PRELIMINARY OBSERVATIONS OF THE DIELECTRIC CONSTANTS OF VAPORS ADSORBED ON ACTIVATED SILICA

1947 ◽  
Vol 25b (6) ◽  
pp. 566-574 ◽  
Author(s):  
R. McIntosh ◽  
L. McLeod ◽  
H. S. Johnson ◽  
N. Hollies
Keyword(s):  
Dielectric Constant ◽  
Ethylene Oxide ◽  
Silica Gel ◽  
Dielectric Constants ◽  
Ethyl Chloride ◽  
Bulk Liquid ◽  
Temperature Coefficients ◽  
Capacity Change

A measure of the dielectric constants of several substances adsorbed on silica gel has been obtained by measuring the change in the capacity of an electrical condenser when measured amounts of the substances were adsorbed on silica gel situated between the plates of the condenser. The substances examined were ethyl chloride, n-butane, and ethylene oxide. The plot of capacity change vs. amount adsorbed was found, in all cases, to consist of two or more quite distinct sections, each approximating to linearity. The temperature coefficients of dielectric constant were evaluated. The dielectric constant calculated for adsorbed n-butane was close to that calculated for the bulk liquid, whereas the value calculated for adsorbed ethyl chloride was significantly lower than the value calculated for the liquid.

NOTE ON THE DIELECTRIC CONSTANTS OF ETHYL CHLORIDE AND n-BUTANE ADSORBED ON NONPOROUS TiO2

1953 ◽  
Vol 31 (11) ◽  
pp. 998-1003 ◽  
Author(s):  
M. H. Waldman ◽  
J. A. Snelgrove ◽  
R. Mcintosh
Keyword(s):  
Temperature Dependence ◽  
Silica Gel ◽  
Porous Silica ◽  
Adsorbed Molecule ◽  
Dielectric Constants ◽  
Ethyl Chloride ◽  
Capacity Change ◽  
Adsorbed Phase ◽  
Porous Silica Gel ◽  
Linear Sections

The dielectric constants of ethyl chloride and n-butane adsorbed on nonporous TiO2 were measured. The plot of capacity change versus volume adsorbed was found to reveal two linear sections in the case of ethyl chloride with an abrupt change in the slope of the plot occurring at the Vm value calculated using the B.E.T. or Hüttig adsorption equations. With n-butane the plot was linear beyond Vm. For ethyl chloride on rutile a slight temperature dependence in the polarization was observed for the volume of gas adsorbed above Vm, while a negligible temperature dependence was noted for the portion below Vm. It is postulated that the observations with the polar gas on the nonporous rutile can be explained by a change from oscillatory to rotational motion of the adsorbed molecule after the monolayer is complete. It was noted that gases adsorbed on nonporous TiO2 behaved differently from gases adsorbed on porous silica gel. This appears to lead to the necessity of postulating changes of density for the adsorbed phase on silica gel.

scholarly journals On the direct determination of the electrostatic moments of molecules

1929 ◽  
Vol 124 (795) ◽  
pp. 689-698 ◽  
Keyword(s):  
Dielectric Constant ◽  
Direct Determination ◽  
Negative Temperature ◽  
Dielectric Constants ◽  
Temperature Coefficients ◽  
Different Temperatures

According to Faraday's ideas, the specific inductive capacity of a substance is due to the polarisation of the molecules as wholes. This is the basis of the old Clausius-Mosotti theory of dielectrics, on which it is shown first that the polarisation P is proportional to the polarising field, i. e. , P = k E, k being the dielectric constant, and second that δ being the density of the dielectric, k - 2/ k + 2 ·1/δ = constant. Now it is known that some substances have large negative temperature coefficients for their dielectric constants which cannot thus be accounted for. To provide for this Debye proposed the theory that the molecules were permanently polarised and that they were systematically orientated in the field. This leads to the equation k - 2/ k + 2 = a T -1 + b T -2 , to represent the change of specific inductive capacity with temperature. This theory has been developed by Gans and others, and a number of measurements have been made by Smyth and others, who have found the molecular moments of many substances by measuring the dielectric constants at different temperatures.

DIELECTRIC CONSTANTS OF LIQUID SULPHUR DIOXIDE, ETHYL CHLORIDE, AND ETHYLENE OXIDE

1957 ◽  
Vol 35 (11) ◽  
pp. 1325-1331 ◽  
Author(s):  
J. D. Nickerson ◽  
R. McIntosh
Keyword(s):  
Ethylene Oxide ◽  
Sulphur Dioxide ◽  
Dipole Moments ◽  
Dielectric Constants ◽  
Ethyl Chloride ◽  
Frequency Range ◽  
Liquid Sulphur

Dielectric constants of sulphur dioxide, ethyl chloride, and ethylene oxide have been measured over the frequency range 9 to 92 Mc./second and at temperatures between −35° and +20 °C. Dipole moments computed from the Debye, Onsager, and Kirkwood equations are reported and compared with the moments which are known from measurements on the gaseous substances.

THE DIELECTRIC CONSTANT OF ETHYL CHLORIDE ADSORBED ON POROUS SILICA GLASS TREATED TO REMOVE SILANOL GROUPS

1966 ◽  
Vol 44 (10) ◽  
pp. 1153-1169 ◽  
Author(s):  
R. Shigeishi ◽  
R. McIntosh
Keyword(s):  
Dielectric Constant ◽  
Porous Glass ◽  
Porous Silica ◽  
Dielectric Constants ◽  
Ethyl Chloride ◽  
Complex Dielectric Constant ◽  
Dielectric Parameters ◽  
Silanol Groups ◽  
Porous Silica Glass ◽  
Lower Slope

The real and imaginary parts of the complex dielectric constant of the composite system ethyl chloride adsorbed on porous glass have been determined over a range of temperature, namely −20 to −190 °C in the frequency range 1 000 to 4 000 Mc/s. The porous glass was treated to remove the majority of the silanol groups. The dielectric constants of the adsorbate are also reported. The major finding was that removal of the silanol groups eliminated the second linear section (of lower slope) of the usual plots. The behavior of the polar adsorbate is then shown to be quite similar to that of polar adsorbates on nonporous rutile. Loss curves as functions of frequency and temperature are given and discussed. There is insufficient evidence to discriminate between Debye-type loss and that of an oscillator or resonator.A method is given of obtaining the dielectric parameters from the standing wave data with greater accuracy than can be obtained from use of Von Hippel plots.

THE DIELECTRIC BEHAVIOR OF VAPORS ADSORBED ON SILICA GEL

1953 ◽  
Vol 31 (1) ◽  
pp. 72-83 ◽  
Author(s):  
J. A. Snelgrove ◽  
H. Greenspan ◽  
R. Mcintosh
Keyword(s):  
Temperature Coefficient ◽  
Silica Gel ◽  
Liquid State ◽  
Saturation Pressure ◽  
Adsorbed Water ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
Ethyl Chloride ◽  
Oscillatory Motion ◽  
Molar Polarization

Experiments to determine the dielectric constants of adsorbed butane, ethyl chloride, and water on an activated silica at frequencies up to 3.7 Mc. per sec. are reported. No Debye-type dispersion was observed for the polar adsorbates down to −30 °C, the lowest temperature employed. Mixtures of ethyl chloride and water, and of butane and water, were also studied. The assumption that adsorption of ethyl chloride and water occurs with both adsorbates sharing two types of sites sufficed to explain the findings for this system. No explanation was apparent to account for the behavior of the butane–water system.Formulae due to Kurbatov and to Snelgrove and McIntosh have been used to interpret the results obtained with polar adsorbates. On the assumption that the adsorbates have densities equivalent to those for the liquid state at the same temperature, it is concluded that adsorbed water undergoes oscillatory motion. The first quantities of ethyl chloride adsorbed behave as though the molecules may rotate freely within an angle of 98°. The ethyl chloride adsorbed nearer the saturation pressure shows oscillatory motion, as a negligible temperature coefficient of the molar polarization is observed.

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.

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.

Microstructure and Microwave Dielectric Properties of BaTi4O9 Ceramics Derived from a Sol-Gel Precursor

2011 ◽  
Vol 326 ◽  
pp. 127-130
Author(s):  
Xian Li Huang ◽  
Fu Ping Wang ◽  
Ying Song
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Sol Gel ◽  
Microwave Dielectric Properties ◽  
Sintering Process ◽  
Temperature Coefficients ◽  
Microwave Dielectric ◽  
Ceramic Samples ◽  
Quality Factor Q

In the present work, the microstructure and microwave dielectric properties of BaTi4O9 ceramics derived from a sol-gel precursor were presented. Density measuring results demonstrated that the largest densities of ceramic sample about 96.7% could be reached by virtue of a cool iso-static press and a sintering process at at 1300 °C for 6 hours. The dielectric constant (εr), quality factor (Q×f) and the temperature coefficients (τf) of the BaTi4O9 ceramic samples were 36.65, 28000 GHz, +20.2 ppm/°C, respectively. XRD, SEM and XPS were used to characterize the microstructure of the ceramics samples. Substantial Ti3+ was proposed to be the cause of dielectric loss.

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.

Sign in / Sign up

Export Citation Format

Share Document