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>

Hollow metal cylinders produced from diacetylenic lipid

2000 ◽  
Vol 15 (11) ◽  
pp. 2368-2374 ◽  
Author(s):  
Dan Zabetakis
Keyword(s):  
Electrical Properties ◽  
Packing Density ◽  
Parallel Plate ◽  
Volume Fraction ◽  
Bulk Material ◽  
Critical Volume ◽  
Critical Volume Fraction ◽  
Specific Packing ◽  
Improved Technique ◽  
Hollow Metal

A method was presented for the formation and metallization of cylindrical tubules from a diacetylenic lipid. This improved technique allowed for the production of metal microcylinders without the need for preliminary lipid purification and in large quantities. The physical and electrical properties of the material were investigated, and composites were used to form parallel plate capacitors. A comparison of the conductivity of the bulk material with the derived conductivity of a composite showing electromagnetic percolation showed the proportionality of the specific packing density and the critical volume fraction characteristic of percolating systems.

scholarly journals The low frequency electrical properties of sea ice

2011 ◽  
Vol 110 (7) ◽  
pp. 074908 ◽  
Author(s):  
S. Buchanan ◽  
M. Ingham ◽  
G. Gouws
Keyword(s):  
Electrical Properties ◽  
Sea Ice ◽  
Low Frequency

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.

Enhanced Dielectric and Electrical Properties in Polyurethane Composites with Graphene Nanosheets

2018 ◽  
Vol 917 ◽  
pp. 117-121 ◽  
Author(s):  
Ardimas ◽  
Chatchai Putson
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Graphene Nanosheets ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Polyurethane Elastomers ◽  
Solution Casting Method ◽  
Lcr Meter ◽  
Polyurethane Composites ◽  
Polyurethane Matrix

The Electrical properties of polyurethane (PU) filled with graphene nanosheets (GRN) at low frequency is investigated. In last decade, polyurethane elastomers have attracted attention in transducer and actuator applications. The dielectric constant is one of the key factors for increasing actuator ability. Graphene nanosheets as conducting fillers have to be filled to increase the dielectric constant. In order to prove this idea, polyurethane composites with various graphene contents have been characterized by SEM and DSC. And their electrical capability has been measured at various frequencies of 101-104 by using LCR meter. To gain the films, polyurethane composites filled with various graphene contents were prepared by solution casting method. The results showed a well homogenous dispersion of the graphene filler in the polyurethane matrix. In addition, it was found that the glass transition temperature (Tg) of the PU/GRN increase as the content of filler increased and it can be affected the interfacial polarization between PU matrix with the GRN fillers. Therefore, it is found that graphene in the polyurethane matrix exhibit high enhanced the electrical properties and the optimal dielectric constant at 2wt% graphene of 9.74.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

Mineral interfacial processes in the method of induced polarization

Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 1105-1114 ◽  
Author(s):  
James D. Klein ◽  
Tom Biegler ◽  
M.D. Horne
Keyword(s):  
Frequency Domain ◽  
Diffusion Layer ◽  
Electrode Potential ◽  
Rotation Speed ◽  
Low Frequency ◽  
Rotating Disk ◽  
Active Species ◽  
Hydrodynamic Theory ◽  
Electrode Polarization ◽  
Disk Electrodes

A phenomenological laboratory investigation has been conducted of the IP response of pyrite, chalcopyrite, and chalcocite. The technique that was used is standard in electrochemistry and employs rotating disk electrodes. The effect of rotation is to stir the electrolyte and thus to restrict the maximum distance available for diffusion of electroactive aqueous species. For high rotation speed and low excitation frequencies, the mean diffusion length exceeds the thickness of the diffusion layer. The net effect is to reduce the electrode impedance at low frequency. The thickness of the diffusion layer and thus the impedance at low frequency can be controlled by the rotation speed. Measurements using rotating disk electrodes have been conducted in both the time domain and the frequency domain. For both pyrite and chalcopyrite, the results were the same: no dependence on rotation was observed. For frequency domain measurements with chalcocite, a strong dependence on rotation was observed. The interpreted diffusion layer thickness was found to depend on rotation speed to the [Formula: see text] power, in agreement with results predicted by hydrodynamic theory. The results of this study imply that there are two physical processes responsible for electrode polarization in the IP method. For chalcocite and perhaps other related copper sulfide minerals, the probable mechanism is diffusion of copper ions in the groundwater. In case, the phenomenon is correctly described by the Warburg impedance. Chalcocite’s distinctive response is thought to be related to its forming a reversible oxidation‐reduction couple with cupric ions in solution. No other common sulfide mineral forms a reversible couple with its cations in solution. For the other minerals of this study, the lack of dependence on rotation implies that diffusion of active species in the electrolyte is not the controlling process. Possible alternate mechanisms include surface controlled processes such as surface diffusion or adsorption phenomena. Ancillary data obtained during this study indicate the interface impedance of chalcopyrite is proportional to the electrode potential which in turn can be controlled by rotation speed, electrolyte composition, or application of an external dc current or voltage. This implies that the surface concentration of active species is dependent on electrode potential.

scholarly journals A magnetic resonance study of temperature-dependent microstructural evolution and self-diffusion of water in Arctic first-year sea ice

2005 ◽  
Vol 40 ◽  
pp. 179-184 ◽  
Author(s):  
C. Bock ◽  
H. Eicken
Keyword(s):  
Magnetic Resonance ◽  
Sea Ice ◽  
Microstructural Evolution ◽  
Volume Fraction ◽  
Bulk Liquid ◽  
Liquid Volume ◽  
Liquid Volume Fraction ◽  
Cross Sectional ◽  
Pore Connectivity ◽  
Pore Number

AbstractThe microstructural evolution of brine inclusions in granular and columnar sea ice has been investigated through magnetic resonance imaging (MRI) for temperatures between –28 and –3˚C. Thin-section and salinity measurements were completed on core samples obtained from winter sea ice near Barrow, Alaska, USA. Subsamples of granular (2–5cm depth in core) and columnar sea ice (20–23 cm depth) were investigated with morphological spin-echo and diffusion-weighted imaging in a Bruker 4.7T MRI system operating at field gradients of 200 mTm–1 at temperatures of approximately –28, –15, –6 and –3˚C. Average linear pore dimensions range from 0.2 to 1 mm and increase with bulk liquid volume fraction as temperatures rise from –15 to –3˚C. Granular ice pores are significantly larger than columnar ice pores and exhibit a higher degree of connectivity. No evidence is found of strongly non-linear increases in pore connectivity based on the MRI data. This might be explained by shortcomings in resolution, sensitivity and lack of truly three-dimensional data, differences between laboratory and field conditions or the absence of a percolation transition. Pore connectivity increases between –6 and –3˚C. Pore-number densities average at 1.4±1.2mm–2. The pore-number density distribution as a function of cross-sectional area conforms with power-law and lognormal distributions previously identified, although significant variations occur as a function of ice type and temperature. At low temperatures (< –26˚C), pore sizes were estimated from 1H self-diffusivity measurements, with self-diffusivity lower by up to an order of magnitude than in the free liquid. Analysis of diffusional length scales suggests characteristic pore dimensions of <1 μm at < –26˚C.

scholarly journals Effects of Polydispersity on the Phase Behavior of Additive Hard Spheres in Solution

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1543
Author(s):  
Luka Sturtewagen ◽  
Erik van der Linden
Keyword(s):  
Phase Behavior ◽  
Critical Point ◽  
Volume Fraction ◽  
Hard Spheres ◽  
Second Virial Coefficient ◽  
Two Phase ◽  
Different Types ◽  
Asymmetric Partitioning ◽  
Average Size ◽  
Liquid Liquid Phase Separation

The ability to separate enzymes, nucleic acids, cells, and viruses is an important asset in life sciences. This can be realised by using their spontaneous asymmetric partitioning over two macromolecular aqueous phases in equilibrium with one another. Such phases can already form while mixing two different types of macromolecules in water. We investigate the effect of polydispersity of the macromolecules on the two-phase formation. We study theoretically the phase behavior of a model polydisperse system: an asymmetric binary mixture of hard spheres, of which the smaller component is monodisperse and the larger component is polydisperse. The interactions are modelled in terms of the second virial coefficient and are assumed to be additive hard sphere interactions. The polydisperse component is subdivided into sub-components and has an average size ten times the size of the monodisperse component. We calculate the theoretical liquid–liquid phase separation boundary (the binodal), the critical point, and the spinodal. We vary the distribution of the polydisperse component in terms of skewness, modality, polydispersity, and number of sub-components. We compare the phase behavior of the polydisperse mixtures with their concomittant monodisperse mixtures. We find that the largest species in the larger (polydisperse) component causes the largest shift in the position of the phase boundary, critical point, and spinodal compared to the binary monodisperse binary mixtures. The polydisperse component also shows fractionation. The smaller species of the polydisperse component favor the phase enriched in the smaller component. This phase also has a higher-volume fraction compared to the monodisperse mixture.

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