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The breakdown strength of gases at low pressures increases regularly with density; using this fact, one can extrapolate the strength of a vapor to densities corresponding to the liquid state. An extrapolation of this type is shown in figure 1 for hexane1,2, for comparison, point X shows a typical observed value of the strength of the liquid3. As may be seen, the liquid strength is appreciably lower...
The accurate measurement of electric breakdown strength in the liquid phase has become possible through the use of short pulse techniques, (1,2,3) and such methods of measurement are by now widely used. On the other hand, the measurements of conduction currents in insulating liquids have continued to rely upon d.c.,(2,4) presumably because of the experimental difficulties inherent in making accurate...
In our investigation of the mechanism of electric breakdown in liquids, we have endeavored to measure a value for the electric strength that is characteristic of the liquid itself; ideally, that value which is free from the influence of all external factors such as electrode composition, surface condition, and configuration. However, because the influence of such factors as these cannot be completely...
A broad-band spectral analysis was undertaken of the dielectric properties of ferrites (polarization, magnetization and conduction) from d.c. to the optical spectral region. After a short description of the various measurement techniques employed, characteristic data are given of electronic conduction, space-charge polarization, infrared absorption, and ferromagnetic resonance. Various additional...
The influence of the nature of the cathode metal upon the breakdown of liquid dielectrics has been studied by many investigators. However, the sensitivity of the electron emission characteristics of a metal to the physical and chemical condition of its surface makes it very difficult to obtain reproducible results, Bragg, Sharbaugh, and Crowe (1) have attempted to bypass this difficulty by using an...
In 1951 it was reported by Salvage (1) that the electric strengths of liquid straight-chain aliphatic hydrocarbons, as measured under d.c. conditions between hemispherical electrodes, increased with increase in the chain length of the hydrocarbon molecules. Until that time, a correlation of electrical breakdown of liquids with known molecular properties had been virtually impossible because of inadequate...
For some twenty-five years the decrease in the measured electric strength of liquids with increasing electrode spacing has been an important subject of study because of its practical as well as theoretical significance. Early investigators were handicapped by the lack of reproducibility of electric strength values as well as their inability to measure accurately small electrode spacings. With the...
Franz (1) has written (in German) a detailed review article concerning the theory of “intrinsic” electric breakdown in solids. The review, fifty-five pages in length, includes twenty-three figures and sixty literature references. Franz devotes a chapter to each of the following topics: (a) theory of electronic processes in crystalline solids, including a discussion of electronic energy states and...
A crucial test of any theory of electrical breakdown is the comparison of observed and predicted temperature dependence of the electric strength. The theories of von Hippel, Seitz, and Callen give the proper temperature dependence at low temperatures (for ionic crystals) but the agreement is lost at high temperature. In order to explain the high temperature region, Fröhlich has adduced another breakdown...
It has been reported-recently by Salvage (1) that the electric strengths of liquid, straight-chain hydrocarbons increase with increase in molecular weight from n-pentane through n-nonane. The purpose of the present work is to verify and investigate more carefully this behavior, and to interpret the results, if possible, in terms of the physical properties of the hydrocarbons.
In this review a year ago a good deal of space was devoted to an extensive development by Heller (1951) of a “steady-state” theory of breakdown of solids. Almost simultaneously W. Franz developed a similar theory, reports of which appeared in German journals in January (1) and June (2) of 1952. The underlying ideas of the work of Franz are in most instances very close to those of Heller, so that the...
The electron emission characteristics of the surface of the cathode used in the study of the electric breakdown of insulators are believed to have a fundamental bearing on electric strengths observed. It has been suggested that the formation of a negative space charge is the mechanism through which this influence is exerted1.
The only theoretical paper, one of considerable interest to the field, contains Heller's calculation of the electric strength of a non-polar crystal1. The calculation is based on a view of the breakdown process which differs in several important ways from those of von Hippel, Fröhlich, Seitz, and Callen based on the avalanche criterion.
In 1936, G. Groetzinger reported apparent increases (See Table I) of as much as 71% in the thermal conductivity of beeswax electrets (See Table II) over that measured for unelectrified beeswax. In view of the technical advantages of such a property, we decided to repeat these experiments. Groetzinger1s experimental conditions were reproduced, but no difference between the thermal conductances of electret...
The second rotational transition, J=1 to J=2, of SiH3Cl35 and SiH3Cl37 has been measured and analysed. The Hughes-Wilson Stark modulation technique was used for detection of the absorption lines; and absorption frequencies were determined by comparison with a crystal-controlled secondary frequency standard.
In the year 1947 the trend in the field of dielectrics has been toward the use of higher frequencies, both as to application and theoretical studies of dielectric systems. Many of the constants of dielectric phenomena formerly obtained by extrapolation, have now been experimentally investigated at these microwave frequencies. The designers of measuring equipment have been concerned with making instruments...
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