摘要:

Single crystals of polypropylene consisting of lamellas have been grown from the melt. Electron diffraction patterns indicate that the molecules are folded within the lamellas and have crystallized in a hexagonal unit cell.

ISSN:0021-8979    

DOI:10.1063/1.1702480

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A thermodynamic analysis is given for an energy conversion process which employs the phase transition in a superconductor. The conversion process is a cyclic one. An expression for the conversion efficiency is obtained. Quantitative estimates are calculated from the formula for several superconducting materials. These indicate that conversion efficiencies as high as 44% may be obtainable under ideal conditions.

ISSN:0021-8979    

DOI:10.1063/1.1702481

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Frank's vector formula defining low‐angle boundaries is rewritten into six independent scalar equations which can be represented in the form of three simple two‐dimensional vector diagrams. These diagrams facilitate the discussion and construction of low‐angle boundaries, and in particular allow to construct four‐grid boundaries due to glide dislocations on arbitrary planes.

ISSN:0021-8979    

DOI:10.1063/1.1702482

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Copper specimens were subjected to large dynamic tensions by colliding relatively thin plates with thick plates holding the samples. The collision first produces strong shock waves, from 300 to 600 kbar, that propagate in both directions from the impact interface. Subsequent interaction of the two rarefaction waves resulting from these shock waves produces tensions that cause the material to disintegrate rather than to break in the ordinary manner. Comparison of these recovery experiments with corresponding hydrodynamic calculations show that the yield strength of copper is in excess of 150 kbar. The equation of state of copper used in the calculations is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702483

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The quantum‐mechanical calculations of Huntington and Seitz, of Huntington, and of Brooks led to a value of about 1 ev for the formation energy of a vacancy in copper. After a brief outline of these calculations, it is shown that in the light of recent experimental and theoretical work, the contributions of the electrostatic self‐energy and Fermi energy of the valence electron must be corrected. These corrections lead to a final value of about 2 ev.

ISSN:0021-8979    

DOI:10.1063/1.1702484

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Photoelectric emission studies have been made for the (111) and (1¯1¯1¯) surfaces of ZnTe which were cleaned in high vacuum by the ion bombardment and annealing process. Differences in the adsorption and etching properties reflected the asymmetry in atomic species on the two faces. The (111) or Zn face was insensitive to oxygen adsorption at room temperature while the (1¯1¯1¯) face adsorbed oxygen with a sticking coefficient of about 10−3. The photoelectric properties of both surfaces were varied by the adsorption of water vapor.

ISSN:0021-8979    

DOI:10.1063/1.1702485

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Changes in the elastic modulus and internal friction of plastically deformed rocksalt, caused by changes in the mean free length of oscillating dislocation segments, have been observed during x‐irradiation at temperatures ranging from 10° to 300°K. The rates at which the modulus and damping changes occur during irradiation are found to be independent of temperature; but during irradiation at helium temperature, the magnitude of the effects are smaller. This decrease in magnitude has been shown to be due to the absence of thermal unpinning. Explanations of the pinning process based on the diffusion of point defects to dislocations appear to be ruled out by the rapidity of the low temperature modulus change.The dislocation pinning produced by irradiation of NaCl, KCl, KBr, and KI at low temperatures is found to be reversible when the crystals are subjected to illumination in, or near, the visible. The wavelength of the illumination which produces the maximum unpinning increases as the lattice constant increases; the effect disappears when the crystals are warmed to room temperature. However, at all temperatures, bleaching a deformed and partially irradiated crystal withFlight causes a further modulus increase. The pinning point produced by low temperature irradiation is identified as a dislocation jog in close association with anFcenter whose absorption band is displaced towards the red by the dislocation strain field. Ionization of theFcenter results in recombination of its vacancy with the jog; warmup allows theFcenter to diffuse beyond recombination range.

ISSN:0021-8979    

DOI:10.1063/1.1702486

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A perturbation analysis of single stream, quasi‐static, nonrelativistic electron flow is developed, based on the nonlinear equation for the velocity field. The analysis is applicable to electron beams originating from a cathode at which the magnetic field is tangential. The consistent development of perturbation theory from the velocity field viewpoint makes unnecessary the tenuous physical arguments usually employed and resolves some of the related controversy. The surface charge and current usually assumed to replace the perturbed flow boundary are shown to be an interpretation justified by the rigorous application of the theory. The generality of the formulation makes simple the writing of the differential equation for the first order perturbation of any flow satisfying the stated conditions.

ISSN:0021-8979    

DOI:10.1063/1.1702487

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Measurements are reported of the number and energy of the electrons which rebound from thick metal targets bombarded at normal incidence by monoenergetic electrons of from 1 to 3 Mev. The ratio of back‐scattered to incident electron current, measured for twelve metal targets, was found to vary from 0.47 for 1‐Mev electrons incident on U to 0.01 for 3‐Mev electrons on Be. The total energy scattered backward from targets of Al, Cu, and Pb bombarded with 1‐ to 3.5‐Mev electrons was determined by calorimetric methods. This energy diminished from 34% of the incident energy for Pb bombarded with 1‐Mev electrons to 1% for Al bombarded with 3.5‐Mev electrons. The dependence of the number and energy of the back‐scattered electrons on the atomic number of the target and on the incident electron energy is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702488

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Crystallographic polarity associated with the zinc‐blende and the wurtzite structures has been studied in the following II‐VI sulfides, selenides and tellurides; ZnS, ZnTe, CdS, CdSe, CdTe, HgSe, and HgTe. The CdS and CdSe have the wurtzite structure and the others the zinc‐blende structure. Consistent with theoretical calculations, the geometric structure factor for x‐ray scattering was found different in opposite directions along the polar axis. Consequently, the two types of surfaces perpendicular to the polar axis were identified. The etching behavior of these surfaces was correlated with the x‐ray results so that simple etching tests were developed for the identification of the {111} (zinc blende) or the {00.1} (wurtzite) surfaces.

ISSN:0021-8979    

DOI:10.1063/1.1702489

出版商:AIP    

年代:1962

数据来源: AIP