• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.190-197
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• 2000

Anions such as C $l^{[-10]}$ , N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$, P $O_4$$^{3-}$, and organic anions, that do not become a part of the clay mineral crystal lattice, are of considerable interest in soils which are a potential sink caused by acid rain. In this paper, elution of native sulfate and breakthrough curves (BTC) were obtained from miscible displacement of non-specifically or specifically adsorbed anions through non-saturated or saturated Bt soil of Chungwon series. The shape and position of the BTC's could be affected by adsoprtion and ion exchange onto the soil particle surfaces. Measured BTC's for oxalic acid under unsaturated and saturated conditions showed that less pore volumes were required to displace the native S $O_4$$^{2-}$S from the soil column, and that maximum detection limit of oxalic acid reached earlier than under unsaturated. The retarded BTC's to the righthand side could be attributed by different adsorption behavior of each anion, although BTC's may be influenced by the smaller order of velocity change. The alternate breakthrough and elution curves show the rapid approach to the maximum detection limit of C/Co = 1, compared to progressive tailing of elution curve to reach to C/Co = 0. The probable explanation for asymmetric elution patterns for both anion is that the anion was selectively adsorbed on the positively charged soil surface from the solution passing in the soil column. On the other hand, the variations of pH in effluent showed that pH was increased to 7 in the first 6 pore volume and then gradually decreased to pH 4.

• Polymer(Korea)
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• v.33 no.1
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• pp.58-66
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• 2009

The thermotropic liquid crystalline behavior of the homologous series of cellulose tri[4-{4'-(nitrophenylazo) phenoxycarbonyl}] alkanoates (NACEn, n=2$\sim$8, 10, the number of methylene units in the spacer) have been investigated. All of the homologoues formed monotropic nematic phases. The isotropic-nematic transition temperature ($T_{iN}$) decreased when n is increased up to 7, but it became almost constant when n is more than 7. The plot of transition entropy at $T_{iN}$ against n had a sharp negative inflection at n=7. The sharp change at n=7 may be attributed to the difference in arrangement of the side groups. The melting temperature ($T_m$) and associated entropy change at $T_m$, in contrast with $T_{iN}$ and associated entropy change at $T_{iN}$, exhibited a distinct odd-even effect, suggesting that the average shape of the side chains in the crystalline phase is different from that in the nematic phase. The thermal stability and degree of order of the nematic phase observed for NACEn were significantly different from those reported for the homologous series of side-chain and combined type liquid crystal polymers bearing azobenzene or biphenyl units in the side chains. The results were discussed in terms of the differences in the chemical structure, the flexibility of the main chain, the mode of chemical linkage of the side group with the main chain, and the number of the mesogenic units per repeating unit.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.639-647
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• 1998

Al-containing titanium silicalite-1 ([Al]-TS-1) catalyst was prepared hydrothermally, and the effects of synthesis parameters such as silica/alumina sources, $SiO_2/TiO_2$ ratio, and aging treatment were investigated. The structure, crystal size, and shape were examined by XRD and SEM, and the extent of titanium incorporation into the zeolite framework was examined using UV-vis DRS spectroscopy. For [Al]-TS-1 catalyst preparation, aging of ca. 24h was essential, and the faster crystallization rates were achieved with Cab-O-Sil than with Ludox or TEOS as a silica source. In addition, the higher crystallinity and faster crystallization rate were obtained using sodium aluminate as an aluminum source. 2-butanol oxidation using $H_2O_2$ as an oxidant was carried out to confirm the redox property of the [Al]-TS-1. Acid sites catalyzed toluene alkylation study indicated that lattice titanium species in [Al]-TS-1 weakened the acid strength, and the para-ethyltoluene selectivity was enhanced as a results.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.90-95
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• 2014

Nylon66 extrudates as a function of the extrusion number were prepared by a twin screw extruder. Chemical structures, thermal properties, melt index, crystal structures, mechanical properties such as the tensile strength, elongation at break and impact strength, and rheological property were measured by FT-IR, $^1H$-NMR, melt indexer, DSC, TGA, XRD, universal tensile tester, Izod impact tester, and rheometer. FT-IR and $^1H$-NMR characterizations indicated that the number of extrusions did not affect the chemical structure. The decrease in the molecular weight was checked by the melt index of extrudates. There were no effects of the thermal history on the melting and degradation temperature. The tensile and impact strength and modulus were found to be similar, regardless of the number of extrusions, but the elongation decreased significantly. The complex viscosity of extrudates at low frequencies decreased with the extrusion number. No structural changes after extrusion were confirmed from the fact that there was no change in the slope and shape of G'-G" plot.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.350-356
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• 1998

$Y_{3-x}La_xFe_5O_{12}$ (x=0.0, 0.25, 0.5, 0.75, 1.0) powders and thin films were fabricated by a sol-gel method and their magnetic properties and crystal structure were investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and Mossbauer spectroscopy. XRD and Mossbauer spectroscopy measurements show that garnet powders annealed at 900 $^{\circ}C$ for 8 hours were single-phased and that thin films fired at 800 $^{\circ}C$ for 2 hours were crystallized without any preferred direction. X-ray diffraction patterns of $Y_{3-x}La_xFe_5O_{12}$ powders annealed at 1000 $^{\circ}C$ had only peaks of the garnet structure in case of x$\leq$0.75 but those of $Y_2LaFe_5O_{12}$ powders consisted of peaks from garnets and $LaFeO_3$. Mossbauer sepectra of garnet powders grown by the sol-gel method had a similar shape of those of powders grown by a conventional ceramic method. Grain sizes of garnet powders were 200~300 nm and the averaged surface roughness was 3.17 nm. Results of VSM measurements show the powders and thin films had soft magnetic properties and that the garnet powders had the largest saturation magnetization, 30 emu/g, and the lowest coercivity, 52 Oe.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.3
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• pp.227-235
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• 2021

In this study, we have prepared pure planar-type ZnO and calamine powder containing both ZnO and Fe₂O₃ components as a raw material for cosmetics with UV and blue band blocking functions. The planar-type ZnO ceramic powder having a high aspect ratio in the range of 20:1 to 50:1 was synthesized by precipitation method in a zinc acetate and sodium citrate mixed solution with the electrolyte obtained by power generation with a zinc-air battery. The content of Fe₂O₃ in the artificial calamine ceramic powder could be increased by increasing the amount of iron chloride solution added, and in this case, some of the blue region of visible light and ultraviolet light were remarkably absorbed. When potassium acetate was added, the decomposition of the Zn(OH)₄^2- anion in the solution was promoted to facilitate the growth of ZnO crystal in the form of a barrier wall in the vertical direction on the (0001) plane, which could increase UV absorption by providing more opportunities. By controlling the amount of iron chloride solution and potassium acetate solution added, the composition and shape of the thin film plate-shaped artificial calamine ceramic powder can be optimized, and when applied to cosmetic formulations, the light transmittance of the blue region can be greatly reduced.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.553-558
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• 2019

In present study, the cylindrical susceptor by the slip casting method was designed to apply high-temperature induction heating by using $(Mo,W)Si_2$ ceramics. $MoSi_2$-based materials were synthesized by SHS (Self-propagating High-temperature Synthesis) method. The phase and crystal structure of $MoSi_2$-based materials were confirmed by XRD analysis. The shape of cylindrical mold was synthesized for various thickness by using the slip casting method. Finally, the susceptor for induction heating was processed by sintering and heat treatment to form $SiO_2$ layer, which was confirmed on the surface of susceptor by SEM/EDS analysis. To evaluate the heating performance of $(Mo,W)Si_2$ cylinder susceptor, we measured the maximum surface temperature and heating rate in comparison with the rod heating element under constantly applied power. The induction heating of the $(Mo,W)Si_2$ cylinder showed excellent heating performance, reaches the maximum temperature of $1457^{\circ}C$, with the average heating rate of $19^{\circ}C/s$ at 2 kW

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.358-366
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• 2011

A homologous series of linear liquid crystal dimers, the ${\alpha},{\omega}$-bis(4-cyano-azobenzene-4'-oxy)alkanes (CATWETn, where n, the number of methylene units in the spacer, is 2~10) were synthesized, and their thermotropic liquid crystalline phase behavior were investigated. The CATWETn with n of 3 and 6 exhibited monotropic nematic phases, whereas other derivatives showed enantiotropic nematic phases. The nematic-isotropic transition temperatures of the dimers and their entropy variation at the phase transition showed a large odd-even effect as a function of n. This phase transition behavior was rationalized in terms of the change in the average shape of the spacer on varying the parity of the spacer. The thermal stability and degree of order in the nematic phase and the magnitude of the odd-even effect of CATWETn were similar to those for the methoxy-, nitro-, and pentyl-substituted dimers, while they were significantly different from those for the monomesogenic compounds, 1-{4-(4'-cyanophenylazo)phenoxy}alkylbromides and the side-chain liquid-crystalline polymers, the poly[1-{4-(4'-cyanophenylazo)phenoxyalkyloxy}ethylene]s. The results were discussed in terms of 'virtual trimer model' by Imrie.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.42-48
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• 2021

Zn and Al added LiNi0.85Co0.15O2 cathode materials were synthesized to improve electrochemical properties and thermal stability using a solid-state route. Crystal structure, particle size and surface shape of the synthesized cathode materials was measured using XRD (X-ray diffraction) and SEM (scanning electron microscopy). CV (cyclic voltammetry), first charge-discharge profiles, rate capability, and cycle life were measured using battery cycler (Maccor, series 4000). Strong binding energy of Al-O bond enhanced structure stability of cathode material. Electrochemical properties were improved by preventing cation mixing between Li+ and Ni2+. Large ion radius of Zn+ increased lattice parameter of NC cathode material, which meant unit-cell volume was expanded. NCZA25 showed 80% of capacity retention at 0.5 C-rate during 100 cycles, which was 12% higher than that of NC cathode. The discharge capacity of NCZA25 showed 104 mAh/g at 5 C-rate. NCZA25 achieved 36 mAh/g more capacity than that of NC cathod. NCZA25 cathode material showed excellent rate capability and cycling performance.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.36-44
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• 2023

Core-shell TiO₂/Ag nanoparticles were synthesized by a modified sol-gel process and the reverse micelle method using acetoxime as a reducing agent in water/dodecylbenzenesulfonic acid (DDBA)/cyclohexane. The structure, shape, and size of the TiO₂/Ag nanoparticles were investigated using X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA). The size of TiO₂/Ag nanoparticles could be controlled by changing the [water]/[DDBA] molar ratio values. The size and the polydispersity of TiO₂/Ag nanoparticles increased when the [water]/[DDBA] molar ratio rose. The resultant Ag nanoparticles over the anatase crystal TiO₂ nanoparticles exhibited a strong surface plasmon resonance (SPR) peak at about 430 nm. The SPR peak shifted to the red side with the increase in nanoparticle size. Conductive pastes with 70 wt% TiO₂/Ag nanoparticles were prepared, and the pastes were coated on the PET films using a screen-printing method. The printed paste films of the TiO₂/Ag nanoparticles demonstrated greater surface resistance than conventional Ag paste in the range of 405~630 μΩ/sq.