• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.591-596
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• 2006

Topology and molecular ordering of NPD(4,4'-bis-[N-(1-naphthyl)-N-phenyl-amino]biphenyl) thin films deposited under magnetic field with post-deposition annealing were investigated. NPD was deposited onto ITO glass substrates via thermal evaporation process in vacuum. It is of great importance for highly oriented organic/metal films to have improved device performances such as higher current density and luminance efficiency. AFM (Atomic Force Microscope) and XRD (X-Ray Diffraction) analyses were used to characterize the topology and structure of oriented NPD films. The multi-source meter was used to observe the current-voltage characteristics of the ITO (Indium-Tin Oxide) / NPD (4,4'bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl) / Al (Aluminum) device. While NPD thin films deposited under magnetic field were not molecularly well aligned according to the XRD results, the films after post-deposition annealing at $130^{\circ}C$ were well-oriented. AFM images show that NPD thin films deposited under magnetic field had a smoother surface than those deposited without magnetic field. The current-voltage performance of NPD thin films was improved due to the enhanced electron mobility in the well-aligned NPD films.

• Applied Chemistry for Engineering
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• v.2 no.2
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• pp.127-137
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• 1991

The dissociation and partial oxidation of $CH_3OH$ on polycrystalline $MoO_3$ powder catalyst were studied using thermal desorption spectrometry(TDS) under high vacuum condition. $CH_3OH$ was dissociatively adsorbed on $MoO_3$ in the forms of surface methoxy($-OCH_3$) and atomic hydrogen(-H). $CH_3OH$ desorbed at 425 K via the re-association of methoxy and adsorbed hydrogen atom, and HCHO desorbed at 545 K through the bond breakage of C-H in methoxy. Water TDS spectra showed two desorption peaks, that is, ${\alpha}$-peak at 428 K and ${\beta}$-peak at 586 K. It was suggested that ${\alpha}$-peak was due to the hydroxyl formed on $MoO_3$ surface during the dissociation of $CH_3OH$, and that ${\beta}$-peak was from the association of lattice oxygen and surface hydrogen atom formed by the bond breakage of C-H in methoxy. Pre-adsorbed oxygen on the surface of $MoO_3$ catalyst increased the amount of adsorption of $CH_3OH$ by promoting the dissociation of $CH_3OH$ on the surface, whereas pre-adsorbed water decreased the amount of adsorption of $CH_3OH$ by blocking of adsorption sites for $CH_3OH$.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.47-52
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• 2012

Porous carbon nanofibers were prepared as a gas sensor electrode to study the $CO_2$ sensing property based on effects of porosity and introduced amine functional groups. Electrospun fibers were obtained by using electrospinning method with polyacrylonitrile precursor and they were treated by the thermal treatment and chemical activation. Amine functional groups were introduced by the liquid state treatment using diethylenetriamine. The specific surface area increased up to $2000m^2/g$ by the chemical activation. The Introduced amine functional group was identified using FT-IR spectroscopy. $CO_2$ gas sensing property was improved as four folds via introduced amine functional groups on the activated carbon nanofiber. In conclusion, the gas sensing property was improved based on the developed porosity by the chemical activation and the chemical attraction of $CO_2$ gas by introduced functional groups.

• Elastomers and Composites
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• v.42 no.4
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• pp.238-248
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• 2007

A series of polyhydroxyamides(PHAs) having ether linkages in the polymer backbone were prepared via solution polycondensation at low temperature. These polymers were studied by FT-IR, $^1H-NMR$, DSC, TGA and PCFC. The PHAs exhibited inherent viscosities in the range of $0.5{\sim}1.1dL/g\;at\;35^{\circ}C$ in DMAc solution. Most of PHAs except PHA 3 were soluble in polar organic solvents such as N,N-dimethylacetamide(DMAc), N-methyl-2-pyrrolidone(NMP), and N,N-dimethylform-amide(DMF). Subsequent thermal treatment of PHAs afforded polybenzoxazols(PBOs). However, the PBOs were insoluble in a variety of solvents. Most of the PBOs except PBO 3 showed glass-transition temperature($T_g$) in the range of $200{\sim}246^{\circ}C$ by DSC and maximum weight loss temperature in the range of $597{\sim}697^{\circ}C$ in nitrogen by TGA. PBOs showed high char yields in the range of $51{\sim}64%$. PCFC results of the PBOs showed the heat release(HR) capacity, $8{\sim}65J/gK$ and total heat release(total HR), $2.4{\sim}4.7kJ/g$.

• Clean Technology
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• v.21 no.4
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• pp.248-256
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• 2015

MnO₂ was prepared by a hydrothermal process method in the range of 120-200 ℃ and 0.5-5 h, calcined at 300 ℃ after induction of precipitation using KMnO₄ and MnCl₂･4H₂O, and its catalytic activity was compared for CO oxidation. The catalysts were characterized using by X-ray diffraction, N₂-sorption, scanning electron microscopy, and temperature programmed reduction of H₂ or CO. The crystalline structure of pure α-MnO₂ or hybrid α/β-MnO₂ was controlled by the preparation conditions. The pure α-MnO₂ showed better catalytic activity and thermal stability than hybrid α/β-MnO₂. Especially, α-MnO₂ prepared at 150 ℃ for 1 h has the highest specific surface area 214 m² g^-1, reducibility and labile lattice oxygen species analyzed by H₂, CO-TPR, respectively. It also showed the best CO oxidation activity in both conditions of temperature programmed and isothermal reaction. The results came from the physicochemical properties of catalysts like the crystalline structure, specific surface area, reducibility and lattice oxygen species, and which are correlated with catalytic performance.

• Membrane Journal
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• v.20 no.4
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• pp.278-289
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• 2010

A series of composite membranes based on sulfonated poly(arylene ether sulfone) (SPAES) were prepared via addition of tetraethyl orthosilicate (TEOS) and solution casting method. The morphological structure, water uptake, proton conductivity of the resulting composite membranes were extensively investigated as function of the content of TEOS. By the sol-gel reaction, TEOS molecules were not completely converted to $SiO_2$ particles, but formed only oligomer-type. Also, EDS confirms that the resulting silicon dioxide was homogeneously distributed in the composite membranes. As the content of TEOS increased, the prepared membranes increased water uptake and proton conductivity at high temperature and low relative humidity condition. In particular, considerably high proton conductivity (0.015 S/cm) at $120^{\circ}C$ and 48%RH was demonstrated in the composite membrane containing 200% TEOS, which is 10 times greater than that of unmodified SPAES membrane. Also, the composite membranes were found to have enhanced thermal stability compared to the unmodified membrane.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.511-521
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• 2006

Homologue and isomer patterns of polychlorinated dibenzo-p-dioxins(PCDDs) and polychlorinated dibenzofurans(PCDFs) congeners formed from phenols in the gas-phase at $600{\sim}700^{\circ}C$ and via particle-mediated reactions at $400^{\circ}C$ were studied in an isothermal flow reactor. A mixture of 20 phenols in relative concentrations found in a municipal waste incinerator(MWI) stack gas was used for this study. PCDDs and PCDFs homologue and isomer patterns obtained from the phenol. From the phenol experiments, gas-phase formation at $600{\sim}700^{\circ}C$ favors PCDFs formation whereas particle-mediated formation at $400^{\circ}C$ favors PCDDs formation. DD and DF were most abundant homologue groups, PCDDs and PCDFs homologue fraction decreased with increasing number of chlorine substituents. PCDDs and PCDFs homologue and isomer fractions were almost constant from gas-phase formation and particle-mediated formation. Unsubstituted phenol, which was present in high concentration, played a significant role in the formation of PCDD/Fs congeners under both sets of experimental conditions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.4
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• pp.127-134
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• 2015

Aluminum nitride (AlN) single crystals have attracted much attention for a next-generation semiconductor application because of wide bandgap (6.2 eV), high thermal conductivity ($285W/m{\cdot}K$), high electrical resistivity (${\geq}10^{14}{\Omega}{\cdot}cm$), and high mechanical strength. The bulk AlN single crystals or thin film templates have been mainly grown by PVT (sublimation) method, flux method, solution growth method, and hydride vapor phase epitaxy (HVPE) method. Since AlN suffers difficulty in commercialization due to the defects that occur during single crystal growth, crystalline quality improvement via defects analyses is necessary. Etch pit density (EPD) analysis showed that the growth misorientations and the defects in the AlN surface exist. Transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD) analyses were employed to investigate the overall crystalline quality and various kinds of defects. TEM studies show that the morphology of the AlN is clearly influenced by stacking fault, dislocation, second phase, etc. In addition EBSD analysis also showed that the zinc blende polymorph of AlN exists as a growth defects resulting in dislocation initiator.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.594-602
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• 2011

The effect of ${\alpha}$-, ${\beta}$- and ${\gamma}$-picolines on the stereochemistry of the coordination compounds of lanthanide(III) nitrates derived from 4[N-(furfural)amino]antipyrine semicarbazone (FFAAPS) has been studied. The general composition of the present coordination compounds is [Ln(FFAAPS)$(NO_3)_3$Pic] (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy or Ho and Pic=${\alpha}$-, ${\beta}$- or ${\gamma}$-picolines). All these coordination compounds have been characterized by elemental analyses, molecular weight, molar conductance, magnetic susceptibility, infrared and electronic spectra. The infrared studies suggest that the FFAAPS behaves as a neutral tridentate ligand with N, N, O donor while ${\alpha}$-, ${\beta}$- or ${\gamma}$-picoline is coordinated to the lanthanide(III) ions via heterocyclic N-atom. Nitrates are bicovalently bonded in these compounds. From the electronic spectral data, nephelauxetic effect (${\beta}$), covalence factor ($b^{1/2}$), Sinha parameter (${\delta}%$) and the covalence angular overlap parameter (${\eta}$) have been calculated. Thermal stabilities of these complexes have been studied by thermogravimetric analysis. The coordination number of lanthanide(III) ions in the present compound is found to be ten. The antibacterial studies screening of the primary ligand FFAAPS and the complexes showed that the present complexes have moderate antibacterial activities.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2691-2696
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• 2009

Effects of representative group II and transition metal ions on the stability of the $poly(dA){\cdot}[poly(dT)]_2$ triplex were investigated by the van’t Hoff plot constructed from a thermal melting curve. The transition, $poly(dA){\cdot}[poly(dT)]_2\;{\rightarrow}\;poly(dA){\cdot}poly(dT)\;+\;poly(dT)$, was non-spontaneous with a positive Gibb’s free energy, endothermic (${\Delta}H^{\circ}$ > 0), and had a favorable entropy change (${\Delta}S^{\circ}$ > 0), as seen from the negative slope and positive y-intercept in the van’t Hoff plot. Therefore, the transition is driven by entropy change. The $Mg^{2+}$ ion was the most effective at stabilization of the triplex, with the effect decreasing in the order of $Mg^{2+}\;>\;Ca^{2+}\;>\;Sr^{2+}\;>\;Ba^{2+}$. A similar stabilization effect was found for the duplex to single strand transition: $poly(dA){\cdot}poly(dT)\;+\;poly(dT)\;→\;poly(dA)\;+\;2poly(dT)$, with a larger positive free energy. The transition metal ions, namely $Ni_{2+},\;Cu_{2+},\;and\;Zn_{2+}$, did not exhibit any effect on triplex stabilization, while showing little effect on duplex stabilization. The different effects on triplex stabilization between group II metal ions and the transition metal ions may be attributed to their difference in binding to DNA; transition metals are known to coordinate with DNA components, including phosphate groups, while group II metal ions conceivably bind DNA via electrostatic interactions. The $Cd_{2+}$ ion was an exception, effectively stabilizing the triplex and melting temperature of the third strand dissociation was higher than that observed in the presence of $Mg_{2+}$, even though it is in the same group with $Zn_{2+}$. The detailed behavior of the $Cd_{2+}$ ion is currently under investigation.