• 제목, 요약, 키워드: Microwave microscopy

검색결과 109건 처리시간 0.031초

복합 페로브스카이트 (1-x)$(Li_{1/2}Sm_{1/2})TiO_3-x (Na_{1/2}Sm_{1/2})TiO_3$(LNST) system의 유전특성 및 미세구조 관찰 [1] (Dielectric Properties and Microstructure Observation of Complex Perovskite (1-x)$(Li_{1/2}Sm_{1/2})TiO_3-x (Na_{1/2}Sm_{1/2})TiO_3$(LNST) system [1])

  • 손진옥;이확주;남산
    • Applied Microscopy
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    • v.34 no.1
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    • pp.61-69
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    • 2004
  • 복합 페로브스카이트 (1-x) $(Li_{1/2}Sm_{1/2})TiO_3-x (Na_{1/2}Sm_{1/2})TiO_3$ (LNST) system의 마이크로파 유전특성과 미세구조를 XRD와 SEM을 이용하여 연구하였다. 이 LNST는 산소팔면체의 antiphase tilting 뿐만 아니라, inphase tilting과 양이온의 antiparallel shift를 가지는 구조변화는 보인다. 또한 LNST계는 $0.0{\leq}x{\leq}0.4$에서 양이온($Li^{+1}$)의 휘발이 일어나서 A-site vacancy ordering에 의해 c축으로 cell doubling이 일어난다. 미세구조의 관찰을 통해 전 범위의 조성에서 비정상 입성장 현상을 관찰하였다. LNST계에서 A-site에 $Li^{+1}$을 치환한 LST의 공진주파수 온도계수는 큰 음의 값($-220ppm/^{\circ}C$)을 가지나, $Na^{+1}$을 치환한 NST는 큰 양의 값($+173ppm/^{\circ}C$)을 가진다. x=0.4일때 4 GHz에서 ${\varepsilon}_r=103,\;Q*f_{0}=3,700GHz$ 그리고 $T_{cf}=+50ppm/^{\circ}C$의 좋은 유전특성을 얻었다.

투과 전자 현미경을 이용한 다이아몬드 박막과 실리콘 기판의 계면 연구 (Investigation of the interface between diamond film and silicon substrate using transmission electron microscopy)

  • 김성훈
    • 한국결정성장학회지
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    • v.10 no.2
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    • pp.100-104
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    • 2000
  • 다이아몬드 박막을 마이크로웨이브 플라즈마 방법을 이용하여 실리콘 기판위에 증착하였다. 증착된 다이아몬드 박막과 실리콘 기판의 단면을 이온 밀링 방법으로 식각한후, 경계면을 투과 전자 현미경으로 분석하였다. 다이아몬드 박막은 실리콘 기판위에 직접 성장되거나 또는 중간층이 형성된후 성장됨을 알 수 있었다. 중간층의 구성은 주로 Sic 또는 무정형 탄소로 이루어졌으며 중간층의 두께는 경계면을 따라 다르게 변하였다. 전자 회절 패턴으로부터, 경계면 주위에 잘 발달된 실리콘 기판과 다이아몬드의 결정면들이 서로 적합하게 성장되었고 있음을 알 수 있었다. 이 결과들로부터 실리콘 기판위에 성장되는 다이아몬드 박막의 초기 성장 형태를 추론할 수 있었다.

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Effect of FTO coated on stainless steel bipolar plate for PEM fuel cells

  • 박지훈;장원영;변동진;이중기
    • 한국재료학회:학술대회논문집
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    • pp.55.2-55.2
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    • 2009
  • A polymer electrolyte membrane (PEM) fuel cell has been getting large interest as a typical issue in useful applications. The PEMFC is composed of a membrane, catalyst and the bipolar plate. SnOx:F films on SUS316 stainless steel were prepared as a function of substrate with using electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) in order to achieve the corrosion-resistant and low contact resistance bipolar plates for PEM fuel cells. The SnOx:F films coated on SUS316 substrate at surface plasma treatment for excellent stability, before/after heat treatment for good crystalline structure and microwave power for were characterized by X-ray diffraction (XRD), auger electron microscopy (AES) and field emission-scanning electron microscopy (FE-SEM). The SnOx:F film coated on SUS316 substrate with various process parameters were able to observe optimum interfacial contact resistance (ICR) and corrosion resistance. It can be concluded that fluorine-doping content plays an important function in electrical property and characteristic of corrosion-protective film.

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Preparation of [C60]Fullerene-CoS2 Nanocomposites and Kinetics Study for Photocatalytic Degradation of Organic Dyes

  • Kim, Jae Jin;Ko, Weon Bae
    • Elastomers and Composites
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    • v.51 no.1
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    • pp.49-55
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    • 2016
  • Nanosized cobalt disulfide ($CoS_2$) particles were synthesized with 0.08 M cobalt chloride hexahydrate ($CoCl_2{\cdot}6H_2O$) and 0.2 M sodium thiosulfate pentahydrate ($Na_2S_2O_3{\cdot}5H_2O$) dissolved in distilled water under microwave irradiation. $[C_{60}]Fullerene-CoS_2$ nanocomposites were prepared with nanosized $CoS_2$ particles and [$C_{60}$]fullerene as heated by $700^{\circ}C$ for 2 h in an electric furnace. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) identified the heated $[C_{60}]fullerene-CoS_2$ nanocomposites. Heated $[C_{60}]fullerene-CoS_2$ nanocomposites were investigated the activity of photocatalytic degradation as a catalyst in various organic dyes like acid yellow 23, methylene blue, methyl orange, and rhodamine B with ultraviolet light at 254 nm by UV-vis spectrophotometer.

레이저 공정을 이용한 초전도 통신소자 제작과 고주파특성 연구 (Study on the synthesis and the frequency response of HTS microwave device fabricated by pulsed laser deposition)

  • 박주형;정영식;이상렬
    • 대한전기학회:학술대회논문집
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    • pp.288-290
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    • 1997
  • Pulsed laser ablation has been used to fabricate superconducting $YBa_2Cu_3O_{7-x}$(YBCO) thin films on MgO substrates. The epitaxial YBCO thin films were grown at $750^{\circ}C$ and oxygen partial pressure of 200 mTorr. The electrical property and the characteristics of the YBCO thin films have been studied by R-T measurement. scanning electron microscopy (SEM) and X-ray diffraction (XRD). A microstrip line resonator has been fabricated using YBCO superconducting thin films by photolithography and wet-etch process. The resonator has linear microstrip line separated by a gap of 0.278 mm. We observed a fundamental resonance peak at the frequency of 10.007 GHz.

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태양에너지를 이용한 자동용접 시스템 개발에 관한 연구 (A Study on the Development of Automatic Welding System using Solor Energy)

  • 김일수;김옥삼;손준식;서주환
    • 전력전자학회:학술대회논문집
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    • pp.532-533
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    • 2006
  • In this research work attempts were made to study the bonding of thermoplastics with adhesives using solar energy. In order to study the curing behaviour necessary experiments were conducted under varying conditions of temperature, exposure time and power. The cured samples were then studied under the optical microscope before subjecting to tensile testing in order to study their mechanical properties. The fracture surfaces were further studied under the Scanning Electron Microscopy in order to study the microstructural changes that are taken place during curing. From the present study it is evident that curing under higher solar energy temperature, generally improves bond strength and quality of the adhesive joints when compared to other modes of curing process expect the microwave curing process.

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테라헤르츠 영역에서의 BST 박막의 유전 특성 평가 (Terahertz dielectric characteristics of (Ba,Sr)$TiO_3$ thin films)

  • 조광환;강종윤;윤석진;이영백;맹인희;손주혁
    • 한국전기전자재료학회:학술대회논문집
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    • pp.28-28
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    • 2007
  • Ferroelectric $(Ba_{0.5}Sr_{0.5})TiO_3$ (BST) thin films of thickness 500nm were deposited on $LaAlO_3$, (LAO) substrates by at $800^{\circ}C$. BST films were characterized for structure using X-ray diffraction (XRD). The surface morphology and thickness of BST the films were characterized by atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM). We measured the dielectric properties at microwave frequencies (1~3 GHz) using a symmetrical stripline resonator with shorted ends and terahertz frequencies (0.2~2.5 THz) using a time-domain terahertz spectroscopy. The real and imaginary parts of the complex dielectric constant of the BST thin films on LAO substrates were in agreement with those previously reported.

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Nickel Nanoparticles: An Ecofriendly and Reusable Catalyst for the Synthesis of 3,4-Dihydropyrimidine-2(1H)-ones via Biginelli Reaction

  • Sapkal, Suryakant B.;Shelke, Kiran F.;Shingate, Bapurao B.;Shingare, Murlidhar S.
    • Bulletin of the Korean Chemical Society
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    • v.31 no.2
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    • pp.351-354
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    • 2010
  • Nickel nanoparticles (Ni NPs) appeared to exhibit the catalytic activity in one-pot cyclocondensation reaction for the preparation of 3,4-dihydropyrimidine-2(1H)-ones via Biginelli reaction from aromatic/heteroaromatic/aliphatic aldehydes, urea/thiourea and ethyl acetoacetate under microwave irradiation has been described. The UV absorbance spectra showed metallic Ni characteristics and appreciate with the particle size determined by Transmission electron microscopy (TEM). After reaction course the Ni NPs can be re-covered and reused without any apparent loss of activity.

Synthesis, Characterization and Catalytic Application of MoO3/CeO2-ZrO2 Solid Heterogeneous Catalyst for the Synthesis of Benzimidazole Derivatives

  • Rathod, Sandip B.;Lande, Machhindra K.;Arbad, Balasaheb R.
    • Bulletin of the Korean Chemical Society
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    • v.31 no.10
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    • pp.2835-2840
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    • 2010
  • A series of $MoO_3/CeO_2-ZrO_2$ catalysts with different Mo content (8 - 20 wt %) were prepared by simple co-precipitation followed by impregnation method and were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy dispersive spectroscopic (EDS) techniques. The prepared materials were tested for catalytic activity by the synthesis of benzimidazole derivatives using condensation of aromatic aldehydes and o-phenylenediamine by conventional and microwave method. Obtained results reveal that the catalytic activity increases with increase in Mo wt % loading. The best catalytic activity was obtained with 20 wt % $MoO_3/CeO_2-ZrO_2$. The particle size or crystallite size was estimated using Debye-Scherrer equation. After completion of reaction, the catalyst can be recovered efficiently and reused with consistent activity.

Thermal Properties of Diamond Films Deposited by Chemical Vapor Depositon

  • Chae, Hee-Baik;Baik, Young-Joon
    • The Korean Journal of Ceramics
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    • v.3 no.1
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    • pp.29-33
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    • 1997
  • Four diamond films were deposited by the microwave plasma assisted chemical vapor deposition method varying CH4 concentration from 2.5 to 10% in the feeding gases. Thermal conductivity was measured on these free standing films by the steady state method from 80 K to 400K. They showed higher thermal conductivity as the film deposited with lower methane concentration. One exception, 7.79% methane concentration deposited film, was observed to be the highest thermal conductivity. Phonon scattering processes were considered to analyze the thermal conductivity with the full Callaway model. The grain size and the concentration of the extended and the point defects were used as the fitting parameters. Microstructure of diamond films was investigated with the scanning electron microscopy and Raman spectroscopy.

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