• Title, Summary, Keyword: Microwave microscopy

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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.

Heating Behavior of Silicon Carbide Fiber Mat under Microwave

  • Khishigbayar, Khos-Erdene;Seo, Jung-Min;Cho, Kwang-Youn
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.707-711
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    • 2016
  • A small diameter of SiC fiber mat can produce much higher heat under microwave irradiation than the other types of SiC materials. Fabrication of high strength SiC fiber consists of iodine vapor curing on polycarbosilane precursor and heat treatment process. The curing stage of polycarbosilane fiber was maintained at $150-200^{\circ}C$ in a vacuum condition under the iodine vapor to fabricate a high thermal radiation SiC fiber. The structure and morphology of the fibers were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG) and scanning electron microscopy (SEM). In this study, the thermal properties of SiC fiber mats under microwave have been analyzed with an IR thermal camera and its image analyzer. The prepared SiC fiber mats radiated high temperature with extremely high heating rate up to $1100^{\circ}C$ in 30 seconds. The fabricated SiC fiber mats were not oxidized after the heat radiation process under the microwave irradiation.

Preparation of Nanocomposite by Microwave Processing (마이크로파 공정을 이용한 나노복합체의 제조)

  • Kim, Tae-Hoon;Son, Se-Mo;Park, Ji-Hwan;Seo, Geum-Suk;Park, Seong-Soo
    • Journal of the Korean Printing Society
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    • v.22 no.2
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    • pp.111-122
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    • 2004
  • The purpose of this study was to investigate the possibility of application of microwave energy for the fabrication of polymer/clay nanocomposite. APES/Clay nanocomposites were prepared at $130^{\circ}C$ for 30min with various amount of MMT or OMMT used the melt-intercalation method applied the classical and microwave heating source. APES/Clay samples were characterized by the means of X-ray diffractometry (XRD), transmitted electron microscopy (TEM) differential scanning calorimetry (DSC), and rheometric dynamic analysis (RDA). It was found that intercalated or exfoliated state of the samples could be controlled by the clay type, clay content, and heating type.

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Low Temperature Sintered $CaZr(BO_3)_2$ Microwave Dielectric Ceramics for LTCC Application ($CaZr(BO_3)_2$ 세라믹스의 저온 소결 및 마이크로웨이브 유전 특성)

  • Nam, Myoung-Hwa;Kim, Hyo-Tae;Kim, Jong-Hee;Mahm, Sahn
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.259-259
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    • 2007
  • The low temperature sintering of dolomite type borates, $CaZr(BO_3)_2$[CZB] ceramics and their microwave dielectric properties were investigated The sintering temperature of CZB ceramics could be reduced from $1150^{\circ}C$ to $925^{\circ}C$ by the addition of sintering additive. $CaZrO_3$, $ZrO_2$ and $CaB_2O_4$ second phases were found in the CZB ceramics. The syntheses, sintering properties, microstructures, and dielectricnproperties of dolomite-type borates were examined by XRD, thermal analysis, electron microscopy, network analyzer, and the results are discussed intensively. The compatibility with silver electrode was also explored.

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Theoretical and Experimental Investigation on the Probe Design of a Ridge-loaded Slot Type for Near-Field Scanning Microwave Microscope

  • Son, Hyeok-Woo;Kim, Byung-Mun;Hong, Jae-Pyo;Cho, Young-Ki
    • Journal of Electrical Engineering and Technology
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    • v.10 no.5
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    • pp.2120-2125
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    • 2015
  • In this paper, a rectangular waveguide probe with a ridge-loaded straight slot (RLSS) is presented for a near-field scanning microwave microscope (NSMM). The RLSS is located laterally at the end wall of the cavity and is loaded on double ridges in a narrow straight slot to improve the spatial resolution compared with a straight slot. The probe consists of a rectangular cavity with an RLSS and a feed section of a WR-90 rectangular waveguide. When the proposed NSMM is located at distance of 0.1mm in front of a substrate without patches or strips, the simulated full width at half maximum (FWHM) of the probe improve by approximately 31.5 % compared with that of a straight slot without ridges. One dimensional scanning of the E-plane on a sample under test was conducted, and the reflection coefficient of the near-field scanning probe is presented.

Synthesis of Carbon Nanowalls by Microwave PECVD for Battery Electrode

  • Kim, Sung Yun;Shin, Seung Kwon;Kim, Hyungchul;Jung, Yeun-Ho;Kang, Hyunil;Choi, Won Seok;Kweon, Gi Back
    • Transactions on Electrical and Electronic Materials
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    • v.16 no.4
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    • pp.198-200
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    • 2015
  • The microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow a carbon nanowall (CNW) on a silicon (Si) substrate with hydrogen (H2) and methane (CH4) gases. To find the growth mechanism of CNW, we increased the growth time of CNW from 5 to 30 min. The vertical and surficial conditions of the grown CNWs according to growth time were characterized by field emission scanning electron microscopy (FE-SEM). Energy dispersive spectroscopy (EDS) measurements showed that the CNWs consisted solely of carbon.

Easy Preparation of Nanosilver-Decorated Graphene Using Silver Carbamate by Microwave Irradiation and Their Properties

  • Yun, Sang-Woo;Cha, Jae-Ryung;Gong, Myoung-Seon
    • Bulletin of the Korean Chemical Society
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    • v.35 no.8
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    • pp.2251-2256
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    • 2014
  • We have successfully decorated reduced graphene oxide (RGO) with silver nanoparticles (AgNPs) by microwaving silver alkylcarbamate for 13 seconds using 1-amino-4-methylpiperazine. Uniform AgNPs (20-40 nm) were effectively prepared, and 1-amino-4-methylpiperazine acted as a reaction medium, reducing agent, and stabilizer. Particle size and morphology were correlated with the silver alkylcarbamate concentration and microwave time. The graphene/AgNPs composites were characterized by Raman, X-ray diffraction, and scanning electron microscopy to confirm that the AgNPs were uniformly decorated onto the graphene. Measurements of the transparent conductive property at room temperature indicated that these graphene/AgNPs nanosheets with 55.45% transmittance were electrically continuous with a sheet resistance of approximately $43{\Omega}/{\Box}$.

Study on Synthesis and Characterization of (Ti.Si)C Composite by SHS Microwave (SHS 마이크로파에 의한 (Ti.Si)C 복합체의 합성 및 소결특성에 관한 연구)

  • 이형복;권상호;이재원;안주삼
    • Journal of the Korean Ceramic Society
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    • v.32 no.9
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    • pp.1009-1018
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    • 1995
  • (Ti.Si)C composite powders were synthesized by SHS method using microwave energy. Compositional and structural characterization of the powder were carried out by using scanning electron microscopy and X-ray diffraction. The average particle size of the synthesized (Ti.Si)C composite powders was smaller than that of the starting materials. From the results of the temperature profile, combustion temperature and velocity were decreased with increasing Si molar ratio. With increasing C molar ratio combustion temperature and velocity did not change. (Ti.Si)C composite was sintered at 185$0^{\circ}C$ for 60 min by using hot-pressing with 30 MPa. The best properties were obtained from the sintered specimen whose composition was 1 : 1 : 1.9 molar ratio of Ti : Si : C. The sintering density, flexural strength and vickers hardness of the sintered body were 4.71 g/㎤, 423 MPa and 21 GPa, respectively.

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Microwave-Assisted Heating of Electrospun SiC Fiber Mats

  • Khishigbayar, Khos-Erdene;Joo, Young Jun;Cho, Kwang Youn
    • Journal of the Korean Ceramic Society
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    • v.54 no.6
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    • pp.499-505
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    • 2017
  • Flexible silicon carbide fibrous mats were fabricated by a combination of electrospinning and a polymer-derived ceramics route. Polycarbosilane was used as a solute with various solvent mixtures, such as toluene and dimethylformamide. The electrospun PCS fibrous mats were cured under a halogen vapor atmosphere and heat treated at $1300^{\circ}C$. The structure, fiber morphology, thermal behavior, and crystallization of the fabricated SiC fibrous mats were analyzed via scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal imaging. The prepared SiC fibrous mats were composed of randomly distributed fibers approximately $3{\mu}m$ in diameter. The heat radiation of the SiC fiber mats reached $1600^{\circ}C$ under microwave radiation at a frequency of 2.45 GHz.

A Study on Adsorption Characteristics of Benzene over Activated Carbons Coated with Insulating Materials and Desorption by Microwave Irradiation (절연물질이 코팅된 활성탄의 벤젠 흡착특성 및 마이크로파에 의한 탈착에 관한 연구)

  • Kim, Ki-Joong;Ahn, Ho-Geun
    • Applied Chemistry for Engineering
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    • v.19 no.4
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    • pp.445-451
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    • 2008
  • In order to regenerate the activated carbon polluted by volatile organic compounds (VOCs) using microwave, adsorption and desorption characteristics of benzene over activated carbon (AC) coated with insulating materials were investigated. Physical characteristics of activated carbon and insulator-coated ACs were investigated by means of $N_2$ gas adsorption and scanning electron microscopy (SEM). The amount of VOC adsorbed showed a positive relationship with the specific surface area of the ACs, and spark discharge over insulator-coated ACs did not occur. Potassium silicate (PS) was the best binder for coating of insulating materials on AC. Amount of benzene desorbed by microwave irradiation was dependent on output power of microwave. Nearly same performance was obtained even though the adsorption-desorption operation under microwave irradiation was repeated 5 times. Finally, it was known that the microwave heating was a very effective mean for regenerating the polluted AC.