• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.719-727
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• 1989

By using commercial zirconia powder CeO2-ZrO2 ceramics containing 8~16mol% CeO2 was made by heat treatment at 1350~155$0^{\circ}C$ for 1~10hr. The minimum amount of CeO2 for obtaining complete tetragonal phase was 12mol%, and in the tetragonal phase region fracture toughness of Ce-TZP was decreased with increasing CeO2 content and the maximum value was obtained when 12mol% CeO2 was added. The bending strength goes through maximum at 14mol% CeO2. Fracture mode of Ce-TZP transformed from intergranular to transgranular fracture with increasing CeO2 content, so the morphology of fracture surface of 16mol% Ce-TZP was wholly transgranular and this tendency was independent on grain size. The crystal structure of the 12mol% Ce-TZP was monoclinic with fringes along the grain boundaries which are lying in the particular plane from the TEM observation. The chemical composition of the sintered body was homogeneous as a whole and some amorphism or air pocket was observed at the triple junction.

• Biomedical Science Letters
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• v.16 no.1
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• pp.33-38
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• 2010

Culinary herbs and spices have received much attention since they contain high concentrations of bioactive ingredients for antioxidant and anti-inflammatory activities. Protection effect of the herb and spice against acute alcohol consumption has been investigated using zebrafish as a vertebrate model. During 30 days bathed in water containing 1% Et-OH and the designated herb or spice, the survival rate of the Et-OH group was decreased sharply (up to 20% at 10 days). The cinnamon-fed group showed the highest and longer survival rate up to 80% up to for 30 days under the presence of Et-OH, while clove-fed group showed 40% survival rate for 25 days. Et-OH group serum exhibited the weakest antioxidant ability from ferric ion removal ability (FRA) assay; FRA ability was increased in the cinnamon-fed group up to 414%, while the clove and laurel group increased 256% and 309%, respectively. Histologic observation and Oil-red O staining showed hepatic tissue damage was severe in the Et-OH group. The cinnamon- or clove-fed group showed much ameliorated hepatic tissue morphology with minimized steatosis. The cinnamon- or clove-fed group showed lower serum GOT and GPT levels than the Et-OH group. Among hepatic tissue extract, the clove-fed group exhibited the lowest level of GOT and GPT. These results suggest that consumption of cinnamon and clove might be beneficial to attenuate progress of acute fatty liver change by alcohol consumption.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.120-120
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• 2003

The metallic oxide nanomaterials including ZnO, Ga$_2$O$_3$, TiO$_2$, and SnO$_2$ have been synthesized by a number of methods including laser ablation, arc discharge, thermal annealing procedure, catalytic growth processes, and vapor transport. We have been interested in preparing the nanomaterials of Ga$_2$O$_3$, which is a wide band gap semiconductor (E$_{g}$ =4.9 eV) and used as insulating oxide layer for all gallium-based semiconductor. Ga$_2$O$_3$ is stable at high temperature and a transparent oxide, which has potential application in optoelectronic devices. The Ga$_2$O$_3$ nanoparticles and nanobelts were produced using GaN single crystals, which were grown by flux method inside SUS$^{TM}$ cell using a Na flux and exhibit plate-like morphologies with 4 ~ 5 mm in size. In these experiments, the conventional electric furnace was used. GaN single crystals were pulverized in form of powder for the growth of Ga$_2$O$_3$ nanomaterials. The structure, morphology and composition of the products were studied mainly by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM).).

• Progress in Superconductivity
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• v.13 no.2
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• pp.122-126
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• 2011

Superconducting $MgB_2$ thin films were fabricated by using a novel aerosol deposition technique wherein the pre-reacted powder is directly transformed into respective thin film. The formed thin films were characterized by X-ray diffraction technique and FE-SEM to understand its structure and morphology and the superconducting behavior has been characterized with the four probe resistivity measurement. The as-deposited thin films were formed into the frustrated amorphous structure, which were relaxed on the further heat treatment at $900^{\circ}C$ for 3 hrs. The relaxed amorphous $MgB_2$ thin films showed a comparatively high superconducting onset at about 38 K.

• Current Photovoltaic Research
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• v.3 no.2
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• pp.61-64
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• 2015

In solar industry, numerous researchers reported about cold spray method among various electrode formation technic, but there are no known a bonding mechanism of metal powder. In this study, a cross-section of copper electrode formed by cold spray method was observed and heterogeneous phase between silicon substrate and copper electrode was analyzed using morphology observation technic. SEM and TEM analysis were performed to analyze a crystallinity and distribution shape of heterogeneous copper phase. Molecular dynamics simulation was performed to calculate glass transition temperature of copper metal. In the result, amorphous copper phase was observed near interface between silicon substrate and metal electrode. The results of the molecular dynamics simulation show that an amorphous copper phase could be formed at a temperature below the melting point of copper because cold spraying resulted in a lower glass transition temperature.

• Journal of Pharmaceutical Investigation
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• v.34 no.5
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• pp.363-368
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• 2004

In order to investigate the effect of bovine serum albumin (BSA), as a pore former, on the controlled release of an antibiotic from a biodegradable polymeric device, polycaprolactone (PCL)-cefadroxil matrices were prepared by the solvent casting method. The amount of cefadroxil released from various formulations at $37^{\circ}C$ was measured by HPLC. The duration of antimicrobial activity of matrices against S. aureus was evaluated by measuring the diameters of the inhibition zone. The morphology of the matrices was investigated by scanning electron microscopy (SEM). The release rate and extent of cefadroxil from PCL matrix increased as the loading dose and particle size of BSA/cefadroxil mixture powder increased. Cefadroxil released from the matrix exhibited antibacterial activity for up to 4 days. SEM of the cross-section of matrix showed the typical channel formation after 3 days of release study. Thus, a biodegradable polymeric matrix loaded with antibiotic/BSA mixture can effectively prevent bacterial infection on its surface, thereby bringing about an enhancement of biocompatibility of biomaterials.

• Bulletin of the Korean Chemical Society
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• v.26 no.9
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• pp.1354-1358
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• 2005

Nano- and microstructured indium nitride crystals were synthesized by the reaction of indium oxide ($In_2O_3$) powder and its pellet with ammonia in the temperature range 580-700 ${^{\circ}C}$. The degree of nitridation of $In_2O_3$ to InN was very sensitive to the nitridation temperature. The formation of zero- to three-dimensional structured InN crystals demonstrated that $In_2O_3$ is nitridated to InN via two dominant parallel routes (solid ($In_2O_3$)-to-solid (InN) and gas ($In_2O$)-to-solid (InN)). The growth of InN crystals with such various morphologies was explained by the vapor-solid (VS) mechanism where the degree of supersaturation of In vapor determines the growth morphology and the vapor was mainly by the reaction of $In_2O$ with ammonia and partially by sublimation of solid InN. The pellet method was proven to be useful to obtain homogeneous InN nanowires.

• Corrosion Science and Technology
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• v.17 no.3
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• pp.91-100
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• 2018

Development of biodegradable implants for treatment of complex bone fractures has recently become one of the priority areas in biomedical materials research. Multifunctional corrosion resistant and bioactive coatings containing hydroxyapatite $Ca_{10}(PO_4)_6(OH)_2$ and magnesium oxide MgO were obtained on Mg-Mn-Ce magnesium alloy by plasma electrolytic oxidation. The phase and elemental composition, morphology, and anticorrosion properties of the coatings were investigated by scanning electron microscopy, energy dispersive spectroscopy, potentiodynamic polarization, and electrochemical impedance spectroscopy. The PEO-layers were post-treated using superdispersed polytetrafluoroethylene powder. The duplex treatment considerably reduced the corrosion rate (>4 orders of magnitude) of the magnesium alloy. The use of composite coatings in inducing bioactivity and controlling the corrosion degradation of resorbable Mg implants are considered promising. We also applied the plasma electrolytic oxidation method for the formation of the composite bioinert coatings on the titanium nickelide surface in order to improve its electrochemical properties and to change the morphological structure. It was shown that formed coatings significantly reduced the quantity of nickel ions released into the organism.

• Particle and aerosol research
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• v.5 no.1
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• pp.1-7
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• 2009

Fe- and V-doped titanium dioxide nanoparticles consisting of spherical primary nanoparticles were synthesized from a mixed liquid precursor by using the flame spray pyrolysis. The effects of dopant concentration on the powder properties such as morphology, crystal structure, and light adsorption were analyzed by TEM, XRD, and UV-Vis spectrophotometer, respectively. As the V/Ti molar ratio increased, pure anatase particles were synthesized. On the contrary, rutile phase particles were synthesized as the Fe/Ti ratio increased. Photocatalytic property of as-prepared $TiO_2:Fe,V$ nanoparticles was investigated by measuring the removal efficiency for volatile organic compounds (VOCs) under the irradiation of visible light. After 2 hrs under visible light, the removal efficiencies of benzene, p-xylene, ethylbenzene, and toluene were reached to 21.9%, 21.4%, 19.8% and 17.6% respectively.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.561-571
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• 1987

In case of glass ceramics and powder preparation from the metalakoxide solutions, metalakoxide solutions with a various species of alkoxy groups have unique characteristics. Therefore, in this study, the mixing ability of homogeneous sol, gel morphology and physical properties of gels were investigated by the changes in terms of the different four alkoxy groups, CH3-, C2H5-, i-C3H7-n-C4H9-, along with the catalyst for the purpose of the observation about the homogenous transition range from sol to gel. As a result, when the fixed condition was mol ratio of H2O/Si(OR)4=2.0 and variables were batch composition and addition amount of catalyst, the characteristics of Tetra-normal-Butoxysilane and Tetra-iso-propoxysilane systems had very narrow sol-gel conversion region than Tetramethoxysilane and Tetraethoxysilane system. And silicon-alkoxide, systems having narrow sol-gel conversion region were enlarged by addition of catalyst. In viewpoint of the weight loss of gel produced by hydrolysis of silicon alkoxide systems with different four alkoxy groups, the amounts of weight loss of gel containing large molecular alkoxy groups were much more than those of small molecular alkoxy group.