• Macromolecular Research
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• v.15 no.6
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• pp.498-505
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• 2007

This study demonstrated the in-situ functionalization with polymers of multi-walled carbon nanotubes (MWNTs) via emulsion polymerization. Polystyrene-functionalized MWNTs were prepared in an aqueous solution containing styrene monomer, non-ionic surfactant and a cationic coupling agent ([2-(methacryloyloxy)ethyl]trime-thylammonium chloride (MATMAC)). This process produced an interesting morphology in which the MWNTs, consisting of bead-string shapes or MWNTs embedded in the beads, when polymer beads were sufficiently large, produced nanohybrid material. This morphology was attributed to the interaction between the cationic coupling agent and the nanotube surface which induced polymerization within the hemimicellar or hemicylindrical structures of surfactant micelles on the surface of the nanotubes. In a solution containing MATMAC alone without surfactant, carbon nanotubes (CNTs) were not well-dispersed, and in a solution containing only surfactant without MATMAC, polymeric beads were synthesized in isolation from CNTs and continued to exist separately. The incorporation of MATMAC and surfactant together enabled large amounts of CNTs (> 0.05 wt%) to be well-dispersed in water and very effectively encapsulated by polymer chains. This method could be applied to other well-dispersed CNT solutions containing amphiphilic molecules, regardless of the type (i.e., anionic, cationic or nonionic). In this way, the solubility and dispersion of nanotubes could be increased in a solvent or polymer matrix. By enhancing the interfacial adhesion, this method might also contribute to the improved dispersion of nanotubes in a polymer matrix and thus the creation of superior polymer nanocomposites.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1119-1126
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• 2007

Hydrogen gas and carbon nanotubes along with nanocarbon were produced from commercial natural gas using fixed bed catalyst reactor system. The maximum amount of carbon (491 g/g of catalyst) formation was achieved on 25% Ni, 3% Cu supported catalyst without formation of CO/CO2. Pure carbon nanotubes with length of 308 nm having balloon and horn type shapes were also formed at 673 K. Three sets of catalysts were prepared by varying the concentration of Ni in the first set, Cu concentration in the second set and doping with K in the third set to investigate the effect on stabilization of the catalyst and production of carbon nanotubes and hydrogen by copper and potassium doping. Particle size analysis revealed that most of the catalyst particles are in the range of 20-35 nm. All the catalysts were characterized using powder XRD, SEM/EDX, TPR, CHN, BET and CO-chemisorption. These studies indicate that surface geometry is modified electronically with the formation of different Ni, Cu and K phases, consequently, increasing the surface reactivity of the catalyst and in turn the Carbon nanotubes/H2 production. The addition of Cu and K enhances the catalyst dispersion with the increase in Ni loadings and maximum dispersion is achieved on 25% Ni: 3% Cu/Al catalyst. Clearly, the effect of particle size coupled with specific surface geometry on the production of hydrogen gas and carbon nanotubes prevails. Addition of K increases the catalyst stability with decrease in carbon formation, due to its interaction with Cu and Ni, masking Ni and Ni:Cu active sites.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.75.2-75.2
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• 2010

We investigate the dependence of occurrence of bar in galaxies on galaxy properties and environment. The environmental conditions considered include the large-scale background density and distance to the nearest neighbor galaxy. We use a volume-limited sample of 33,296 galaxies brighter than $M_r$=-19.5+5logh at $0.02{\leqq}z{\leqq}0.05489$, drawn from the Sloan Digital Sky Survey Data Release 7. We classify the galaxies into early and late types, and identify bars by visual inspection. We find that the fraction of barred galaxies ($f_{bar}$) is 18.2% on average in the case of late-type galaxies, and depends on both u-r color and central velocity dispersion $(\sigma);f_{bar}$ is a monotonically increasing function of u-r color, and has a maximum value at intermediate velocity dispersion (${\sigma}{\simeq}170km\;s^{-1}$). This trend suggests that bars are dominantly hosted by systems having intermediate-mass with no recent interaction or merger history. We also find that $f_{bar}$ does not directly depend on the large-scale background density as its dependence disappears when other physical parameters are fixed. We discover the bar fraction decreases as the separation to the nearest neighbor galaxy becomes smaller than 0.1 times the virial radius of the neighbor regardless of neighbor's morphology. These results imply that it is difficult for bars to be maintained during strong tidal interactions, and that the source for this phenomenon is gravitational and not hydrodynamical.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.266-271
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• 2011

Single-walled carbon nanotube (SWCNT)/Epoxy composites were prepared for improving thermal conductivities and dispersion of SWCNTs in the epoxy matrix. Composites obtained different types of SWCNTs which are pristine and functionalized of the SWCNTs by acid and amine treatments. Three types of SWCNTs were dispersed in diglycidyl ether of bisphenol A (DGEBA) and bisphenol F (DGEBF). Enhanced interaction between functional groups on SWCNT and epoxy resins was evidenced by an improvement in the dispersion of the SWCNTs in the epoxy matrix. Thermal conductivity of composites containing acid SWCNTs were found to be much better than those containing pristine and amine treated SWCNTs.

• Polymer(Korea)
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• v.38 no.4
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• pp.411-416
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• 2014

Due to the polar characteristics of silica compared to carbon black, the degree of silica dispersion, which affects the mechanical properties of rubber compounds, is an important issue. Wolff first introduced the in-rubber structure of particles (${\alpha}_F$) to express the structure development in the compounds; however, with the introduction of bifunctional silanes, his theory could not explain the 3-dimensional network structure of the compounds. Later his theory was expanded to express the composite interaction parameter (in-rubber structure of the compound) (${\alpha}_C$), which included Wolff's filler-filler interaction parameter (${\alpha}_F$), however, there was no reported experimental result proving the theory. This research first experimentally expressed the in-rubber structure of the compound ${\alpha}_C$ (= ${\alpha}_F+{\alpha}_{FP}$(filler-silane-rubber interaction parameter) + ${\alpha}_P$ (rubber-rubber interaction parameter)) upon mono- and bifunctional silane treated silica filled natural rubber (NR) compounds. Using different structure silanes, i.e. PTES, OTES, TESPD, and TESPT, the ${\alpha}_C$ value of each compound was measured and calculated. The ${\alpha}_C$ value of TESPT treated silica filled compound was 1.64, which composed of ${\alpha}_F$ (0.99), ${\alpha}_{FP}$ (0.31), and ${\alpha}_P$ (0.34).

• Korean Journal of Environment and Ecology
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• v.31 no.3
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• pp.287-296
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• 2017

In order to check host plant diversity and to confirm the potential risk to be invaded, we documented host plant flora and plant part of C. pentagona, an invasive parasitic plant in field survey and induced parasitic infection by them in the laboratory experiment. Parasitic interaction(12% of total tree species) was found in twig and leaf of tree such as Quercus mongolica and Abies holophylla that was not developed into ligninfication. There were most host plant species belong to Compositae, but the species parasitic rate of family was higher in Cyperaceae, Polygonaceae and Leguminoceae. Through the inducible infection experiment with C. pentagona, all species except one species show parasitic interaction between host plan and C. pentagona. These result means that the limiting stage for invading area is dispersion process for invading other area in Korea. Infection plant part by C. pentagona was dominantly both shoot and leaf, rather than only leaf or only shoot. We found newly 12 families and 45 host plant species including 33 herbacious one and 12 woody one. Crop plant such as Setaria italica and 6 endangerd one such as Scrophularia takesimensis, especially the later rare endemic plant was to death by parasitic infection of C. pentagona. These results indicate that C. pentagona is potential risk to both wild and cultivated plant in Korea.

• Journal of the Korean Chemical Society
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• v.29 no.2
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• pp.98-103
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• 1985

Orbital interactions between two nonbonding orbitals have been investigated for heteroatom analogues of trimethylene diradical using MINDO/3 and STO-3G methods. The results showed that the conformers in which significant ${\sigma}$-aromatic stabilization is involved exhibited level order reversal to $n_-$ below $n_+$ as it was found for trimethylene diradical. Lone pair orbitals (LPO) were found to be stabilized by charge dispersion accompanying vicinal trans $n-{\sigma}^*$ interaction and hydrogen bonding. In systems with different heteroatoms, N and O, the contribution of the LPO of oxygen, $n_O$ was always greater in the lower level whereas that of nitrogen, nN, was greater in the higher level as can be expressed as : $n_{\pm}$(lower) = $n_O{\pm}{\lambda}_Nn_N.\;n_{\pm}(higher)\;=\;n_N{\pm}{\lambda}_On_O$. where ${\lambda}_i$< 1.0

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.857-863
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• 2014

In determining interaction between plasma and electromagnetic wave, plasma frequency and collision frequency are two key parameters. They are derived from electron density and temperature, which vary in an extremely wide range, depending on a plasma generator. Because the parameters are usually unknown, traditional researches have utilized simplified electron density model and constant electron temperature approximation. Introduction of plasma fluid model to electromagnetics is suggested to utilize relatively precise time dependent variables for given generator. Dielectric barrier discharge(DBD) generator is selected due to its simple geometry which allows us to use one dimensional analysis. Time dependent property is analyzed when microwave is launched toward parallel plate DBD plasma. Afterwards, attenuation tendency with the change of electron density and temperature is demonstrated.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.52.2-52.2
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• 2013

We explore the relative importance of the role of small-scale environment and large-scale environment in triggering nuclear activity of the local galaxies using a volume-limited sample with $M_r$ < -19.5 and 0.02 < z < 0.0685 selected from the Sloan Digital Sky Survey Data Release 7. The active galactic nuclei (AGN) host sample is composed of Type II AGNs identified with flux ratios of narrow emission lines with S/N > 6 and the central velocity dispersion of the sample galaxies is limited to have a narrow range between 130 < ${\sigma}$ < 200($km\;s^{-1}$), corresponding to 7.4 < $log(M_{BH}/M_{\odot})$ < 8.1 in order to fix the mass of the supermassive black hole at the center of its host galaxy. In this study, we find that the AGN fraction ($f_{AGN}$) of late-type galaxies are larger than of early-type galaxies and that for target galaxy with late-type nearest neighbor, $f_{AGN}$ starts to increase as the target galaxy approaches the virial radius of the nearest neighbor (about a few hundred kpc scale). The latter result may support the idea that the hydrodynamic interaction with the nearest neighbor as well as tidal interaction and merger also plays an important role in triggering the nuclear activity of galaxy. We also find that early-type cluster galaxies show decline of AGN activity compared to ones in lower density regions, whereas the direction of dependence of AGN activity for late-type galaxies is opposite.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.22 no.3
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• pp.85-93
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• 2016

Flower-like zinc oxide (FZnO) was successfully synthesized via a sonochemical process. The chemical structure, morphology, and antimicrobial properties of as- prepared FZnO were investigated. Additionally, pure LDPE and five different LDPE/FZnO composite films were prepared with different FZnO content by using a twin screw extruder. According to the FTIR and SEM analyses, there exists weak interfacial interaction between LDPE and FZnO. Compared with pure LDPE, the LDPE/FZnO composite films showed UV barrier and enhanced antimicrobial activity against Escherichia coli (E. coli) as a Gram-negative micro-organism and Staphylococcus aureus (S. aureus) as a Gram-positive micro-organism. To enhance the interfacial interaction and good dispersion of FZnO into the LDPE matrix, and resultantly to such as UV barrier and antimicrobial properties of LDPE/FZnO composite films as the packaging materials, further efforts are required.