• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.604-609
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• 2002

Nanosized $BaCeO_3$ powders with the stoichiometric composition of a molecular level were synthesized by the citrate process based on the Pechini method. Polymeric precursor was formed by use of citric acid and ethylen glycol, as chelating agent of metal ions and reaction medium, respectively. Single phase orthorhombic structured $BaCeO_3$powders, about 100 nm sized and uniform shaped were obtained through the calcination of the polymeric precursor at $900^{\circ}C$ for 4 h. Extremely small quantities of carbonate ions($CO_^{2-}$) were completely decomposed at over $1100^{\circ}C$. The mean size of the powders was increased twice, however, it has very uniform distribution in its size and shape.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.122-129
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• 1999

Alumina tapes, having various weight ratios of alumina powder/(alumina+binder+plasticizer), X, and binder / (binder+plsticizer), Y, were prepared and their complex modulus was measured using Micro Fourier Rheometer. As the X and Y ratios increased, Transfer function(TF) magnitude and Transfer function (TF) phase increased and decreased, respectively, indicating that the elastic modulus of the tapes depends on the weight ratios. The temperature dependence of the viscosity of the tapes was visualized by the decreased TF magnitude and the increased TF phase. The Y ratio dependence of the complex modulus related to the glass transition temperature of the tapes and the moduls change by the Y ratio was higher than that by the X ratio within the comperature of the tapes and the modulus changes by the Y ratio was higher than that by the X ratio within the composition range, investigated in the present study. The measurement of the complex modulus of the alumina tapes suggested that the TF phase should be higher that 17$^{\circ}$for the tapes to be utilized for 3-dimensional shaping.

• Journal of the Korean Ceramic Society
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• v.39 no.5
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• pp.467-472
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• 2002

Long Carbon Nanotubes(CNTs) were cut by diamond lapping film followed by observation using SEM. The paste was prepared by mixing shortened CNT powder, ${\alpha}$-terpineol used as a solvent, and ethylcellulose as a binder. This paste was deposited on glass substrate by screen printing and extruded by syringe. After screen printing, several post-treatments were performed to control the alignment of CNTs perpendicular to the substrate. The deposited CNTs were scratched by sand paper or diamond lapping film. It was also treated by attachment followed by an immediate detachment using the adhesive tape. SEM observation indicates that excellent vertical alignment of CNTs could be achieved by simple post-treatments from the screen printed-CNTs paste. Similar alignment of CNTs is also observed in the as-extruded CNTs paste.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.587-591
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• 2009

Lithium salt have been used mainly as electrolyte of thermal battery for electricity storage. Recently, The 3phase lithium salt(LiCl-LiF-LiBr) is tried to use as electrolyte of thermal battery for high electric power. It is reported that LiCl-LiF-LiBr salt have high ion mobility due to its high lithium ion concentration. Solid lithium salt is melt to liquid state at above $500{^{\circ}C}$. The lithium ion is easily reacted with support materials. Because the melted lithium ion has small ion size and high ion mobility. For the increasing mechanical strength of electrolyte pellet, the research was started to apply ceramic filter to support of electrolyte. In this study, authors used SiOC web and glass fiber filter as ceramic mat for support of electrolyte and impregnated LiCl-LiF-LiBr salt into ceramic mat at above $500{^{\circ}C}$. The fabricated electrolyte using ceramic mat was washed with distilled water for removing lithium salt on ceramic mat. The washed ceramic mat was observed for lithium ion reaction behavior with XRD, SEM-EDS and so on.

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.918-923
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• 2002

In this work, CdTe films were deposited on CdS/ITO/glass substrate by a close spaced sublimation (CSS) method. A $Cu_2$Te layer was deposited on the CdTe film by evaporating $Cu_2$Te powder. Then the samples were annealed for p+ ohmic contact. TEM and XRD analysis showed that $CdTe/Cu_2$Te interface exhibited different forms with various annealing temperature. A good p+ ohmic contact was achieved when the annealing temperature was between $180^{\circ}C$ to $200^{\circ}C$. Best cell efficiency of 12.34% was obtained when post annealing temperature was $200^{\circ}C$ for 5 min. Thermal stress test of the CdS/CdTe cells with carbon back contact showed that the $Cu_2$Te contact was stable at $50^{\circ}C$ in $N_2$ and was slowly degraded at $100^{\circ}C$ in $N_2$. In comparison to the conventional carbon contact, the $Cu_2$Te contact showed a better thermal stability.

• The Journal of Advanced Prosthodontics
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• v.8 no.6
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• pp.479-488
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• 2016

PURPOSE. The aim of this study was to test the modulus of elasticity (E) across the interfaces of yttria stabilized zirconia (YTZP) / veneer multilayers using nanoindentation. MATERIALS AND METHODS. YTZP core material (KaVo-Everest, Germany) specimens were either coated with a liner (IPS e.max ZirLiner, Ivoclar-Vivadent) (Type-1) or left as-sintered (Type-2) and subsequently veneered with a pressable glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). A $5{\mu}m$ (nominal tip diameter) spherical indenter was used with a UMIS CSIRO 2000 (ASI, Canberra, Australia) nanoindenter system to test E across the exposed and polished interfaces of both specimen types. The multiple point load - partial unload method was used for E determination. All materials used were characterized using Scanning Electron Microscopy (SEM) and X - ray powder diffraction (XRD). E mappings of the areas tested were produced from the nanoindentation data. RESULTS. A significantly (P<.05) lower E value between Type-1 and Type-2 specimens at a distance of $40{\mu}m$ in the veneer material was associated with the liner. XRD and SEM characterization of the zirconia sample showed a fine grained bulk tetragonal phase. IPS e-max ZirPress and IPS e-max ZirLiner materials were characterized as amorphous. CONCLUSION. The liner between the YTZP core and the heat pressed veneer may act as a weak link in this dental multilayer due to its significantly (P<.05) lower E. The present study has shown nanoindentation using spherical indentation and the multiple point load - partial unload method to be reliable predictors of E and useful evaluation tools for layered dental ceramic interfaces.

• Journal of the Korean Chemical Society
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• v.27 no.4
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• pp.273-278
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• 1983

With the synthetic standards, valuable metals $(Ta_2O_5, Nb_2O_5, TiO_2, SnO_2$, and $ZrO_2$) in the tin slags have been determined by the x-ray fluorescence spectrometry. The powder sample and the standards are homogeneously mixed with anhydrous $Li_2B_4O_7$ and La_2O_3$ in weight ratio of 15 : 42 : 3 respectively. The mixed material is fused at $1,150^{\circ}C$ for 30 minutes to be changed into the glass bead. The bead is ground to (-) 325 mesh size and pelletized. The analytical results obtained in this work are consistent with the data obtained by other common methods within allowable error range. The standard deviation for $Ta_2O_5$ in PTS-H sample is 0.12 % at level of 3.40 % content.

• Polymer(Korea)
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• v.27 no.6
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• pp.549-554
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• 2003

Emeraldine salt of polyaniline-dodecylbenzenesulfdnic acid (PANI-DBSA) in organic solvents such as toluene and xylene was obtained by a direct one-step emulsion polymerization technique. When the molar ratio of DBSA to aniline monomer was 1.5:1, its solubility and electric property showed a maximum value and then the solid contents of PANI-DBSA was 8 wt% in toluene. The cast film of PANI-DBSA with no binder was obtained on glass or plastic substrates under ambient conditions. PANI solution can be also easily blended with polyurethane and polystyrene polymers in toluene. Improved electrical performance up to 5 S/cm was achieved with good light-transmittance up to 70% at 500 m thickness. They also showed more homogeneous morphology than that prepared with PANI-DBSA kom aqueous dispersion polymerization. The partially dispersed PANI-DBSA showed particles sizes of 50-400 m in organic solvents and their XRD pattern were observed from the powder sample.

• Journal of the Korean institute of surface engineering
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• v.35 no.1
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• pp.39-46
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• 2002

$Cu_2$$ZnSnS_4$(CZTS) thin film is one of the candidate materials for the solar cell. It has an excellent optical absorption coefficient as well as appropriate 1.4~1.5eV band gap. The purpose of this study is replacing a half of high-cost Indium(In) atoms with low-cost Zinc(Zn) atoms and the other half with low-cost Tin(Sn) atoms in the lattice of CIS. Thin films were deposited on ITO glass substrates using a compact target which were made by $Cu_2$S, ZnS, SnS$_2$ powder at room temperature by rf magnetron sputtering and were annealed in the atmosphere of Ar and $S_2$(g). We investigated potentialities of a low-cost material for the solar cell by measuring of thin film composition, the structure and optical properties. We could get an appropriate $Cu_2$$ZnSnS_4$ composition. Structure was coarsened with increasing temperature and (112), (200), (220), (312) planes appeared to conform to all the reflection Kesterite structure. A (112) preferred orientation was advanced with increasing the annealing temperature as shown in the diffraction peaks of the CIS cells and was available for photovoltaic thin film materials. The band gap increased from 1.51 to 1.8eV as the annealing temperature increased. The optical absorption coefficient of the thin film was about $10^4$$cm^{-1}$.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.72-72
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• 2018

The root of Angelica gigas Nakai (AGN) is used as a traditional herbal medicine in Korea for the treatment of many diseases. However, a major challenge associated with the usage of the active compounds from AGN is their poor water solubility. Therefore, this work aimed to enhance the solubility of active compounds by a chemical (viz. surfactant) and physical (hot melt extrusion) crosslinking method (CPC). Infrared Fourier transform spectroscopy (FT-IR) revealed multiple peaks in extrudate solids representing new functional groups including carboxylic acid, alkynes and benzene derivatives. Differential scanning calorimetry (DSC) analysis of the extrudate showed lower glass transition temperature (Tg) and lower enthalpy (${\Delta}H$) (Tg: $43^{\circ}C$; ${\Delta}H$: <6 (J/g)) compared to the non-extrudate (Tg $68.5^{\circ}C$; ${\Delta}H$: 123.2) formulations. X-ray powder diffraction (XRD) analysis revealed amorphization of crystal materials in extrudate solid. In addition, nanonization, enhanced solubility and higher extraction of phenolic compounds were achieved in the extrudate solid. Among the different extrudates, acetic acid- and Span 80-mediated formulations showed superior extractions. We conclude that the CPC method successfully enhanced the production of amorphous nano dispersions from extrudate solid formulations.