DIELECTRIC EVIDENCE FOR THE MATERIAL DESIGN OF ER FLUIDS

1996 ◽  
Vol 10 (23n24) ◽  
pp. 2885-2893 ◽  
Author(s):  
Tian Hao ◽  
Yuanze Xu
Keyword(s):  
Dielectric Constant ◽  
Material Design ◽  
Dielectric Constants ◽  
Wagner Model ◽  
Ac Electric Field ◽  
Theoretical Predictions ◽  
Temperature Ranges ◽  
Working Frequency ◽  
Er Fluids ◽  
Good Agreement

The dielectric and electrorheological measurements of anhydrous ER fluids based upon oxidized polyacrylonitrile and zeolite under AC electric field are described It was found that the yield strength was not only determined by dielectric constant of suspensions, but also by dielectric loss. The formulation based on Wagner model, which describes the polarization of heterogeneous dielectrics, was employed to predict the yield stress as a function of electric frequency. The good agreement between experimental and theoretical predictions indicated that conductivity of the dispersed particle and the dielectric constants of ER suspension are decisive factors in the design of ER fluids. The way of material design is discussed concerning working frequency, rate and temperature ranges

DIELECTRIC CONSTANT AND SEEBECK COEFFICIENT FOR SEMICONDUCTORS: THERMODYNAMIC AND DFT STUDIES

2013 ◽  
Vol 12 (06) ◽  
pp. 1350057 ◽  
Author(s):  
HSIU-YA TASI ◽  
CHAOYUAN ZHU
Keyword(s):  
Boundary Condition ◽  
Dielectric Constant ◽  
Seebeck Coefficient ◽  
Gas Phase ◽  
Present Method ◽  
Dielectric Constants ◽  
Semiconductor Materials ◽  
Electronic Polarizability ◽  
Seebeck Coefficients ◽  
Good Agreement

Dielectric constants and Seebeck coefficients for semiconductor materials are studied by thermodynamic method plus ab initio quantum density functional theory (DFT). A single molecule which is formed in semiconductor material is treated in gas phase with molecular boundary condition and then electronic polarizability is directly calculated through Mulliken and atomic polar tensor (APT) density charges in the presence of the external electric field. This electronic polarizability can be converted to dielectric constant for solid material through the Clausius–Mossotti formula. Seebeck coefficient is first simulated in gas phase by thermodynamic method and then its value divided by its dielectric constant is regarded as Seebeck coefficient for solid materials. Furthermore, unit cell of semiconductor material is calculated with periodic boundary condition and its solid structure properties such as lattice constant and band gap are obtained. In this way, proper DFT function and basis set are selected to simulate electronic polarizability directly and Seebeck coefficient through chemical potential. Three semiconductor materials Mg 2 Si , β- FeSi 2 and SiGe are extensively tested by DFT method with B3LYP, BLYP and M05 functionals, and dielectric constants simulated by the present method are in good agreement with experimental values. Seebeck coefficients simulated by the present method are in reasonable good agreement with experiments and temperature dependence of Seebeck coefficients basically follows experimental results as well. The present method works much better than the conventional energy band structure theory for Seebeck coefficients of three semiconductors mentioned above. Simulation with periodic boundary condition can be generalized directly to treat with doped semiconductor in near future.

Investigation on dielectric properties of the polyetherketone nanocomposite with lead titanate ultrafines

2001 ◽  
Vol 79 (5) ◽  
pp. 847-855 ◽  
Author(s):  
W Shi ◽  
C Fang ◽  
S Guo ◽  
Q Ren ◽  
Q Pan ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Constants ◽  
Inorganic Nanoparticles ◽  
Complex Dielectric Constant ◽  
Nanocomposite Polymer ◽  
Local Field Theory ◽  
Constant Expression ◽  
Space Polarization ◽  
Good Agreement

The dielectric properties of polymer composites with inorganic nanoparticles were investigated. In the demonstration of the dielectric constant expression of the nanocomposite polymer, the dielectric contributions of the displacement polarization, the orientation polarization, and the space polarization in the nanocomposite polymer were all considered. In the demonstration, two dielectric relaxation models were used, that of Debye for inorganic nanoparticles and the Havriliak–Negami function model for polymers. Then the expression of the complex dielectric constant of the nanocomposite polymer was obtained by using Onsager's local field theory. Furthermore, the nanocomposite polymer thin films that consist of PbTiO3 nanoparticles and polyetherketone were prepared. The real parts of the dielectric constants were measured and calculated, respectively. It was found that our calculated results are in good agreement with our measured results. PACS Nos.: 77.20, 77.55, 81.20T

The Measurement of Dielectric Constant and Electrical Conductivity of ER Fluids

2013 ◽  
Vol 711 ◽  
pp. 51-55
Author(s):  
Nan Hui Yu ◽  
Ji Jun Fan
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Dielectric Constants ◽  
Ion Concentration ◽  
Frequency Method ◽  
Electrical Field Strength ◽  
Electrical Fields ◽  
Electrical Conductivities ◽  
Er Fluids ◽  
Er Fluid

In this paper, the dielectric constants of ER fluids with different particle concentration were measured by frequency method, and their electrical conductivities under different external electrical fields were also measured by method of conductivity cell constant. The results obtained from above measurements are as follows: the dielectric constant of ER fluid increases with the increasing of concentration; its electrical conductivity of the same concentration increases with the increasing of electrical field strength; for gradually increasing concentration, the conductivity first increases, then decreases. From analysis, it is suggested that the change of effective ion concentration of ER fluid is an important reason for its variation of conductivity.

Evaluation of the Degree of Crystallization in Glass-Ceramics by Dielectric Constant Measurements

2009 ◽  
Vol 79-82 ◽  
pp. 2279-2282
Author(s):  
Ye Han ◽  
Shu Yu Yao ◽  
Hai Qing Sun ◽  
Wei Wei Zhang
Keyword(s):  
Dielectric Constant ◽  
Fly Ash ◽  
Glass Ceramics ◽  
Dielectric Constants ◽  
Accurate Estimation ◽  
Fly Ashes ◽  
Degree Of Crystallization ◽  
Theoretical Procedure ◽  
Good Agreement

A theoretical procedure was developed with the aim of obtaining a rapid and accurate estimation of the degree of crystallization in glasses obtained from fly ash by measuring the dielectric constants. Compositions were prepared by melting the mixture of fly ashes, nucleators, fusing agents and clearing agents at 1500°C. Dielectric constant measurements were carried out by means of universal bridge. The results were compared with the degree of crystallization as evaluated by the method of density and showed a good agreement.

scholarly journals Molecular Simulation Study of Dielectric Constants of Pure Fluids and Mixtures

2021 ◽  
Author(s):  
Maximilian Kohns
Keyword(s):  
Dielectric Constant ◽  
Dielectric Constants ◽  
Molecular Models ◽  
Liquid Equilibrium ◽  
Pure Fluids ◽  
Wide Range ◽  
Equilibrium Data ◽  
Simulation Results ◽  
Temperature And Pressure ◽  
Good Agreement

The static dielectric constant of fluids is studied with molecular models from the literature. The employed molecular models were developed using only vapor-liquid equilibrium data. No information on the dielectric properties was used, so that the simulation results are predictions. A wide range of different fluids, from slightly to strongly polar, is investigated. Most of the studied models underestimate the dielectric constant, which can be explained by the way the models were developed. For the pure fluids dimethyl ether and acetone, the temperature and pressure dependence of the dielectric constant are also studied. A good agreement with experimental data is found. Additionally, binary mixtures are investigated. Thereby, the validity of several mixing rules for the dielectric constant is assessed.

scholarly journals A Generalized Approach for Evaluating the Mechanical Properties of Polymer Nanocomposites Reinforced with Spherical Fillers

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 830
Author(s):  
Julio Cesar Martinez-Garcia ◽  
Alexandre Serraïma-Ferrer ◽  
Aitor Lopeandía-Fernández ◽  
Marco Lattuada ◽  
Janak Sapkota ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Polymeric Nanocomposites ◽  
Mechanical Reinforcement ◽  
Future Studies ◽  
Three Phase ◽  
Theoretical Predictions ◽  
Filler Network ◽  
New Research ◽  
Good Agreement ◽  
Research Avenue

In this work, the effective mechanical reinforcement of polymeric nanocomposites containing spherical particle fillers is predicted based on a generalized analytical three-phase-series-parallel model, considering the concepts of percolation and the interfacial glassy region. While the concept of percolation is solely taken as a contribution of the filler-network, we herein show that the glassy interphase between filler and matrix, which is often in the nanometers range, is also to be considered while interpreting enhanced mechanical properties of particulate filled polymeric nanocomposites. To demonstrate the relevance of the proposed generalized equation, we have fitted several experimental results which show a good agreement with theoretical predictions. Thus, the approach presented here can be valuable to elucidate new possible conceptual routes for the creation of new materials with fundamental technological applications and can open a new research avenue for future studies.

scholarly journals Comment on “investigation of dielectric constants of water in a nano-confined pore” by H. Zhu, F. Yang, Y. Zhu, A. Li, W. He, J. Huang and G. Li, RSC Adv., 2020, 10, 8628

RSC Advances ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 5179-5181
Author(s):  
Sayantan Mondal ◽  
Biman Bagchi
Keyword(s):  
Dielectric Constant ◽  
Dielectric Constants ◽  
Static Dielectric Constant ◽  
Inherent Anisotropy ◽  
Nanoconfined Water

Neglects of inherent anisotropy and distinct dielectric boundaries may lead to completely erroneous results. We demonstrate that such mistakes can give rise to gross underestimation of the static dielectric constant of cylindrically nanoconfined water.

The Reduction of Bias Error in Transfer Function Estimates Using FFT-Based Analyzers

1984 ◽  
Vol 106 (1) ◽  
pp. 29-35 ◽  
Author(s):  
P. Cawley
Keyword(s):  
Transfer Function ◽  
Random Excitation ◽  
Analogue Computer ◽  
Bias Error ◽  
Testing Time ◽  
Theoretical Predictions ◽  
Set Up ◽  
Modal Mass ◽  
Time Required ◽  
Good Agreement

The susceptibility to bias error of two methods for computing transfer (frequency response) functions from spectra produced by FFT-based analyzers using random excitation has been investigated. Results from tests with an FFT analyzer on a single degree-of-freedom system set up on an analogue computer show good agreement with the theoretical predictions. It has been shown that, around resonance, the bias error in the transfer function estimate H2 (Syy/Sxy*) is considerably less than that in the more commonly used estimate, H1 (Sxy/Sxx). The record length, and hence the testing time, required for a given accuracy is reduced by over 50 percent if the H2 calculation procedure is used. The analysis has also shown that if shaker excitation is used on lightly damped structures with low modal mass, it is important to minimize the mass of the force gage and the moving element of the shaker.

scholarly journals A note on some further determinations of the dielectric constants of organic bodies and electrolytes at very low temperatures

1898 ◽  
Vol 62 (379-387) ◽  
pp. 250-266 ◽  
Keyword(s):  
Dielectric Constant ◽  
Low Temperatures ◽  
Tuning Fork ◽  
Dielectric Constants ◽  
The Past ◽  
Method Of Measurement ◽  
The Given ◽  
Past Summer

In several previous communications we have described the investigations made by us on the dielectric constants of various frozen organic bodies and electrolytes at very low temperatures. In these researches we employed a method for the measurement of the dielectric constant which consisted in charging and discharging a condenser, having the given body as dielectric, through a galvanometer 120 times in a second by means of a tuning-fork interrupter. During the past summer we have repeated some of these determinations and used a different method of measurement and a rather higher frequency. In the experiments here described we have adopted Nernst’s method for the measurement of dielectric constants, using for this purpose the apparatus as arranged by Dr. Nernst which belongs to the Davy-Faraday Laboratory.

Contributions to Silicon-Hydrogen Bond-Stretching Frequency in Amorphous Si Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
Z. Jing ◽  
J. L. Whitten ◽  
G. Lucovsky
Keyword(s):  
Experimental Data ◽  
Hydrogen Bond ◽  
Dielectric Constant ◽  
Ab Initio ◽  
Effective Dielectric Constant ◽  
Bond Energies ◽  
Calculated Frequency ◽  
Bond Stretching ◽  
Amorphous Si ◽  
Good Agreement

ABSTRACTWe have performed ab initio calculations and determined the bond-energies and vibrational frequencies of Si-H groups that are: i) attached to Si-atoms as their immediate, and also more distant neighbors; and ii) attached to three O-atoms as their immediate neighbors, but are connected to an all Si-atom matrix. These arrangements simulate bonding geometries on Si surfaces, and the calculated frequency for i) is in good agreement with that of an Si-H group on an Si surface. To compare these results with a-Si:H alloys it is necessary to take into account an additional factor: the effective dielectric constant of the host. We show how to do this, demonstrating the way results of the ab initio calculations should then be compared with experimental data.

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