• Title, Summary, Keyword: Microwave microscopy

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Gasification characteristics of glass fiber-reinforced plastic (GFRP) wastes in a microwave plasma reactor

  • Yun, Young Min;Seo, Myung Won;Ra, Ho Won;Yoon, Sang Jun;Mun, Tae-Young;Moon, Ji-Hong;Kook, Jin Woo;Kim, Yong Ku;Lee, Jae Goo;Kim, Jae Ho
    • The Korean Journal of Chemical Engineering
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    • v.34 no.10
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    • pp.2756-2763
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    • 2017
  • The effects of plasma power (1-1.8 kW), oxygen/fuel (0-2.5) and steam/fuel ratios (0-1) on the gasification characteristics of glass fiber-reinforced plastic (GFRP) wastes have been determined in a microwave plasma reactor. GFRP, which is thermosetting plastic composed of glass fibers embedded within a polymer matrix, was used as an experimental sample. While carbon conversion increased with oxygen/fuel ratio, syngas heating value and cold gas efficiency decreased with oxygen supply due to the onset of combustion. With increasing steam/fuel ratio, water-gas shift and ion-reforming reaction favored higher concentration of $H_2$. Increasing the plasma power was found to promote the conversion of carbon dioxide to carbon monoxide. The char surfaces of GFRP that were subjected to variable power and oxygen supplies were analyzed by scanning electron microscopy.

Microstructural Characterization of $CaTiO_3-NdAlO_3$-Based Ceramics

  • Suvorov, Danilo;Drazic, Goran;Valant, Matjaz;Jancar, Bostjan
    • Korean Journal of Crystallography
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    • v.11 no.4
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    • pp.195-199
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    • 2000
  • Ceramics based on CaTiO₃-NdAlO₃ solid solutions were synthesized in order to study their dielectric microwave properties. Microstructural analysis was performed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using different analytical methods such as energy-dispersive X-ray spectroscopy (EDXS). It was observed that the heating conditions during sintering and cooling strongly affect the microstructural development of CaTiO₃-NdAlO₃-based ceramics. Various types and concentrations of structural defects were identified, for example, dislocations, twins and/or antiphase boundaries. all such defects resulted in a degradation of the dielectric microwave properties, in particular the quality factor Q. Dielectric properties of CaTiO₃-NdAlO₃-based ceramics can be improved by an appropriate thermal treatment of ceramics which results in a decrease in the concentrations of the identified microstructural defects.

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Nondestructive measurement of surface resistance of indium tin oxide(ITO) films by using a near-field scanning microwave microscope (근접장 마이크로파 현미경을 이용한 ITO 박막의 표면저항의 비파괴 관측 특성 연구)

  • Yun, Soon-Il;Na, Sung-Wuk;You, Hyun-Jun;Lee, Yeong-Joo;Kim, Hyun-Jung;Lee, Kie-Jin
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.137-141
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    • 2004
  • 저항특성이 다른 ITO박막의 구조특성과 표면특성을 XRD와 AFM(atomic force microscopy), SEM(scanning electron microscopy)을 이용하여 관측하였다. 접촉방식인 4단자 법을 사용하여 ITO박막의 표면전기저항을 측정하였다. 관측된 구조 및 표면특성을 바탕으로 비파괴 비접촉방식을 이용한 근접장 마이크로파 현미경을 이용하여 얻은 ITO박막의 표면저항특성과 비교 연구하였다.

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Microwave-Assisted Synthesis of Flower-like and Plate-like CuO Nanopowder and Their Photocatalytic Activity for Polluted Lake Water

  • Xu, Ling;Xu, Hai-Yan;Wang, Feng;Zhang, Feng-Jun;Meng, Ze-Da;Zhao, Wei;Oh, Won-Chun
    • Journal of the Korean Ceramic Society
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    • v.49 no.2
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    • pp.151-154
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    • 2012
  • Flower-like and plate-like CuO nanopowder has been successfully synthesized using a facile microwave-assisted synthetic route. The morphology and size of the final products strongly depended on microwave power. The phase, structures and morphologies of the as-prepared products were investigated in detail by BET surface area analysis, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). In addition, the chemical oxygen demand of polluted lake water was employed for characterization of these new photocatalysts. The results showed correlations between the morphology of CuO micro-crystals and their catalytic properties.

Narrow Resonant Double-Ridged Rectangular Waveguide Probe for Near-Field Scanning Microwave Microscopy

  • Kim, Byung-Mun;Son, Hyeok-Woo;Cho, Young-Ki
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.406-412
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    • 2018
  • In this paper, we propose a narrow resonant waveguide probe that can improve the measurement sensitivity in near-field scanning microwave microscopy. The probe consists of a metal waveguide incorporating the following two sections: a straight section at the tip of the probe whose cross-section is a double-ridged rectangle, and whose height is much smaller than the waveguide width; and a standard waveguide section. The advantage of the narrow waveguide is the same as that of the quarter-wave transformer section i.e., it achieves impedance-matching between the sample under test (SUT) and the standard waveguide. The design procedure used for the probe is presented in detail and the performance of the designed resonant probe is evaluated theoretically by using an equivalent circuit. The calculated results are compared with those obtained using the finite element method (Ansoft HFSS), and consistency between the results is demonstrated. Furthermore, the performance of the fabricated resonant probe is evaluated experimentally. At X-band frequencies, we have measured the one-dimensional scanning reflection coefficient of the SUT using the probe. The sensitivity of the proposed resonant probe is improved by more than two times as compared to a conventional waveguide cavity type probe.

Effective Thermal Inactivation of the Spores of Bacillus cereus Biofilms Using Microwave

  • Park, Hyong Seok;Yang, Jungwoo;Choi, Hee Jung;Kim, Kyoung Heon
    • Journal of Microbiology and Biotechnology
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    • v.27 no.7
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    • pp.1209-1215
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    • 2017
  • Microwave sterilization was performed to inactivate the spores of biofilms of Bacillus cereus involved in foodborne illness. The sterilization conditions, such as the amount of water and the operating temperature and treatment time, were optimized using statistical analysis based on 15 runs of experimental results designed by the Box-Behnken method. Statistical analysis showed that the optimal conditions for the inactivation of B. cereus biofilms were 14 ml of water, $108^{\circ}C$ of temperature, and 15 min of treatment time. Interestingly, response surface plots showed that the amount of water is the most important factor for microwave sterilization under the present conditions. Complete inactivation by microwaves was achieved in 5 min, and the inactivation efficiency by microwave was obviously higher than that by conventional steam autoclave. Finally, confocal laser scanning microscopy images showed that the principal effect of microwave treatment was cell membrane disruption. Thus, this study can contribute to the development of a process to control food-associated pathogens.

Microwave Sintering of Silver Thick Film on Glass Substrate (유리기판 위에 Ag 후막의 마이크로웨이브 소결)

  • Hwang, Seong-Jin;Veronesi, Paolo;Leonelli, Cristina;Kim, Hyung-Sun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.22-22
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    • 2009
  • The silver thick film has been used in many industries such as display, chip, solar cell, automobile, and decoration with conventional heating. The silver thick film is fired with optimal time and temperature. However, decreasing the fabrication time is required due to high production power. Furthermore, there is a problem that silver in electrode is diffused throughout any substrates. For inhibiting the Ag diffusion and long fabrication time we considered a microwave heating. We investigated firing of silver thick film with conventional and microwave heating. The temperature of substrate was measured by thermal paper and the temperature of substrate was under $100\;^{\circ}C$ The shrinkage of electrode was measured with optical microscopy and optical profilometry. The shrinkage of electrode heat treated with microwave for 5min was similar to the that fired by the conventional heating for several hours. After firing by two types of heating, the diffusion of silver was determined using a optical microscope. The microstructure of sintered silver thick film was observed by SEM. Based on our results, the microwave heating should be a candidate heating source for the fabrication electronic devices in terms of saving the tact time and preventing the contamination of substrate.

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Preparation of Nanosized Gold Particles by Microwave Irradiation and Kinetics Study for Reduction of 4-Nitroaniline under Various Conditions

  • Kim, Jae Jin;Ko, Weon Bae
    • Elastomers and Composites
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    • v.50 no.4
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    • pp.274-278
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    • 2015
  • Nanosized gold particles were synthesized by microwave irradiation in a mixture composed of potassium tetrachloroaurate(III) n-hydrate, sodium citrate dihydrate and Tween 20. The synthesized gold particles were characterized by UV-vis spectrophotometer, scanning electron microscopy, and X-ray diffraction techniques. Using UV-vis spectroscopy, it was confirmed that gold nanoparticles act as a catalyst in the reduction of 4-nitroaniline with sodium borohydride to form 1,4-diaminobenzene. Additionally, we studied the kinetics of this reductive reaction in the presence of these gold nanoparticles under various conditions.

Microwave Dielectric Properties of Bi2O3-TiO2 Composite Ceramics

  • Axelsson, Anna-karin;Sebastian, Maladil;McN Alford, Neil
    • Journal of the Korean Ceramic Society
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    • v.40 no.4
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    • pp.340-345
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    • 2003
  • B $i_2$ $O_3$-Ti $O_2$ composite dielectric ceramics have been prepared by a conventional solid state ceramic route. The composite ceramics were prepared with starting materials of different origin and the microwave dielectric properties were investigated. The sintered ceramics were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, Raman and microwave methods. Structural and microstructural analyses identified two separate phases: Ti $O_2$(rutile) and B $i_2$ $Ti_4$0$_{11}$. The separate grains of titania and bismuth titanate were distributed uniformly in the ceramic matrix. The composition 0.88Ti $O_2$-0.12B $i_2$ $Ti_4$ $O_{11}$ was found to have a Q$\times$f of 9300 GHz (measured at a frequency of 3.9 GHz), a temperature coefficient of frequency, $\tau$$_{cf}$ near zero and a high relative permittivity, $\varepsilon$r of 83. The microwave dielectric properties were measured down to 20$^{\circ}$K K. The quality factor increased on cooling the ceramic samples.les.

Enhanced Electrical Conductivity of Gold Doped Graphene Films by Microwave Treatment

  • Kim, Yoo-Seok;Song, Woo-Seok;Cha, Myoung-Jun;Lee, Su-Il;Cho, Ju-Mi;Kim, Sung-Hwan;Park, Chong-Yun
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.188-188
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    • 2012
  • Graphene, with its unique physical and structural properties, has recently become a proving ground for various physical phenomena, and is a promising candidate for a variety of electronic device and flexible display applications. Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ${\sim}60{\Omega}$/sq and ~85% transmittance in the visible range, the chemical vapor deposition (CVD) synthesized graphene electrodes have a higher transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. In this study, we report a creative strategy, irradiation of microwave at room temperature under vacuum, for obtaining size-homogeneous gold nano-particle doping on graphene. The gold nano-particlization promoted by microwave irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping. These results clearly revealed that gold nanoparticle with ${\geq}30$ nm in mean size were decorated along the surface of the graphene after microwave irradiation. The fabrication high-performance transparent conducting film with optimized doping condition showed a sheet resistance of ${\geq}100{\Omega}$/sq. at ~90% transmittance. This approach advances the numerous applications of graphene films as transparent conducting electrodes.

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