chapter
In the preparation of barium titanate ceramics for dielectric and piezoelectric applications careful attention must be given to a great many factors which determine the ultimate performance of the ceramic. Attention is drawn to structural differences observed with the aid of electron micrographs as the time and temperature of firing are varied. At lower temperatures and shorter firing intervals crystals...
chapter
Offenbacher and Callen (1) have shown that the orientation of electrical breakdown paths may be due to the existence of asymmetrical electron scattering from the borders of the Brillouin zone for lattice vibrations. Observations of the orientation of electrical breakdown paths in the alkali halide crystals indicate that other sources of anisotropic electron scattering are present. This additional...
chapter
While many intensive investigations have been made on a few gases (e.g. the noble gases, hydrogen, nitrogen and air) in an effort to elucidate the mechanism of spark breakdown, little effort has been made to correlate the sparking potential with molecular structure (la). We have attempted to do this by studying a series of closely related saturated hydrocarbons from C1 through C6, including straight...
chapter
Previous measurements made in this laboratory have shown that elongated and flat molecules, and in general, non-spherical molecules, have a viscosity-dependent relaxation time, whereas the nearly spherical molecules exhibit relaxation times which are virtually independent of the viscosity of the medium. This paper will present some data which substantiates the viscosity independence of the relaxation...
chapter
The present AIEE Standard No. 1 — “General Principle upon which Temperature Limits are Based in the Rating of Electric Machines and Apparatus” — was first introduced about 1913. This standard has provided a firm basis for many years despite the arbitrary way in which materials are defined by their chemical composition. In recent years many new insulating materials have become available. The problems...
chapter
A specimen holder and associated equipment were required which would permit the accurate measurement of the dielectric constant and dissipation factor of dielectric materials at temperatures up to 500°C and over as wide a frequency range as possible. Holders have been designed for use at elevated temperatures (l, 2, 3), hut none were found which would cover the temperature and frequency ranges required.
chapter
Measurements of dielectric constant, dielectric loss and d.c. conductivity of Teflon were made from room temperature to temperatures just below the 327°C first order transition point and from frequencies of 102 to 105 c/s on the high temperature sample holder described in the previous paper. Throughout this entire temperature and frequency range the dissipation factor never exceeds the smallest observable...
chapter
By an adaptation of the Roberts and von Hippie “short circuit-line” method the dielectric constant and loss at 3.20 cm. wavelength of dl-camphor, d-camphor and isoborneol have been measured in the solid state over a wide range of temperatures and in the liquid phase just above the melting point. The values here obtained are compared with the radio-frequency values found in the literature. At 3.20...
chapter
The introduction in recent years of many new insulating materials has led to the realization that the present national and international insulation temperature standards are not only inadequate but difficult to interpret and often lead to ambiguities. This has resulted in relatively recent decisions go revise not, only our own but also the international insulation temperature.
chapter
Detailed analyses are presented for the decomposition products from a U.S.P. white mineral oil subjected to alternating voltage stress. On the assumption that free radical fragments are split from the parent hydrocarbon molecules of the oil, a free-radical mechanism is presented which accounts for the observed decomposition products.
chapter
The dielectric relaxation times associated with a single-axis polar rotator which may occupy several sites as it turns about its axis were calculated in terms of the probabilities of transition from one site to another. Two special cases were considered in detail; (a) that in which all of the sites are equivalent, and (b) that in which one site was stable with respect to the others. It was assumed...
chapter
The new techniques of nuclear magnetic resonance and pure quadrupole magnetic resonance were discussed, particularly in so far as they contribute to the solution of problems of interest in the study of dielectric properties. Results of recent investigations of the motions of molecules and parts of molecules in molecular solids by these methods show that they are often complimentary to the information...
chapter
In recognition of the general need for a more exact method for determining thermal stability of plasticized polyvinyl chloride compounds used for electrical insulation, it should be pointed out that existing methods are inadequate. Amongst the electrical and mechanical properties of an insulating material at elevated temperatures underlies a fundamental property of thermal stability or resistance...
chapter
A previous paper (Annual Report of the Conference on Electrical Insulation, 1952 meeting, p. 51) contained a brief account of a new phenomenon in the field of ferromagnetics: the spontaneous formation of rectangular hysteresis loops in ceramic ferric-oxide bodies. The rectangular hysteresis loop originates in these ferrites directly with no need for annealing, grain orientation or external stress...
chapter
The thermal shock resistance of ceramic dielectric insulation is affected by many factors, among them size and shape. These two factors vary so radically that most thermal shock resistance studies have merely been qualitative. The object of this work is to quantitatively determine the thermal shock resistance of ceramic dielectric insulation and the effect of certain physical properties. This is only...
chapter
Previous work on polymeric systems containing dissolved electrolytes (R. M. Fuoss, J. Amer. Chem. Soc., 61, 2329 (1939); D. J. Mead and R. M. Fuoss, ibid., 67, 1566 (1945): W. N. Maclay and R. M. Fuoss, ibid., 73, 4065 (1951)) has shown that such systems, as usually measured, exhibit an ionic conductance which depends on the voltage used, in the measurements and on the duration of the test. Furthermore,...
chapter
As part of a general investigation of insulating oils, a study was made of the effect that different types of additives have on the dielectric strength of mineral oil and oil impregnated paper capacitors. The additives were chosen from a group of compounds having known effects on the gassing of oils under a.c. voltage and on the d.c. life of capacitors.
chapter
In recent years repeated reports from the Los Angeles area have described phenomenally high concentrations of ozone attended by accelerated cracking of stressed rubber. These incidents are associated with aerial “smog” in which, among other pollutants relatively high concentrations of organic peroxides are noted. Since the accelerated cracking of rubber is said to occur only in periods of sunshine...
