Microstructure-Electrical Propertyrelationships in Cement-Based Materialss

1994 ◽  
Vol 370 ◽  
Author(s):  
R.A. Olson ◽  
G.M. Moss ◽  
B.J. Christensen ◽  
J.D. Shane ◽  
R.T. Coverdale ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Freezing Point ◽  
Relative Dielectric Constant ◽  
Precise Determination ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
Direct Result ◽  
Solvent Exchange ◽  
Early Hydration ◽  
Variable Nature

AbstractThere has been much recent progress on the application of impedance spectroscopy (IS) to the study of microstructure and transport in cement-based materials. The IS spectrum allows for the precise determination of bulk resistance, which is a measure of the pore phase interconnectivity, and calculation of the relative dielectric constant, which is related to the capillary pore size and distribution. High values of the relative dielectric constant (σ105) observed in cement paste at early hydration times are the direct result of the microstructure inducing dielectric amplification. Solvent exchange and freezing experiments, combined with digital-image-based computer modeling, have confirmed the role of large capillary pores in the dielectric amplification in young pastes.The conductivities (σ) and relative dielectric constants (εr) of ordinary portland cement (OPC) pastes were monitored during cooling and solvent exchange with isopropanol and methanol. Dramatic decreases in σ and εr, in some cases over two orders of magnitude, occurred at the initial freezing point of the aqueous phase in the macropores and large capillary pores. The same dramatic decreases in a and er were observed at the onset of solvent exchange. Both effects provide experimental support for the dielectric amplification mechanism within the microstructure on the μm-scale. A secondary dielectric amplification was observed in the frozen and solvent exchanged pastes, which produced dielectric constants on the order of 103. This effect is attributed to amplification on the nm-scale within the layered calcium silicate hydrate (C-S-H) gel microstructure. Additional insight into the variable nature of the C-S-H microstructure was obtained by comparing the dielectric behavior of methanol-exchanged OPC pastes to isopropanolexchanged OPC pastes.

scholarly journals Model of Е-polarized wave propagation in a multilayer dielectric structure

2021 ◽  
Vol 2021 (3) ◽  
pp. 111-118
Author(s):  
P.I. Zabolotnyi ◽  
Keyword(s):  
Dielectric Constant ◽  
Electromagnetic Wave ◽  
Reflection Coefficient ◽  
Incidence Angle ◽  
Relative Dielectric Constant ◽  
Normal Incidence ◽  
Dielectric Constants ◽  
Dielectric Structure ◽  
Range Of Variation ◽  
Multilayer Dielectric

This paper addresses the determination of the dielectric constant of multilayer dielectric structures by radiowave interferometry. In the general case, in interferometry measurements to one measured value of the reflection coefficient there may correspond an infinity of dielectric constants. This ambiguity may be resolved by first determining the effect of different parameters of the probing electromagnetic wave on the reflection coefficient. In particular, it is important to have a preliminary estimate of the effect of the incidence angle and the polarization on the range of variation of the reflection coefficient with the variation of one of the structure parameters. This paper considers the case where a plane E-polarized electromagnetic wave, i.e. a wave whose magnetic field is perpendicular to the incidence plane, is incident on a multilayer dielectric structure. The aim of this work is to develop a model of the propagation of an E-polarized electromagnetic wave through a multilayer dielectric structure at an arbitrary incidence angle and to determine the range of variation of the reflection coefficient with the variation of the dielectric constants of the layers. The paper presents a model of the propagation of an E-polarized electromagnetic wave in a two-layer dielectric structure. A metal base, which is an ideal conductor, underlies the structure. The electromagnetic wave is incident from the air at an arbitrary incidence angle. Based on the model, a method is proposed for measuring the relative dielectric constant and the dielectric loss tangent. It is shown that at a normal incidence the reflection coefficient magnitude is the same both for H- and E-polarization. Because of this, determining the relative dielectric constant and the loss tangent from the measured reflection coefficient magnitude calls for measurements not only at a normal incidence, but also at an oblique incidence, at which the reflection coefficient magnitudes will be different for H- and E-polarization.

scholarly journals Investigating the dielectric properties of barium titanate nanocomposites using transmission electron microscopy image processing

MRS Advances ◽  
2021 ◽  
Author(s):  
Gio Ferro ◽  
Dithi Ganjam ◽  
Maia Gibson ◽  
Katie Partington ◽  
Akshay Trikha ◽  
...  
Keyword(s):  
Image Processing ◽  
Dielectric Constant ◽  
Energy Storage ◽  
Barium Titanate ◽  
Computational Models ◽  
Transmission Electron Microscopy Image ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
Transmission Electron ◽  
High Dielectric

AbstractBarium titanate (BTO) is a ferroelectric perovskite material used in energy storage applications because of its high dielectric constant. A previous study showed that the dielectric constant for BTO nanoparticles drastically increases to over 15,000 at a particle size of 70 nm. This result is highly contested, but its implications to energy storage motivated our investigation into the dielectric constants of BTO nanoparticles that are incorporated into a polymer matrix. We developed a novel method of using image processing techniques on transmission electron microscope images of BTO-polymer nanocomposites. Data on the positions, shapes, sizes, and orientations of BTO nanoparticles were used to build more realistic computational models that simulate the dielectric behavior of the nanocomposites. Here, we investigate the relationship between regions of enhanced electric field and the composite dielectric constant.

High dielectric constants in BaTiO3 doped 90V2O5−10Bi2O3 oxide glasses obeying Debye-type dielectric relaxation behavior

1994 ◽  
Vol 9 (8) ◽  
pp. 1932-1935 ◽  
Author(s):  
Sahana Chakraborty ◽  
A.K. Bera ◽  
S. Mollah ◽  
B.K. Chaudhuri
Keyword(s):  
Dielectric Constant ◽  
Dielectric Relaxation ◽  
Dilution Effect ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
Relaxation Behavior ◽  
Oxide Glasses ◽  
Base Glass ◽  
Dielectric Relaxation Behavior ◽  
High Dielectric

BaTiO3 doped 90V2O5−10Bi2O3 (VB) oxide glasses show a larger dielectric constant (102-104) compared to that of the base glass VB (∼102). The VB glass with 15 wt.% BaTiO3 shows the largest dielectric constant, and all the glasses show a Debye-type dielectric relaxation behavior. The increase in dielectric constant appears to be mainly due to the formation of microcrystalline clusters of BaTiO3 (1.8–8 μm, depending on the BaTiO3 concentration present in the base glass). Other than the dilution effect with BaTiO3, the glass-former oxide Bi2O3 also influences the dielectric behavior of BaTiO3 doped VB glasses.

Characterization of Porous Silicate Low-k Films by Ellipsometric Porosimetry and Variable-energy Positron Annihilation Spectroscopy

2003 ◽  
Vol 788 ◽  
Author(s):  
Kenji Ito ◽  
Yoshinori Kobayashi ◽  
Ryoichi Suzuki ◽  
Toshiyuki Ohdaira ◽  
Runsheng Yu ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Positron Annihilation ◽  
Open Porosity ◽  
Average Pore Size ◽  
Relative Dielectric Constant ◽  
Positron Annihilation Spectroscopy ◽  
Dielectric Constants ◽  
Ellipsometric Porosimetry ◽  
Variable Energy

ABSTRACTWe a pplied ellipsometric porosimetry and variable-energy positron annihilation spectroscopy to the pore characterization of spin-on-glass silicon-oxide-backboned porous thin films with different relative dielectric constants between 2.3 and 3.2. It was found that the relative dielectric constant decreases linearly with increasing open porosity deduced by ellipsometric porosimetry. Comparison of the open porosity with the average pore size deduced by positron annihilation lifetime spectroscopy suggested that mesopores less contribute to open porosity and are not so effective in decreasing film relative dielectric constant in comparison with micropores.

Monitoring Early Hydration of Concrete with Ground Penetrating Radar

2017 ◽  
Vol 726 ◽  
pp. 115-119
Author(s):  
Ya Po Tian ◽  
Ding Ce Huang ◽  
Bo Li
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Portland Cement ◽  
Ground Penetrating Radar ◽  
Relative Dielectric Constant ◽  
Electric Resistivity ◽  
Time Curve ◽  
Early Hydration ◽  
Concrete Mix ◽  
Ground Penetrating

A nondestructive method is designed and employed to monitoring the early hydration of concrete mixes. The concrete mixes are prepared with Portland cement content and water to cement ratio 0.45. Retarder (citric acid) and accelerator (triethanolamine) are used to investigate the effects on the hydration process. The variations of dielectric constant and the intensity of reflected EM wave (amplitude) are measured within the frequency of 1.5GHz using Ground Penetrating Radar (GPR) at 25 °C for each sample from 10min to 3 days after mixing with water. The electric resistivity of Portland cement paste samples is measured using a non-contacting electric resistivity device at 25 °C.The amplitude tested changes sharply corresponding to the changes of microstructure and hydration products in the concrete mix during early hydration. The relative dielectric constant decreases with increasing hydrating time. The electrical resistivity changes in agreement with the dielectric properties. The dielectric properties mainly depend on the electrical properties and water content. The test results of samples in presence of retarder and accelerator shows that the relative dielectric constant decrease slower and faster respectively compared to the plain sample. The effect of these two admixtures can be reflected on the amplitude-time curve. The results demonstrate that the dielectric properties of concrete mix can be used as an effective ways of studying the hydration progress of concrete during hydration.

Studies in the Vulcanization of Rubber. V. Dielectric Constant and Power Factor of Vulcanized Rubber

1932 ◽  
Vol 5 (3) ◽  
pp. 367-383
Author(s):  
Donald W. Kitchin
Keyword(s):  
Dielectric Constant ◽  
Sulfur Content ◽  
Power Factor ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
Low Dielectric ◽  
Vulcanized Rubber ◽  
Wide Range ◽  
Hard State ◽  
Critical Experiment

Abstract 1. Power factor and dielectric constant data have been given for vulcanized rubber samples tested over a wide range of composition, temperature, and frequency. 2. The real identity of the agents responsible for the peculiar dielectric behavior is not known. It seems probable that these agents are the rubber-sulfur molecules themselves. because the effects increase, under proper conditions, directly with per cent combined sulfur. 3. The effect of increasing sulfur content on the dielectric behavior is complex; it modifies not only these supposed agents themselves, but also the stiffness of their environment. Moreover, at a given sulfur content the agents are not identical but differ widely in relaxation time, and therefore in ability to respond; and with progressive addition of sulfur, the rubber does not increase continuously in stiffness, but, at a composition which depends on the temperature, passes rather abruptly from a soft to a hard state. 4. The temperature at which the transition from one state to the other occurs increases almost linearly with the sulfur content from −90° to +90° C. 5. In the soft state the behavior of vulcanized rubber with respect to compressibility, thermal expansion, dielectric constant, and power factor, and probably other properties, resembles that of a viscous liquid; in the hard state, that of a solid. 6. Rubber with less than 2 per cent combined sulfur shows low dielectric constant and power factor over the whole temperature and frequency range investigated; hard rubber, only at room temperature, where its rigidity restricts the response to the field. 7. Hard rubber, although not an electret, can hold an electric charge for 24 hours or more. The low dielectric constants of high-sulfur rubber samples found in measurements with a ballistic galvanometer were due to the disparity between its period of about one second and the long discharge periods of the samples. This led to the idea of dipole compensation shown to be incorrect by the high temperature results. 8. At temperatures sufficiently high to permit free response, the dielectric constant increases with sulfur content over the whole range. 9. If a dipole mechanism is involved, addition of sulfur to more than half the double bonds does not cause the dipole moment of the molecules to vanish owing to compensation. 10. The power factor of vulcanized rubber sheets decreases on stretch. 11. The data neither prove nor disprove a dipole mechanism. A critical experiment to settle this question is still wanting.

scholarly journals Reply to the ‘Comment on “Investigation of dielectric constants of water in a nano-confined pore”’ by S. Mondal and B. Bagchi, RSC Adv., 2020, 10, DOI: 10.1039/D0RA02726J

RSC Advances ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 5753-5754
Author(s):  
Haochen Zhu ◽  
Han Hu ◽  
Bo Hu ◽  
Wenzhi He ◽  
Juwen Huang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Strong Dependence ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
Diverse Range

It is true that dielectric constant is a tensor and exhibits a strong dependence on the shape and the size of the enclosure in a confined phase. Thus, dielectric behavior of water become anisotropic in nature and exhibits a diverse range of anomalies.

scholarly journals Silica Aerogel: An Intrinsically Low Dielectric Constant Material

1995 ◽  
Vol 381 ◽  
Author(s):  
Lawrence W. Hrubesh
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Solid Material ◽  
Dielectric Strength ◽  
Silica Aerogels ◽  
Dielectric Constants ◽  
Porous Solids ◽  
Direct Result ◽  
Low Dielectric ◽  
Normal Transport

AbstractSilica aerogels are highly porous solids having unique morphologies in which both the pores and particles have sizes less than the wavelength of visible light. This fine nanostructure modifies the normal transport mechanisms within aerogels and endows them with a variety of exceptional physical properties. For example, aerogels have the lowest measured thermal conductivity and dielectric constant for any solid material. The intrinsically low dielectric properties of silica aerogels are the direct result of the extremely high achievable porosities, which are controllable over a range from 75% to more than 99.8%, and which result in measured dielectric constants from 2.0 to less than 1.01. This paper discusses the synthesis of silica aerogels, processing them as thin films, and characterizing their dielectric properties. Existing data and other physical characteristics of bulk aerogels (e.g., thermal stablity, thermal expansion, moisture adsorption, modulus, dielectric strength, etc.), which are useful for evaluating them as potential dielectrics for microelectronics, are also given.

Solvothermal approach to nanocrystalline Li–Ti–O insertion hosts–solvent polarity effect

2008 ◽  
Vol 23 (4) ◽  
pp. 1136-1146 ◽  
Author(s):  
Tereza Kostlánová ◽  
Marina V. Makarova ◽  
Petr Krtil
Keyword(s):  
Dielectric Constant ◽  
Structural Model ◽  
Specific Capacity ◽  
Relative Dielectric Constant ◽  
Solvent Polarity ◽  
Dielectric Constants ◽  
Solvothermal Reaction ◽  
Ternary Compounds ◽  
Octahedral Sites ◽  
Li Content

The cubic nanocrystalline Li–Ti–O oxides were prepared by the solvothermal reaction of TiO2 and LiOH at 200 °C in water and aliphatic alcohols with different dielectric constants. The reaction in all solvents leads to the formation of white ternary compounds containing Li, Ti, and O. The actual Li content in the prepared materials increases with decreasing polarity of the used solvent. All prepared materials are crystalline, and their structure can be described using a spinel structural model. The structure of materials prepared at a relative dielectric constant (ϵr) value higher than 33 is characterized by Ti disorder when the Ti atoms are distributed between both types of the available octahedral sites with approximately the same probability. The tendency to form phases with Ti disorder decreases with decreasing ϵr of the solvent. All prepared materials are active toward electrochemical Li insertion. The observed specific capacity ranges between 60 and 150 mAh/g.

High Dielectric Constant Polymer Ceramic Composites

1999 ◽  
Vol 600 ◽  
Author(s):  
Y. Bai ◽  
V. Bharti ◽  
Z.-Y. Cheng ◽  
H. S. Xu ◽  
Q. M. Zhang
Keyword(s):  
Dielectric Constant ◽  
Relative Dielectric Constant ◽  
Ceramic Composites ◽  
Dielectric Behavior ◽  
Breakdown Field ◽  
Clean Environment ◽  
The Matrix ◽  
High Dielectric ◽  
Breakdown Field Strength ◽  
Room Temperature Dielectric Constant

AbstractA new polymer-ceramic composite, using the newly developed relaxor ferroelectric polymer that has a high room temperature dielectric constant as the matrix, is reported. Different kinds of ceramic powders were studied and homogeneous composite thin films (20μm) were fabricated. It was observed that the increase of the dielectric constant of the composites with the ceramic content could be described quite well by the expression developed by Yamada et al., when the ceramic content is below 60% by volume. The experimental data shows that the relative dielectric constant of composites using PMN-PT powders can reach more than 250 with weak temperature dependence (i.e., the dielectric constant changes little in a broad temperature range). In addition to high permittivity, the composite prepared in clean environment also has high breakdown field strength (120MV/m), which yields an energy storage density more than 14J/cm3. The dielectric behavior of the composite at various frequencies was also studied and the results show that the material is promising for high frequency applications.

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