• Food Science and Biotechnology
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• v.17 no.1
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• pp.20-25
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• 2008

Effects of commercial and lab-generated gellan gums on the textural properties, structure, and aging of wheat and maize starch gels were investigated using a rapid visco-analyzer (RVA), rheometer, scanning electron microscope (SEM), and X-ray diffractometer. Gellan and guar gums increased the peak and final viscosities, but xanthan gum and gum arabic reduced them. The maize starch had higher breakdown viscosity than the wheat starch, regardless of the type of gum. The hardness of all starch gels increased during storage, but their cohesiveness and springiness decreased. The degree of the gel hardness showed higher in maize starch than in wheat starch and the effect of gum addition had a difference with gum type. The wheat starch-guar and -gellan gum mixed gels showed higher elasticity and cohesiveness after storage. The starch-gellan gum mixed gels had dense and stable network structures, and were well maintained even after 7 days of storage. Most of the gums had anti-aging effect on X-ray diffraction pattern of starch gels.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.127-134
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• 2016

A series of Ce-doped ZnO (Ce/ZnO) nanostructures were fabricated using the co-precipitation method, then a simply nontoxic hydrothermal approach was proposed for preparation of reduced graphene oxide (rGO)-Ce/ZnO composites. The synthesized composites were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), electrochemical impedance spectroscopy (EIS), UV-vis diffuse reflectance spectroscopy (DRS) techniques and Raman pattern. The as-synthesized rGO-Ce/ZnO composites showed high photodecomposition efficiency in comparison with the rGO-ZnO, Ce/ZnO, pure ZnO under UV, visible-light and sunlight irradiation. The degradation of methylene blue (MB) (10 mg/L, 100ml) by 95.8% within 60 min by using rGO-2 (10 mg) under sunlight irradiation was observed. The repeated use of the rGO-2 was investigated, and the results showed almost no decay in the catalytic activity.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.393-397
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• 2012

We report a new route to synthesize high quality zinc blende CdS and ZnS nanocrystals in noncoordinating solvent 1-octadecene, using dodecanethiol (DDT) molecules as both the sulfur source and surface capping ligands. Different reaction temperatures and Cd(Zn)/DDT molar ratios were tested to optimize the synthesis conditions. Absorption photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) pattern, and transmission electron microscopy (TEM) were used to characterize assynthesized nanocrystals. The narrow half width at the half-maximum on the long wavelength side of the firstexcitonic absorption peak and TEM images demonstrated nearly monodisperse size distributions of asprepared CdS, ZnS, and CdS/ZnS core/shell nanocrystals. Only trap emissions of the nanocrystals were detected when the amount of DDT was excessive, this came from the strong quenching effect of thiol groups on the nanocrystal surfaces. After overcoating with ZnS shells, band-gap emissions of CdS nanocrystals were partially recovered.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.1995-2000
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• 2013

Layered $Li_{1.2}(Fe_{0.16}Mn_{0.32}Ni_{0.32})O_2$ was prepared by the mixed hydroxide method at various temperatures. Xray diffraction (XRD) pattern shows that this material has a ${\alpha}-NaFeO_2$ layered structure with $R{\bar{3}}m$ space group and that cation mixing is reduced with increasing synthesis temperature. Scanning electron microscopy (SEM) reveals that nano-sized $Li_{1.2}(Fe_{0.16}Mn_{0.32}Ni_{0.32})O_2$ powder has uniform particle size distribution. X-ray absorption near edge structure (XANES) analysis is used to study the local electronic structure changes around the Mn, Fe, and Ni atoms in this material. The sample prepared at $700^{\circ}C$ delivers the highest discharge capacity of 207 $mAhg^{-1}$ between 2-4.5 V at 0.1 $mAcm^{-2}$ with good capacity retention of 80% after 20 cycles.

• Corrosion Science and Technology
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• v.5 no.2
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• pp.77-83
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• 2006

The plasma electrolytic oxidation (PEO) process is a relatively new surface treatment technique that produces a chemically stable and environment-friendly electrolytic coating that can be applied to all types of magnesium alloys. In this study, the characteristics of oxide film were examined after coating the extruded AZ31 alloy through the PEO process. Hard ceramic coatings were obtained on the AZ31 alloy by changing the coating time from 10min to 60min. The morphologies of the surface and the cross-section of the PEO coatings were examined by scanning electron microscopy and optical microscopy, and the thickness of the coating was measured. The X-ray diffraction pattern of the coating shows that the coated layer consists mainly of the MgO and $Mg_2SiO_4$ phases after the oxidation reaction. The hardness of the coated AZ31 alloy increased with increasing coating time. In addition, the corrosion rates of the coated and uncoated AZ31 alloys were examined by salt spray tests according to ASTM B 117 and the results show that the corrosion resistance of the coated AZ31 alloy was superior to that of the un-coated AZ31 alloy.

• Advances in nano research
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• v.6 no.2
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• pp.183-200
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• 2018

In the present study silver nanoparticles (AgNPs) were successfully synthesized using aqueous extract of Sargassum muticum. The aqueous extract (10%) treated with 1 mM silver nitrate solution resulted in the formation of AgNPs and the surface plasmon resonance (SPR) of the formed AgNPs was recorded at 360 nm using UV-Visible spectrophotometer. The molecules involved in the formation of AgNPs were identified by Fourier transform infrared spectroscopy (FT-IR), surface morphology was studied by using scanning electron microscopy (SEM), SEM micrograph clearly revealed the size of the AgNPs was in the range of 40-65 nm with spherical, hexagonal in shape and poly-dispersed nature, and X-ray diffraction spectroscopy (XRD) was used to determine the crystalline structure. High positive Zeta potential (36.5 mV) of formed AgNPs indicates the stability and XRD pattern revealed the crystal structure of the AgNPs by showing the Bragg's peaks corresponding to (111), (200), (311) and (222) planes of face-centered cubic crystal phase of silver. The synthesized AgNPs exhibited effective anticancerous activity (at doses 25 and $50{\mu}g/ml$ of AgNPs) against Breast cancer cell line (MCF7).

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.406-410
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• 2016

Carbon-coated sodium iron pyrophosphate ($Na_2FeP_2O_7$) was prepared by a simple and low-cost pyro-synthesis route for further use as the cathode for Na-ion batteries. The X-ray diffraction (XRD) pattern of the sample annealed at $650^{\circ}C$ confirmed the pure triclinic phase of $Na_2FeP_2O_7$. Electron microscopy studies revealed a cross linked plate shape morphology of the $Na_2FeP_2O_7$ sample. When tested for application in Na-ion battery, the $Na_2FeP_2O_7$ cathode showed two redox pairs in the potential window of 2.0-4.0 V. The cathode registered initial discharge and charge capacities of 80.85 and 90 mAh/g, respectively, with good cycling performance.

• Transactions of the Korean hydrogen and new energy society
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• v.4 no.1
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• pp.31-39
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• 1993

In order to improve the hydrogen storage capacity and the activation property of the $MmNi_{4.5}Al_{0.5}$ alloy, the multiphase alloy system are prepared by adding the excess Zr in $MmNi_{4.5}Al_{0.5}$ alloy. It is estimated from the X-ray diffraction pattern and the energy dispersive X-ray analysis that the 2nd phases in $MmNi_{4.5}Al_{0.5}Zr_x$ alloys are $ZrNi_3$, ${\beta}$-Zr. Their morphology is also examined by the scanning electron microscope, and it shows the needle-like precipitation. As the Zr contents increase, the activation time and the plateau pressure decrease, sloping of the plateau pressure increase. Amount of the 2nd phases increase with Zr contents in $MmNi_44.5Al_{0.5}Zr_x$ alloys. The $MmNi_44.5Al_{0.5}Zr_{0.05}$ alloy, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage.

• Korean Journal of Materials Research
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• v.28 no.3
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• pp.159-165
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• 2018

In order to increase the efficiency of the sputtering method widely used in thin film fabrication, a dc sputtering apparatus which supplies both high frequency and magnetic field from the outside was fabricated, and cobalt thin film was fabricated using this apparatus. The apparatus can independently control the applied voltage, the target-substrate distance, and the target current, which are important parameters in the sputtering method, so that a stable glow discharge is obtained even at a low gas pressure of $10^{-3}$ Torr. The fabrication conditions using the sputtering method were mainly performed in $Ar+O_2$ mixed gas containing about 0.6 % oxygen gas under various Ar gas pressures of 1 to 30 mTorr. The microstructure of Co thin films deposited using this apparatus was examined by electron diffraction pattern and X-ray techniques. The magnetic properties were investigated by measuring the magnetization curves. The microstructure and magnetic properties of Co thin films depend on the discharge gas pressure. The thin film fabricated at high gas pressure showed a columnar structure containing a large amount of the third phase in the boundary region and the thin film formed at low gas pressure showed little or no columnar structure. The coercivity in the plane was slightly larger than that in the latter case.

• Journal of Powder Materials
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• v.15 no.3
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• pp.210-213
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• 2008

Elongated CdSe nanoparticles with a diameter of 3-7nm have been successfully synthesized using two surfactants of trioctylphospine (TOP) and hexadecylamine (HDA) at $160^{\circ}C$. The formation of elongated CdSe nanoparticles is possibly due to the cooperative effects from both the different binding capability of two surfactants (TOP and HDA) and intrinsically anisotropic crystal structure of the CdSe. The electron diffraction pattern of CdSe nanoparticles revealed the formation of wurzite phase. The CdSe samples showed red-shifted wavelength from 560 to 580nm with increasing the refluxing time due to the gradual growth of CdSe nanoparticles. The relatively broad absorption band can be attributed to the surface state of CdSe nanoparticles. The possible formation mechanism of elongated CdSe nanoparticles was proposed and the characteristics of CdSe have been discussed as well.