摘要:

Photomicrographs were made of the electrode gap between a spherical molybdenum anode and a like stainless steel cathode at voltages near the breakdown limit. At a discrete voltage for a particular gap, ionized patches of about 0.05 mm in diameter appeared on the anode surface. These ionized areas increased in luminosity and number with voltage until one or more degenerated into a highly unstable incandescent spot undergoing severe localized heating. Both of these events lead to breakdown at these sites, providing evidence for a complex vacuum breakdown process related to the prebreakdown discharges observed.

ISSN:0021-8979    

DOI:10.1063/1.1729561

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Single‐crystal films of copper of 700–800 Å thickness have been prepared showing high densities of wide stacking faults. Variations in the annealing treatment of the films affect the nature of the imperfections occurring in the film.

ISSN:0021-8979    

DOI:10.1063/1.1729562

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

In the general liquid‐like binary three radial densities relating toA‐A, B‐B, andA‐Bpairs are needed to characterize the scattering. The three densities can be obtained by the Fourier inversion of the weighted combination of three diffraction patterns, each of which differs by the alteration of the scattering of one or both components. If the density of atoms regardless of type is the same around both components, then only two functions, one this distribution, and the other involving the order betweenA‐Bpairs is needed to characterize the scattering. This case is the liquid analog of the crystalline alloy with short‐range order. These two functions can be obtained by the Fourier inversion of a weighted combination of two patterns differing by the alteration of the scattering of the components.

ISSN:0021-8979    

DOI:10.1063/1.1729563

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Equations are derived giving the temperature distribution within a thin slab of material which has received a short pulse of energy on one surface, for the case in which energy loss at the surfaces (by radiation or convection) is not negligible. An analysis of these equations indicates that measurement of thermal diffusivity by the pulse method should be feasible even when losses are so large that the maximum temperature of the far face is only 10 or 20% of the no‐loss value; this includes nearly all materials, and temperatures to 2500°K or higher.

ISSN:0021-8979    

DOI:10.1063/1.1729564

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The collision of plates at high velocity sometimes causes them to be metallurgically bonded. A study has been made of the nature of the bonds and of the conditions required to produce bonding. A necessary requirement is the formation of a jet in the space ahead of the region of impact. When the collision region moves along the plates at a velocity which exceeds the bulk sound velocity of both materials, the relative velocity of the plates must exceed a critical value for jetting. Clarification of these critical conditions in symmetric collisions, and a correct extension to asymmetric collisions have been obtained by consideration of the effect of downstream boundary conditions on the configuration of the shock waves attached to the collision line in the jetless case. When the velocity of the collision is subsonic, bonding is obtained when the elastic strength of the material is exceeded. Metallographic examination shows that three types of bond may be formed: (1) a direct bond, (2) a uniform layer of solidified melt, and (3) a wavy interface with discrete regions of solidified melt alternating with regions of direct bond. Consideration of the flow indicates the following: (1) the direct bond results from the removal of the surface layers as part of the jet, (2) the alloy results from the melting caused by entrapment of the high‐velocity jet between the plates, and (3) the wavy interface is caused by an oscillation in the jet flow which produces the mixed type of bonding. The thickness of the continuous alloy layer, which greatly exceeds the calculated jet thickness, indicates that entrapment of the jet dissipates most of the kinetic energy lost in the collision. Analysis of the layer indicates a composition and structure which is expected from the rapid quenching of a well‐mixed melt.

ISSN:0021-8979    

DOI:10.1063/1.1729565

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

An experimental program was conducted to investigate the properties of the unresolved rotational fine structure of the NO &ggr;00band. The experimental values were taken spectroscopically in absorption at controlled temperatures.An analytic expression representing the unresolved fine structure is utilized to compute absorption coefficients and absorption intensities for the experimental temperatures. A doublet model and a singlet model of the band are investigated.From the experimental absorption coefficients, temperatures are determined to within 6% of the directly measured values. The rotational constants of the upper and lower states are determined to accuracies of 13 and 6%, respectively, of the known values.

ISSN:0021-8979    

DOI:10.1063/1.1729566

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Evaporated or sputtered metal films of less than 100 Å average thickness are generally discontinuous and consist of a plane array of finite but very small particles. The level spacing of quantized electronic states becomes greater thankTfor microparticles of this size. The electrical conduction mechanism of tunneling is dominated by transitions from the first excited level of one particle to the corresponding level in the next. The electrical conductivity is derived assuming tunneling as the conduction mechanism and results in an exponential dependence on reciprocal temperature in the limit of zero applied electric field. The activation energy depends on the particle size and is the difference in energy between the ground and first excited electronic levels in the particle. The results are in good agreement with published experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1729567

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Zinc sulfide powder was heated in a double crucible arrangement at 1150°C for one to three hours. X‐ray diffraction measurements showed the development of hexagonal sulfide (wurtzite) and some oxide (zincite). On a thin platinum ribbon introduced to aid the study of crystal growth, several well‐developed hollow crystals were found. By transmission electron diffraction measurement, these unusual crystals were identified as hexagonal zinc sulfide.

ISSN:0021-8979    

DOI:10.1063/1.1729568

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The general analysis of uniformly moving dislocations in anisotropic media is applied to investigate the dynamical behavior of dislocations in the primary slip systems of body‐centered cubic crystals. Both edge and screw dislocations on the {110}, {112}, and {123} slip planes are considered; in each case, the Burgers vector of the dislocation lies along a ⟨111⟩ direction. Numerical solutions are obtained for the force exerted by a uniformly moving dislocation on a parallel dislocation of similar type on the same slip plane. The bcc elements treated are niobium, molybdenum, vanadium, tungsten, tantalum, iron, potassium, sodium, and lithium. Calculated values of the limiting velocities both of edge and screw dislocations are presented, as well as the threshold velocities for the interaction of two edge or two screw dislocations. These calculations determine, for each slip system in each of the elements listed, the extent of the velocity range of anomalous behavior in which two like dislocations attract rather than repel each other.

ISSN:0021-8979    

DOI:10.1063/1.1729569

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Pulsed laser operation has been produced by complete internal reflection in a ruby ring at room temperature. The linearized equations of Statz and de Mars give a good description of the steady state laser operation. The lifetime of the excited Cr3+ions is found to be ∼1 &mgr;sec under operating conditions. We have observed short‐lived transient oscillations rather than spikes in the laser output. This result can be tentatively explained by assuming a cavityQof 108–109.

ISSN:0021-8979    

DOI:10.1063/1.1729570

出版商:AIP    

年代:1963

数据来源: AIP