• Korea-Australia Rheology Journal
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• v.20 no.2
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• pp.73-77
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• 2008

The rheological properties of polar solutions are very sensitive to preparative methods as well as measuring conditions. The effects of dissolution temperature on the rheological properties of the solutions of polyvinyl alcohol (PVA) in dimethyl sulfoxide were investigated over the range of dissolution temperatures $70-130^{\circ}C$. Viscosity was increased as dissolution temperature was increased. PVA solutions prepared at 120 and $130^{\circ}C$ showed Bingham behavior, which became less noticeable with decreasing dissolution temperature. The modified Cole-Cole plot of the solutions gave slope less than 2, suggesting the solutions were a heterogeneous system irrespective of optical transparency. Further, the slope was decreased with increasing dissolution temperature, indicating that the solid character got more prominent as dissolution temperature was increased. However, the relaxation time of the solutions was little dependent on dissolution temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.182-182
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• 2009

The effect of Re-oxidation on the PTCR properties of Sm-doped barium titanate ceramics was investigated by means of impedance spectroscopy. Electrical properties such as resistance vs. temperature, I-V curve were measured and microstructure was observed with SEM photography. Sample was fabricated with thick film process such as tape casting of green sheet, screen printing of electrode pattern, stacking, firing in reduced atmosphere and re-oxidation, etc. As the temperature of re-oxidation increases, resistance jump as a function of temperature enhances but resistance at room temperature increases. These behavior of resistance as a function of temperature, dependent on the re-oxidation condition, is analyzed with Cole-Cole impedance plot and is shown to be related with the degree of oxidation of grain boundary regardless of grain core during re-oxidation process of sample.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.9-13
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• 1995

The effect of WO$_3$ addition and sintering condition on the electrical properties of SrTiO$_3$ceramic have been investigated. Resistivity and capacitance of grains and grain boundaries were obtained by applying impedance spectroscopy. From the result it could be concluded that the temperature dependance of capacitance of WO$_3$doped specimens were influenced directly by the variation of grain boundary capacitance. It was also found that the dispersion frequency increased as the degree of reduction of the specimen increased. The dispersion frequency characteristics showed discernably that the resistivity of the specimen varied with WO$_3$ content. The dielectric properties were influenced directly by the reduction of the specimens. The dielectric constant of grain boundaries of BL capacitor could be obtained by Cole-Cole plot and was influeneced by the amount of WO$_3$ added.

• The Korean Journal of Rheology
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• v.1 no.1
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• pp.20-28
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• 1989

비닐 알코올의 함량이 62(EVOH-62) 및 71(EVOH-71) mole%인 에틸렌 비닐알코올 공중합체와 나일론(나일론-6, 나일론-6/12 및 나일론-12)과의 블렌드를 이축압출기에서 제 조하였으며 이들블렌드의 형택학 및 유변학적 성질을 SEM, TEM 및 RDS로 측정하였다. EVOH-61/나일론-6 및 EVOH-7/나일론-6 블렌드는 나일론의 조성이 많은 영역에서는 균 일상을 EVOH 조성이 많은 영역에서는 미세한 상분리(약 0.2$\mu$)를 나타내었다. 한편 EVOH-71/나일론-6/12 및 EVOH-71/나일론-12 블렌드는 상분리가 뚜렸하였으며 EVOH조 성이 많은 영역에서는 피브릴화가 나타났다. 낮은 진동주파수 영역에서 점도 대 조성곡선은 전반적으로 양의 편차를 보였으나 Cole-Cole plot은 나일론-6과의 블렌드가 나일론-6/12나 나일론-12와의 블렌드에 배해 유변학적인 측면에서보다 상용성이 우수함을보였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.543-546
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• 2004

Bias and frequency-dependent impedance is a technique for the investigation of complex conductivity. At low frequency, complex impedance is dominated by resistive component, and at high frequency by capacitive component. We are going to present the results of the bias and frequency-dependent complex impedance in the device structure of $ITO/Alq_3/Al$ in the temperature range between 10K and 300k. And we will show to change radius of Cole-Cole plot. It will be decrease resistance by temperature. Also equivalent electrical circuit and dielectric relaxation can be accomplished by using the complex impedance analysis.

• Korea-Australia Rheology Journal
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• v.19 no.1
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• pp.1-5
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• 2007

By combining ultrasonic energy which is essential for the chain scission of polymer molecules and a multifunctional agent (MFA) having double bonds at its ends, we were able to modify the molecular structure of polycarbonate (PC) from linear to a branched structure during melt processing. The three double bonds in chain ends of MFA were expected to act as sites for trapping macroradicals of PC during the course of ultrasound-assisted mixing process. The transformation of molecular structure of PC was confirmed by the measurements of rheological properties of the modified PC. After the ultrasonic irradiation of PC together with MFA, increase in complex viscosities and shear-thinning behavior were observed. The Cole-Cole plot and measurement of extensional viscosities revealed the characteristic features of branched structure with well-defined extensional behavior which is comparable to that of a commercial branched PC.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1739-1741
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• 2000

DC current density-voltage and impedance spectroscopy studies have been performed on indium-tin-oxide(ITO)/para-sexiphenyl(6p)/aluminium organic electroluminescent device. The device exhibited a blue color emission, The turn-on voltage of the device is observed at 5V from the current density-voltage measurements. The impedance spectroscopy measurements show that a resonance frequency shift with applied DC bias is observed and a single semi-circle Cole-Cole plot is confirmed. The bias-dependent bulk resistance and bias-independent bulk capacitance is observed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04a
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• pp.13-17
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• 2004

펜틸시아노비페놀(PCB) 액정셀은 저주파 영역에서 유전율이 대단히 크게 나타나는 현상이 보인다. 그 원인은 액정셀 내의 불순물 이온의 거동이라고 생각된다. 액정셀 내에 존재하는 불순물 이온의 거동을 관찰하기 위하여 PCB 액정셀의 유전 분산특성을 측정하여 온도의존성, 막 두께 의존성, 직류전압 의존성등을 측정하였다.

• Polymer(Korea)
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• v.24 no.3
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• pp.358-365
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• 2000

Miscibility itnd thermal behavior of blends of synthetic biodegradable aliphatic polyester (Bionolle) with poly(epichlorohydrin) (PECH) were investigated by a differential scanning calorimetry (DSC), a dynamic mechanical thermal analyzer (DMTA) and a rotational rheometer. Observed both single glass transition temperatures from the DSC in agreement with the Fox equation and single T$_{g}$ changes as a function of composition from the DMTA indicate that these blend mixtures are miscible. In addition, the miscibility of this blend system was also observed from the single curve of the Cole-Cole Plot of log G′($\omega$) vs. log C"($\omega$) from the dynamic test using a rotational rheometer. This was further verified from the cryogenically fractured surface of BDP/PECH blends by scanning electron microscopy.

• Bulletin of the Korean Chemical Society
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• v.18 no.7
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• pp.715-719
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• 1997

In order to study the dielectric properties of the oriental lacquer films, three different films have been prepared differing purification and curing procedures. Dielectric properties were measured in the frequency range of 1 Hz to 105 Hz at various temperatures between - 50 ℃ and 150 ℃. The DEA using 1 Hz showed that glass transition and secondary relaxation temperatures of oriental lacquer film are very time dependent. In addition, the frequency-independent negative peak between 25 ℃ and 45 ℃ was observed, which could represent the formation of crosslink by laccase enzyme during heating. On the contrary, the high temperature cured film showed a hardly noticeable negative peak at the temperature range. The relationship between thermodynamic properties and chemical structures has been discussed based on the analysis of the dielectric relaxation behavior using the Cole-Cole plot and the dielectric relaxation intensity.