Internal Electrical Resistance Research Articles

Einfluß von Neutronenbestrahlung bei 4 °K auf den Schermodul von Kupfer, Aluminium und Platin

Abstract The change of the shearmodulus of pure polycrystalline Al, Cu and Pt due to reactor neutron irradiation at 4 °K has been studied. The shearmodulus was determined by measuring the vibrational frequencies of a helical spring in two different modes (between 50 and 300 Hz) together with internal friction and electrical resistance. Large relative decreases of the shearmodulus ΔG/G per molar fraction c of Frenkel defects were found, namely ΔG/Gc - 47, - 39, - 67 for Al, Cu and Pt, respectively. The absolute values are much larger than expected from lattice theory. The effects cannot be explained by a relaxation of the defects.

Dielectric Breakdown and Recovery of X-Cut Quartz under Shock-Wave Compression

While a shock wave is traversing a disk of X-cut quartz, a piezoelectric current flows in an external circuit connected across the faces of the disk. In this paper measurements of this current are used to study dielectric breakdown and subsequent recovery which occurs in quartz. Quartz specimen disks were impacted at various stress levels in such a way as to produce shock waves that propagated along the X axis either in the direction of or opposite to that of the pressure-induced polarization. In the latter case, short-circuit current measurements show that breakdown occurs at a threshold stress greater than 10 and less than 13 kbar. Since the impact experiment produced one-dimensional electrical and mechanical conditions in the specimen disk, it was possible to formulate a mathematical model that permitted solutions for internal electrical fields and resistivity in terms of the measured current. Computations with this model show that the field in the stressed portion of the disk at breakdown is about 7.0×105 V/cm, which is an order of magnitude lower than the value observed at atmospheric pressure. Computations with the model also show that recovery from breakdown to essentially infinite values of resistivity occurs during the transit time of the shock wave when the field in the stressed region of the disk is ``quenched'' to a value of about 1.9×105 V/cm. This critical field appears to be the same for all shock stress levels investigated from 13 to 35 kbar. The dependence of the initiation of breakdown on the direction of wave propagation relative to the polarization direction indicates that the shock-wave front furnishes a source of free electrons.

Semiconducting ceramic barium lanthanum titanate doped with iron

The formation of semiconductive properties in polycrystalline barium titanate when doped simultaneously with lanthanum and iron is brought about by a substitution mechanism similar to that proved to work in BaTiO3 doped with bismuth and iron. A broader validity has thus been confirmed of the substitution model previously proposed to explain the considerable change in internal electric resistance of barium titanate containing trivalent ions in barium positions when iron ions are introduced. In contrast to barium bismuth titanate, with barium lanthanum titanate an increasing addition of iron leads to the successive formation and destruction of several types of perovskite crystals differing in electrical conductivity and Curie temperature.

Equation of state and electrical resistivity of liquid mercury at elevated temperatures and pressures

Abstract Experimental results have been obtained for the density and electrical resistivity of liquid mercury as functions of the independent variables temperature (20°c–1000°c) and pressure (0–1000 bars). Basic equipment for both measurements consisted of a steel vessel containing an internal electrical resistance furnace and pressurized with argon gas. The equation of state was determined with an accuracy of about ±1/4% using Archimedes' method by employing a series of totally immersed radioactive sinkers whose rise or fall in the mercury was detected with a γ-ray counter external to the pressure vessel. The electrical resistivity was measured with an accuracy of about ±1/2% using a four-lead resistance cell fabricated in fused silica. The two measurements have also been combined to give electrical resistivity at constant volume.

Electrode kinetic aspects of electrochemical energy conversion

The basic similarities and dissimilarities among the three electrochemical devices-electrochemical substance producer, electrochemical electricity producer and electrochemical electricity storer — are presented. Expressions are derived for the terminal cell potential, differential resistance, efficiency and power of an electrochemical electricity producer as a function, of the current drawn from it. These expressions have been used in numerical calculations to examine the effect of the various factors ( e.g., exchange currents, limiting currents, ohmic internal resistance) on the performance of the electrochemical energy converter. Analytical expressions for the maximum power, the terminal cell potential and the current, when the power is a maximum, are derived for two special cases. The importance of electrocatalysis from the point of view of improving the performance of electrochemical electricity producers is stressed. Recent work on the kinetics of the important oxygen electrode reaction and on the mechanism of electroorganic oxidation is discussed. Some models of electrode design for increasing the apparent current density (and thereby reduce efficiency and power losses) are dealt with theoretically.

銅-鉄合金の高温時効に伴なう内部摩擦の変化について

The changes in internal friction, hardness, electrical resistivity, magnetic properties and microscopic structure of 2.3, 5.4 and 9.6 wt% iron-copper alloys by aging at the temperatures from 600° to 750°C, were studied. During the aging process, the hardness change shows a single peak, while the electrical resistivity decreases in the stage of age-hardening and reaches an equilibrium state before the hardness reaches a maximum. In 2.3 wt% iron-copper alloys, there is no change of internal friction in the stage of age-hardening, but in the stage of over-aging, the internal friction increases remarkably. At the same time, the amplitude dependence appears and the break-away point shifts to the lower amplitude side with aging time. In the 5.4 and 9.6 wt% iron-copper alloys, the internal friction decreases in the stage of age-hardening and the change of internal friction in the stage of over-ageing is similar to that of the 2.3 wt% iron-copper alloys. The above change of internal friction in the stage of over-ageing begins at a shorter aging time with rising aging temperature and increasing iron concentration. This change of internal friction is related to the growth of the precipitate particles. Internal friction of copper-iron alloys in this study is neither a relaxation-type of energy loss nor a magnetomechanical hysteresis energy loss due to the precipitate, but it is a hysteresis energy loss of vibrating dislocation. On the basis of these results, the change of coherency between the matrix and the precipitate and hardening mechanism in these alloys have been discussed.

Kinetics of carbon precipitation in irradiated iron—III. Calorimetry

Internal friction and electrical resistivity measurements associated with the removal of carbon from solution in iron have indicated that in irradiated specimens the carbon is trapped at defects before it precipitates. The binding energy of carbon to these defect traps was measured by calorimetry and found to be 0.41 eV/atom. It is concluded, therefore, that no precipitate with a binding energy for carbon of less than 0.41 eV/atom will be formed in an iron-carbon alloy that has been irradiated to a dosage sufficient to trap all of the carbon atoms. In unirradiated iron-carbon the energy released per carbon atom in forming the metastable carbide precipitate was found to be 0.27 eV/atom, which explains why this carbide is not formed in irradiated alloys.

内熱法によって製造されたフッ素金雲母壁開面のHFによるetch

内熱法によって製造されたフッ素金雲母壁開面のHFによるetch

Internal Stress and Electrical Resistivity of Evaporated Antimony Films

Internal stress and electrical resistivity are simultaneously determined for evaporated antimony films during and after evaporation. At first antimony is deposited in the amorphous state. When a critical thickness is reached, the film begins to cristallize giving rise to large intrinsic stress. The dependence of stress upon film thickness, evaporation rate and substrate temperature is experimentally studied. The results can be explained by variation in the effective critical thickness, deff, which is defined as the film thickness at which crystallization of the antimony film proceeds most vigorously.

内熱式電気溶融法による合成雲母製造における通電開始法の改良と定電圧徐冷方式による実験

内熱式電気溶融法による合成雲母製造における通電開始法の改良と定電圧徐冷方式による実験

内熱式電気溶融法による合成雲母製造実験(第1報)

内熱式電気溶融法による合成雲母製造実験(第1報)

Die teilchenform bei der karbidausscheidung aus dem α-eisen

Precipitation of carbide in α-iron is investigated in more detail, combining the two experimental methods of internal friction and electrical resistivity. This combination yields a parameter which is solely dependent on particle shape. The parameter is equal to a coefficient β, which indicates the variation of electrical resistance caused by unit precipitation. The dependence of the parameter on particle shape is theoretically computed. Using experimental data, the values of the deduced parameter indicate that the precipitated particles are plate-like. Furthermore, during precipitation the ratio “plate-diameter: plate-thickness” decreases, i.e., coagulation takes place. These results are compared with those of electron micrographs published elsewhere and with Zener's growth law of precipitation.

Some Properties of Columbium Containing Nitrogen

Quench aging of supersaturated solid solutions of nitrogen in columbium takes place in reasonable times in the temperature range 300° to 500°C. Changes in internal friction, hardness, and electrical resistivity are found to accompany this change.

RECENT METHODS AND TECHNIQUE OF PHOTOELECTRIC PHOTOMETRY

During the last ten years a number of changes have been made in the methods of electrical photometry. True, the fundamental principles involved are still the same; the art depends upon the current generated by a photoelectric cell for a given amount of incident light, but the means of measuring this current have undergone considerable improvement. The photocell is an electrical device having an extremely high internal electrical resistance; the natural result is that the current generated by the cell is small, and the electrical circuit of the cell itself, loosely connected to the rest of the circuit as it is, is of high sensitivity and therefore easily influenced by variations in surrounding conditions. Ten years ago the photocurrent was not measured directly; instead, a rate of accumulation of charge was measured by means of timing the deflection of a sensitive electrometer. This method had several drawbacks which have been rectified by the introduction of the amplifying tube in 1932. The electrometer is, mechanically, a very frail and sensitive instrument, not well adapted to semiportable operation on the end of a telescope. The natural result was that under such unfavorable conditions, a special rugged type of electrometer was employed, and theoretical limits of sensitivity and stability were not attained. In addition, the fact that the electrometer depended upon the air for its damping effect made it necessary to operate the entire sensitive portion of the electrical circuit in this somewhat subversive medium. Even when care was taken to insure dryness of the air by some artificial means, the performance of the photometer could not always be depended upon, and photometers sometimes behaved in strange and quite exasperating ways. The introduction of the low-grid-current Pliotron type of vacuum tube made it possible to remove the mechanically delicate parts of the equipment from the telescope itself, and furthermore made practical the removal of air from the vicinity of the sensitive photocell circuit. The use of direct-current amplification with photocell and ampli-