Electrode Polarization Relaxation Time Research Articles

The Debye length and anionic transport properties of composite membranes based on supported ionic liquid-like phases (SILLPS).

An analysis of the ionic transport properties of BMIM [NTf2] in supported ionic-liquid-like phase (SILLP)-based membranes has been carried out based on experimental impedance spectroscopy measurements. The direct current (dc)-conductivity was analyzed to determine the temperature and frequency dependence. The fit of the loss tangent curve data with the Cole-Cole approximation of the electrode polarization model provides the conductivity, diffusivity, and density of charge carriers. Among these quantities, a significant increase in conductivity is observed when an ionic liquid is added to the polymeric matrix containing imidazolium fragments. The use of a recent generalization of Eyring's absolute rate theory allowed the elucidation of how the local entropy restrictions, due to the porosity of the polymeric matrix, control the conductive process. The fit of the conductivity data as a function of temperature manifests the behavior of the excess entropy with respect to the temperature. The activation entropy and enthalpy were also determined. Our results correlate the Debye length (LD) with the experimental values of conductivity, electrode polarization relaxation time, and sample relaxation time involved. Our work provides novel insights into the description of ionic transport in membranes as the diffusivity, mobility, and free charge density depend on the LD. Moreover, we discuss the behavior of the polarization relaxation time, the sample relaxation time, and the static permittivity as a function of the temperature.

Dielectric study of mixtures of benzaldehyde and methanol at 293.15 K temperature

Complex dielectric permittivity ε∗ω=ε'ω-jε"ω of benzaldehyde, methanol and their mixtures of varying range 20 Hz to 2 MHz at 293.15 K temperature. The measured value of ε∗ω are used to evaluate electrical properties such as complex modulus M*(ω) and complex impedance Z*(ω). Different relaxation times like, ionic conductivity relaxation time τσ and electrode polarization relaxation time τEP are also determined. The value of τσand τEP are found to increase with an increase of the concentration of benzaldehyde in methanol. Frequency and concentration dependent behaviour of the complex relative dielectric functionε∗ω, complex modulus M*(ω) and complex impedance Z*(ω) of benzaldehyde, methanol and their binary mixtures are analysed.

Dielectric spectroscopic study of solutions of amino silicone oil in the polar solvent mixtures of methyl ethyl ketone and methyl iso butyl ketone

The complex permittivity, complex modulus, alternating current electrical conductivity and complex impedance of the ternary mixtures of amino silicone oil in methyl ethyl ketone and methyl iso butyl ketone have been investigated at 303.15 K temperature over the frequency regime 200 Hz to 2 MHz. Complex permittivity and complex impedance data have been fitted to the Coelho model and Nyquist plot respectively. The Coelho model of complex permittivity data provides the electrode polarization relaxation time related to electric double layer relaxation processes. Nyquist plot of complex impedance data exhibits Debye type dispersion corresponding to conduction relaxation processes and electric double layer relaxation processes. Electrode polarization relaxation time (τEP), relaxation time (τEP′), ionic conductivity relaxation time (τσ), geometric relaxation time (τg) and double layer relaxation time (τdl) have been calculated using the different formalism. Static permittivity (ε0), DC conductivity (σdc) and refractive index (nD) have also been determined for all the ternary mixtures. Solvent effect interaction in amino silicone oil with methyl ethyl ketone, methyl iso butyl ketone and with their mixtures is also discussed in the paper. Systematic variation is observed in all the parameters with change in concentration of amino silicone oil in methyl ethyl ketone and methyl iso butyl ketone.

Dielectric spectroscopic study of the binary mixtures of amino silicone oil and methyl ethyl ketone in the frequency range of 100 Hz to 2 MHz at 298.15 K temperature

Complex dielectric function ε⁎(ω) = ε′(ω) − ε″(ω) of the binary mixtures of amino silicone oil and methyl ethyl ketone were measured using precision LCR meter in the frequency range 100 Hz to 2 MHz at 298.15 K temperature. Complex dielectric function data are represented in different formalisms like complex a.c. conductivity σ⁎(ω), complex modulus M⁎(ω) and complex impedance Z⁎(ω). The refractive index of the same system was determined at 298.15 K temperature using Abbe's refractometer. These presentations are used to find out different parameters such as electrode polarization relaxation time (τEP), relaxation time (τEP′), ionic conduction relaxation time (τσ), dc conductivity (σdc) and static permittivity (ε0) of the liquid samples. Determined parameters are used to gain information about the effect of concentration variation on dielectric and electrical properties of the mixtures. Complex impedance Z⁎(ω) data were fitted to an equivalent circuit, having four elements including capacitance (C2) representing electrode double layer capacitance. The geometric relaxation time was calculated using product of resistor (R2) and capacitor (C1) of the equivalent circuit. Lower frequency dielectric data is dominated by the EP effect. The systematic change is observed in all the parameters with change in concentration of amino silicone oil in methyl ethyl ketone. Viscosity dependence of dc conductivity of the system is also investigated.

Static permittivities, viscosities, refractive indices and electrical conductivities of the binary mixtures of acetonitrile with poly(ethylene glycol)-200 at temperatures 288.15–318.15 K

Relative static permittivities, viscosities, refractive indices and electrical conductivities of the binary mixtures of acetonitrile (ACN) with poly(ethylene glycol) (PEG; Mw = 200 g mol−1) over the whole composition range and temperatures from 288.15 K to 318.15 K have been reported. The excess properties determined from the volume fraction based additive relation confirm that the hydrogen-bond interactions between the ACN and PEG molecules in their mixtures contribute to permittivities slight positively, whereas, these interactions greatly reduce the viscosities of the mixtures. The viscosity activation energy and conductivity activation energy values for the ACN–PEG mixtures are found decreasing with the increase of ACN concentration in the mixtures. The charge conduction behaviour in the dielectric viscous media of these binary mixtures has been analyzed by using the values of ac electrical conductivity and viscosity product which further included with static permittivity at different temperatures. The complex permittivity, ac electrical conductivity, and impedance spectra over the frequency range from 20 Hz to 1 MHz at 298.15 K have also been investigated for these mixtures. The static permittivity frequency range over which the dielectric and electrical spectra of these mixtures are affected by the electrode polarization process has been explored. A correlation between electrode polarization relaxation time and dc electrical conductivity has been observed for the ACN–PEG mixtures.

Dielectric studies of Poly (Ethylene glycol)-Polyurethane/Poly (Methylmethacrylate)/Montmorillonite Composite

Semi Inter penetrating Polymer Network (IPN) of [poly (ethylene glycol)-polyurethane-polymethylmethacrylate] [60:40]-montmorillonite (MMT) nanocomposites with different weight percentages of MMT are synthesized. The formation of the composite and its structural properties are characterized by Fourier transform infrared, X-ray diffraction pattern (XRD) and scanning electron microscopy (SEM) images. Differential scanning calorimetry (DSC) and XRD patterns show the amorphous nature of the composites. The Thermo Gravimetric Analysis (TGA) shows the enhanced thermal stability of the composite compared with the semi IPN without fillers. The conductivity behavior, frequency dependent modulus properties and dielectric properties of these prepared composites are studied by using ac impedance spectroscopy (EIS) in the frequency range 1Hz-1MHz. It is found from the impedance results that conductivity increases from 2.17×10−7 S/cm to 2.32×10−6 S/cm with increase of MMT concentration up to 5wt % and it decreases with further increase of MMT content. The dielectric analysis shows that dielectric permittivity (ɛ′) and dielectric loss (ɛ″) values decreases with increase in frequency at lower frequency region whereas frequency independent behavior is observed in the high frequency region. The electrical modulus representation shows a peak in the imaginary component. The ionic conduction relaxation times of the composites obtained from this peak maximum are in good correlation with the electrode polarization relaxation time and conductivity values.

Dielectric properties of PEO–PVP–MMT nanocomposite hydrocolloids

The relative complex dielectric function, electric modulus, alternating current electrical conductivity and complex impedance behaviour of aqueous poly(ethylene oxide) (PEO) and poly(vinyl pyrrolidone) (PVP) blend with montmorillonite (MMT) clay nano-platelets as colloidal suspensions have been investigated over the frequency range 20 Hz to 1 MHz at 15, 30 and 45 °C. The direct current ionic conductivity and real part of permittivity of the hydrocolloids have increased whereas electrode polarization relaxation time has decreased with the increase of MMT concentration, and these dielectric parameters have significantly varied with change of the temperature. The hydrogen bond complex formation between PEO, PVP and dispersed MMT nano-platelets in aqueous solutions has been discussed. The correlation between complex structures and the dielectric parameters of these materials have been confirmed.

Dielectric spectroscopy and viscosity studies of aqueous poly(ethylene oxide) and poly(vinyl pyrrolidone) blend

The complex dielectric function, electric modulus, impedance and ac electrical conductivity behaviour of aqueous solutions of 5 wt% poly(ethylene oxide) (PEO) and poly(vinyl pyrrolidone) (PVP) and their different volume percent blends were investigated in the frequency range 20 Hz to 1 MHz at 15, 30 and 45 °C. It is found that the real part of dielectric function of these blends at 1 MHz decreases with the increase of PEO concentration and their dc electrical conductivity has strong correlation with the electrode polarization relaxation time. The static permittivity, ionic conductivity, electrode polarization relaxation time and apparent viscosity have linear behaviour with temperature variation at fixed volume concentration of the aqueous polymers blend. The viscosity of these aqueous polymeric blends increases with the increase of PEO concentration. The behaviour of hydrogen bond interactions between the polar segments of PEO and PVP were explored from the comparative change in dielectric parameters and viscosity of the two phase aqueous polymeric systems.

Dielectric spectroscopy of hydrophilic polymers–montmorillonite clay nanocomposite aqueous colloidal suspension

Frequency-dependent complex dielectric function, loss tangent, electric modulus, alternating current electrical conductivity, and impedance spectra of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), poly(ethylene glycol) (PEG), and blends of PVA–PVP and PVA–PEG, loaded with polymer grade montmorillonite (MMT) clay upto 5 wt% of solute (polymer + clay) in aqueous colloidal suspensions, have been investigated in the frequency range 20 Hz to 1 MHz at 27 °C. These materials show the dielectric dispersion corresponding to ionic conduction and electrode polarization phenomena in the experimental frequency range. The loss tangent peak frequency which separates the contribution of the bulk material and the electrode polarization phenomenon was used to evaluate the electrode polarization relaxation time corresponding to the dynamics of electric double layers. The dielectric and electrical conductivity spectra were interpreted as a result of these material complex structures formed by constituents H-bonding interactions, and the clay intercalation and exfoliation that alter the conduction pathways. Results show that the dielectric/electrical properties of the polymer–clay nanocomposites aqueous colloidal suspension have good resemblance to their structural properties, which were explored from other spectroscopic and morphological techniques. A close look on the dielectric parameters of the investigated materials proves the suitability for the synthesis of new materials with desirable and predicted properties.

Characterization of solvent effect on low-frequency dielectric dispersion and relaxation behaviour of ethylene glycol oligomers

The complex relative dielectric function ɛ⁎( ω) = ɛ′ − jɛ″, electric modulus M⁎( ω) = M′ + jM″, alternating current electrical conductivity, and loss tangent tan δ = ɛ″ / ɛ′ spectra of binary mixture of ethylene glycol oligomers (EGOs) namely, ethylene glycol (EG), diethylene glycol (DEG) and poly(ethylene glycol)s (PEGs) of average molecular weight 200, 300, 400 and 600 g mol − 1 with water (W), ethyl alcohol (EA) and 1,4-dioxane (Dx) in the frequency range 20 Hz to 1 MHz were investigated at 298 K. In the lower-frequency range, the EGOs + W, EGOs + EA and EGOs + Dx mixtures show the direct current conductivity behaviour, and their values can be monitored by concentration variation of the mixture constituents, specially in case of EGOs + W and EGOs + Dx mixtures. The frequency value corresponding to tan δ peak, separates the contribution of the bulk and the electrode polarization phenomena, which is used to evaluate the electrode polarization relaxation time. The M″( f) peak frequency value is considered to evaluate the ionic conduction relaxation time. In these binary mixtures, as compared to rigid chain EG and DEG molecules, the flexible chain EGOs of higher molecular weight have significantly different dielectric response.