• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.712-718
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• 1989

PMN ceramics with excess MgO addition in the range of 0 to 70m/o were prepared, and their electrical properties, such as dielectric constant, tan$\delta$, diffuseness coefficient, remanent polarization, coercive field and electrical conductivity were measured. Dielectric constant and remanent polarization increased with up to 5m/o excess MgO and then decreased presumely due to the precipitation of second phase, etc. Electrical conductivity slightly increased with the addition of excess MgO.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.6
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• pp.538-543
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• 2008

Nanostructured materials are attracting increased interest and application. Exciting perspectives may be offered by electrical insulation. Epoxy/Organoclay nanocomposites may find new and upgraded applications in the electrical industry, replacing conventional insulation to provide improved performances in electric power apparatus, e.g, high voltage motor/generator stator winding insulation, dry mold transformer, etc. In the paper work, the electrical and thermal properties of epoxy/organoclay nanocomposites materials were studied. The electrical insulation characteristics were analyzed through the permittivity characteristics. by analyzing the permittivity spectra, it was found that dielectric constant becomes smaller with increase frequency and becomes larger with increase temperature. This indicates restriction of molecular motion and strong bonds at the epoxy/organoclay nanocomposites. The morphology of nanocomposites obtained was examined using TEM and X-ray diffraction. It has been shown that the presence of polar groups leads to an increased gallery distance and partial exfoliation. Nevertheless, full exfoliation of clay platelets has not been achieved.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.219-223
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• 2001

The on-line cure monitoring during the cure process of composite materials is important for better quality and productivity. The dielectric sensor for cure monitoring consists of base film and electrodes. Because the characteristic of dielectric sensor for the on-line cure monitoring is dependent on the base material, width and number of electrode, etc, the dielectric sensor should be standardized. And the selection of base film material of sensor is very important. In order to prevent the measuring errors generated from the increase of environmental temperature, the base film material should have stable dielectric constant with respect to environmental temperature. In this study, the newly developed dielectric sensor for cure monitoring was designed and the dissipation factor which is function of degree of cure was measured using the sensor. The relationship between the dissipation factor and degree of cure with respect to environmental temperature was investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.872-875
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• 2003

Carbon nitride($CN_x$) thin films were deposited on quartz substrates using reactive RF magnetron sputtering system at uarious deposition conditions and investigated dielectric characteristics. Samples for capacitance measurements were of the MIM(Metal-Insulator-Metal) type devices. Aluminum film electrodes were prepared by a vacuum thermal evaporation method before and after the deposition of carbon nitride films. Capacitances were measured by a FLUKE PM6306 RCL Meter at room temperature. Current-voltage(I-V) characteristics and resistivity were measured by a CATS CA-EDA semiconductor test and analyzer. The carbon nitride films showed ${\alpha}-C_3N_4$ and ${\beta}-C_3N_4$ etc. peaks through Raman and FTIR. Observed surface of film and side structure using SEM(Scanning Electron Microscope), and measured thickness of film by ${\alpha}-step$. We can find that the dielectric constant was the lowest value in 50% nitrogen ratio and the resistivity was the highest value in 70% nitrogen ratio.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.453-456
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• 2010

Tantalum oxide ($Ta_2O_5$) films are of considerable interest for a range of application, including optical waveguide devices, high temperature resistors, and oxygen sensors. In this paper, we establish an anode oxidation process of tantalum thin film. The voltage drop in the electrolyte is affected not in voltage change but in current change. If the voltage drop in the electrolyte is same with cathode oxidation voltage, the current changes logarithmically in proportion to the voltage drop in interface of tantalum oxide and electrolyte. As a result of the measurement on the electrical property of tantalum oxide thin film, when the thickness of the insulator film is $1500{\AA}$, the breakdown voltage is 350volts and dielectric constant is 29.

• Journal of the Korean Chemical Society
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• v.18 no.4
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• pp.251-258
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• 1974

The rate constants for the nucleophilic substitution reactions of substituted benzoyl chlorides with p-nitroaniline in such solvents as acetone, acetonitrile, methanol, ethanol, etc. were conductometrically determined, and the activation thermodynamic parameters were also evaluated. In result, the reaction rates were faster in protic solvents than in aprotic solvent; in the solvents of similar property, the reaction rate in the solvent of the large dielectric constant was faster than that in the solvent of the small dielectric constant. Hammett plots in individual solvents showed the straight lines with positive slope; and we concluded that the reaction occurred via the addition-elimination mechanism.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.226-227
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• 2007

Nanostructured materials are attracting increased interest and application. Exciting perspectives may be offered by electrical insulation. Epoxy/Organoclay nanocomposites may find new and upgraded applications in the electrical industry, replacing conventional insulation to provide improved performances in electric power apparatus, e.g, high voltage motor/generator stator winding insulation, dry mold transformer, etc. This paper shows that electrical and thermal properties of epoxy/organoclay nanocomposites insulating materials for dsc, dielectric constant, I-V characteristics, breakdown volatge, can improve significantly with respect to the basic, virgin materials.

• Journal of the Korean Chemical Society
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• v.10 no.3
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• pp.119-128
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• 1966

The glass electrode was empirically calibrated in methanol-and 2-propanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. The thermodynamic dissociation constants of hydrogen cupferrate in methanol-and 2-propanol-water solution were potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength and 25$^{\circ}C$. The empirical formula of the constants with mole fraction (n) of the organic solvent are as follow: methanol-water solution $pK_a$= 2.24n + 4.29 at ${\mu}$ = 0.01 n = 0.0476∼0.642 $pK_a$ = 2.35n + 4.38 at ${\mu}$ = 0.05 n= 0.0446~0.642 2-propanol-water solution $pK_a$= 5.50n + 4.48 at ${\mu}$ = 0.05 n = 0.0253~0.259 The relationships between $pK_a$ of acetic acid, propionic acid and HCup and dielectric constant of some mixed solvents were discussed. It would be considered that the factors effecting $pK_a$ value of weak acid in mixed-solvent are not only dielectric constants but acid-base character and solvation effect of the solvent, etc.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.3
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• pp.7-12
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• 2002

In the measurement of the RF properties, the LTCC substrate must be considered as a system including various conductor patterning processes. In this paper, the LTCC substrate system is compared with a conventional PCB(Printed Circuit Board) substrate such as FR-4, Duroid and Teflon, etc. The microstrip resonator method is employed for the measurement of the RF properties in the range of DC to 20 GHz. Experimental results show that the ring resonator method is suitable for system loss measurement, and the series gap resonator method for dielectric constant measurement. The process of conductor patterning and its effect on the system loss were also studied.

• Journal of the Korean Ceramic Society
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• v.20 no.2
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• pp.153-160
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• 1983

This study was carried out to research the change of mineral phases and the characteristics(apparent specific gra-vity water absorption firing shrinkage modulus of rupture thermal expansion and specific dielectric constant) of the sintered bodies manufactured by kaolin and limestone. Samples were composed of the same theoretical composition as it of anorthite and fired up to 145$0^{\circ}C$ Investigated the change and micro-structure of the mineral phases by XRD and SEM the characterisdtics of the sintered bodies by TMA Automatic Capacitance Bridge and etc. The results were as follow. 1. Reactions of sintering are occurred between 860-95$0^{\circ}C$ and 1200-138$0^{\circ}C$ and state of bloating is occurred at 1410-145$0^{\circ}C$ 2. For the inclusion of feldspar and its fine particles of materials the temperature of producing and collapsing is decreased. 3. Pseudo-wollastonite and gehlenite are formed about 95$0^{\circ}C$ 4. At 114$0^{\circ}C$ anorthite are begin to forming and increase continuously to 138$0^{\circ}C$. Above 141$0^{\circ}C$ content of anorthite are decreased. 5. The variations of bending strength with sintering temperature reflect similar trend of sintered contraction and in-crease continuously from 120$0^{\circ}C$. At 145$0^{\circ}C$ reached about 680kg/cm2. 6. Specific dielectric constant$($\varepsilon$_s)$ of specimen sintered at 141$0^{\circ}C$ is 7.12 and that value is most favorable.