• Title/Summary/Keyword: Interfacial temperature

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The Structural and Electrical Properties of the BST Thin Film Prepared by Sol-Gel method. (Sol-Gel법으로 제조한 BST 박막의 구조 및 전기적 특성)

  • Kim, Kyoung-Duk;Chung, Jang-Ho;Bae, Seon-Gi;Lee, Young-Hie
    • Proceedings of the KIEE Conference
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    • 1997.11a
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    • pp.291-293
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    • 1997
  • In this study, Sol-Gel derived $(Ba_{0.7}Sr_{0.3})TiO_3$ thin films were fabricated and investigated. The stock solution was synthesized and spin-coated on Pt/Ti/$SiO_2$/Si substrate at 4000(rpm] and then, annealed at $650{\sim}750[^{\circ}C]$. Crystallization condition, microstructural properties and interfacial structure were observed by XRD, AFM, SEM and TEM. It was found that the BST thin films were completely crystallized at 750[$^{\circ}C$] and showed nano-sized grains. The dielectric constant and loss of the BST thin films were 220, 0.01 at 1[kHz] respectively. Increasing the temperature, the dielectric constant and loss characteristics were not varied widely. At the applied voltage of 1.5[V], the leakage current density was under the $10^{-9}[A/cm^2]$.

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Useful Effects of Fumed Silica Nanoparticles in an Ionic Liquid Electrolyte for High Temperature Supercapacitor (고온작동 수퍼커패시터용 이온성 액체 전해질에서의 흄드 실리카의 효과)

  • Kim, Dong Won;Jung, Hyunyoung
    • Korean Journal of Materials Research
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    • v.28 no.1
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    • pp.43-49
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    • 2018
  • The demand for energy storage devices capable of operating at high temperatures is increasing. In order to operate at high temperatures, a device must have excellent thermal stability and no risk of explosion. Ionic liquids are electrolytes that satisfy the above conditions, and studies on improving their performance have attracted great interest. Here, we report the results of a study on the fabrication of a supercapacitor that has a composite electrolyte prepared by dispersing fumed silica in an ionic liquid. The fumed silica filler exhibits improved ionic conductivity and lower interfacial resistance. In particular, the silica nanoparticles with diameters of 10 nm exhibit better electrochemical properties than fillers of other diameters and have excellent device performance of 33 times higher than the pristine ionic liquid at high temperatures. This study can be used to improve the electrolytes of electrochemical devices, such as the next generation battery or lithium ion battery.

Zn-Ion Coated Structural $SiO_2$ Filled LDPE: Effects of Epoxy Resin Encapsulation

  • Reddy C. S.;Das C. K.;Agarwal K.;Mathur G N.
    • Macromolecular Research
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    • v.13 no.3
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    • pp.223-228
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    • 2005
  • In the present work, a low-density polyethylene (LDPE) composite, filled with Zn-ion coated structural silica encapsulated with the diglycidyl ether of bisphenol-A (DGEBA), was synthesized using the conventional melt-blending technique in a sigma internal mixer. The catalytic activity of the Zn-ions (originating from the structural silica) towards the oxirane group (diglycidyl ether of bisphenol-A (DGEBA): encapsulating agent) was assessed by infrared spectroscopy. Two composites, each with a filler content of $2.5 wt\%$ were developed. The first one was obtained by melt blending the Zn-ion coated structural silica with LDPE in a co-rotating sigma internal mixer. The second one was obtained by melt blending the same LDPE, but with DGEBA encapsulated Zn-ion coated structural silica. Epoxy resin encapsulation of the Zn-ion coated structural silica resulted in its having good interfacial adhesion and a homogeneous dispersion in the polymer matrix. Furthermore, the encapsulation of epoxy resin over the Zn-ion coated structural silica showed improvements in both the mechanical and thermal properties, viz. a $33\%$ increase in the elastic modulus and a rise in the onset degradation temperature from 355 to $371^{\circ}C$, in comparison to the Zn-ion coated structural silica.

Dielectric Properties depending on Frequency in Organic Light-emitting Diodes using $Alq_3$ (Alq3를 이용한 유기 발광 소자의 주파수에 변화에 따른 유전 특성)

  • Oh, Y.C.;Lee, D.K.;Chung, D.H.;Lee, H.S.;Park, G.H.;Kim, T.W.;Lee, J.U.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.11a
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    • pp.293-294
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    • 2005
  • We have investigated dielectric properties depending on frequency in organic light -emitting diodes using 8-hydroxyquinoline aluminum ($Alq_3$) as an electron transport and emissive material. We analyzed the dielectric properties of organic light-emitting diodes using impedance of characteristics. impedance characteristics was measured complex impedance Z and phase $\Theta$ in the frequency range of 40 Hz to $10^8$ Hz. We obtained complex electrical conductivity, dielectric constant, and loss tangent (tan$\delta$) of the device at room temperature. From these analyses, we are able to interpret a conduction mechanism and dielectric properties contributed by an interfacial and orientational polarization.

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Property Evaluation of HVOF Sprayed Multi-walled Carbon Nanotube Aluminum Composite Coatings (고속 화염 용사를 통하여 형성된 다중벽 탄소 나노튜브 알루미늄 복합소재 코팅의 특성 평가)

  • Kang, Ki-Cheol;Park, Hyung-Kwon;Lee, Chang-Hee
    • Journal of Surface Science and Engineering
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    • v.45 no.1
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    • pp.1-7
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    • 2012
  • Multi-walled carbon nanotube (MWCNT) aluminum composite powders were deposited to form coatings using a high velocity oxygen fuel (HVOF) spraying process. High thermal energy and contact with atmospheric oxygen were supplied as the MWCNT aluminum composite particles were exposed to a gas flow field at high temperature (${\sim}3.0{\times}10^3$ K) during HVOF spraying. As a result, the particles underwent full or partial melting and rapid solidification due to the high thermal energy, and the exposure to oxygen induced the interfacial reaction of MWCNTs within the particle. The electrical and mechanical properties of MWCNT aluminum composite coatings were evaluated based on microstructure analysis. Electrical resistivity, elastic modulus, and micro-hardness, of the MWCNT aluminum composite coatings were higher than those of pure aluminum coating. The contribution of MWCNTs to the aluminum matrix can be attributed to their high electrical conductivity, dispersion hardening and anchoring effects. The relationship among the properties and the interaction of the MWCNTs with the aluminum matrix is discussed.

Surface Treatment of Carbon Fiber by Hydrogen Sulfide (탄소섬유 표면의 H2S 처리에 관한 연구)

  • Shin, Kyoung-Han;Han, Jeong-Ryeon
    • Applied Chemistry for Engineering
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    • v.1 no.2
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    • pp.176-181
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    • 1990
  • For the purpose of the improvement of interfacial shear strength in carbon fiber/aluminum matrix composite material, polyacrylonitrile-based carbon fibers were surface treated by hydrogen sulfide gas continuously between 400 and $600^{\circ}C$. Surface treated carbon fibers were analysed by scanning electron microscope. The existence of sulfur compound on treated carbon fiber surfaces was confirmed, and carbon and oxygen contents of the fiber surfaces were examined by X-ray photoelectron spectroscopy. Optimum treating temperature for the adsorption of sulfur on the carbon fiber surface was $500^{\circ}C$. Sulfur compounds on the carbon fiber surfaces form the structures of disulfide, $(S)_n$ and thiophene. The decrease in the tensile strength of the carbon fibers was observed less than about 5%.

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A study on the properties of thermally stimulated current of $(Sr_{0.85}-Ca_{0.15})$$TiO_3$ grain boundary layer ceramic ($(Sr_{0.85}-Ca_{0.15})$$TiO_3$ 입계층 세라믹의 열자력전류 특성에 관한 연구)

  • 김진사;김성열;유영각;최운식;이준웅
    • Electrical & Electronic Materials
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    • v.9 no.4
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    • pp.396-403
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    • 1996
  • In this paper, the (S $r_{0.85}$.C $a_{0.15}$)Ti $O_{3}$ of paraelectric grain boundary layer (GBL) ceramics were fabricated, and the analysis of microstructuye and the thermally stimulated current(TSC) were investigated for understanding effects of GBL's interfacial phenomenon on variations of electrical properties. As a result, the three peaks of .alpha., .alpha. and .betha. were obtained at the temperature of -20 [.deg. C], 20[.deg. C] and 80[.deg. C], respectively. The origins of these peaks are that the .alpha. peak observed at -20[.deg. C] looks like to be ascribed to the ionization excitation from donor level in the grain, and the .alpha.' peak observed at 20[.deg. C] appears to show up by detrap of the trapped carrier of border between the oxidation layer and the grain, and the .betha. peak observed at 80[.deg. C] seems to be resulted from hopping conduction of existing carrier in the trap site of the border between the oxidation and second phase. and second phase.

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Integral Analysis of the Effects of Non-absorbable gases on the Heat Mass Transfer of Laminar Falling Film

  • Kim, Byong-Joo
    • International Journal of Air-Conditioning and Refrigeration
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    • v.6
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    • pp.56-66
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    • 1998
  • The absorption process of water vapor in a liquid film is an important process in LiBr-Water absorption system. The composition of the gas phase, in which a non-absorbable gas is combined with the absorbate, influences the transport characteristics. In the present work, the absorption processes of water vapor into aqueous solutions of lithium bromide in the presence of non-absorbable gas are investigated. The continuity, momentum, energy and diffusion equations for the solution film and gas are formulated in integral forms and solved numerically. It is found that the mass transfer resistance in gas phase increases with the concentration of non-absorbable gas. However the primary resistance to mass transfer is in the liquid phase. As the concentration of non-absorbable gas in the absorbate increases, the interfacial temperature and concentration of absorbate in solution decrease, which results in the reduction of absorption rate. The reduction of mass transfer rate is found to be significant for the addition of a small amount of non-absorbable gas to the pure vapor, especially at the outlet of tube where the non-absorbable gas accumulates. At higher non-absorbable gas concentration, the decrease of absorption rate seems to be linear to the concentration of non-absorbable gas.

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Synthesis of ZrTiO4 and Ta2Zr6O17 Films by Composition-Combinatorial Approach through Surface Sol-Gel Method and Their Dielectric Properties

  • Kim, Chy-Hyung
    • Bulletin of the Korean Chemical Society
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    • v.28 no.9
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    • pp.1463-1466
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    • 2007
  • Single phases of multi-component oxides films, ZrTiO4 and Ta2Zr6O17, could be synthesized by using the combinatorial approach through surface sol-gel route, coating the appropriate mole ratio of 100 mM zirconium butoxide, tantalum butoxide and titanium butoxide precursors on Pt/Ti/SiO2/Si (100) substrate, following pyrolysis at 450 oC, and annealing them at 770 oC. Both the films and bulks of ZrTiO4 and Ta2Zr6O17 showed very stable dielectric properties in temperature range, ?140 to 60 oC, and frequency range, 100 Hz to 1 MHz, promising their applications in wide range of temperatures and frequencies. The dielectric constants of the films were lower and a little more dependent on frequency than those of the bulks. The reduction of dielectric property in the film was mainly due to the interfacial effects that worked as series and parallel-connected capacitances toward the substantial film capacitance.

Interfacial Reactions between W Thin Film and 6H-SiC during Heat Treatments (열처리에 따른 W 박막과 6H-SiC의 계면반응에 관한 연구)

  • Shin, Yang-Soo;Lee, Byung-Taek
    • Korean Journal of Materials Research
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    • v.8 no.6
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    • pp.545-550
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    • 1998
  • Phase reactions at W /6H- SiC interfaces during heat treatments were investigated by X- Ray diffractometer and transmission electron microscopy. No detectable reactions were found after annealing at up to 900$0^{\circ}C$ whereas formation of $W_5Si_3$ and $W_2C$$0^{\circ}C$ This result is consistent with a previous report that the reactions between 3C-SiC and W occurs at llOOoe, and suggests that $W_5Si_3$ and $W_2C$ are the stable phases in this temperature range.

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