• Bulletin of the Korean Chemical Society
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• 제9권6호
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• pp.368-376
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• 1988

Transition metal PSSA ionomers containing Co(II), Ni(II), Cr(III), Ru(III), and Rh(III) are investigated by IR, Far-IR, UV-Vis and DSC. Reliable IR Spectroscopic criteria are established for assessing the degree of ion-exchange of PSSA ionomers and the local structures around metal cations in them. In the hydrated transition metal PSSA ionomers, the ionic groups are solvated by water molecules and there is no significant interactions between sulfonate group and metal cations. The visible spectra indicated that metal cations are present as [M$(H_2O)_6$]$^{n+}$ with Oh symmetry. Their $T_g$ values increase as the extent of ionic site concentration increases, but there is no direct dependence of $T_g$ on the nature of metal cations or their oxidation states. Thus, the water content in PSSA ionomer is found to have dominant influence on $T_g$ of hydrated transition metal PSSA ionomers. Dehydration of the hydrated transition metal PSSA ionomers results in direct interaction between ionic groups and significant color changes of the ionomers due to the changes of the local structures around metal cations. On the base of spectral data, their local structures are discussed. In case of dehydrated 12.8 and 15.8 mol % transition metal PSSA ionomers, no glass transition is observed in 25-$250^{\circ}C$ region and this is believed to arise from the formation of highly crosslinked structures caused by direct coordination of sulfonate groups of metal cations. In the 6.9 mol % transition metal PSSA ionomers, the glass transition is always observed whether they are hydrated or dehydrated and this is though to be caused by the sufficient segmental mobility of the polymer backbone.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.1236-1239
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• 2004

We developed a new cholesteric material for bistable LCDs. The material consists of dispersion of sub-micron ferroelectric particles in cholesteric host. We found that the doping of the cholesteric with ferroelectric particles in small concentration (< 1% by weight) strongly improved basic characteristics of the transition between poly-domain planar texture and focal conic texture. Decrease of the driving voltage, increase of the reflection contrast and the steepness of the transition is associated with giant steady dipole and dielectric constant of the ferroelectric particles.

• 한국세라믹학회지
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• 제31권2호
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• pp.201-205
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• 1994

Glasses being prepared, measurements and investigations of glass transition temperature and IR edge optical absorption have been performed for the compositions of 56ZrF4-14BaF2-6LaF3-4AlF3-(20-x)NaF-xLiF. Values for transition temperature of these glasses decrease in proportion to increasing LiF mol%(x) in the range of 0

• 한국대기환경학회지
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• 제21권6호
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• pp.625-630
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• 2005

This study was focused on the catalytic activity for the combustion of low-concentration methane using various commerical catalysts (six transition metal catalysts in Russia and one rare earth metal (Honeycomb) catalyst in Korea). Catalytic activity was strongly influenced by the type and loading content of metal supported in catalyst. Catalytic performance showed the highest activity in Honeycomb catalyst including rare earth metal, which was the most expensive catalyst, while the next was the catalyst supported Cu with high content (AOK-78-52) and also that supported Cr and Co (AOK-78-56). However, both AOK-78-52 and AOK-78-56 catalysts that were very cheap had lower activation energy than Honeycomb catalyst. In the economical field, both AOK-78-52 and AOK-78-56 catalysts with transition metals showed a good alternative catalyst on the combustion of methane.

• Tribology and Lubricants
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• 제20권2호
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• pp.91-96
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• 2004

Wear behavior of self-mated stainless steels in NaCl solution has been investigated. The experiment was done in the corrosive liquid of which NaCl concentration of $0\~3\%$ and temperature of $15\~90^{\circ}C$. Two kinds of wear type were observed: one is 'severe wear' type which shows gradually increasing wear volume with increasing sliding distances, the other is 'mild wear' type which shows change of wear rate from high value to low at transition distance. The specific wear rate in severe wear type was not sensitive to the liquid temperature and concentration of NaCl but stable at value of $1\times10^{-3}\;mm^3$ approximately.

• 한국잠사곤충학회지
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• 제42권2호
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• pp.114-119
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• 2000

Effects of ethanlo treatment on the structural and thermal characteristics of regenerated Antheraea pernyi silk fibroin (RSF) were investigated. Infrared spectroscopy and X-ray diffractometry showed that the conformational transition of RSF might be affected by concentration of ethanol and its treatment time. The structure of RSF was rapidly changed from random coil to $\beta$-sheet conformation when RSF was treated with les than 75% ethanol concentration. However, RSF treated with ethanol(100%) did not show conformational change. Differential scanning calorimetry showed that exotherm at 232$\^{C}$ disappeared and the intensity of endotherm at 228$\^{C}$ decreased with treatment of 75% ethanol. Dynamic thermal analysis showed that loss modulus (E") and tan $\delta$$\_$E/ of RSF treated with aqueous ethanol was broaden and shifted to higher temperature in comparison with those of untreated RSF.

• 반도체디스플레이기술학회지
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• 제11권1호
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• pp.35-39
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• 2012

$YAlO_3:Tb{_x}^{3+}$ has been synthesized by a combustion process and the concentration x of Tb was varied from 0.001 and 0.05 mol% per mole of $YAlO_3$. The emission optical properties on the $YAlO_3:Tb{_x}^{3+}$ have been investigated by time-resolved photoluminescence spectra and decay curves of center wavelength. The emission color changes from blue to green with increasing the $Tb^{3+}$ concentration from x= 0.001 to 0.05 mole fraction in $YAlO_3$ host. This emission color change can be explained in terms of cross-relaxation processes. Decay curves of emission intensity indicate that the type of energy transfer is donor-acceptor transition.

• 한국세라믹학회지
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• 제36권5호
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• pp.478-482
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• 1999

SrTiO3 :Al, Pr phosphor as an oxide compound phosphor is expect to be applied for a field emission display(FED). In this phosphor the excitation spectrum shows a different tendency according to an addition Al3+ and Pr3+ In this excitation spectrum the main peak at 359 nm represent excitation level of Pr3+(1S0longrightarrow1D2 transition) and the absorption characteristic according to Ti/Sr molar ratio is influenced by the structure symmetry. The emission spectrum exhibits the red luminescence with the radiative decay of the 1D2 states(1D2 longrightarrow3H4 transition) The concentration quenching phenomena at 1D2 state shows up as Al3+ and Pr3+ ion concentration increases.

• 반도체디스플레이기술학회지
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• 제9권3호
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• pp.1-4
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• 2010

First-principles calculations based on spin density functional theory are performed to study the spin-resolved electronic properties of AlN doped with a Cu concentration of 6.25%-18.75%. The ferromagnetic state is more energetically favorable state than the antiferromagnetic state or the nonmagnetic state. For $Al_{0.9375}Cu_{0.0625}N$, a global magnetic moment of 1.26 mB per supercell, with a localized magnetic moment of 0.75 $m_B$ per Cu atom is found. The magnetic moment is reduced due to an increase in the number of Cu atoms occupying adjacent cation lattice position. For $Al_{0.8125}Cu_{0.1875}N$, the magnetism of the supercell disappears by the interaction of the neighboring Cu atoms. The nonmagnetic to ferromagnetic phase transition is found to occur at this Cu concentration. The range of concentrations that are spin-polarized should be restricted within very narrow.

• Progress in Superconductivity
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• 제3권1호
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• pp.5-12
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• 2001

Our experimental research focuses on manipulating pinning deflects to alter the phase diagram of vortex matter, creating new vortex phases. Vortex matter offers a unique opportunity for creating and studying these novel phase transitions through precise control of thermal, pinning and elastic energies. The vortex melting transition in untwinned YB $a_2$C $u_3$ $O_{7-}$ $\delta$/ crystals is investigated in the presence of disorder induced by particle irradiation. We focus on the low disorder regime, where a glassy state and a lattice state can be realized in the same phase diagram. We follow the evolution of the first order vortex melting transition line into a continuous transition line as disorder is increased by irradiation. The transformation is marked by an upward shift in the lower critical point on the melting line. With columnar deflects induced by heavy ion irradiation, we find a second order Bose glass transition line separating the vortex liquid from a Bose glass below the lower critical point. Furthermore, we find an upper threshold of columnar defect concentration beyond which the lower critical point and the first order melting line disappear together. With point deflect clusters induced by proton irradiation, we find evidence for a continuous thermodynamic transition below the lower critical point..