• Title, Summary, Keyword: Dielectric relaxation

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Physico-chemical and dielectric relaxation studies of ionic surfactants in Time Domain Reflectometry (TDR)

  • Kalaivani, Thirunavukarasu;Krishnan, Subramanian;Nithiyanantham, Subramanian
    • The Korean Journal of Chemical Engineering
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    • v.34 no.8
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    • pp.2325-2330
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    • 2017
  • The properties of aqueous surfactant solutions with external additives are extensively useful in surfactant-based systems. To study the dielectric relaxation studies of aqueous ionic surfactants (SDS, CTAB, DPC) and aqueous butanol, benzyl alcohol, aniline and tributylamine were carried out for different concentrations at 303k. Dielectric relaxation spectroscopy (DRS) is valuable for understanding the dynamic process mainly in micellar systems. Time domain dielectric data were obtained through HP54750A oscilloscope and TDR plug-in-module. The relaxation times were determined through the well-known Cole-Cole method. The superposition of two relaxation times gives the dielectric relaxation time obtained from the hydrated water molecule with rotations around the micelle, ions and another hydrophobic inner side of the micelle. Viscosity measurements were used to correlate the dielectric data. The Kirkwood correlation factor ($g_f$), effective Kirkwood correlation factor ($g_{eff}$), Bruggeman Factor ($f_B$), excess inverse relaxation time $(1/{\tau})^E$, excess dielectric constant (${\varepsilon}^E$) and free energy of activation (${\Delta}F_t$) were also calculated. The effects of dielectric relaxation and viscous flow were interpreted and discussed.

Anomalously high dielectric strength and low frequency dielectric relaxation of a bent-core liquid crystal with a large kink angle

  • Srivastava, Anoop Kumar;Kim, Jongyoon;Yeo, Sunggu;Jeong, Jinyoung;Choi, E-Joon;Singh, Vijay;Lee, Ji-Hoon
    • Current Applied Physics
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    • v.17 no.6
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    • pp.858-863
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    • 2017
  • We investigated the dielectric dispersion property of a bent-core liquid crystal (BLC) with a large kink angle in the frequency range of 1.0 Hz-5.5 MHz in a planar aligned cell. Single dielectric dispersion was observed in the smectic A, nematic, and isotropic phase of the planar aligned sample. The dielectric strengths, relaxation frequencies, distribution parameters, and dc conductivity were measured as a function of temperature. The dielectric strength of the observed relaxation mode was anomalously high (~70), whereas the relaxation frequency was low at ~500 Hz. The relaxation mode observed in the planar aligned cell was attributed to the fluctuations in the polarization direction due to the cooperative motion of the molecules.

Dielectric Relaxation of Siloxane-Epoxy Copolymers

  • Kim, Chy-Hyung;Shin, Jae-Sup
    • Bulletin of the Korean Chemical Society
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    • v.23 no.3
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    • pp.413-416
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    • 2002
  • The dielectric responses of 10 and 40 wt% siloxane-epoxy copolymers were investigated in temperature range near the glass transition of polydimethylsiloxane at which the dielectric transitions were also observed. On the other hand, the pure epoxy did not show any dielectric transition in measurement temperature range -90 to 150 $^{\circ}C.$ The experimental data showed that for the copolymer investigated, the temperature-frequency super-position principle could be applied to the dielectric response. From the Cole-Cole equation, the dielectric relaxation of the 10 wt% siloxane near the glass transition temperature resulted in a broad distribution with ${\beta}=$ 0.19 and the relaxation time at -70 $^{\circ}C$ was 5.3 ${\times}$ $10^{-2}$s. The glass transition temperature, 188 K, was estimated by using WLF relation, which was consistent with the data presented in experiment.

Dielectric Relaxation Characteristics of Biology Thin Film (생체박막의 유전완화특성)

  • Song, Jin-Won;Cho, Su-Young;Lee, Kyung-Sup;Sin, Hun-Gyu
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.107-110
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    • 2003
  • In this paper, We introduced that the method for determing the dielectric relaxation time $\tau$ of floating monolayers on water interface. Displacement current flowing across monolayers is analyzed using a rod-like molecular model. It is revealed that the dielectric relaxation time $\tau$of monolayers in the isotropic polar orientational phase is determined using a linear relationship between the monolayer compression speed $\alpha$ and the molecular area Am. here Displacement current gives a peak at A = Am. The dielectric relaxation time $\tau$ of organic monolayers was examined on the basis of the analysis developed here.

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Static Dielectric Constant and Relaxation Time for the Binary Mixture of Water, Ethanol, N. N-Dimethylformamide, Dimethylsulphoxide, and N, M-Dimethylacetamide with 20Hethoxyethanol

  • Ajay Chaudgari;N. M. More;S. C. Mehrotra
    • Bulletin of the Korean Chemical Society
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    • v.22 no.4
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    • pp.357-361
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    • 2001
  • Frequency spectra of the complex permittivity of 2-methoxyethanol (2-ME) with water, ethanol, dimethylsulphoxide (DMSO), N,N-dimethylformamide (DMF) and N,N-dimethylacatamide (DMA) have been determined over the frequency range of 10 MHz to 20 GHz at 25 $^{\circ}C$, using the Time domain reflectometry method, for 11 concentrations for each system. The static dielectric constant, dielectric constant at microwave frequency, relaxation time, excess dielectric parameters, and Kirkwood correlation factor have been determined. The relaxation in these systems within the frequency range can be described by a single relaxation time constant, using the Debye model. The parameters show a systematic change with the concentration.

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A study on the Dielectric Relaxation Phenomena of phospolipid monolayers Film (인지질 단분자막의 유전완화현상에 관한 연구)

  • Cho, Su-Young;Lee, Kyung-Sup
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.431-434
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    • 2003
  • In this paper, We introduced that the method for deforming the dielectric relaxation time $\tau$ of floating monolayers on water interface. Displacement current flowing across monolayer is analyzed using a rod-like molecular model. It is revealed that the dielectric relaxation time $\tau$ of monolayers in the isotropic polar orientational phase is determined using a linear relashionship between the monolayer compression speed a and the molecular area $A_m$. A displacement current gives a peak at A=$A_m$. The dielectric relaxation time $\tau$ of phospolipid monolayers was examined on the basis of the analysis developed here.

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Dielectric Relaxation Properties of Organic Ultra Thin Films for Nanotechnology (나노기술을 위한 유기초박막의 유전완화특성)

  • Cho, Su-Young;Song, Jin-Won;Lee, Kyung-Sup
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.9-13
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    • 2004
  • In this paper, evaluation of physical properties about dielectric relaxation phenomena by the detection of the surface pressures and displacements current on the monolayer films of phospolipid monomolecular DLPC, DMPC using pressure stimulus. As a result, the changed surface pressure, displacement current and the transition forms of dipole moment of phospolipid monomolecular in area per molecular by pressure stimulus were conformed well. It was known that the monolayers by linear relationship for decision of dielectric relaxation time between compressure speed and molecule area By according to the linear relationship relation get that frictional constant, DLPC was $1.89{\times}10^{-19}$[Js] and DMPC was $0.722{\times}10^{-19}$[Js]. It is found that the phospolipid monolayer of dielectric relaxation takes a little time and depend on the molecular area.

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A Comparison of the Dielectric Behavior of Aromatic and Aliphatic Polyurethanes in Relation to Transitional Phenomena

  • Kim, Chy Hyung
    • Transactions on Electrical and Electronic Materials
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    • v.18 no.4
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    • pp.211-216
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    • 2017
  • The dielectric properties of two polyurethanes (PUs) with different hard segments, i.e., aromatic methylene di-p-phenyl diisocyanate (MDI) and aliphatic hexamethylene diisocyanate (HDI), were investigated in the temperature range of -100 to $100^{\circ}C$ and in the frequency range of 1 Hz to 3 kHz. The ${\alpha}$-relaxations induced by the glass transition of the equivalent soft segments in the two PUs occurred at relaxation times of ${\tau}=3.46{\times}10^{-3}s$ for MDI-PU and ${\tau}=3.39{\times}10^{-2}s$ for HDI-PU at $-20^{\circ}C$, in accord with the temperature-frequency superposition principle, resulting in similar shifting factors. However, different I-relaxations were observed for the two PUs. The I-relaxation of MDI-PU occurred due to the mobility of the chain extenders near $80^{\circ}C$ with a slower shifting rate than the ${\alpha}$-relaxation. On the other hand, I-relaxation arising from both the extender and the unconstrained hard segments of HDI-PU occurred at $70{\sim}100^{\circ}C$, indicating complicated dielectric behavior due to partial interaction with the ${\alpha}$-relaxation at high frequencies. Thus, the I-relaxation of HDI-PU did not follow the superposition principle. The dielectric behaviors of the PUs were mainly influenced by their phase transitions, which were affected by the structure and components of the materials.

A Circuit Model of the Dielectric Relaxation of the High Dielectric $(Ba,Sr)Tio_3$ Thin Film Capacitor for Giga-Bit Scale DRAMs (Giga-Bit급 DRAM을 위한 고유전 $(Ba,Sr)Tio_3$박막 커패시터의 유전완화 특성에 대한 회로 모델)

  • Jang, Byeong-Tak;Cha, Seon-Yong;Lee, Hui-Cheol
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.37 no.4
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    • pp.15-24
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    • 2000
  • The dielectric relaxation of high-dielectric capacitors could be understood as a dynamic property of the capacitor in the time domain, which is regarded as a primarily important charge loss mechanism during the refresh time of DRAMs. Therefore, the equivalent circuit of the dielectric relaxation of the high-dielectric capacitor is essentially required to investigate its effects on DRAM. Nevertheless, There is not any theoretical method which is generally applied to realize the equivalent circuit of the dielectric relaxation. Recently, we have developed a novel procedure for the circuit modeling of the dielectric relaxation of high-dielectric capacitor utilizing the frequency domain. This procedure is a general method based on theoretical approach. We have also verified the feasibility of this procedure through experimental process. Finally, we successfully investigated the effect of dielectric relaxation on DRAM operation with the obtained equivalent circuit through this new method.

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The structural and dielectric polarization characteristics of composite oxide material in $(Ba Ca)TiO_3$-Zn (복합산화물 $(Ba Ca)TiO_3$-ZnO의 구조적 및 유전분극 특성)

  • 홍경진;임장섭;정우성;민용기;김용주;김태성
    • Electrical & Electronic Materials
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    • v.10 no.3
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    • pp.239-246
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    • 1997
  • The ZnO is stabilize dielectric constant over a broad temperature range because its addition makes the relaxation time short. In this study, the composite oxide material (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_{3}$ was mixed by ZnO additive material and the dielectric polarization characteristics was studied. The relative density was over 90[%] at all specimen in the structural characteristics. Among of the specimen, the relative density of (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_{3}$ with ZnO (0.4mol) has a 95[%]. The grain size of composite oxide material with an increasing ZnO increased and it was 1.0[.mu.m]-1.22[.mu.m]. In the electrical characteristics, the charge and discharge current was increased by ZnO addition. The dielectric relaxation time was increased by space charge polarization at above 110[.deg. C] and the dielectric relaxation time was fixed by space charge polarization of para-dielectric layer at below 110[.deg. C]. The dielectric relaxation time was maximum when the grain size was small. The dielectric relaxation time is decreased with an additive material ZnO and interface polarization, existing void at the grain and grain boundary. The remnant polarization is increased and the coercive electric field is decreased by ZnO.

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