摘要:

A specimen of iron containing 0.01% of C in solid solution has been cold worked by 7% and aged at room temperature. After this treatment it shows a new peak of magnetic viscosity at 180°C. The diffusion process giving rise to the peak is controlled by an activation energy of about 32 000 cal/g atom and a time constant at infinite temperature of about 10−14sec. These figures agree with those of a peak of internal friction observed in similar specimens by Keˆ and by Ko¨ster, and interpreted as due to diffusion of C atoms in the surroundings of the dislocations. Hence the peak of magnetic viscosity can be related to the same mechanism.

ISSN:0021-8979    

DOI:10.1063/1.1735045

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The sintering of zinc oxide spheres has been studied in the temperature range 700 to 900°C in air, oxygen, helium, and hydrogen. Fresh zinc oxide sinters rapidly in air and oxygen, but it does not sinter appreciably in helium in the same temperature range. Zinc oxide spheres annealed separately in air may not be sintered in air at temperatures as high as 1100°C. On the other end, fresh spheres, separately air annealed and subsequently treated in an hydrogen atmosphere, do sinter in the temperature range 700 to 900°C. These facts are explained on the basis of a mechanism involving the diffusional transfer of stoichiometric excess of zinc ions. The diffusion equation for zinc ions is derived, and the experimental points fit the equation satisfactorily. The treatment shows that the relationship between the width of bridges connecting sintering spheres and time varies with extent of sintering. This fact invalidates the use of this relationship as a unequivocal diagnostic criterium for the sintering mechanism in nonstoichiometric oxides.

ISSN:0021-8979    

DOI:10.1063/1.1735046

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

An attempt is made in this discussion to determine the energy deposited in a small sample in terms of impinging reactor radiations, both neutron and gamma ray. The intensities of various radiations from a nuclear reactor are often presented in terms which are difficult to manipulate or interpret for energy deposition considerations. For example, the epithermal neutron flux is usually given as the integral neutron flux above the 0.4 ev cadmium resonance. However, for some energy deposition mechanisms, such as proton recoil, the neutron energy distribution is of utmost importance. These difficulties are partly resolved in this paper by using some empirical evidence of the characteristics of reactor radiations to convert the usual expression of intensities into energy deposited per gram‐hour in polyethylene. This can be easily extended to other materials, particularly polymers. It is also emphasized in this paper, by specific calculations for two reactor types, that certain simplifying assumptions, which are often made with regard to the characteristics of reactor radiation, are invalid in energy deposition considerations.

ISSN:0021-8979    

DOI:10.1063/1.1735047

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The distribution of imperfections within the interior of crystals has been studied using ``projection topographs'' which are x‐ray diffraction images showing a projection of a slice of crystal and the imperfections in it. Individual dislocations have been observed in single crystals of diamond, silicon, germanium, lithium fluoride, sodium chloride, silver chloride, magnesium oxide, calcite, quartz, and aluminum. From the variation of dislocation contrast with the orientation of the x‐ray reflecting plane the direction of Burgers vector can be found. Dislocations can be seen with good contrast when the product of linear absorption coefficient &mgr; and slice thicknesstis of the order of unity or less. If &mgr;t≫1 the contrast is reversed through the Borrmann effect. Stereo pairs of projection topographs can be prepared from the pair of reflectionshklandh¯k¯l¯.

ISSN:0021-8979    

DOI:10.1063/1.1735048

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

An ultrasonic interferometer technique for measuring the temperature dependence of relative changes in elastic constants has been utilized to study the variation ofc11for germanium. Results are reported for measurements carried out as a function of frequency from 30 Mc/sec to 170 Mc/sec for compressional wave propagation along the [100] direction in two sets of compatible germanium samples over the temperature range from −60°C to 0°C. The mean value of (1/c11) (dc11/dT) is 78.87×10−6(°C)−1, and no systematic frequency dependence of (1/c11) (dc11/dT) was found.

ISSN:0021-8979    

DOI:10.1063/1.1735049

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A mathematical analysis has been made of the breakup of liquid drops in an air stream; only the mechanism in which the drops flatten, become bowl‐shaped, inflate like a parachute, and finally burst is considered. The analysis provides an understanding of this process of breakup and the conditions for which the viscosity and surface tension become important factors. An estimate of the breakup time for a wide range of conditions is obtained as a function of the drop diameter, surface tension, viscosity, drop density, air density, and velocity difference. The results are compared with the available experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1735050

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Small metal spheres are bombarded by uniform Hg+ion beams of low energy (125 to 800 ev). Comparison of shadow micrographs of the spheres before and after sputtering makes it possible to determine the influence of the angle of incidence on sputtering yields. Fe, Ta, and Mo showed a pronounced increase in yield at more oblique incidence of the ions while Au, Ag, and Pt showed this effect only slightly.

ISSN:0021-8979    

DOI:10.1063/1.1735051

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The resistance of diamond to wear is a strong function of its orientation. The observed facts can be explained by assuming that a scratched diamond surface fails in tension behind the scratching particle. The octahedral cleavage planes are most easily pulled apart and give rise to the strong dependence of wear on crystal orientation.

ISSN:0021-8979    

DOI:10.1063/1.1735052

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Frequently, the only serious obstacle which prevents one from obtaining a physically interpretable solution to a Wiener‐Hopf problem is the explicit factorization of the ``kernel'' of that problem. A technique whereby an easily factored kernel replaces the original without serious loss of accuracy is illustrated by several examples.

ISSN:0021-8979    

DOI:10.1063/1.1735053

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Calculations are made for the power output and the efficiency of energy conversion of a thermomagnetic generator. Particular attention is paid to the use of the ferromagnetic element gadolinium as a suggested material for a practical device for the generation of electrical power from a low grade heat source (i.e., in the neighborhood of 20°C).

ISSN:0021-8979    

DOI:10.1063/1.1735054

出版商:AIP    

年代:1959

数据来源: AIP