摘要:

A study by transmission electron microscopy was made of the microstructure of pure polycrystalline nickel foil after explosive‐shock loading and subsequent heat treatments between 600° and 780°C. In the instance of specimens shocked at 70 and 320 kbar, the deformation substructures resemble those normally caused by cold work, but the recovery process consists mainly in dislocation migration and recombination; no polygonization, nucleation, or grain growth are observed. Nickel shocked at 1000 kbar on the other hand, exhibits an extremely high density of dislocations, point defect clusters, and microtwins arranged in complex patterns. In this instance, heat treatment causes nonuniform polygonization, nucleation, and grain‐boundary migration. This results in a significantly lower dislocation density after annealing, particularly at the higher temperatures, and considerably more extensive softening than is the case for nickel shocked at lower pressures.

ISSN:0021-8979    

DOI:10.1063/1.1658110

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The Hugoniot of wrought tungsten which was 99.6% of the crystalline density and 99.92% pure has been determined to 80 kbar at room temperature and at 950°C. Measurements of the stress‐particle velocity relationship were made by impacting a sapphire‐faced quartz gauge assembly onto the tungsten sample. In the room temperature experiments, transmitted wave profiles were determined with quartz gauges. At room temperature, the elastic wave velocity was 5.22±0.05 mm/&mgr;sec and the Hugoniot elastic limit for 9.5 mm thick specimens was 37.7±0.8 kbar. The stress‐particle velocity Hugoniot at 950°C, while nearly parallel to the room temperature Hugoniot, was displaced about 15 kbar downward due to a decrease in the Hugoniot elastic limit at this temperature. This decrease is associated with a temperature induced brittle‐ductile transition. The application of these data in calculating the Gru¨neisen parameter is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1658111

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Thin films of the rare‐earth alloys of the Co&sngbnd;Sm system with and without the addition of Cu have been found to have exceptionally high coercive forces. A coercive force of 30 000 Oe was realized with Co3.65Cu1.35Sm films, 4000‐Å thick prepared at a substrate temperature of 500°C using getter sputtering. This technique avoids troublesome oxidation problems usually encountered in preparing films of active materials such as the rare‐earth compounds.

ISSN:0021-8979    

DOI:10.1063/1.1658112

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A simple model is proposed which predicts the composition of sputtered multicomponent thin films. The model is applied to such problems as alloy sputtering, gas incorporation into thin films, and compound formation. Several practical systems are considered such as the sputtering of Gd3Fe5and Ni4Fe alloys and the incorporation of argon, oxygen, and nitrogen into tungsten films. The results of these studies suggest that the film composition is a strong function of vapor pressure, sputtering rate, atomic size, system geometry, sticking probabilities, and sputtering coefficients.

ISSN:0021-8979    

DOI:10.1063/1.1658113

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Continued investigations of the thermoelectric properties of Au&sngbnd;Ni thin‐film thermocouples have been made. The thickness dependence of the Seebeck coefficient for Ni films of variable thickness on bulk Au was determined and found to be sensitive to the thermal history of the thin film thermocouples. By developing suitable preparation techniques for these thermocouples, involving several periods of annealing, time‐invariant calibration curves were obtained. The thickness dependence of the Seebeck coefficient was found to follow closely the predictions of the size‐effect theory of Mayer.

ISSN:0021-8979    

DOI:10.1063/1.1658114

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Experiments are described which examine the electrostatic contribution to the adhesion of powder particles to substrates. The fine powder in these experiments was dispensed over the large surface area of an assembly of glass beads and the adhesion of the particles to the larger beads was measured with a centrifuge. Complementing the adhesion measurements were charge measurements where the average charge density and also the incremental charge density were measured by gradually blowing the powder from the beads. A purely electrostatic point‐charge model for the adhesion of the particles was consistent with the observations in most cases. In some situations, however, an additional term was needed to better describe the adhesion, and this may have been either an electrostatic multipole phenomenon or a van der Waals contribution.

ISSN:0021-8979    

DOI:10.1063/1.1658115

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The physical parameters of colloidal carbon particles in an insulating liquid have been measured by several independent techniques. The particle size and charge, the Debye screening distance, and the interparticle distance are found and are used to interpret the electrographic development process (toning). The nature of the developed image depends upon the magnitude of the initial surface charge density and upon the time in the toning bath. The optical density for full development of an electrostatic charge image is shown to be proportional to the charge density in the image indicating that arriving particles overlap in a random manner. Measurements on the development process as a function of time shows that particles are being drawn out of the colloid in the intermediate range where both diffusion and mobility must be considered in determining the motion of the particles.

ISSN:0021-8979    

DOI:10.1063/1.1658116

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The effect of the detector slit length in measurements of the angular correlation of annihilation radiation is treated theoretically. A general formula is derived, which expresses the coincidence rate from a single crystal in terms of the anisotropic momentum distribution, and its behavior is investigated in the limits of very long and very short slits. The result for the special case of an isotropic momentum distribution is compared with an earlier result of Arifov, Gol'danskii, and Sayasov. It is further concluded that line slits are to be preferred to point slits for the measurement of strongly anisotropic momentum distributions, about which noa prioriinformation is available.

ISSN:0021-8979    

DOI:10.1063/1.1658117

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The heat capacity of colorless synthetic sapphire (&agr; Al2O3, corundum) has been measured from 2 to 25 K. The data above 14 K can be expressed asCv= 1.755×10−3T3+1.905×10−7T5mJ/K·g‐atom. This equation forCvgives &THgr;0= 1035 K, in good agreement with the values calculated from elastic constant data. An extrapolation of these results to higher temperatures is consistent with other data. Below 14 K an anomalous heat‐capacity contribution appears which is about 1.5% ofCvat its maximum. The magnitude of this anomaly corresponds to that which would be given by a few ppm of gaseous or transition‐metal impurities.

ISSN:0021-8979    

DOI:10.1063/1.1658118

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Internal partition functions for 18 diatomic molecules were computed by three different methods. The computations were performed for temperatures from 500° to 30 000°K. The methods of computation are (a) Mayer and Mayer approximation, (b) direct summation to dissociation limit, and (c) direct summation including states above dissociation limit. The variation in numerical results using these three methods is negligible up to temperatures of 5000°K, although there are some exceptions for molecules containing hydrogen. At higher temperatures the Mayer and Mayer approximation gives, for most molecules, excessive values for the partition function. An indication of the importance of including excited electronic states and excluding some first rotational states is also given.

ISSN:0021-8979    

DOI:10.1063/1.1658119

出版商:AIP    

年代:1969

数据来源: AIP