• The Transactions of the Korean Institute of Electrical Engineers
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• v.34 no.8
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• pp.323-330
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• 1985

Dielectric loss tangent and ac dielectric strength of GFRP (Glass Fiber Reinforced Plastics, G-10)was investigated as parameters of mechanical and thermal stresses, in order to study the basic dielectrical characteristics of composite insulating materials. The dielectric loss tangent was increased and the ac dielectric strength was decreased with increase in the mechanical stresses beyond the mechanical yield point on account of fiber-matrix debonding, but the dielectric constant was not varied sigificantly. the dielectric strength of G-10 was about 2 MV/cm and the dielectric constant was about 4.8.

• Journal of Biosystems Engineering
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• v.24 no.2
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• pp.123-134
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• 1999

The electrical properties such as dielectric constant, dielectric loss factor and AC conductivity of grain were presented to measure the moisture content of grain using RF impedance. At frequency ranging from 1 to 10MHz and room temperature, $20^{\circ}C$, vector network analyzer(HP4195) and coaxial type sample holder were used to analyze the electrical properties of paddy(11∼24%w.b.), brown rice(11∼18%w.b.), barley(11∼21%w.b.) and wheat(11∼23%w.b.) depending on the moisture content, frequency and bulk density. The dielectric constant and AC conductivity of grain samples increased with moisture content and bulk density. The dielectric constants decreased with frequency and could be expressed as function of the moisture density(decimal moisture $content{\times}bulk$ density).

• Journal of the Korean Ceramic Society
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• v.28 no.4
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• pp.329-337
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• 1991

The Ni-MgO composites were prepared by coprecipitation of NiO-MgO solid solutions and their selective reduction in a hydrogen atmosphere. We report on the measurements of both ac conductivity $\sigma$ ($\omega$, f) and dielectric constant $textsc{k}$'($\omega$, f) for the Ni-MgO composites in the frequency range from 10 Hz to 10 MHz at room temperature. The frequency exponents of conductivity and dielectric constant, x and y, are found to be x=0.98$\pm$0.05 and y=0.05$\pm$0.01. These results are in good agreement with a general scaling relation $\chi$-y=1, although these values are different from the theoretical predications. The dielectric constant exponent ($textsc{k}$' f-fc -s) is found to be s=0.62$\pm$0.07 with estimated percolation threshold fc=0.20$\pm$0.02.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.120-125
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• 2002

AC powder EL devices were fabricated by screen printing method with the dielectric materials in insulating layer and the electrical resistivity of rear electrode. Brightness and current density were measured at voltage range of 50∼300 $V_{rms}$ to estimate optoelectrical properties of AC powder EL devices, respectively. Frequency generator was used as system producing frequency and voltage of a sine wave. Brightness and current density were measured by luminometer and multimeter. Also, dielectric constant for dielectric layer was measured by impedance analyser after preparing thick film. Dielectric constant was improved with amount of $TiO_2$ to $BaTiO_3$ powder. By applying such a process to dielectric layer of low cost AC powder EL device, brightness was improved to 50 cd/$m^2$ at similar current density. Dielectric constant $BaTiO_3$ powder by solution combustion process is better than commercial $BaTiO_3$ powder. By applying to that of low power consumption AC powder EL device, brightness was improved to 85 cd/$m^2$. Brightness of AC powder EL device was relatively decreased by control of electrical resistivity of rear electrode, current density was also decreased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.12
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• pp.1118-1123
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• 2008

High voltage multilayer ceramic capacitors (MLCCs) are classified into two classes-those for temperature compensation (class I) and high dielectric constant materials (class II). We manufactured high voltage MLCC with temperature coefficient characteristics of C0G and X7R and studied the characteristics of electric properties. Also we studied the characteristics of dielectric breakdown voltage (V) as the variation of thickness in the green sheet and how to pattern the internal electrodes. The dielectric breakdown by electric field was caused by defects in the dielectric materials and dielectric/electrode interface, so the dielectric thickness increased, the withstanding voltage per unit (E) thickness decreased. To overcome this problem, we selected the special design like as floating electrode and this design affected the increasing breakdown voltage(V) and realized the constant withstanding voltage per unit thickness(E). From these results, high voltage application of MLCCs can be expanded and the rated voltage can also be develop.

• Macromolecular Research
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• v.11 no.1
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• pp.9-13
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• 2003

Poly (vinylidene fluoride) (PVDF) samples were implanted by using high energy (MeV)F$^{2+}$ and Cl$^{2+}$ ions. We observed that AC dielectric constant of the ion-implanted PVDF samples decreased from 10.5 to 2.5 at 1 kHz as the ion dosage increased from 10$^{11}$ to 3 $\times$ 10$^{14}$ ions/$\textrm{cm}^2$. From differential scanning calorimetry experiments, we observed that PVDF samples become more disordered state through the ion implantation. The decrease of the number of bonding of C-H and C-F and the increase of unsaturated bonding were observed from X-ray photoelectron spectroscopy experiments. The emission of HF and H$_2$ molecules during the ion implantation was detected by residual gas analyzer spectrum. Based upon the results, we analyzed that the low AC dielectric constant of the MeV ion-implanted PVDF samples originated from the reduction of polarization due to the structural change of the CF$_2$ molecules in the MeV ion-implanted PVDF samples.les.

• Journal of the Korean Chemical Society
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• v.56 no.1
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• pp.20-27
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• 2012

Complex permittivity spectra of Allyl Chloride (AC), 2-Butanone (2-BU) and their binary mixtures over the entire range of concentration were obtained using the Time Domain Reflectometry (TDR) technique in microwave frequency range at various temperatures. Static dielectric constant and relaxation time are obtained from complex permittivity spectra. Density ($\rho$) and refractive index ($n_D$) are also measured. These parameters are used to determine excess dielectric constant, excess inverse relaxation time, excess molar volume, excess molar refraction, polarity, Bruggeman factor and thermodynamic parameters viz. enthalpy of activation and entropy of activation. The values of static dielectric constant and relaxation time increases while density and refractive index decreases with the percentage of 2-Butanone in Allyl Chloride increases. Excess parameters were fitted to a Redlich-Kister equation.

• 전기의세계
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• v.18 no.2
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• pp.15-20
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• 1969

The main focus of this paper is on the study of the .gamma. ray irradiation effect upon the electrical properties of a B-kind insulator which is one of the inorganic insulators. The mica is so typical of the B kind insulators as to be selected for a sample. DC, AC, and Impulse voltage is applied to the variable .gamma. ray irradiated dose samples with the constant time duration and the time variable samples with the .gamma. ray irradiated dose. The dielectric breakdown voltage and dielectric constant are measured from the samples and we get the experimental data that the dielectric breakown voltage variations are relatively large, but the dielectric constants are almost constant. The above conclusion is useful for the selection and application of the inorganic insulators under the irradiation effects, and we expect that the conclusion can apply to not only B-kind insulators but also the inorganic insulators.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.254-255
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• 2008

In this study, electrical properties of polyethylene of raised temperature resistance (PE-RT) have been studied through an examination of AC conductivity, dielectric constant, and space charge distributions. A dielectric constant was investigated by Dielectric Analyzer (DEA). Measurements of space charge distributions for PE-RT were carried out using Pulsed Electroacoustic (PEA) techniques, and it was possible to observe the negative charge near the cathode overlapped with the positive induced charge peak, the polarity of which remains unchanged after a short circuit.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.12
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• pp.1633-1640
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• 2018

Epoxy resin is a polar thermosetting polymer that is widely employed in different branches of industry and everyday life, due to their stable physical and chemical properties. Of all the polymer materials currently being used in the electrical insulation industry, epoxy resin is the most widely used kind, chosen as the base polymer material in the present study. Composites were prepared according to the mixing ratio (MS: MA, 1: 9, 3: 7, 5: 5, 7: 3, 9: 1)of mixture for Heterogeneous Minerals(Micro Silica:MS, Micro Alumina:MA) (MS+MA). We have investigated for AC electrical insulation breakdown characteristics and the dielectric properties (permittivity, dielectric loss, and conductivity) with frequency changes. The electrical AC insulation breakdown performance was improved with the increase of the mixing ratio of MS according to heterogeneous mineral material mixture(MS+MA). As Dielectric properties, the dielectric constant and dielectric loss increased with decreasing frequency and decreased with increasing MS content ratio of heterogeneous mineral mixture. Tensile strength and flexural strength according to the mixing ratio (MS + MA) of epoxy / heterogeneous mineral mixture were studied by mechanical properties. The performance of mechanical tensile and flexural strength was significantly improved as the fill contents ratio of MS increased.