• 공업화학
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• 제28권5호
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• pp.593-596
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• 2017

본 연구에서는 염기조건에서 수열합성법으로 소듐 티타네이트 나노시트를 합성하였다. 합성한 소듐 티타네이트 나노시트를 $RuCl_3$ 수용액에서 자외선을 조사하여 루테늄을 소듐 티타네이트 나노시트의 표면에 도입하였다. X-선 회절분석과 투과전자현미경 및 에너지 분산형 분광기 실험을 통하여 샘플의 결정성과 형태를 분석하였고, 그 결과 루테늄원자가 소듐 티타네이트 표면에 균일하게 흡착되어 있는 것을 확인할 수 있었다. 또한 유도결합플라즈마 발광분광분석법을 통하여 소듐 티타네이트 나노시트에 도입된 루테늄을 정량하였다. 루테늄이 도입된 소듐 티타네이트 나노시트의 경우 산소를 산화제로 이용한 알코올 산화반응에 응용하였으며, 특히 루테늄이 7% 도입된 소듐 티타네이트 나노시트는 $105^{\circ}C$, 1기압 상에서 벤질 알코올을 다른 부산물 없이 벤즈알데하이드로 산화시키는 데 있어서 turnover frequency가 $2.1h^{-1}$인 촉매활성을 보였다.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.129-137
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• 2015

The study of photocatalysis of nano titanium dioxideon the cotton fabrics have been investigatedthrough self-cleaning properties. The mini-emulsion technique was employed to prepare the encapsulation of titanium dioxide nano particles in polystyrene beads prior used. The mini-emulsion was coated on the cotton fabrics using Pad-dry method.The loading amount of TiO2particles into the mini-emulsion were various from 1%wt to 40%wt. The particles sizes of the TiO2-encapsulated polystyrene mini-emulsion were investigated by dynamic light scattering. It was noticed that the particle size of the mini-emulsion was in the range of 100- 200 nm. The morphology of treated cotton fabrics were investigated using scanning electron microscopy. The crystal structure of TiO2-encapsulated PS mini emulsion which coated on cotton fabrics were examined by X-ray diffraction spectroscopy. In order to investigate the photocatalytic activities of TiO2 through the selfcleaning characteristics of the cotton fabrics, colorant stains were created on the samples. Coffee stains were used as colorant organic stains. The result shown that the coffee stained on the cotton fabrics significantly showed the improving of the self-cleaning properties under UV radiation.

• 한국재료학회지
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• 제23권11호
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• pp.655-660
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• 2013

Photoelectrochemical cells have been used in photolysis of water to generate hydrogen as a clean energy source. A high efficiency electrode for photoelectrochemical cell systems was realized using a ZnO hierarchical nanostructure. A ZnO nanofiber mat structure was fabricated by electrospinning of Zn solution on the substrate, followed by oxidation; on this substrate, hydrothermal synthesis of ZnO nanorods on the ZnO nanofibers was carried out to form a ZnO hierarchical structure. The thickness of the nanofiber mat and the thermal annealing temperature were determined as the parameters for optimization. The morphology of the structures was examined by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The performance of the ZnO nanofiber mat and the potential of the ZnO hierarchical structures as photoelectrochemical cell electrodes were evaluated by measurement of the photoelectron conversion efficiencies under UV light. The highest photoconversion efficiency observed was 63 % with a ZnO hierarchical structure annealed at $400^{\circ}C$ in air. The morphology and the crystalline quality of the electrode materials greatly influenced the electrode performance. Therefore, the combination of the two fabrication methods, electrospinning and hydrothermal synthesis, was successfully applied to fabricate a high performance photoelectrochemical cell electrode.

• 한국재료학회지
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• 제27권7호
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• pp.381-385
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• 2017

In order to replace 14K white gold alloys, the properties of 5K white gold alloys (Au20-Ag80) were investigated by changing the contents of In (0.0-10.0 wt%). Energy dispersive X-ray spectroscopy (EDS) was used to determine the precise content of alloys. Properties of the alloys such as hardness, melting point, color difference, and corrosion resistance were determined using Vickers Hardness test, TGA-DTA, UV-VIS-NIR-colorimetry, and salt-spray tests, respectively. Wetting angle analysis was performed to determine the wettability of the alloys on plaster. The results of the EDS analysis confirmed that the Au-Ag-In alloys had been fabricated with the intended composition. The results of the Vickers hardness test revealed that each Au-Ag-In alloy had higher mechanical hardness than that of 14K white gold. TGA-DTA analysis showed that the melting point decreased with an increase in the In content. In particular, the alloy containing 10.0 wt% In showed a lower melting temperature (> $70^{\circ}C$) than the other alloys, which implied that alloys containing 10.0 wt% In can be used as soldering materials for Au-Ag-In alloys. Color difference analysis also revealed that all the Au-Ag-In alloys showed a color difference of less than 6.51 with respect to 14K white gold, which implied a white metallic color. A 72-h salt-spray test confirmed that the Au-AgIn alloys showed better corrosion resistance than 14K white gold alloys. All Au-Ag-In alloys showed wetting angle similar to that of 14K white gold alloys. It was observed that the 10.0 wt% In alloy had a very small wetting angle, further confirming it as a good soldering material for white metals. Our results show that white 5K Au-Ag-In alloys with appropriate properties might be successful substitutes for 14K white gold alloys.

• 한국재료학회지
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• 제28권2호
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• pp.89-94
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• 2018

The properties of 18 K red gold solder alloys were investigated by changing the content of In up to 10.0 wt% in order to replace the hazardous Cd element. Cupellation and energy dispersive X-ray spectroscopy (EDS) were used to check the composition of each alloy, and FE-SEM and UV-VIS-NIR-Colormeter were employed for microstructure and color characterization. The melting temperature, hardness, and wetting angle of the samples were determined by TGA-DTA, the Vickers hardness tester, and the Wetting angle tester. The cupellation result confirmed that all the samples had 18K above 75.0wt%-Au. EDS results showed that Cu and In elements were alloyed with the intended composition without segregation. The microstructure results showed that the amount of In increased, and the grain size became smaller. The color analysis revealed that the proposed solders up to 10.0 wt% In showed a color similar to the reference 18 K substrate like the 10.0 wt% Cd solder with a color difference of less than 7.50. TGA-DTA results confirmed that when more than 5.0 wt% of In was added, the melting temperature decreased enough for the soldering process. The Vickers hardness result revealed that more than 5.0 wt% In solder alloys had greater hardness than 10.0 wt% Cd solder, which suggested that it was more favorable in making a wire type solder. Moreover, all the In solders showed a lower wetting angle than the 10.0 wt% Cd solder. Our results suggested that the In alloyed 18 K red gold solders might replace the conventional 10.0 wt% Cd solder with appropriate properties for red gold jewelry soldering.

• Bulletin of the Korean Chemical Society
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• 제31권1호
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• pp.112-115
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• 2010

Transparent conducting undoped and Al impurity doped ZnO films were deposited on glass substrate by spin coat technique using 24 days aged ZnO precursor solution with solution of ethanol and diethanolamine. The films were characterized by UV-Visible spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), electrical resistivity ($\rho$), carrier concentration (n), and hall mobility ($\mu$) measurements. XRD data show that the deposited film shows polycrystalline nature with hexagonal wurtzite structure with preferential orientation along (002) crystal plane. The SEM images show that surface morphology, porosity and grain sizes are affected by doping concentration. The Al doped samples show high transmittance and better resistivity. With increasing Al concentration only mild change in optical band gap is observed. Optical properties are not affected by aging of parent solution. A lowest resistivity ($8.5 \times 10^{-2}$ ohm cm) is observed at 2 atomic percent (at.%) Al. With further increase in Al concentration, the resistivity started to increase significantly. The decrease resistivity with increasing Al concentration can be attributed to increase in both carrier concentration and hall mobility.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2371-2376
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• 2009

Three phenoxazine-based conjugated polymers, namely, the aryl substituted phenoxazine homopolymer (P1) as well as the dimeric phenoxazine-fluorene (P2) and phenoxazine-bithiophene (P3) copolymers, were synthesized via the Ni(0) mediated Yamamoto reaction and the palladium-catalyzed Suzuki coupling reaction. The weight-averaged molecular weights ($M_w$) of P1, P2, and P3 were found to be 27,000, 22,000, and 15,000, respectively, and their polydispersity indices were 3.6, 1.8, and 2.1. All the polymers were soluble in common organic solvents such as chloroform, toluene, and so on. The UV-visible absorption maxima for P1, P2, and P3 in the film state were located at 421, 415 and 426 nm, respectively, and the ionization potentials of the polymers ranged between 4.90 and 5.12 eV. All the studied phenoxazine-based polymers exhibited amorphous behavior, as confirmed by X-ray diffraction (XRD) and atomic force microscopy (AFM) studies. Thin film transistors were fabricated using the top-contact geometry. P1 showed much better thin-film-transistor performance than P2 or P3: A thin film of P1 gave a saturation mobility of 0.81 ${\times}\;10^{-3}\;cm^2V^{-1}s^{-1}$ and an on/off ratio of about $10^2$.

• Bulletin of the Korean Chemical Society
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• 제29권4호
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• pp.817-821
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• 2008

We have investigated the influence of the crystal structure on the chemical bonding nature and photocatalytic activity of cubic and hexagonal perovskite A[$Cr_{1/2}Ta_{1/2}$]O3 (A = Sr, Ba) compounds. According to neutron diffraction and field emission-scanning electron microscopy, the crystal structure and particle size of these compounds are strongly dependent on the nature of A-site cations. Also, it was found that the face-shared octahedra in the hexagonal phase are exclusively occupied by chromium ions, suggesting the presence of metallic (Cr-Cr) bonds. X-ray absorption and diffuse UV-vis spectroscopic analyses clearly demonstrated that, in comparison with cubic Sr[$Cr_{1/2}Ta_{1/2}$]$O_3$ phase, hexagonal Ba[$Cr_{1/2}Ta_{1/2}$]$O_3$ phase shows a decrease of Cr oxidation state as well as remarkable changes in interband Cr d-d transitions, which can be interpreted as a result of metallic (Cr-Cr) interactions. According to the test of photocatalytic activity, the present semiconducting materials have a distinct activity against the photodegradation of 4-chlorophenol. Also the Srbased compound was found to show a higher photocatalytic activity than the Ba-based one, which is attributable to its smaller particle size and its stronger absorption in visible light region.

• 동력기계공학회지
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• 제17권5호
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• pp.78-85
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• 2013

A high thermal conductivity material, namely graphene is treated by planetary ball milling machine to transport the heat by increasing the temperature. Experiments were performed to assess the heat transfer enhancement benefits of coating the bottom wall of copper substrate with graphene. It is well known that the graphene is unable to disperse into base fluid without any treatment, which is due to the several reasons such as attachment of hydrophobic surface, agglomeration and impurity. To further improve the dispersibility and thermal characteristics, planetary ball milling approach is used to grind the raw samples at optimized condition. The results are examined by transmission electron microscopy, x-ray diffraction, Raman spectrometer, UV-spectrometer, thermal conductivity and thermal imager. Thermal conductivity measurements of structures are taken to support the explanation of heat transfer properties of different samples. As a result, it is found that the planetary ball milling approach is effective for improvement of both the dispersion and heat carriers of carbon based material. Indeed, the heat transfer of the ground graphene coated substrate was higher than that of the copper substrate with raw graphene.

• 대한화학회지
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• 제38권8호
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• pp.608-615
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• 1994

양식산 새우(P.orientalis)로부터 0.05M 인산염 완충용액(pH 7.0)으로 carotenoprotein을 추출하고 DEAE-셀룰로오스, 반포화 황산암모늄 친전 및 GPC로 $\alpha$-form과 ${\beta}$-form 두 종류의 carotenoprotein을 분리 정제하였다. 최대 흡수파장은 ${\lambda}_{max}$= 480, 409, 318 및 280 nm였다. SEM과 XRD로 분자구조를 관찰하였으며, GPC와 PAGE로 측정한 분자량은 $\alpha$-form이 170KDa으로 분리되는 불균일한 이합체 구조였다. carotenoprotein 복합체의 아미노산, 중성지질, 인지질 및 유리지방산 조성을 분석하였고, 여러 가지 유기화학 반응과 UV/Vis,IR, $^1H$-NMR, MS 등으로 carotenoids분자구조를 측정한 결과 lipid-protein의 보호그룹으로서는 astaxanthin과 그 ester임이 확인되었다.