depending on reaction time. The pore size distribution of exfoliated graphite was in the range of $10-170{\mu}m$, which exhibites both mesoporosity and macroporosities. This result indicates that the direct reaction of graphite paricles with gaseous $SO_3$ can be proposed as an another route for the exfoliated graphite having excellent physical properties.

• Bulletin of the Korean Chemical Society
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• 제34권7호
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• pp.2041-2043
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• 2013

A layered perovskite of Dion-Jacobson phase, $RbLaTa_2O_7$, was successfully exfoliated into colloidal suspension via successive ion-exchange and intercalation reaction. The pristine perovskite $RbLaTa_2O_7$ was synthesized by conventional solid-state reaction, and then, it was ion-exchanged with hydrochloric acid to obtain a protonic form of perovskite. The resulting proton-exchanged perovskite was reacted with ethylamine to increase interlayer spaces for further intercalation reaction. Finally, the ethylamine-intercalated form was exfoliated into nanosheets via an intercalation of bulky organic cations (tetrabutylammonium). According to X-ray diffraction (XRD) analysis, the TBA-intercalated form showed remarkably increased interlayer spacing (${\Delta}d$ = 1.67 nm) in comparison with that of the pristine material. Transmission electron microscopic image of exfoliated perovskite clearly revealed that the present exfoliated perovskite were composed of very thin layers. This exfoliated perovskite nanosheets could be applicable as building blocks for fabricating functional nanocomposites.

• 폴리머
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• 제26권3호
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• pp.375-380
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• 2002

합성한 polyamic acid의 말단기인 anhydride기와 반응시키기 위하여 나트륨 몬모릴로나이트에 diamine (p-phenylenediamine, m-phenylenediamine, and n-hexamethylenediamine)을 삽입시켰다. 그리고 4,4'-oxydianilline : 1,2,4,5-benzene tetracarboxylic dianhydride의 몰비를 1.50 : 1.53으로 하여 말단기가 anhydride된 polyamic acid를 합성하였다. 이렇게 치환된 몬모릴로나이트를 말단기가 anhydride된 polyamic acid와 N-methyl-2-pyrrolidone용액에서 반응시켰다 (polyamic acid/clay nanocomposite) 이것을 열이미드화하여 polyimide/clay 나노복합재료를 제조하였다. XRD와 TEM으로 관찰한 결과 실리케이트 층이 단일층으로 폴리이미드 매트릭스에 잘 분산되어 있는 박리형 폴리이미드 나노복합재료가 제조되었음을 알 수 있었다. 이들의 기계적 특성을 관찰한 결과 박리형 폴리이미드 나노복합재료의 경우가 순수한 폴리이미드와 삽입형 폴리이미드 나노복합재료의 경우보다 우수함을 알 수 있었다.

• Macromolecular Research
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• 제11권6호
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• pp.410-417
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• 2003

Poly(methyl methacrylate-co-acrylonitrile) [P(MMA-co-AN)]/Na-MMT nanocomposites were synthesized through emulsion polymerization with pristine Na-MMT. The nanocomposites were exfoliated up to 20 wt% content of pristine Na-MMT relative to the amount of MMA and AN, and exhibited enhanced storage moduli, E', relative to the neat copolymer. The exfoliated morphology of the nanocomposite was confirmed by XRD and TEM. 2-Acryla-mido-2-methyl-1-propane sulfonic acid (AMPS) widened the galleries between the clay layers before polymerization and facilitated the comonomers, penetration into the clay to create the exfoliated nanocomposites. The onset of the thermal decomposition of the nanocomposites shifted to a higher temperature as the clay content increased. By calculating areas of tan$\delta$ of the nanocomposites, we observed that the nanocomposites show more solid-like behavior as the clay content increases. The dynamic storage modulus and complex viscosity increased with clay content. The complex viscosity showed shear-thinning behavior as the clay content increased. The Young's moduli of the nano-composites are higher than that of the neat copolymer and they increase steadily as the silicate content increases, as a result of the exfoliated structure at high clay content.

• 한국포장학회지
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• 제19권2호
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• pp.95-102
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• 2013

고밀도 폴리에틸렌(High density polyethylene, HDPE)을 수분에 민감한 전기전자제품, 의약품 등을 위한 하이배리어 패키징 소재로써 적용하기 위해서 높은 가로세로비(High aspect ratio)를 가진 Exfoliated graphite (이하 EFG)를 필러로 도입하였다. 또한, 효과적인 분산성과 혼화성을 위해서 상용화제를 첨가하여 HDPE/EFG 나노복합필름을 제조하였다. HDPE/EFG 나노복합필름의 EFG 함량에 따른 화학적 특성, 모폴로지(Morphology), 열적 특성 및 수분차단 특성을 조사하였다. HDPE와 EFG 사이에 화학적 결합이나 상호작용이 약하지만, EFG를 첨가함에 따라 수증기 투과도는 127에서 78 (70 ${\mu}m{\cdot}g/m^2$, $day{\cdot}atm$)까지 감소되었다. 특히, HDPE/EFG 나노복합필름은 EFG의 함량이 0.5%일 때 가장 효과적이며, 그 이상의 함량에서는 물성이 향상되지 않았다. 따라서, 물성의 극대화를 위해서는 EFG의 분산성 향상 및 HDPE와 EFG의 화학적 결합 등의 혼화성 개선에 관한 추가적인 연구가 필요하다.

• Carbon letters
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• 제13권2호
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• pp.121-125
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• 2012

In the present work, exfoliated graphite nanoplatelets (EGN) of 1 ${\mu}m$ in average particle size, which were prepared by heating at $900^{\circ}C$ and then subjected to ultrasonic, ball-milling, and vibratory ball-milling techniques, were uniformly incorporated into phenylethynyl-terminated polyimide (PETI-5) resin. The fracture surface morphology and the electrical resistivity of the EGN/PETI-5 composites were investigated. The results showed that the fracture surfaces and the electrical resistivity strongly depended on the EGN content. The fracture surfaces became more ductile and roughened with increasing EGN and the electrical resistivity was gradually decreased with increased EGN loading, indicating the percolation threshold at 5 wt% EGN.

• Carbon letters
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• 제2권1호
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• pp.55-60
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• 2001

Graphite intercalation compounds (GIC) were prepared by direct reaction of $SO_3$ gas with flake graphite. The intercalated $SO_3$ molecules were ejected by rapid heating to $950^{\circ}C$ under an oxidizing atmosphere for about 1 minute, resulting in surprisingly high expansion in the direction of c-axis. The characteristics of the micro-structure and pore size distribution were examined with a SEM and mercury intrusion porosimetry. The XRD analysis and spectroscopic analysis were used for the identification of the graphite and surface chemistry state. The pore size distribution of the exfoliated graphite (EG) was a range of $1{\sim}170{\mu}m$. The higher expanding temperature the higher expanded volume, so oil sorption capacities were 58.8 g of bunker-C oil and 34.7 g of diesel oil per 1 g of the the EG. The sorption equilibrium was achieved very rapidly within several minutes. As the treatment temperature increases, bulk density decreases.

• Bulletin of the Korean Chemical Society
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• 제33권1호
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• pp.209-214
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• 2012

In this work, the reduced graphene nanosheets were synthesized from pre-exfoliated graphite flakes. The pristine graphite flakes were firstly pre-exfoliated to graphite nanoplatelets in the presence of acetic acid. The obtained graphite nanoplatelets were treated by Hummer's method to produce graphite oxide sheets and were finally exfoliated to graphene nanosheets by ultrasonication and reduction processes. The prepared graphene nanosheets were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). From the results, it was found that the preexfoliation process showed significant influence on preparation of graphite oxide sheets and graphene nanosheets. The prepared graphene nanosheets were applied to the preparation of conductive materials, which yielded a greatly improved electrical resistance of $200{\Omega}/sq$.

• Fibers and Polymers
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• 제4권3호
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• pp.97-101
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• 2003

Polymer/silicate nanocomposites were prepared via two-step manufacturing process: a master batch preparation and then mixing with matrix polymer. A hybrid of PMMA and Na-MMT with exfoliated structure was first prepared by emulsion polymerization of MMA in the presence of Na-MMT. For the case that SAN24, miscible with PMMA, is used as matrix, we could prepare a nanocomposite with exfoliated structure. However, SAN31 nanocomposite shows the aggregation and/or reordering of the silicate layers due to the immiscibility between SAN31 and PMMA.