• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.122-130
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• 2005

Layered silicate was synthesized at hydrothermal condition from silica adding to various materials. Nano-clay was synthesized by intercaltion of various amine compounds into synthetic layered silicate. The products were analysed by XRD, SEM, and FT-IR in order to examine the condition of synthesis and intercalation. From the results, it was confirmed that kaolinite was synthesized from precipitated silica and gibbsite at $220^{\circ}C$ during 10 days, and hetorite was synthesized from silica sol at $100^{\circ}C$ during 48 h. Na-Magadiite was synthesized from silica gel at $150^{\circ}C$ during 72 h, and Na-kenyaite was synthesized from silica gel at $160^{\circ}C$ during 84 h. Nano-clay was prepared using synthetic layered silicate intercalated with various amine compounds. Kenyaite was easily intercalated by various organic compounds, and has the highest basal-spacing value among other layered silicates. Basal-spacing was changed according to the length of alkyl chain of amine comopounds. Polymer can be easily intercalated by dispersion with large space of interlayer. Finally, epoxy/nano-clay nanocomposite can be easily prepared.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.30-34
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• 1999

A polyacrylonitrile(PAN)-based carbon fiber tow was heat-treated by directly passing electric current through the tow. The effects of the stretching stress applied during high temperature heat-treatment of PAN-based carbon fibers were investigated by measuring the electric resistance changes taking place during the internal resistance heating. The structure parameters characterizing the stacks of carbon layer, such as interlayer spacing, sizes and orientation of the carbon fibers heat-treated with hot-stretching were evaluated as a function of surface temperature of tow during heat treatment in the range of $1000~2400^{\circ}C$. Though the layer extent in the fiber axis direction depends strongly on the electric resistance, the changes in a crystallite parameter is independent of the longitudinal strain.

• Macromolecular Research
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• v.11 no.6
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• pp.425-430
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• 2003

Two types of poly(n-butyl acrylate) copolymer/silicate nanocomposites have been produced: poly(n-butyl acrylate-co-methyl methacrylate) [P(BA-co-MMA)]/silicate nanocomposites and poly(n-butyl acrylate-co-styrene) [P(BA-co-ST)]/silicate nanocomposites. The P(BA-co-MMA)/silicate nanocomposites shows the exfoliated structures but a P(BA-co-ST)/silicate nanocomposites have intercalated structures, because the BA/MMA comonomer has a higher polarity (e-value in Q-e scheme) than the BA/ST comonomer. The BA/MMA comonomer expanded the interlayer space of the silicate wider than did the BA/ST comonomer. The thermal degradation onset point of the P(BA-co-MMA)/silicate nanocomposites was 43$^{\circ}C$ higher than that of pure P(BA-co-MMA). P(BA-co-MMA)T5%, P(BA-co-MMA)T10%, and P(BA-co-MMA)T20% exhibit 134,302, and 195% increases, respectively, in their storage moduli at -20$^{\circ}C$ relative to the pure copolymer.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.292-295
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• 2004

Recently, polymer-clay hybrid materials have received considerable attention from both a fundamental research and application point of view. This organ-inorganic hybrid, which contains a nanoscale dispersion of the layered silicates, is a material with greatly improved thermal and mechanical characteristics. Two classes of nanocomposites were synthesized using an unsaturated polyester resin as the matrix and sodium montmorillonite as well as an organically modified montmorillonite as the reinforcing agents. X -ray diffraction pattern of the composites showed that the interlayer spacing of the modified montmorillonite were exfoliated in polymer matrix. The mechanical properties also supported these findings, since in general, tensile strength, modulus with modified montmorillonite were higher than the corresponding properties of the composites with unmodified montmorillonite. Adding organically modified clay improved the tensile strength of unsaturated polyester by $22\%$ and the tensile modulus of unsaturated polyester was also improved by $34\%$.

• Carbon letters
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• v.1 no.3_4
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• pp.138-142
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• 2001

The effect of electrochemical surface treatments in KOH chemical solution on microstructures of carbon blacks was investigated in terms of surface functional values and XRD measurements. And their mechanical interfacial properties of the carbon blacks/rubber composites were studied by the composite tearing energy ($G_{IIIC}$). It was found that the development of basic-surface functional groups lead to the significant physical changes of carbon blacks, such as, decrease of the interlayer spacing ($d_{002}$), increase of the crystalline size along c-axis ($L_c$), and increase of degree of crystalline (${\chi}_c$). This treatment is possibly suitable for carbon blacks to be incorporated in a hydrocarbon rubber matrix, resulting in improving the hardness and tearing energy of the resulting composites.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.227-227
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• 2010

The intercalation chemistry of graphite presents an attractive route to obtain few-layered graphene platelets based on the expanded interlayer spacing. We report that the lithium can be intercalated into the graphite in a controllable manner by adjusting the variables such as temperature, pressure, and reaction time. From the X-ray diffraction experiments, the lithium-graphite intercalaltion compounds (Li-GICs) can be produced as the first stage compounds ($LiC_6$), the second-stage compounds ($LiC_{12}$), and the mixtures, which is most likely to be dependent on the temperature and reaction time. Since these Li-GICs are expected to facilitate the exfoliation of graphite, we investigated the feasibility of Li-GICs as a effective precursors for the generation of single-or few-layered graphite nano-platelets.

• Carbon letters
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• v.2 no.2
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• pp.99-104
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• 2001

Partial mesophase (PM) pitch precursor was prepared from fluidized catalytic cracking-decant oils (FCC-DO) by chemical reaction in the presence of $Br_2$. The PM pitch heated-treatment at $420^{\circ}C$ for 9 h exhibited the softening point of $297^{\circ}C$ with 23% yield, and 55% anisotropic content. The PM pitch precursor was melt-spun through circular nozzle by pressurized $N_2$, stabilized at $310^{\circ}C$, carbonized at $700^{\circ}C$, $1000^{\circ}C$, and $1200^{\circ}C$. The enough stabilization introduced 16.4% of the oxygen approximately. The stacking height ($L_{c002}$) and interlayer spacing ($d_{002}$) of the as-spun fibers were 4.58 nm and $3.45{\AA}$ and the value became minimum and maximum at $700^{\circ}C$ respectively in the carbonization procedure. The tensile strength increased with an increase in the heat treatment temperature exhibiting highest value of 750 MPa at $1200^{\circ}C$ carbonization.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.167-167
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• 2014

Graphite is used as a negative electrode active material of Lithium ion capacitor (LIC). At the cathod, electrostatic reaction of EDLC is a very high reaction rate compared to a oxidaion reduction reaction. When the graphite was expanded that the length between the sheet, the intercalation of lithium ions is smoothed. And thus, the power density increases. By measuring the XRD, it was confirmed that the increase in interlayer spacing of graphite. And by measuring an electrochemical reactionin Lithium Ion Battery (LIB), it was confirmed the tendency of power density is improved.

• Journal of Magnetics
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• v.1 no.1
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• pp.9-13
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• 1996

The effects of surface relaxation on surface and interface magnetism in Fe/Cr (001) are investigated using the highly precise all-electron total-energy full-potential linearized augmented plane wave method. The Fe-Cr interlayer spacing is deter-mined by total-energy calculation and it is found to be relaxed downward by 18%. For the relaxed system, the magnetic moment of surface Fe is highly suppressed to be $1.72\mu_B$compared to the unrelaxed case ($2.39\mu_B$). This reduction of magnetic moment is considered as a result of the enhanced hybridization between Fe-d and Cr-d states, which can be seen from the calculated density of states. This work suggests the importance of effect of relaxation to the surface and interface magnetism in Fe/Cr system.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.10 no.1
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• pp.49-74
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• 1984

Rheology of gels prepared with stearyl dimethyl benzyl ammonium hectorite (SDBAH) and various polar additives in n-butyl acetate was investigated by measuring the viscosity and rheogram. Including generally recognized polar additives, additional studies on the rheogram and viscosity were made with ether-type methyl cellosolve and carbitol, with dimethyl sulfoxide (DMSO) having sulfonyl group, and furthermore with above-mentioned polar additives containing small quantity of water, It was observed that molecular size, dipole moments and dielectric constants of polar additives had a great influence on viscosity increase and rheology of SDBAH gel, and the increase of SDBAH interlayer spacing was important factor in gel formation and viscosity change. It was also shown that thixotropy effect was increased with the increase of polar additive concentration, finally changed to rheopexy from thixotropy as the concentration of polar additives was increased more than about 40% of SDBAH weight. In addition thixotropy changed to rheopexy as the increase of shear rate. It was further found that the aqueous solutions of polar additives (water content, 5-25%) had more effects on rheology than additives without water, and particularly 95clo DMSO solution was the most effective. And the optimum concentration of polar additives showing maximum viscosity in the same SDBAH concentration system was examined.