• 전기의세계
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• 제25권2호
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• pp.100-106
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• 1976

A comparative study on thermal, static mechanical and dielectric characteristics were made over a temperature range of ca.20.deg.C to 320.deg.C and a frequency range of KHZ to MHZ band on low density polyethylene specimens crosslinked, respectively, by radiation and chemical method. The thermal property of both specimens shows that softening point appears to unchange by crosslinking, however, melting and liquidizing temperatures attain rapid increase at the imitiation of crosslinking. Mechanical properties show little difference to both specimens crosslinked by different method, further the behaviors were discussed in connection with the relaxation of molecular segments in amorphous phase. Dose dependent dielectric characteristics observed at ambient temperature under several fixed frequencies exhibit extremities at ca. 20 Mrad and the behaviors also were interpreted qualitatively by taking into consideration of dipole concentration change in amorphous phase together with the role of specimen geometry to the depth of oxidative layer. Observing frequency dependent dielectric characteristics, it was also proved that ionic conduction loss is appreciably greater in the specimen prepared by chemical method than that by radiation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1177-1179
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• 1993

A study has been carried out on the characteristics of dielectric consent and the dissipation factor of Eicosamethyl Eneasiloxane as a function of frequency($30{\sim}10^5$[Hz]) and temperature(-70[$^{\circ}C$] to 65[$^{\circ}C$]). The result shows that a well-defined maxima of the absorption curves characterized by a dipole loss mechanism at a low temperature range. For temperatures in the vicinity of room temperature and higher, the loss in the range of power frequencies are predominantly of ionic nature. The increase of ionic conduction is attributed to the presence of ionizable oxidation products and their increased dissocation feature. The effect of viscosity upon the dipole loss intensity appeared to be considerably less pronounced than that upon ionic conduction loss.

• Transactions on Electrical and Electronic Materials
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• 제10권4호
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• pp.116-120
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• 2009

Ceramic-polymer composites have been investigated for their suitability as embedded capacitor materials because they combine the processing ability of polymers with the desired dielectric properties of ceramics. This paper discusses the dielectric properties of the ceramic ($BaTiO_3$)-polymer (Epoxy) composition as a function of ceramic particle size at a ceramic loading of 40 vol%. The dielectric constant of these ceramic-polymer composites increases as the powder size decreases. Results show that ceramic-polymer composites have a high dielectric constant associated with the $BaTiO_3$ powder with a 200 nm particle size, high insulation resistance, high breakdown voltage (> 22 KV/mm), and low dielectric loss (0.018-0.024) at 1 MHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1989년도 춘계학술대회 논문집
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• pp.21-25
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• 1989

Theory and experimental results are presented to show the possibility of using a dielectric rod resonator method for characterizing dielectric materials at microwave frequency. The measuring structure is a resonator made up of a cylindrical dielectric rod placed between two parallel conducting plates. In this system, the TE$\_$011/ mode frequency was adapted to minimize the effect of the air-gap between the rod and the conducting plates. The dielectric properties are computed from the resonance frequencies, structure dimensions and 3-dB bandwidth.

• 한국재료학회지
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• 제2권4호
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• pp.263-269
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• 1992

본 실험에서는 낮은 음의 온도계수를 갖는 저온 소결 유전체에 대해 연구하였다. 새로 개발된 재료의 조성은 Ti$O_2$(100-X) CuOx(X=1~5wt%)에 미량의 Mn$O_2$를 첨가 하였다. CuO를 첨가하지 않은 경우에는 저온 (90$0^{\circ}C$) 에서 소결이 진행되지 않았다. CuO 함량이 증가할수록 저온에서 소결이 가능하였으나, 유전율이 낮아지고 유전손실은 증가 하였다. Mn$O_2$를 0.6wt% 첨가한 경우 유전율과 Q값이 가장 높게 나타났다.

• 한국재료학회지
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• 제12권6호
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• pp.442-446
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• 2002

Design of microwave absorbers using high frequency properties of fiber reinforced composites are investigated. Two kinds of composite materials (glass and carbon) are used and their complex permittivity and permeability are measured by transmission/reflection technique using network analyzer. Low dielectric constant and nearly zero dielectric loss are determined in glass fiber composite. However, carbon fiber composites show the high dielectric constant and large conduction loss which is increased with anisotropy of fiber arrangement. It is, therefore, proposed that the glass and carbon fiber composites can be used as the impedance transformer (surface layer) and microwave reflector, respectively. By inserting the foam core or honeycomb core (which can be treated as an air layer) between glass and carbon fiber composites, microwave absorption above 10 dB (90% absorbance) in 4-12 GHz can be obtained. The proposed fiber composites laminates with sandwitch structure have high potential as lightweight and high strength microwave absorbers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.304-306
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• 1987

The dielectric loss ($tan{\delta}$) and the Capacitance (C) of the PPMKA(plasma-polymerized methyl metacrylate) films were measured in the frequency range of 1KHz - 5MHz at $25^{\circ}C$. The effects of the oxidation and the heating and the plasma treatment for $tan{\delta}$ and C of PMMA were investigated. Dielectric loss of PPMMA films was inceased with the oxidized products like CO and OH. As condidates for their origin the existence of low molecula moieties and free radicals in the PPMMA, and the crosslinking made by the heating and plasma treatment have been considered.

• 전자공학회논문지A
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• 제32A권3호
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• pp.471-481
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• 1995

Measurement factors for the dielectric properties of low dielectric loss materials (tan${\dalta}{\le}10^{-4}$) were investigated using the dielectric rod resonator method. It was shown that the relative conductivity (${\sigma}_{r}$) should be controlled within a 5% to obtain the standard deviations of less than 0.07 for permittivity .epsilon.r and 0.06${\times}10^{-4}$ for tan.delta.respectively. Surface resistivity (R$_s$) could be reduced when the surface roughness of parallelled conducting plate was less than 0.07 .mu.m. Measurement error for the permittivity was $\pm$0.02% independent of probe loop size, whereas the error in Q value was reduced with the decrease in probe loop size and also with the increase in the absolute values of Q. Reliable Q values were determined with the probe loop size of less than 4mm. The accurate for the distance between the measuring probe loop and the sample could be obtained when the insertion loss of resonant frequency ranged -15dB - -30dB.

• Elastomers and Composites
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• 제18권2호
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• pp.51-59
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• 1983

고분자물질의 유전특성은 고분자의 분자구조를 연구하는데 대단히 중요하다. 황가황에 의한 천연고무의 유전흡수특성을 25[$^{\circ}C$]의 온도에서 주파수영역 10[KHz]부터 32[KHz] 사이에서 연구하였는데, 결과로서 황 4phr 이하의 가황 천연고무에서는 계면분극과 쌍극자 분극에 의한 두종류의 유전손실이 나타났고 황 7phr 이상의 가황 천연고무에서는 쌍극자분극에 의한 손실만이 존재함을 확인하였다. 더욱이 황의 증가로 저주파수쪽으로 이동되는 유전 손실스펙트럼의 최대치 $tan{\delta}$는 황에 의해 변화되며 체적고유저항은 황의 첨가와는 무관하였고 그 크기는 $10^{7}{\sim}10^{11}[{\Omega}{\cdot}cm}]$이였다.

• 한국전기전자재료학회논문지
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• 제20권12호
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• pp.1039-1043
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• 2007

In this paper, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator application, PMN-PZN-PZT ceramics were fabricated using $LiCO_3,\;Bi_2O_3$ and CuO as sintering aids. And also, their piezoelectric and dielectric properties were investigated according to the milling time. All the specimens sintered at $930\;^{\circ}C$ showed tetragonal phases without secondary phases. With increasing milling time, piezoelectric and dielectric characteristic of specimens increased up to 60 hours milling time and then decreased due to the agglomeration of fine particle. Accordingly, it seems that 60 hour is optimum milling condition. At the sintering temperature of $930\;^{\circ}C$ and milling time of 60 hour, density, dielectric constant(${\varepsilon}_r$), electromechanical coupling factor (kp), mechanical quality factor (Qm), piezoelectric d constant showed the optimum value of $7.95\;g/m^3$, 1382, 0.546, 1749, 330 pC/N, respectively for multilayer piezoelectric actuator application.