• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1534-1535
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• 2005

Highly luminescent efficiency phosphors have been successfully produced by surface modification and microwave irradiation treatment. The SEM image and XRD analysis reveal that the surface morphology of the white-light phosphors can be notably modified by microwave irradiation and exhibit with better crystalline property. The VUV PL spectra show that the microwave irradiation treatment can effectively enhance the luminescent efficiency by a factor of 1.5 times for intensity compared to that without microwave treatment. A further improvement in all visible emission can be made by modifying surface composition through MgO coating on the phosphor powder. These results demonstrate that such a simple approach can provide for improving luminescent efficiency of phosphors for the optoelectronic devices.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.390-393
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• 1989

Diamond is synthesized from the gaseous mixture of carbon monoxide and hydrogen by microwave PECVD. $10{\times}10mm^2$ silicon wafers are used as the substrate,and it can be raised more than $900^{\circ}C$ by microwave absorption, radiation by plasma and bombardment of ions. The changes of the morphology and the growth rates of the deposits with the experimental conditions are examined by Scanning Electron Microscopy. The d values of all the deposited films concide with those of powder diffraction data in XRD. In Raman spectra, the peak of the deposit coincides with that of the natural diamond which has a value of 1332.5 $cm^{-1}$, and the broad peak from 1360 $cm^{-1}$to 1600 $cm^{-1}$which represents the amorphous graphite was observed in the higher concentration of carbon monoxide.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.980-983
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• 2003

The preparation of ZnS:Mn,Cl phosphor has been carried out by combustion method. Manganese nitrate was decomposed with an organic fuel at $500^{\circ}C$ to give fine sized crystallites in presence of alkali metal halides at a lower temperature than the conventional synthesis. The phosphors thus obtained were then heated at 900 to $1200^{\circ}C$ in an inert atmosphere, for 3hours to get better luminescent properties. The phosphors were prepared at different temperatures and at different doping concentrations of manganese to determine the optimal conditions for synthesizing the phosphors with superior optical properties. Scanning electron microscopy (SEM) investigations have been carried out to observe the particle morphology and the grain size. Powder X-ray diffraction(XRD) was also performed to characterize the phosphors.

• Journal of the Korean Ceramic Society
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• v.45 no.5
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• pp.297-302
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• 2008

To direct the evolution of nanostructure and immobilize ${\gamma}-Al_2O_3$ catalyst, nanocrystalline La-doped-$Al_2O_3$ powder were prepared by the sol-gel process with addition of an amphiphilic block copolymer template (pluronic P123: $(poly(ethyleneoxide)_{20}-poly(propyleneoxide)_{70}-poly(ethyleneoxide)_{20})$. The dried gel is amorphous, whereas heating at temperature above $700^{\circ}C$ leads to the formation of nanocrystalline ${\gamma}$ and ${\delta}-Al_2O_3$ and these two phases is kept until $1100^{\circ}C$. ${\alpha}-A1_2O_3 $starts to form at $1200^{\circ}C$ with $LaAl_{11}O_{18}$. The surface morphology and crystal structure has been observed by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD). Solid state $^{27}Al$ MAS NMR indicates two types of local environment, i.e. octahedral and tetrahedral sites. The surface area and pore size was compared among these powders using the BET nitrogen adsorption measurements.

• Composites Research
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• v.25 no.5
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• pp.159-163
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• 2012

The coating of metal surface with carbon nanotubes(CNTs) has been studied for the heat transfer enhancement of the boiling and condensation of refrigerant. The multiwalled carbon nanotube/copper oxide(CuO) composite powder, which has been surface modified by dispersant and polyvinyl alcohol solution, was ultrasonically sprayed and sintered on a copper wafer. In this paper, experiments were performed to assess the characterization and comparison of the carbon nanotube before and after sinterning and the morphology changes of the CNT/CuO-coated surface by using different dispersants. The dispersants used are THF (Tetrahydrofuran), SDBS(Dodecylbenzenesulfonic acid sodium salt), SDS(Sodium dodecy sulfate). The samples were examined by scanning electron microscopy(SEM), thermogravimetric analysis(TGA), differential scanning calorimeter(DSC) and Raman spectroscopy.

• Advances in nano research
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• v.3 no.1
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• pp.1-11
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• 2015

Thin film ethanol sensors made from ${\alpha}-Fe_2O_3$ decorated with multiwall carbon nanotubes(MWCNTs) were manufactured by the electron beam deposition method. The morphology of the decorated ${\alpha}-Fe_2O_3$/MWCNTs (25:1 weight ratios) nanocomposite powder was investigated using the scanning electron microscopy and X-ray diffraction techniques. The thickness of thin films has been determined from ellipsometric measurements. The response of manufactured sensors was investigated at different temperatures of the sensor work body and concentration of gas vapors. Good response of prepared sensors to ethanol vapors already at work body temperature of $150^{\circ}C$ was shown.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.4
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• pp.219-224
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• 2006

Silver paste with low sintered temperature has been developed in order to apply electronic parts, such as bus electrode, address electrode in PDP (Plasma Display Panel) with large screen area. In this study, nano-sized silver particles with 10-30 nm were synthesized from silver nitrate ($AgNO_3$) solution by chemical reduction method and silver paste with low sintered temperature was prepared by mixing silver nanoparticles, conventional silver powder with the particle size 1.6 um and Pb-free frit. Conductive thick film from silver paste was fabricated by screen printing on alumina substrate. After firing at $540^{\circ}C$, the cross section and surface morphology of the thick films were analyzed by FE-SEM. Also, the sheet resistivity of the fired thick films was measured using the four-point technique.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.67-74
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• 1986

To investigate the effects of unreacted silicon on the $\alpha$/$\beta$transfornation variation of morphology and mechanical strength of Sintered Reaction Bonded Silicon Nitride the mixtures of $\alpha$-$Si_3N_4$ and Si powder and Reaction Bonded Silicon Nitride were heat treated. The heat-treatments were performed in Ar atmosphere in order to inhibit the nitridation of silicon. In the mixtures heat-trated at 1$700^{\circ}C$ the amount of $\beta$-TEX>$Si_3N_4$transformed from $\alpha$-TEX>$Si_3N_4$was sigmoidally increased and the equiaxed $\alpha$-TEX>$Si_3N_4$grains elongated with the amount of silicon and heat treating time. And large $\beta$-TEX>$Si_3N_4$grains grown into silicon were observed. On the other hand there was no change in the heat-treatment of pure $\alpha$-TEX>$Si_3N_4$In case of the heat-treatment of RBSN the same phenomena due to the silicon appearing from the decomposition of $\alpha$-Smatte and needle were observed. From the three point bending test the strength of the sintered specimens with the and without 5wt% silicon addition had 53Kg/$mm^2$ and 73Kg/$mm^2$ respectively.

• Journal of Hydrogen and New Energy
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• v.25 no.2
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• pp.131-138
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• 2014

Highly conductive bipolar plate for polymer electrolyte membrane fuel cell (PEMFC) was prepared using phenol novolac-type epoxy/graphite powder (GP)/carbon fiber filament (CFF) composite, and a rubber-modified epoxy resin was introduced in order to give elasticity to the bipolar plate graphite fiber (GF) was incorporated in order to improve electrical conductivity. To find out the cure condition of the mixture of novolac-type and rubber-modified epoxies, differential scanning calorimetry (DSC) was carried out and their data were introduced to Kissinger equation. And tensile and flexural tests were carried out using universal testing machine (UTM) and the surface morphology of the fractured specimen and the interfacial bonding between epoxy matrix and CFF or GF were observed by a scanning electron microscopy (SEM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.155-159
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• 2003

The preparation and luminescence characterization of yttrium oxide doped with trivalent europium phosphors by sol-gel method have been investigated. Aqueous metal nitrate solution was mixed with EDTA which was chosen by the most suitable material of sol-gel formation one of appled various chelating agents. we noticed that the samples when are heated with EDTA at a temperature of $100^{\circ}C$ for 1hrs, produced brownish and crisp powders due to condensation reaction on decomposition, dehydration and formation of sol-gel. Hence, when the powder pre-heated was then heated at $1200^{\circ}C$ for 3hrs in atmosphere, the luminescence characterization of resultant $Y_{2}O_{3}:Eu^{3+}$ phosphor was enhanced upto maximum 30% significantly than conventional method through increasing porous region and decreasing particle sizes.