• Title, Summary, Keyword: Dielectric liquid

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Electrical Insulating Characteristics of Epoxy Resin by the Fusion Blend Method (용융 블랜드법에 의한 에폭시 수지의 전기 절연특성에 관한 연구)

  • Hong, Kyoung-Jin;Jeong, Woo-Seong;Gu, Hai-Bon;Kim, Tae-Seoung
    • Proceedings of the KIEE Conference
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    • pp.275-278
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    • 1990
  • This study investigated electrical characteristics of solid and liquid epoxy rosins by measuring dielectric breakdown and dielectric loss when epoxy resins were exposed to a mixing cure, i.e., Fusion Blend Method. It was found that mixing epoxy resins were superior to dielectric breakdown and has shorter curing time compare with those of pure liquid epoxy resins.

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Synthesis and Physical Properties of Novel Fluorinated Liquid Crystalline Compounds

  • Keum, Hye-Won;Roh, Su-Dong;Do, Yun-Sun;Lee, Jae-Ho;Kim, Yong-Bae
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1142-1146
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    • 2004
  • The synthetic route and physical properties for three-ring derivatives, trans-2,3,2',3'-tetrafluoro-4-alkyl-4'-(4-alkyl-cyclohexyl)-biphenyl and 4-alkyl-cyclohexane carboxylic acid 2,3,2',3',4'-pentafluoro-biphenyl-4-yl ester are presented. They exhibit broad range nematic phases exceeding 30K and low viscosity of nematic liquid crystal mixtures containing these materials. Their viscosity is compared with that of homologues with a lateral isothiocyanate group and show large negative dielectric anisotropies. The threshold voltage $V_{th}$ was low enough to be operated at a driving voltage of 5V. Our novel LC compounds are suitable materials for the improvement of dielectric anisotropy of vertical align liquid crystal displays (VA-LDCs).

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Study of the Electro-Optic Characteristics Depending on Electric Characteristic of the Black Matrix in a Homogeneous Liquid Crystal Cell Driven by Fringe-Electric Field (프린즈 전기장에 의해 구동되는 수평 배향 액정셀에서 black matrix의 전기적 특성이 셀의 전기광학 특성에 미치는 영향에 관한 연구)

  • 김미숙;김향율;고재완;이승희
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.11
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    • pp.1008-1013
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    • 2003
  • We have studied the effect of black matrix (BM) according to the dielectric anisotropy of liquid crystals (LCs) for a homogeneously aligned LC cell driven by fringe-electric field. The results show that for a LC with positive dielectric anisotropy (+LC) there is a large transmittance change when using a conductive BM, whereas the transmittance change is low for a LC with negative dielectric anisotropy (-LC). The conductive BM existing on top substrate produces vertical electric field, which makes the LC molecules be tilt upward from the substrate and have small twist angle for the +LC. However, for the -LC the conductive BM affects the LC distribution only slightly due to characteristic of the -LC orienting perpendicular to the field. Therefore, for the +LC the electro-optic characteristics are strongly dependent on conductivity of the BM on top substrate in a homogeneous liquid crystal cell driven by fringe-electric field.

Phase Evolution, Microstructure and Microwave Dielectric Properties of Zn1.9-2xLixAlxSi1.05O4 Ceramics

  • Kim, Yun-Han;Kim, Shin;Jeong, Seong-Min;Kim, So-Jung;Yoon, Sang-Ok
    • Journal of the Korean Ceramic Society
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    • v.52 no.3
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    • pp.215-220
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    • 2015
  • Phase evolution, microstructure, and microwave dielectric properties of $Li_2O$ and $Al_2O_3$ doped $Zn_{1.9}Si_{1.05}O_4$, i.e., $Zn_{1.9-2x}Li_xAl_x-Si_{1.05}O_4$, ceramics (x = 0.02 ~ 0.10) were investigated. The ceramics were densified by $SiO_2$-rich liquid phase composed of the Li-Al-Si-O system, indicating that doped Li and Al contributed to the formation of the liquid. As the secondary phase, ${\beta}$-spodumene solid solution with the composition of $LiAlSi_3O_8$ was precipitated from the liquid during the cooling process. The dense ceramics were obtained for the specimens of $$x{\geq_-}0.06$$ showing the rapid densification above $1000^{\circ}C$, implying that a certain amount of liquid is necessary to densify. The specimen of x = 0.06 sintered at $1050^{\circ}C$ exhibited good microwave dielectric properties; the dielectric constant and the quality factor ($Q{\times}f_0$) were 6.4 and 11,213 GHz, respectively.

Formulation of the Sucrose-Free Simulant Human Tissue for SAR Measurement at CDMA Mobile Band

  • Gimm, Yoon-Myoung
    • Journal of electromagnetic engineering and science
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    • v.7 no.2
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    • pp.53-58
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    • 2007
  • A general method to formulate the tissue-equivalent liquids for SAR measurement is proposed to make sucrose-free brain tissue applicable at 835 MHz as an example We suggest the tissue composition can be determined by measuring the dielectric constants and conductivities with the DI water and salt addition variation to the pre-manufactured auxiliary liquid of DGBE and TritonX-100 The manufactured liquid satisfies the specified electrical parameters of international standard at 835 MHz.

Sintering and Microwave Dielectric Properties of $ZnWO_4$ ($ZnWO_4$ 소결특성 및 고주파 유전특성)

  • 이경호;김용철
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.386-389
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    • 2001
  • In this study, development of a new LTCC material using non-glassy system was attempted with respect to reducing the fabrication process steps and cost down. Lowering the sintering temperature can be achieved by liquid phase sintering. However, presence of liquid phases usually decrease dielectric properties, especially the quality factor. Therefore, the starting material must have quality factor as high as possible in microwave frequency range. And also, the material should have a low dielectric constant for enhancing the signal propagation speed. Regarding these factors, dielectric constants of various materials were estimated by the Clausius-Mosotti equation. Among them, ZnWO$_4$ was turned out the suitable LTCC material. ZnWO$_4$ can be sintered up to 98% of full density at 105$0^{\circ}C$ for 3 hours. It's measured dielectric constant, quality factor, and temperature coefficient of resonant frequency were 15.5, 74380GHz, and -70ppm/$^{\circ}C$, respectively In order to modify the dielectric properties and densification temperature, B$_2$O$_3$ and V$_2$O$_{5}$ were added to ZnWO$_4$. 40 mol% B$_2$O$_3$ addition reduced the dielectric constant from 15.5 to 12. And the temperature coefficient of resonant frequency was improved from -70 to -7.6ppm/$^{\circ}C$. However, sintering temperature did not change due to either lack of liquid phase or high viscosity of liquid phase. Incorporation of small amount of V$_2$O$_{5}$ in ZnWO$_4$-B$_2$O$_3$ system enhanced liquid phase sintering. 0.lwt% V$_2$O$_{5}$ addition to the 0.6ZnWO$_4$-0.4B$_2$O$_3$ system, reduced the sintering temperature down to 95$0^{\circ}C$ Dielectric constant, quality factor, and temperature coefficient of resonant frequency were 9.5, 16737GHz, and -21.6ppm/$^{\circ}C$ respectively.ively.

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Characteristics of Dielectric Breakdown in Liquid Nitrogen (액체질소의 절연파괴특성)

  • 추영배;류경우;류강식;김상현
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.37 no.12
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    • pp.872-878
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    • 1988
  • During the past few years, a great deal of attention has been directed to the application of superconductivity to the electrical systems such as superconducting power transmission lines, superconducting magnet energy storage and so on. Yet in order to develop the practical model of these electrical equiqments utilizing suprconductivety and other phenomena at cryogenic temperautre, it is necessary to know the dielectric behaviour of insulating materials at cryogenic temperature in view of reliability, safety and economy of these machines. Investigation of dielectric properties of cryogenic liquids is very important due to the dual role of those as the dielectric and cooling medium. In this study, we investigated results measured over several kinds of dielectric characteristics of liquid nitrogen taking into consideration for application of high Tc superconductor. Dependence of breakdown voltage of gap width, polarity and pressure is reported in this paper and time delay characteristics of breakdown is also the subject of this discussion.

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Dielectric and Optical Study of Polymer Nematic Liquid Crystal Composite

  • Manohar, S.;Shukla, S.N.;Chandel, V.S.;Shukla, J.P.;Manohar, R.
    • Transactions on Electrical and Electronic Materials
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    • v.14 no.3
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    • pp.111-115
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    • 2013
  • The dielectric anisotropy and dispersion of the real and imaginary part of the permittivity of commercially important nematic mixture E-24 and its polymer composite were investigated in the frequency range from 1 kHz to 10 MHz, and temperature range $14^{\circ}C$ to $55^{\circ}C$. The percentage optical transmittance and density have also been measured for both the systems. The results have been explained by assuming molecular rotation about the long molecular axis, under a hindering nematic potential. The dielectric anisotropy ${\Delta}{\varepsilon}$ is positive, and the mean dielectric permittivity falls with rising temperature. ${\Delta}{\varepsilon}$ is also used to determine the order parameter with varying temperature.

Study of Dielectric Properties of a Potential RBD Palm Oil and RBD Soybean Oil Mixture as Insulating Liquid in Transformer

  • Azmi, Kiasatina;Ahmad, Azmier;Kamarol, Mohamad
    • Journal of Electrical Engineering and Technology
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    • v.10 no.5
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    • pp.2105-2119
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    • 2015
  • This paper reported the experimental result of dielectric properties of Refined, Bleached and Deodorized Palm Oil (RBDPO) combined with 0-50% of Refined, Bleached and Deodorized Soybean Oil (RBDSO). The dielectric strength and relative permittivity of RBDPO/RBDSO was higher compared to mineral oil at all ranges of ratios and temperatures which indicated a positive sign for its possible use as insulating liquid in a transformer. All ratios of the RBDPO/RBDSO mixture also demonstrated lower dissipation factor compared to mineral oil at 40℃, 70℃ and 90℃. Apart from that, the kinematic viscosity for the oil mixtures shown exceeded the IEC 60296 as well as the mineral oil results. 70%RBDPO/30%RBDSO mixture ratio was chosen as the best mixing percentage after comparison was made with the mineral oil and IEC 60296 standard where the mixture accumulated the most satisfactory of dielectric properties hence making it as the potential candidate for palm and soybean-based transformer oil.

A Transflective Liquid Crystal Display Driven by the Fringe Field Using a Liquid Crystal with a Negative Dielectric Anisotropy

  • Kim, Jin-Ho;Her, Jung-Hwa;Lim, Young-Jin;Kumar, Pankaj;Lee, Seung-Hee;Park, Kyoung-Ho;Lee, Joun-Ho;Kim, Byeong-Koo
    • Transactions on Electrical and Electronic Materials
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    • v.11 no.3
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    • pp.134-137
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    • 2010
  • We have proposed a transflective liquid crystal display (LCD) driven by the fringe field using a liquid crystal (LC) with a negative dielectric anisotropy. The device used different twist angles of the liquid crystals (LC) in the transmissive (T) and the reflective (R) regions when voltage is applied. With the optimization of the pixel electrode width and the distance between them, the LC directors in the R- and T-regions can be rotated by about $22.5^{\circ}$ and $45^{\circ}$ on an average, respectively. As a result, a high image quality transflective LCD with a single gap, a single gamma, and a wide viewing angle characteristics in both the R- and T- regions can be realized.