scholarly journals Poly Meta-Aminophenol: Chemical Synthesis, Characterization and Ac Impedance Study

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Thenmozhi Gopalasamy ◽  
Mohanraj Gopalswamy ◽  
Madhusudhana Gopichand ◽  
Jayasanthi Raj
Keyword(s):  
Ac Conductivity ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Bimodal Distribution ◽  
Dissipation Factor ◽  
Ac Impedance ◽  
Ammonium Persulfate ◽  
Relaxation Processes ◽  
Two Phase ◽  
H Nmr

The present work is an investigation of AC impedance behaviour of poly(meta-aminophenol). The polymer was prepared by oxidative chemical polymerization of meta-aminophenol in aqueous HCl using ammonium persulfate as an oxidant at 0–3°C. The synthesized polymer was characterized by GPC, Elemental analysis, UV-VIS-NIR, FT-IR, 1H NMR, XRD, SEM, and TGA-DTA. The AC conductivity and dielectric response were measured at a temperature range from 303 to 383 K in the frequency range of 20 Hz to 106 Hz. The AC conductivity data could be described by the relation σacω=AωS, where the parameter “S” and Rb values decrease in the entire range of study and hence follow Correlated Barrier Hopping conduction mechanism. Both dielectric constant and dielectric loss increase with the decrease of frequency exhibiting strong interfacial polarization at low frequency and the dissipation factor also decreases with frequency. Complex electric modulus and dissipation factor exhibit two relaxation peaks, indicating two-phase structure as indicated by a bimodal distribution of relaxation process. The activation energies corresponding to these two relaxation processes were found to be 0.07 and 0.1 eV.

scholarly journals Epoxy-Based/BaMnO4 Nanodielectrics: Dielectric Response and Energy Storage Efficiency

Electronics ◽  
2021 ◽  
Vol 10 (22) ◽  
pp. 2803
Author(s):  
Despoina I. Batsouli ◽  
Anastasios C. Patsidis ◽  
Georgios C. Psarras
Keyword(s):  
Energy Storage ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Energy Performance ◽  
Relaxation Processes ◽  
Broadband Dielectric Spectroscopy ◽  
Dielectric Data ◽  
Optimum Energy ◽  
Harvesting Systems ◽  
Energy Storage Efficiency

Compact capacitive energy storing/harvesting systems could play a key role in the urgent need for more energy-efficient technologies to address both energy and environmental issues. Therein, the purpose of the present work is to develop and investigate epoxy/BaMnO4 nanocomposites at various filler concentrations, which could be applicable as compact materials systems for energy storage and harvesting. Broadband dielectric spectroscopy was used for studying the dielectric properties and the relaxation processes of the examined nanodielectrics. The energy storing/retrieving ability of the nanocomposites was also evaluated via DC charge–discharge experiments. The coefficient of energy efficiency (neff) was found for all prepared nanocomposites to evaluate the energy performance of the systems. Dielectric data divulge the existence of two matrix-related relaxations, i.e., α-mode and β-mode, attributed to the glass-to-rubber transition of the polymer matrix and re-orientation of polar side groups, respectively. Interfacial polarization was also identified in the low-frequency and high-temperature region. The 7 phr BaMnO4 nanocomposite exhibits the best performance in terms of the stored and harvested energies compared to all systems. On the other hand, the 5 phr, 3 phr and 1 phr nanocomposites display optimum energy performance, reaching high values of neff.

scholarly journals Низкочастотная диэлектрическая релаксация в стеклообразной системе Ge-=SUB=-28.5-=/SUB=-Рb-=SUB=-15-=/SUB=-S-=SUB=-56.5-=/SUB=- с примесью железа

2018 ◽  
Vol 52 (9) ◽  
pp. 1038
Author(s):  
Р.А. Кастро ◽  
Г.И. Грабко ◽  
А.А. Кононов
Keyword(s):  
Dielectric Relaxation ◽  
Glass Matrix ◽  
Cluster Structure ◽  
Dissipation Factor ◽  
Phase Model ◽  
Relaxation Processes ◽  
Iron Impurity ◽  
Glassy System ◽  
Two Phase ◽  
Doped Glass

AbstractThe dielectric relaxation processes in Ge_28.5Pb_15S_56.5 glassy system are investigated. The introduction of an iron impurity into a glass matrix is shown to sharply increase the permittivity ε' and decrease the dissipation factor tanδ. The found regularities are explained within the cluster structure (two-phase) model of doped glass.

Fabrication, Structural and AC Impedance Studies of Layer-Structured Bi4Ti3O12 Ceramics

2011 ◽  
Vol 56 (4) ◽  
pp. 1137-1148 ◽  
Author(s):  
H. Bernard ◽  
A. Lisińska-Czekaj ◽  
J. Dzik ◽  
K. Osińska ◽  
D. Czekaj
Keyword(s):  
Chemical Composition ◽  
Impedance Spectroscopy ◽  
Ac Conductivity ◽  
Complex Impedance ◽  
Nonlinear Least Squares ◽  
Ac Impedance ◽  
Orthorhombic Symmetry ◽  
Relaxation Processes ◽  
Cell Parameters ◽  
Impedance Data

Fabrication, Structural and AC Impedance Studies of Layer-Structured Bi4Ti3O12 Ceramics In the present research bismuth titanate Bi4Ti3O12 (BiT) ceramics was synthesized by the standard solid-state reaction method from the mixture of oxides, followed by free sintering at temperature T=1000°C. BiT ceramics was studied in terms of its chemical composition (EDS), crystalline structure (X-ray), microstructure (SEM) and dielectric properties (ac technique of complex impedance spectroscopy) over a range of frequency (ƒ=100Hz to ƒ=1MHz) and temperature (T=200-500°C). Experimental results confirmed the phase formation. It was found that BiT ceramics crystallized in orthorhombic symmetry, best described with Fmmm space group and the following elementary cell parameters: a=5.409(6)°A, b=5.449(2)°A and c=32.816(2)°A. It was also found that BiT ceramics exhibited the plate-like microstructure and stoichiometric chemical composition. Impedance spectroscopy measurements showed contribution of three overlapping relaxation processes (three semicircles in the complex impedance diagrams were observed) ascribed to bulk, grain boundary and electrode/interface polarization phenomena. Impedance data were fitted to the corresponding equivalent circuit using the complex nonlinear least squares (CNLS) method. The ac conductivity for grains, grain boundaries and electrode processes was calculated from CNLS fit of the impedance data and thus the activation energy of ac conductivity (σAC) and relaxation (τ) was calculated for the three revealed components of the impedance spectra from the slopes of σAC and τ versus 1000/T plots (semi log scale) in the range of ΔT=200-500°C.

scholarly journals Polyaniline/Polystyrene Blends: In-Depth Analysis of the Effect of Sulfonic Acid Dopant Concentration on AC Conductivity Using Broadband Dielectric Spectroscopy

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Noora Al-Thani ◽  
Mohammad K. Hassan ◽  
Jolly Bhadra
Keyword(s):  
Dielectric Spectroscopy ◽  
Ac Conductivity ◽  
Sulfonic Acid ◽  
Low Frequency ◽  
Lone Pair ◽  
Interfacial Polarization ◽  
Low Frequencies ◽  
Broadband Dielectric Spectroscopy ◽  
Wide Range ◽  
Depth Analysis

This work presents an in-depth analysis of the alternating current (AC) conductivity of polyaniline-polystyrene (PANI-PS) blends doped with camphor sulfonic acid (CSA) and prepared using an in situ dispersion polymerization technique. We prepared the blends using fixed ratios of PS to PANI while varying the concentration of the CSA dopant. The AC conductivity of the blends was investigated using broadband dielectric spectroscopy. Increasing CSA resulted in a decrease in the AC conductivity of the blends. This behaviour was explained in terms of the availability of a lone pair of electrons of the NH groups in the polyaniline, which are typically attacked by the electron-withdrawing sulfonic acid groups of CSA. The conductivity is discussed in terms of changes in the dielectric permittivity storage (ε′), loss (ε′′), and modulus (M′′) of the blends over a wide range of temperatures. This is linked to the glass transition temperature of the PANI. Dielectric spectra at low frequencies indicated the presence of pronounced Maxwell-Wagner-Sillars (MWS) interfacial polarization, especially in samples with a low concentration of CSA. Electrical conduction activation energies for the blends were also calculated using the temperature dependence of the direct current (DC) conductivity at a low frequency (σdc), which exhibit an Arrhenius behaviour with respect to temperature. Scanning electron microscopy revealed a fibrous morphology for the pure PANI, while the blends showed agglomeration with increasing CSA concentrations.

scholarly journals The Low Frequency Electrical Properties of Sea Ice

2021 ◽  
Author(s):  
◽  
Sean Thomas Buchanan
Keyword(s):  
Electrical Properties ◽  
Sea Ice ◽  
Volume Fraction ◽  
Bulk Material ◽  
Electrical Response ◽  
Low Frequency ◽  
Impedance Measurement ◽  
Interfacial Polarization ◽  
Electrode Polarization ◽  
Two Phase

<p>This thesis summarises an experimental and theoretical study of the low frequency electrical properties of sea ice. The aim of the research was to first demonstrate, and then gain a physical understanding of, the microstructural dependence of a sea ice impedance measurement. In particular, we sought to realise how the effective electrical properties of the medium depended on the volume fraction, orientation, dimensions, and connectivity of the dispersed brine phase. The experimental portion of the project was performed on laboratory grown, artificial sea ice. We monitored the variation with time, and temperature, of the broadband sea ice impedance using four-electrode measurement cells embedded within the ice. The four-electrode measurement allowed us to realise and eliminate the contribution of electrode polarization to the measured impedance. By representing the electrical response of sea ice as a complex conductivity, we formulated a broadband physical model to describe the medium. The model distinguished bulk conduction, bulk polarization, and interfacial polarization. A complex non-linear least squares fitting procedure revealed the individual contribution of these physical processes and we studied their variation with temperature. We found that the bulk material underwent a dielectric relaxation with activation energy Ea = 0.20 + and - 0.04eV. We linked the bulk material properties with a two phase microstructural model, with realistic input parameters.</p>

scholarly journals The Low Frequency Electrical Properties of Sea Ice

2021 ◽  
Author(s):  
◽  
Sean Thomas Buchanan
Keyword(s):  
Electrical Properties ◽  
Sea Ice ◽  
Volume Fraction ◽  
Bulk Material ◽  
Electrical Response ◽  
Low Frequency ◽  
Impedance Measurement ◽  
Interfacial Polarization ◽  
Electrode Polarization ◽  
Two Phase

<p>This thesis summarises an experimental and theoretical study of the low frequency electrical properties of sea ice. The aim of the research was to first demonstrate, and then gain a physical understanding of, the microstructural dependence of a sea ice impedance measurement. In particular, we sought to realise how the effective electrical properties of the medium depended on the volume fraction, orientation, dimensions, and connectivity of the dispersed brine phase. The experimental portion of the project was performed on laboratory grown, artificial sea ice. We monitored the variation with time, and temperature, of the broadband sea ice impedance using four-electrode measurement cells embedded within the ice. The four-electrode measurement allowed us to realise and eliminate the contribution of electrode polarization to the measured impedance. By representing the electrical response of sea ice as a complex conductivity, we formulated a broadband physical model to describe the medium. The model distinguished bulk conduction, bulk polarization, and interfacial polarization. A complex non-linear least squares fitting procedure revealed the individual contribution of these physical processes and we studied their variation with temperature. We found that the bulk material underwent a dielectric relaxation with activation energy Ea = 0.20 + and - 0.04eV. We linked the bulk material properties with a two phase microstructural model, with realistic input parameters.</p>

scholarly journals Study of Influence of Electrode Geometry on Impedance Spectroscopy

2010 ◽  
Author(s):  
Riaz Ahmed ◽  
Kenneth Reifsnider
Keyword(s):  
Impedance Spectroscopy ◽  
High Frequency ◽  
Low Frequency ◽  
Effective Area ◽  
Ac Impedance ◽  
Local Geometry ◽  
Electrode Geometry ◽  
Electrode Area ◽  
Impedance Response ◽  
Working Electrode

Electrochemical Impedance Spectroscopy (EIS) is a powerful and proven tool for analyzing AC impedance response. A conventional three electrode EIS method was used to perform the investigation in the present study. Saturated potassium chloride solution was used as the electrolyte and three different material rods were used as working electrodes. Different configurations of electrode area were exposed to the electrolyte as an active area to investigate electrode geometry effects. Counter to working electrode distance was also altered while keeping the working electrode effective area constant to explore the AC response dependence on the variation of ion travel distance. Some controlled experiments were done to validate the experimental setup and to provide a control condition for comparison with experimental results. A frequency range of 100 mHz to 1 MHz was used for all experiments. In our analysis, we have found a noteworthy influence of electrode geometry on AC impedance response. For all electrodes, impedance decreases with the increase of effective area of the electrolyte. High frequency impedance is not as dependent on geometry as low frequency response. The observed phase shift angle drops in the high frequency region with increased working electrode area, whereas at low frequency the reverse is true. Resistance and capacitive reactance both decrease with an increase of area, but resistance response is more pronounce than reactance. For lower frequencies, small changes in working area produce very distinctive EIS variations. Electrode material as well as geometry was systematically varied in the present study. From these and other studies, we hope to develop a fundamental foundation for understanding specific changes in local geometry in fuel cell (and other) electrodes as a method of designing local morphology for specific performance.

scholarly journals Protected Gold Nanoparticles with Thioethers and Amines As Surrogate Ligands

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
M. Rafiq H. Siddiqui
Keyword(s):  
Gold Nanoparticles ◽  
Variable Temperature ◽  
Size Control ◽  
Analytical Techniques ◽  
High Resolution Electron Microscopy ◽  
Phase Method ◽  
Two Phase ◽  
H Nmr ◽  
Resolution Electron ◽  
Vis Spectroscopy

Dodecyl sulfide, dodecyl amine, and hexylamine were shown to act as surrogate ligands (L) via metastable gold nanoparticles. By collating analytical and spectroscopic data obtained simultaneously, empirical formula Au24L was assigned. These impurity-free nanoparticles obtained in near quantitative yields showing exceptional gold assays (up to 98%Au) were prepared by a modification of the two-phase method. Replacement reactions on the Au24L showed that Au:L ratios may be increased (up to Au55:L (L= (H25C12)2S)) or decreased (Au12:L (L= H2NC12H25and H2NC6H13)) as desired. This work encompassing the role of analytical techniques used, that is, elemental analysis, variable temperature1H NMR, FAB mass spectrometry, UV-Vis spectroscopy, thin film X-ray diffraction, and high-resolution electron microscopy (HREM) has implications in the study of size control, purity, stability, and metal assays of gold nanoparticles.

Films in narrow tubes

2014 ◽  
Vol 762 ◽  
pp. 68-109 ◽  
Author(s):  
Georg F. Dietze ◽  
Christian Ruyer-Quil
Keyword(s):  
Liquid Film ◽  
Silicone Oil ◽  
Low Frequency ◽  
Cylindrical Tube ◽  
Film Coating ◽  
Two Phase ◽  
Integral Boundary ◽  
Tube Cross Section ◽  
Free Liquid Film ◽  
Low Dimensional

AbstractWe consider the axisymmetric arrangement of an annular liquid film, coating the inner surface of a narrow cylindrical tube, in interaction with an active core fluid. We introduce a low-dimensional model based on the two-phase weighted residual integral boundary layer (WRIBL) formalism (Dietze & Ruyer-Quil, J. Fluid Mech., vol. 722, 2013, pp. 348–393) which is able to capture the long-wave instabilities characterizing such flows. Our model improves upon existing works by fully representing interfacial coupling and accounting for inertia as well as streamwise viscous diffusion in both phases. We apply this model to gravity-free liquid-film/core-fluid arrangements in narrow capillaries with specific attention to the dynamics leading to flooding, i.e. when the liquid film drains into large-amplitude collars that occlude the tube cross-section. We do this against the background of linear stability calculations and nonlinear two-phase direct numerical simulations (DNS). Due to the improvements of our model, we have found a number of novel/salient physical features of these flows. First, we show that it is essential to account for inertia and full interphase coupling to capture the temporal evolution of flooding for fluid combinations that are not dominated by viscosity, e.g. water/air and water/silicone oil. Second, we elucidate a viscous-blocking mechanism which drastically delays flooding in thin films that are too thick to form unduloids. This mechanism involves buckling of the residual film between two liquid collars, generating two very pronounced film troughs where viscous dissipation is drastically increased and growth effectively arrested. Only at very long times does breaking of symmetry in this region (due to small perturbations) initiate a sliding motion of the liquid film similar to observations by Lister et al. (J. Fluid Mech., vol. 552, 2006, pp. 311–343) in thin non-flooding films. This kickstarts the growth of liquid collars anew and ultimately leads to flooding. We show that streamwise viscous diffusion is essential to this mechanism. Low-frequency core-flow oscillations, such as occur in human pulmonary capillaries, are found to set off this sliding-induced flooding mechanism much earlier.

scholarly journals The effects of additive on microstructure and electrical properties of batio3 ceramics

2004 ◽  
Vol 1 (3) ◽  
pp. 89-98 ◽  
Author(s):  
Vesna Paunovic ◽  
Ljiljana Zivkovic ◽  
Ljubomir Vracar ◽  
Vojislav Mitic ◽  
Miroslav Miljkovic
Keyword(s):  
Dielectric Constant ◽  
Curie Temperature ◽  
Room Temperature ◽  
Low Frequency ◽  
Dissipation Factor ◽  
The Other ◽  
Uniform Microstructure ◽  
Average Grain Size ◽  
Solid State Sintering ◽  
Curie Temperatures

In this paper comparative investigations of microstructure and dielectric properties of BaTiO3 ceramics doped with 1.0 wt% of Nb2O5, MnCO3 and CaZrO3 have been done. BaTiO3 samples were prepared using conventional method of solid state sintering at 13000C for two hours. Two distinguish micro structural regions can be observed in sample doped with Nb2O5. The first one, with a very small grained microstructure and the other one, with a rod like grains. In MnCO3 and CaZrO3 doped ceramics the uniform microstructure is formed with average grain size about 0.5- 2?m and 3-5?m respectively. The highest value of dielectric permittivity at room temperature and the greatest change of permittivity in function of temperature were observed in MnCO3/BaTiO3. In all investigated samples dielectric constant after initially large value at low frequency attains a constant value at f = 6kHz. A dissipation factor is independent of frequency greater than 10 kHz and, depending of systems, lies in the range from 0.035 to 0.25. At temperatures above Curie temperatures, the permittivity of all investigated samples follows a Curie- Weiss law. A slight shift of Curie temperature to the lower temperatures, in respect of Curie temperature for undoped BaTiO3, was observed in all investigated samples.

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