scholarly journals An Impedance Study of the Membrane Polarisation Effect in Simulated Rock Systems

2021 ◽  
Author(s):  
◽  
Michael Charles Harold McKubre
Keyword(s):  
Low Frequency ◽  
Impedance Measurement ◽  
Impedance Analysis ◽  
Laboratory Model ◽  
Pore Geometry ◽  
Impedance Spectra ◽  
Clay Rock ◽  
Polarisation Effect ◽  
Diffusional Limitation ◽  
Electrochemical Model

<p>Work is reported on the development of a high precision, low frequency impedance bridge, and the use of impedance measurement in characterising the induced polarisation effect of unmineralised material. Impedance spectra for a variety of laboratory model clay/rock/electrolyte systems are analysed in terms of an equivalent circuit. By measuring the dependence of the parameters of this circuit, on such variables as electrolyte type and concentration, temperature and pore geometry, an electrochemical model for membrane polarisation has been developed. Polarisation is considered to arise from diffusional limitation of cations at the membrane/electrolyte interface of clay aggregations in rock pores, and this is found to be amenable to a Warburg diffusional impedance analysis.</p>

scholarly journals An Impedance Study of the Membrane Polarisation Effect in Simulated Rock Systems

2021 ◽  
Author(s):  
◽  
Michael Charles Harold McKubre
Keyword(s):  
Low Frequency ◽  
Impedance Measurement ◽  
Impedance Analysis ◽  
Laboratory Model ◽  
Pore Geometry ◽  
Impedance Spectra ◽  
Clay Rock ◽  
Polarisation Effect ◽  
Diffusional Limitation ◽  
Electrochemical Model

<p>Work is reported on the development of a high precision, low frequency impedance bridge, and the use of impedance measurement in characterising the induced polarisation effect of unmineralised material. Impedance spectra for a variety of laboratory model clay/rock/electrolyte systems are analysed in terms of an equivalent circuit. By measuring the dependence of the parameters of this circuit, on such variables as electrolyte type and concentration, temperature and pore geometry, an electrochemical model for membrane polarisation has been developed. Polarisation is considered to arise from diffusional limitation of cations at the membrane/electrolyte interface of clay aggregations in rock pores, and this is found to be amenable to a Warburg diffusional impedance analysis.</p>

scholarly journals The impedance analysis of small intestine fusion by pulse source

2020 ◽  
Vol 15 (1) ◽  
pp. 808-818
Author(s):  
Yifan Wang ◽  
Kefu Liu ◽  
Xiaowei Xiang ◽  
Caihui Zhu ◽  
Hao Wang
Keyword(s):  
Small Intestine ◽  
Pressure Gauge ◽  
Equivalent Circuit Model ◽  
Impedance Measurement ◽  
Impedance Analysis ◽  
Duty Ratio ◽  
Feedback Signal ◽  
Pulse Source ◽  
Compression Pressure ◽  
Output Time

AbstractThe radiofrequency-induced intestine fusion has been widely studied as an alternative for traditional suture in surgery, but fusion quality cannot be evaluated directly. Impedance measurement can evaluate fusion quality, but the relation between impedance and the fusion quality needs optimization for best results. The present study reports the optimum resistance of small intestine fusion. As the feedback signal, resistance was considered the indicator of the fusion completion for the device design of intestine fusion and an in-depth study of microstructure change. A self-design pulse source was used for the small intestine fusion with adjustable voltage, duty ratio, frequency and output time. A frequency of 440 kHz was set, whereas voltage, output time and compression pressure (CP) of the small intestine were independent variables. Different conditions of voltage, CP and time were investigated for achieving the highest burst pressure (BP) measured with a pressure gauge and a peristaltic pump. Each parameter of the equivalent circuit model was calculated by an experimental waveform. Hematoxylin–eosin staining of fusion samples was used for assessing the quality of fusion. The real-time current was measured and recorded during the fusion for the calculation of capacitance and resistance. The highest BP of 38.9 mmHg was achieved with a CP of 900 kPa, a voltage of 50 V and a time of 5 s. Finally, an optimum extracellular resistance range of 61.0–86.2 Ω was found as the optimum resistance for the end of fusion, thus indicating automatic fusion with the best fusion quality.

Impedance Analysis of Layer Structured NBT–CBT Mixed Ceramics

1998 ◽  
Vol 12 (11) ◽  
pp. 433-441 ◽  
Author(s):  
P. S. Rama Sastry ◽  
T. Bhimasankaram ◽  
G. S. Kumar ◽  
G. Prasad
Keyword(s):  
Comparative Study ◽  
Complex Impedance ◽  
Impedance Analysis ◽  
Equivalent Circuits ◽  
Impedance Spectra ◽  
Ceramic System ◽  
Different Temperatures ◽  
Mixed Ceramics ◽  
Mixed Ceramic ◽  
Complex Impedance Spectra

Complex impedance spectra of ferroelectric mixed ceramic system ( Na 0.5 Bi 0.5)1-x Ca x Bi 4 Ti 4 O 15 with x=0, 0.1, 0.3, 0.5, 0.7 and 1 was studied as a function of frequency and temperature in the range 1 KHz to 10 MHz and 30°C to 620°C respectively. Equivalent circuits involving resistive and capacitive elements at different temperatures, activation energies of relaxations and conduction were evaluated using impedance plots. A comparative study of impedance and conductivity facilities an insight in understanding the electrical nature of these electroceramics.

Investigating the dielectric properties and low-frequency relaxation process of TlGaSe2 crystals

2017 ◽  
Vol 31 (12) ◽  
pp. 1750134 ◽  
Author(s):  
Oktay Samadov ◽  
Oktay Alakbarov ◽  
Arzu Najafov ◽  
Samir Samadov ◽  
Nizami Mehdiyev ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Relaxation Time ◽  
Constant Electric Field ◽  
Low Frequency ◽  
Constant Field ◽  
Impedance Spectra ◽  
Ionic Contribution ◽  
Frequency Relaxation ◽  
Average Relaxation Time ◽  
Diagram Analysis

The dielectric and impedance spectra of TlGaSe2 crystals have been studied at temperatures in the 100–500 K range in the alternating current (AC [Formula: see text]1 V). It has been shown that the conductivity of TlGaSe2 crystals is mainly an ionic characteristic at temperatures above 400 K. The well-defined peak at the frequency dependence of the imaginary part of impedance [Formula: see text] is observed in the 215–500 K temperature range. In a constant field, there occurs a significant decrease in electrical conductivity [Formula: see text] in due course. The ionic contribution to conductivity (76% at [Formula: see text]) has been estimated from a kinetic change in electrical conductivity [Formula: see text] under the influence of a constant electric field. The diagram analysis in a complex plane [Formula: see text] has been conducted by applying the method of an equivalent circuit of the substation. It has been determined that the average relaxation time of the electric module of the sample is [Formula: see text].

scholarly journals Comparison of the influence of nitrate ions on the electrochemical behaviour of iron and carbon steels in sulphate solutions

2002 ◽  
Vol 67 (6) ◽  
pp. 425-436 ◽  
Author(s):  
Houy Ma ◽  
Shenhao Chen ◽  
Chao Yang ◽  
Jingli Luo
Keyword(s):  
Electrochemical Impedance ◽  
Electrochemical Behaviour ◽  
Low Frequency ◽  
Open Circuit ◽  
Carbon Steels ◽  
General Corrosion ◽  
Impedance Spectra ◽  
Nitrate Ions ◽  
Capacitive Loop ◽  
Acidic Sulphate

The effect of nitrate ions on the electrochemical behaviour of iron (ferrite) and two carbon steels (martensite and pearlite) in sulphate solutions of different pH values was investigated by cyclic voltammetry polarization and electrochemical impedance spectroscopy. The pitting inhibiting effect of nitrate ions on ferrite in sulphate media is pH dependent. Nitrate ions were unable to inhibit the pitting on ferrite in neutral sulphate solutions, but did effectively protect passivated ferrite from pitting in acidic sulphate solutions. No pitting occurred on the surface of the martensite and pearlite specimens in sulphate solutions regardless of the pH of the solutions. At the open-circuit corrosion potentials, the three materials underwent general corrosion. The impedance spectra for the three materials measured in neutral sulphate solutions containing nitrates and chlorides at the corrosion potentials all showed a capacitive loop, while in acidic sulphate solutions their impedance spectra were greatly reduced in size and displayed at least a low frequency impedance loop (inductive or capacitive loop) besides the well-known high frequency capacitive loop. The variation of the impedance behaviour with pH is explained.

scholarly journals Inductive Low‐Frequency Processes in PEMFC‐Impedance Spectra

Fuel Cells ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 499-506
Author(s):  
A. Schiefer ◽  
M. Heinzmann ◽  
A. Weber
Keyword(s):  
Low Frequency ◽  
Impedance Spectra

scholarly journals Relationship between moisture content and electrical impedance of carrot slices during drying

2015 ◽  
Vol 29 (1) ◽  
pp. 61-66 ◽  
Author(s):  
Ákos Kertész ◽  
Zuzana Hlaváčová ◽  
Eszter Vozáry ◽  
Lenka Staroňová
Keyword(s):  
Moisture Content ◽  
Electrical Impedance ◽  
Fruits And Vegetables ◽  
Physiological State ◽  
Impedance Measurement ◽  
Biological Tissues ◽  
Impedance Spectra ◽  
Frequency Range ◽  
Impedance Parameters ◽  
Precision Balance

Abstract Electrical properties of food materials can give information about the inner structure and physiological state of biological tissues. Generally, the process of drying of fruits and vegetables is followed by weight loss. The aim of this study was to measure the impedance spectra of carrot slices during drying and to correlate impedance parameters to moisture content in different drying periods. Cylindrical slices were cut out from the carrot root along the axis. The slices were dried in a Venticell 111 air oven at 50°C. The weight of the slices was measured with a Denver SI-603 electronic analytical and precision balance. The weighing of the samples was performed every 30 min at the beginning of drying and every 60 min after the process. The moisture content of the samples was calculated on wet basis. The magnitude and phase angle of electrical impedance of the slices were measured with HP 4284A and 4285A precision LCR meters in the frequency range from 30 Hz to 1 MHz and from 75 kHz to 30 MHz, respectively, at voltage 1 V. The impedance measurement was performed after weighting. The change in the magnitude of impedance during drying showed a good correlation with the change in the moisture content.

Impedance analysis of porous electrode structures in batteries and fuel cells

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
André Weber
Keyword(s):  
Fuel Cells ◽  
Porous Electrode ◽  
Relaxation Times ◽  
Lithium Ion ◽  
Impedance Analysis ◽  
Wide Frequency Range ◽  
Impedance Spectra ◽  
Transmission Line Model ◽  
Error Sources ◽  
Lithium Ion Cells

AbstractToday technical electrodes in batteries and fuel cells rely on complex multiphase microstructures that facilitate electronic, ionic and, in case of fuel cells, diffusive gas transport to the active reaction sites distributed in the electrode volume. The impedance of such electrodes can be described by the well-established transmission line model (TLM) approach. In a TLM, transport, charge transfer phenomena and capacitive effects are coupled considering microstructural features of the electrode. Its application for impedance data analysis of technical cells is challenging as the TLM impedance extends over a wide frequency range and quite often a strong overlapping with other contributions takes place.In this paper the application of the distribution of relaxation times (DRT) to the analysis of technical electrodes in batteries and fuel cells is elucidated. Different examples how to apply the DRT to analyze impedance spectra of solid oxide-, polymer electrolyte- and lithium ion-cells will be discussed. It will be shown that the TLM is usually represented by multiple peaks in the DRT, which might be strongly affected if contributions of different electrode layers overlap in the spectra. Related error sources and countermeasures are illustrated. Approaches how the DRT can be applied for the analysis of measured spectra and how it is able to support CNLS-fitting are presented.

Sign in / Sign up

Export Citation Format

Share Document