scholarly journals Dielectric Constants of a Binary Solution Near the Critical Solution Temperature

1973 ◽  
Vol 51 (4) ◽  
pp. 545-550 ◽  
Author(s):  
I. Lubezky ◽  
R. McIntosh
Keyword(s):  
High Frequency ◽  
Binary Solution ◽  
Critical Concentration ◽  
Low Frequency ◽  
Dielectric Constants ◽  
Solution Temperature ◽  
Dielectric Losses ◽  
Theoretical Studies ◽  
Critical Solution Temperature ◽  
Experimental Knowledge

The dielectric constants and dielectric losses of solutions of nitrobenzene and 2,2,4-trimethyl pentane have been measured near the critical solution temperature over a concentration range of 22–75% by weight and in the frequency regions of 5–60 and 1000 – 4000 kHz. It was found that below a critical concentration of 35% maxima existed in ε′ and ε″ at a temperature of 0.3 °C above the critical solution temperature. At higher concentrations the maxima disappeared and phase separation was preceded only by changes in the thermal coefficients dε′/dT and dε″/dT. The present study combined with others indicates that two regions of loss exist for the system near the critical temperature: low frequency losses of a conductive nature and high frequency losses of the Debye type. The published experimental knowledge of such systems remains insufficient to enable a thorough test of the theoretical studies published recently by Snider.

Properties relating to critical phenomena in the acetic anhydride – acetone – carbon disulfide system

1970 ◽  
Vol 48 (6) ◽  
pp. 904-909 ◽  
Author(s):  
A. N. Campbell ◽  
E. M. Kartzmark
Keyword(s):  
Acetic Anhydride ◽  
Carbon Disulfide ◽  
General Rule ◽  
Dielectric Constants ◽  
Excess Volumes ◽  
Solution Temperature ◽  
Critical Solution Temperature ◽  
Heats Of Mixing ◽  
Upper Critical Solution Temperature ◽  
Molar Polarization

The following physical properties of the acetic anhydride – acetone – carbon disulfide system have been investigated: congruent compositions, excess volumes, dielectric constants. For the system acetone – carbon disulfide, the excess volumes and the molar polarizations are much greater than those required by the mixture rule. From this we deduced that this system is very non-ideal and might, at a suitable temperature, form two layers; two liquid layers did indeed form at −73 °C, the upper critical solution temperature occurring somewhere between this temperature and 0 °C. We offer it as a general rule that, if the deviation from additivity of molar polarization is large and positive, two layers will form at a sufficiently low temperature, provided that solid phases do not intervene. This deduction becomes almost a certainty if large positive deviations from additivity of molar volume and large positive heats of mixing are also present.

Densities, Excess Volumes, Surface Tensions, Viscosities, and Dielectric Constants of the Systems: Methanol–Cyclohexane, Acetone–Methanol, Acetone–Cyclohexane, and Methanol–Cyclohexane–Acetone

1972 ◽  
Vol 50 (8) ◽  
pp. 1109-1114 ◽  
Author(s):  
A. N. Campbell ◽  
S. C. Anand
Keyword(s):  
Surface Tension ◽  
Ternary System ◽  
Binary Systems ◽  
Dielectric Constants ◽  
Molecular Surface ◽  
Solution Temperature ◽  
Critical Solution Temperature ◽  
Constant Change ◽  
Molar Polarization ◽  
Horizontal Portion

The density, dielectric constant, change of volume on mixing, refractive index, surface tension, and viscosity of the methanol–cyclohexane system have been investigated experimentally at temperatures ranging from 25° to 50°. The same properties of the binary systems acetone–methanol and acetone–cyclohexane, as well as of the ternary system methanol–cyclohexane–acetone were determined experimentally at 25°. The critical region of the partially miscible system methanol–cyclohexane has been investigated by determining the above physical properties at temperatures above and below the critical solution temperature. A similar investigation of the ternary system has been made, isothermally at 25°, by investigating solutions lying in the neighborhood of the plait point.The surface tension or a derived function of it, viz. the molecular surface energy, does not show a horizontal portion of the isotherm in the methanol–cyclohexane system, but the ternary system does show such a constant surface tension, probably fortuitously, all along the tangential line. The viscosity exhibits anomaly.All the systems show azeotropic behavior. The methanol–cyclohexane and acetone–cyclohexane systems show marked deviations in molar polarization from linearity and this agrees with the thermodynamic data, which indicate larger than unity values for the activity coefficients of the components' behavior (1). The viscosity isotherms of all these systems give no indication of the formation of any stable compound.

scholarly journals Phase Behavior and Heat Capacity of {DPnP + Water} Mixtures at the Temperature Range of 273.15–338.15 K

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Mariola Tkaczyk ◽  
Henryk Piekarski ◽  
Paweł Góralski
Keyword(s):  
Heat Capacity ◽  
Critical Concentration ◽  
Homogeneous Solution ◽  
Solution Temperature ◽  
Miscibility Gap ◽  
Differential Heat ◽  
Scanning Calorimetry ◽  
Critical Solution Temperature ◽  
Dipropylene Glycol ◽  
Capacity Data

The differential scanning calorimetry method (DSC) was used to examine the miscibility in the{dipropylene glycol propyl ether (DPnP) + water}system. Based on recorded curves of differential heat flow on temperature, HF=f(T), the range (composition, temperature) of the occurrence of miscibility gap, the values of lower critical solution temperature (LCST), and critical concentration were determined. On the basis of the experimentally determined specific heat capacity data the partial molar heat capacities (Cp,2) of DPnP in the mixtures with water were calculated. Analyzing changes in the course ofCp,2=f(x2)function, the boundary of transition from a homogeneous solution was determined, in which the monomers of amphiphile dominate, to the region, in which aggregates of the cluster type appear.

Design and Preparation of Benzoxazine Resin with High-Frequency Low Dielectric Constants and Ultralow Dielectric Losses

2019 ◽  
Vol 1 (4) ◽  
pp. 625-630 ◽  
Author(s):  
Jiangbing Chen ◽  
Ming Zeng ◽  
Zijian Feng ◽  
Tao Pang ◽  
Yiwan Huang ◽  
...  
Keyword(s):  
High Frequency ◽  
Dielectric Constants ◽  
Dielectric Losses ◽  
Low Dielectric

Heats of mixing and dielectric constants of some partially miscible liquid pairs

1969 ◽  
Vol 47 (4) ◽  
pp. 619-623 ◽  
Author(s):  
A. N. Campbell ◽  
E. M. Kartzmark
Keyword(s):  
Experimental Data ◽  
Hydrogen Bonding ◽  
Acetic Anhydride ◽  
Carbon Disulfide ◽  
Dielectric Constants ◽  
Solution Temperature ◽  
Negative Deviation ◽  
Critical Solution Temperature ◽  
Heats Of Mixing ◽  
Partially Miscible

The physical properties mentioned in the title have been determined for the six systems: (a) aniline–hexane, (b) methanol–cyclohexane, (c) methanol–carbon disulfide, (d) acetic anhydride–carbon disulfide, (e) acetic anhydride–cyclohexane, and (f) triethylamine–water, over the complete range of composition. All six systems are partially miscible, above or below a critical solution temperature (c.s.t.).From the experimental data, the partial molal heats of mixing have been calculated, using the Redlich and Kister equations. The enthalpy of hydrogen bonding in the triethylamine–water compound appears to be about −1.33 kcal per hydrogen bond.The orientation polarization, according to the Syrkin formula, appears always to exhibit negative deviation from ideality, at least over part of the concentration range.

THE LOW-FREQUENCY DIELECTRIC PROPERTIES OF ETHYLENE OXIDE AND ETHYLENE OXIDE HYDRATE

1963 ◽  
Vol 41 (6) ◽  
pp. 1424-1434 ◽  
Author(s):  
D. W. Davidson ◽  
G. J. Wilson
Keyword(s):  
Ethylene Oxide ◽  
High Frequency ◽  
Low Temperatures ◽  
Low Frequency ◽  
Dielectric Constants ◽  
Water Molecules ◽  
Kcal Mole ◽  
Absorption Region ◽  
Experimental Values ◽  
Static Dielectric Constants

The static dielectric constant of liquid ethylene oxide has been measured between 158 and 286 °K. The hydrate of ethylene oxide exhibits a dispersion–absorption region characterized by static dielectric constants about one-third as large as those of ice and by relatively large "high-frequency" dielectric constants (ε1 = 7.5 at 0 °C). This region may be approximately described as a circular arc locus, but may be represented somewhat better by a superposition of two (or three) semicircular dispersions. In either case, the activation energy for the relaxation of water molecules, to which this region is ascribed, is ca. 6.7 kcal/mole, except at low temperatures, where it becomes smaller. Experimental values of ε1 agree roughly with those calculated for comparatively rapid orientation of ethylene oxide molecules in the cavities of the hydrate. Such orientation may account for absorption maxima observed at 11 Mc/sec and above 100 Mc/sec at 90 °K.

scholarly journals Compact 20-W GaN Internally Matched Power Amplifier for 2.5 GHz to 6 GHz Jammer Systems

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 375
Author(s):  
Min-Pyo Lee ◽  
Seil Kim ◽  
Sung-June Hong ◽  
Dong-Wook Kim
Keyword(s):  
Output Power ◽  
Power Amplifier ◽  
High Frequency ◽  
Continuous Wave ◽  
Low Frequency ◽  
Single Layer ◽  
Dielectric Constants ◽  
High Electron ◽  
Active Device ◽  
Power Added Efficiency

In this paper, we demonstrate a compact 20-W GaN internally matched power amplifier for 2.5 to 6 GHz jammer systems which uses a high dielectric constant substrate, single-layer capacitors, and shunt/series resistors for low-Q matching and low-frequency stabilization. A GaN high-electron-mobility transistor (HEMT) CGH60030D bare die from Wolfspeed was used as an active device, and input/output matching circuits were implemented on two different substrates using a thin-film process, relative dielectric constants of which were 9.8 and 40, respectively. A series resistor of 2.1 Ω was chosen to minimize the high-frequency loss and obtain a flat gain response. For the output matching circuit, double λ/4 shorted stubs were used to supply the drain current and reduce the output impedance variation of the transistor between the low-frequency and high-frequency regions, which also made wideband matching feasible. Single-layer capacitors effectively helped reduce the size of the matching circuit. The fabricated GaN internally matched power amplifier showed a linear gain of about 10.2 dB, and had an output power of 43.3–43.9 dBm (21.4–24.5 W), a power-added efficiency of 33.4–49.7% and a power gain of 6.2–8.3 dB at the continuous-wave output power condition, from 2.5 to 6 GHz.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

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