摘要:

On the assumption that the colors observed on the fracture surfaces of poly(methyl methacrylate) are due to interference in a thin layer of structurally modified material, the peculiar arrangement of the colors can be explained if (a) the mean fracture plane lies centrally within modified layer and (b) the fracture surface is regularly biplanar. Compliance with the first condition would be expected from the mechanical system which obtains during fracture. Interference microscopy shows that the surface topography is in accord with second condition. The occurrence of hyperbolic surface features, due to the initiation of a secondary fracture, introduces only a temporary disturbance in the general pattern. Evidence for the mechanism of formation of the hyperbolas is also found in the interference micrographs.

ISSN:0021-8979    

DOI:10.1063/1.1728820

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The relation between the dislocation density &rgr; in the surface of a crystal and the dislocation length per unit volume &Lgr; is calculated assuming either isotropic distribution in space or isotropic distribution in one or several glide planes. It is found that for practically all purposes the relation &Lgr;=2&rgr; can be used.

ISSN:0021-8979    

DOI:10.1063/1.1728821

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

It has been found that various refractory oxides can be crystallized from molten PbO&sngbnd;PbF2and Bi2O3&sngbnd;BiF3solutions. The PbO&sngbnd;PbF2solvent has proved successful for the growth of high alumina compounds including aluminum garnets, rare‐earth orthoaluminates, spinels, magnetoplumbite‐type aluminates, aluminum oxide, and the divalent oxides BeO and MnO. The Bi2O3&sngbnd;BiF3system has proven successful for the growth of the ferrite GaFeO3. The stability ranges of these various compounds is discussed in addition to problems of doping and attainment of large single crystals.

ISSN:0021-8979    

DOI:10.1063/1.1728822

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Crystals of aluminum, oriented for single slip, were deformed up to 1% glide strain. Specimens for diffraction electron microscopy were prepared, and direct observations on dislocations were made. The presence of three‐dimensional tangles as well as small prismatic dislocation loops was established. Considerations have been made as to how the tangles were formed. It was further concluded that dislocations move in glide zones, mainly between tangles which can act as sources for dislocations and as obstacles against their motion.

ISSN:0021-8979    

DOI:10.1063/1.1728823

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Neilson and Benedick have reported an anomalous piezoelectric behavior for negatively‐oriented synthetic alpha‐quartz crystals when subjected to transient stress of about 65 kbar. This paper describes the piezoelectric behavior of negatively‐oriented quartz in the stress region of from 5 to 50 kbar. The first indication of anomalous behavior occurs at 8 kbar. Between 8 and 24 kbar the negativex‐current waveforms show evidence of partial electric breakdown in the quartz. Between 25 and 34 kbar disruptive breakdown occurs. Above 34 kbar disruptive breakdown is followed by gross conduction with positive currents being observed for stress greater than about 50 kbar. The fields associated with the piezoelectric behavior are lower than the field for steady‐state electric breakdown at atmospheric pressure. It is proposed that the anomaly is triggered by stress‐induced dislocation motion resulting in liberated electrons which are accelerated into the stressed region of the specimen by the high negative electric field.

ISSN:0021-8979    

DOI:10.1063/1.1728824

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A new technique for measuring relative changes in thin film thickness is utilized as a means of monitoring sputtering yields at low energies. The apparatus consists of a Hitachi HU‐10 electron microscope with an ion source attached to it which allows exposure of the specimen to ion bombardment before and after monitoring transmission current of electrons through it. Operating the microscope in the selected area diffraction mode, the electron beam current is monitored by a Faraday cup placed in the microscope at the position of the final diffraction pattern image. Relative changes in thickness as low as 4 Å for 100‐Å thick films are measured. A scanning technique avoids contamination buildup during the electron transmission measurement. The specimens monitored have shown a high degree of uniformity with variations in sample thickness less than the estimated error of the measurement. The sensitivity of this method is limited only by available ion current densities rather than total current to the specimen. In principle, mass losses of 2×10−14g are detectible by the electron beam probe of 2‐&mgr; diameter. The apparatus has been applied to measuring sputtering yields of polycrystalline silver thin films as a function of energy at normal incidence utilizing argon, krypton, and neon as the bombarding ions. The results in an energy range from 30 to 200 ev agree qualitatively with those of Koedam, particularly with regard to the mass variation. The sputtering yields for Kr+ions on Ag is intermediate to that of Ar+and Ne+. At 30 evS≃2×10−4for Kr+on Ag.

ISSN:0021-8979    

DOI:10.1063/1.1728825

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

On the basis of observations on the etching and dissolution behavior of LiF crystals in aqueous solutions of fatty acids, it is suggested that certain solution phenomena previously considered anomalous are no longer so, once the significant role of lattice defects and step‐poisons in the dissolution process is appreciated.

ISSN:0021-8979    

DOI:10.1063/1.1728826

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A simplified cylindrical distribution function is proposed, which yields a considerable amount of structural information concerning moderately oriented noncrystalline fibers. This function can be obtained with only a small fraction of the labor required for the complete cylindrical distribution function. It is the transform of the difference between the scattered intensity and its average over the polar angle in reciprocal space, and is calculated by means of an expansion of the Fourier‐Bessel integral in spherical harmonics. Because all isotropic contributions to the scattered intensity are automatically omitted from the calculation, no consideration need be given to independent scattering, air scattering or, as a rule, the contribution of extraneous wavelengths. The resulting function is the difference between the cylindrical and radial distribution functions on an arbitrary scale, measured from an unknown baseline. Although these features limit the information obtained, that which is obtained is of considerable use in elucidating fiber structures.

ISSN:0021-8979    

DOI:10.1063/1.1728827

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Four types of measurement on thin Permalloy films are discussed which in the coherent‐rotation theory yield equivalent values for the anisotropy fieldHk: (A) Hysteresis loop; (B) high field torque; (C) rotational hysteresis; (D) torque 90° to the easy axis. Results reported for several films show that the values obtained from (A) and (B) agree reasonably well, while the values from (C) and (D) are found to be too high and too low, respectively. These discrepancies are explained in terms of a dispersion in both the magnitude and direction of the anisotropy. A torque method to determine an effective dispersion is outlined and illustrated for a particular case.

ISSN:0021-8979    

DOI:10.1063/1.1728828

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

It is shown that the very low threshold energies for sputtering, measured with highly sensitive methods (surface ionization, radioactive deposits, spectroscopic method), immediately after applying a ``clean‐up'' sputtering with higher ion energy, are due to the fact that the applied intermediate sputtering produces on the target upper‐most surface atoms with reduced binding energies ranging from a maximum to a minimum number of bonds. The lowest ion energy, at which a yield can be measured in the described manner, is just sufficient to remove the latter atoms and is defined as the ``minimum‐bond'' threshold. The thresholds, formerly determined for polycrystalline targets at normal ion incidence without intermediate sputtering for many metal‐ion combinations by ``detection of deposits'', correspond to the ``full‐plane'' thresholds, necessary for sputtering of atoms, having the maximum number of bonds, and represent the lowest ion energies at which continuous, i.e., plane by plane, sputtering of the target surface is feasible. The ratios of the ``full‐plane'' thresholds to the ``minimum‐bond'' thresholds, the latter measured at exclusively normal ion incidence with a sensitive method, after intermediate sputtering with a higher ion energy, are assumed to be the same (about 2:1) as calculated for a polycrystalline surface from the ratio of the binding energies of an atom in a full plane to the binding energies of an atom on top of a full‐plane area. The larger ratios (about 3:1) of the formerly measured ``full‐plane'' thresholds to the very low thresholds, as measured with highly sensitive methods, are shown to be probably due to boubly‐charged ions and to oblique ion incidence, which are exclusively active at the lowest ion energies.

ISSN:0021-8979    

DOI:10.1063/1.1728829

出版商:AIP    

年代:1962

数据来源: AIP