• Transactions on Electrical and Electronic Materials
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• v.15 no.2
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• pp.87-90
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• 2014

The effects of electric field frequency on the ac electrical treeing phenomena in an epoxy/reactive diluent/layered silicate (1.5 wt%) were carried out, in needle-plate electrode arrangement. A layered silicate was exfoliated in an epoxy base resin, by using our ac electric field apparatus. To measure the treeing propagation rate, constant alternating current (AC) of 10 kV with three different electric field frequencies (60, 500 and 1,000 Hz) was applied to the specimen, in needle-plate electrode arrangement, at $30^{\circ}C$ of insulating oil bath. As the electric field frequency increased, the treeing propagation rate increased. At 500 Hz, the treeing propagation rate of the epoxy/PG/nanosilicate system was $0.41{\times}10^{-3}$ mm/min, which was 3.4 times slower than that of the epoxy/PG system. The electrical treeing morphology was dense bush type at 60 Hz; however, as the frequency increased, the bush type was changed to branch type, having few branches, with very slow propagation rate.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.649-656
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• 2013

A conventional epoxy-microsilica composite (EMC) and an epoxy-microsilica-nanosilicate composite (EMNC) were prepared in order to apply them to mold-type transformers, current transformers (CT) and potential transformers (PT). Nanosilicate was exfoliated in a epoxy resin using our electric field dispersion process and AC insulation breakdown strength at $30{\sim}150^{\circ}C$, glass transition temperature and viscoelasticity were studied. AC insulation breakdown strength of EMNC was higher than that of EMC and that value of EMNC was far higher at high temperature. Glass transition temperature and viscoelasticity property of EMNC was higher than those of EMC at high temperature. These results was due to the even dispersion of nanosilicates among the nanosilicas, which could be observed using transmission electron microscopy (TEM). That is, the nanosilicates interrupt the electron transfer and restrict the mobility of the epoxy chains.

• Journal of the Korean Graphic Arts Communication Society
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• v.22 no.2
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• pp.111-122
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• 2004

The purpose of this study was to investigate the possibility of application of microwave energy for the fabrication of polymer/clay nanocomposite. APES/Clay nanocomposites were prepared at $130^{\circ}C$ for 30min with various amount of MMT or OMMT used the melt-intercalation method applied the classical and microwave heating source. APES/Clay samples were characterized by the means of X-ray diffractometry (XRD), transmitted electron microscopy (TEM) differential scanning calorimetry (DSC), and rheometric dynamic analysis (RDA). It was found that intercalated or exfoliated state of the samples could be controlled by the clay type, clay content, and heating type.

• Journal of Integrative Natural Science
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• v.6 no.3
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• pp.183-186
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• 2013

Well defined 1-dimentional (1-D) photonic crystals of polystyrene replicas have been successfully obtained by removing the porous silicon from the free-standing rugate porous silicon/phenylmethylpolysiloxane composite film. Rugate porous silicon was prepared by an electrochemical etching of silicon wafer in HF/ethanol mixture solution. Exfoliated rugate porous silicon was obtained by an electropolishing condition. A composite of rugate porous silicon/phenylmethylpolysiloxane composite film was prepared by casting a toluene solution of phenylmethylpolysiloxane onto the top of rugate porous silicon film. After the removal of the template by chemical dissolution, the phenylmethylpolysiloxane castings replicate the photonic features and the nanostructure of the master. The photonic phenylmethylpolysiloxane replicas are robust and flexible in ambient condition and exhibit an excellent reflectivity in their reflective spectra. The photonic band gaps of replicas are narrower than that of typical semiconductor quantum dots.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.190-190
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• 2006

The approach used in present work allows achieving highly exfoliated state of layered silicate s through confinement of the charged nanobeads within the gallery of swollen pristine clay. The latter is principally promoted by ion exchange that involves polar functional groups on the surface of nanobeads and sodium cation in the interlayer gallery of layered silicates. Surface functionality of the nanobeads plays crucial role in establishment of strong interactions with silicate surface, and eventually, dispersion of individual silicate nanoplatelets.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.291-291
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• 2006

Two different sources of clay, Na-Bentonite (Thai local clay) and Na-Montmorillonite were modified with Hexadodeccyltrimethyl ammonium bromide. The nanocomposites of polypropylene were successfully prepared via melt blending in a co-rotating twin screw extruder by using PP-g-MA as a compatibilizer at various contents of organoclays. The morphology of nanocomposites was investigated by using XRD and SEM. The results showed that the intercalated and exfoliated structures were obtained. The thermal behavior was also studied by using DSC and TGA. The degradation temperature of filled PP was greater than that of unfilled PP by 20%. And, the tensile strength and modulus were improved when a small amount of organoclays were added.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.280-280
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• 2006

Na-bentonite (local clay mineral) and Na-montmorillonite were treated with quaternary alkylammonium cations. The effect of the molecular structure and functional groups of the surfactants on the organoclays was investigated by X-ray diffraction (XRD). For the preparation of nanocomposites, organoclays were melt-blended with polypropylene in a twin screw extruder and $Surlyn^{(R)$. ionomer was used as a reactive compatibilizer. The clay dispersions in the composites were investigated by X-ray diffraction (XRD). XRD spectra showed no peak at low angle indicated that the silicate clay layer has a nearly exfoliated dispersion in the polymer matrix. Thermal and mechanical properties of nanocomposites were higher than those of PP.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.281-281
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• 2006

In this study, the polyurethane which has versatile applications has been reinforced with the natural clay, hectorite. The hectorite has better properties than montmorillonite. There are studies on polyurethane and montmorillonite but polyurethane and hectorite composite is published first time. Polyurethane is industrial polyurethane which makes the study to be applicable to the industry. Exfoliated structure has been obtained without using organic modifiers due to the hydrophilic nature of the polymer matrix and the mineral clay. Mechanical properties have been improved as well.

• Journal of Environmental Science International
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• v.13 no.4
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• pp.429-434
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• 2004

The purpose of this study was to investigate the possibility of application of microwave energy for the fabrication of polymer/clay nanocomposite. APES/Clay nanocomposites were prepared at 13$0^{\circ}C$ for 30min with various content of clay by melt-intercalation method under classical and microwave heating source. APES/Clay samples were characterized by the means of X-ray diffractometry(XRD), thermal gravimetric analysis(TGA), and rheometric dynamic analysis(RDA). It was found that intercalated or exfoliated state was obtained in the samples according to the condition of organic modification, clay content, and heating source.

• Carbon letters
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• v.20
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• pp.26-31
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• 2016

In this study, we report a general method for preparation of a one-dimensional (1D) arrangement of Au nanoparticles on single-walled carbon nanotubes (SWNTs) using biologically programmed peptides as structure-guiding 1D templates. The peptides were designed by the combination of glutamic acid (E), glycine (G), and phenylalanine (F) amino acids; peptides efficiently debundled and exfoliated the SWNTs for stability of the dispersion and guided the growth of the array of Au nanoparticles in a controllable manner. Moreover, we demonstrated the superior ability of 1D nanohybrids as flexible, transparent, and conducting materials. The highly stable dispersion of 1D nanohybrids in aqueous solution enabled the fabrication of flexible, transparent, and conductive nanohybrid films using vacuum filtration, resulting in good optical and electrical properties.