Showing papers in "Journal of Applied Physics in 1960"
TL;DR: In this paper, the surface energies of several simple crystals have been measured at −196°C by means of quantitative cleavage experiments and the measured values of their respective surface energies (ergs/cm2) are: 340, 1200, 450, 280, 230, 1240, and 105.
Abstract: By means of quantitative cleavage experiments, the surface energies of several simple crystals have been measured at −196°C. The crystals and their cleavage planes are: LiF (100), MgO (100), CaF2 (111), BaF2 (111), CaCO3 (1010), Si (111), and Zn (0001). Measured values of their respective surface energies (ergs/cm2) are: 340, 1200, 450, 280, 230, 1240, and 105. The measured values for LiF and MgO are in good agreement with simple ionic lattice theory. Values for the other crystals seem consistent with their binding energies.Under irreversible conditions an effective surface energy is measured. This quantity increases rapidly with increasing temperature for the metallic crystals, Zn and Fe (3% Si). The increase correlates with increasing plastic flow in these crystals. In contrast, the effective surface energy of LiF and MgO is only moderately dependent on temperature.A small amount of cadmium (0.1 at.%) markedly increases the cleavage surface energy of zinc.
740 citations
TL;DR: In this article, an effective Hamiltonian of an interaction between the orbital states of the Jahn-Teller ions through a canonical transformation was obtained, which associates each electronic state with a local lattice distortion, and by use of the mean field approximation.
Abstract: A theoretical overview of the cooperative Jahn-Teller effect in the insulating phase is given. We obtain an effective Hamiltonian of an interaction between the orbital states of the Jahn-Teller ions through a canonical transformation, which associates each electronic state with a local lattice distortion, and by use of the mean field approximation. The effective Hamiltonian yields a simple unified picture of cooperative distortions of various types. The competing effect of the spin-orbit coupling is discussed also. Electron itinerancy is briefly discussed at the end.
647 citations
TL;DR: Olsen and Hultgren as mentioned in this paper devised a technique by which small amounts of liquid alloys can be cooled at rates high enough to prevent the normal process of nucleation and growth of equilibrium phases.
Abstract: A technique has been devised by which small amounts of liquid alloys can be cooled at rates high enough to prevent the normal process of nucleation and growth of equilibrium phases. The classical method for achieving high rates of cooling consists of injecting a small droplet of molten alloy into a liquid quenching bath. Olsen and Hultgren used such a technique in a study of the effect of the rate of cooling on the homogeneity of solid solutions.(1)
627 citations
TL;DR: Graphite whiskers have been grown in a dc arc under a pressure of 92 atmospheres of argon and at 3900°K as discussed by the authors, with recoverable lengths up to 3 cm. They are embedded in a solid matrix of graphite which builds up by diffusion of carbon vapor from the positive to the negative electrode.
Abstract: Graphite whiskers have been grown in a dc arc under a pressure of 92 atmospheres of argon and at 3900°K. They are embedded in a solid matrix of graphite which builds up by diffusion of carbon vapor from the positive to the negative electrode. Diameters range from a fraction of a micron to over five microns, with recoverable lengths up to 3 cm. They consist of one or more concentric tubes, each tube being in the form of a scroll, or rolled‐up sheet of graphite layers, extending continuously along the length of the whisker, with the c axis exactly perpendicular to the whisker axis. They exhibit a high degree of flexibility, tensile strengths up to 2000 kg‐mm−2, Young's modulus in excess of 7×1012 dyne‐cm−2, and values of room‐temperature resistivity of around 65 μohm‐cm, which approximates the single crystal value.
592 citations
TL;DR: In this paper, the authors extended the Hugoniot loci into the one-to-two-megabar region for 19 metallic elements: Ag, Au, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sn, Th, Ti, Tl, V, W, Zn, Bi, Fe, Sb.
Abstract: Plane‐wave explosive systems were used to accelerate thin metal plates to high velocities. Shock pressures resulting from the collision of these driver plates with a stationary target plate are approximately three times greater than the original shock pressure in the driver plate. The photographic flash‐gap technique was used to record velocities associated with the shock waves. The new experimental data extend the Hugoniot loci into the one‐to two‐megabar region for 19 metallic elements: Ag, Au, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sn, Th, Ti, Tl, V, W, Zn, Bi, Fe, Sb.The Hugoniot P, V, E data have been extended to a more complete P, V, E, T equation of state by use of the Mie‐Gruneisen theory. The thermodynamic variable, γ=V(∂P/∂E)v, necessary for this extension, was obtained by solving the Dugdale‐MacDonald relation.
541 citations
TL;DR: In this article, photographic light scattering technique permits a measurement of the size, anisotropy, radial periodicity, packing, and internal structure of polymer spherulites.
Abstract: The photographic light scattering technique permits a measurement of the size, anisotropy, radial periodicity, packing, and internal structure of polymer spherulites. The theory of some of these effects is described, and experiments are presented showing changes occurring in the melting and growth of spherulites.
466 citations
TL;DR: In this paper, a more detailed analysis of the motion of the edge gives this result; the neglected contribution arises from inelastic acceleration of the undisturbed fluid up to the velocity of the edges.
Abstract: Subsequent to puncturing at a point, a horizontal soap film develops a hole whose edge, owing to surface tension, propagates outward from the point of puncture at apparently constant velocity. Measurements by Ranz [1] yielded results roughly 10% lower than those calculated on the basis of a simple energy conservation suggested by Rayleigh [2]. The discrepancy was attributed to an additional retarding viscous stress not included in the analysis. It appears, however, that the energy balance quoted [1] neglects an important contribution, indeed related to th viscous effect noted by Ranz, but which reduces the calculated values to 20% below those measured. A more detailed analysis of the motion of the edge gives this result; the neglected contribution arises from inelastic acceleration of the undisturbed fluid up to the velocity of the edge. The concomitant loss in mechanical energy may be identified with viscous dissipation which is estimated to be confined to a relatively thin region. Lack of agreement between calculated and measured values of the edge velocity seems to be causes by a second-order effect in the method used [1] to determine the thickness of the film.
462 citations
TL;DR: The role of the twin planes in the rapid dendritic propagation of germanium crystals is examined on the basis of corner nucleation in this article, and it is shown that at least two twin planes must be present for continued easy propagation in directions.
Abstract: The role of the twin planes in the rapid dendritic propagation of germanium crystals is examined on the basis of corner nucleation A model is proposed, and it is shown that at least two twin planes must be present for continued easy propagation in directions, in good agreement with experimental observations The absence of the dendrite with only one twin is explained
388 citations
TL;DR: In this paper, the velocities of unpinned edge dislocations in 3¼% silicon-iron have been measured as a function of stress over a range of five orders of magnitude in velocity from 10−7 cm/sec to 10−2 cm /sec.
Abstract: A method has been developed whereby the velocity of motion of fresh dislocations introduced into a crystal by scratching the surface may be measured as a function of stress. The velocities of unpinned edge dislocations in 3¼% silicon‐iron have been measured as a function of stress over a range of five orders of magnitude in velocity from 10−7 cm/sec to 10−2 cm/sec. The velocity has been found to be very sensitive to the applied stress in this velocity range. Measurements of velocity as a function of stress have been made for four temperatures in the range 78°K to 373°K. It has been found that over this range of temperature the yield stress changes with temperature in the same way as the stress to produce a constant velocity of dislocation motion. From the result it is concluded that the rise in yield stress at low temperatures exhibited by this silicon iron is due primarily to an increase in the lattice resistance to dislocation motion and not to an increase in the Cottrell locking force. Preliminary expe...
383 citations
TL;DR: In this article, the authors present experiments of dislocation multiplication, defect structure left behind by a moving dislocation, and cross-glide of individual dislocations in LiF crystals.
Abstract: Experimental observations are presented of dislocation multiplication, of the defect structure left behind by a moving dislocation, and of cross‐glide of individual dislocations in LiF crystals. New dislocation loops form at many different sites in the wake of a moving dislocation. These loops have the same Burgers vector as the parent dislocation but do not, in general, lie on the same atomic plane. The rate of formation of new loops depends upon the magnitude of the applied stress. Such creation of new loops leads eventually to the formation of a wide glide band.A moving screw dislocation trails many line defects behind it that lie parallel to its direction of motion. The existence and nature of these trails and the observed dislocation multiplication can be explained in terms of a mechanism which involves the formation, by cross‐glide, of jogs on a screw dislocation. This cross‐glide multiplication mechanism was originally proposed by Orowan and by Koehler. It is demonstrated that cross glide occurs easily in LiF, so that this mechanism is plausible. Some interesting complications arise when jogs are formed that are longer than several atomic spacings but less than several hundred. The defect trails exert a dragging of the screw dislocations that is not negligible compared to the yield stress of a crystal.
334 citations
TL;DR: In this paper, a self-shadowing model is proposed to explain chain growth, i.e., the area behind a crystallite is left vacant because it is in the crystallite's shadow.
Abstract: Magnetic anisotropy has been observed in evaporated Permalloy films deposited at oblique incidence of the vapor. Electron micrographs of such films reveal chains of crystallites whose long axes are oriented perpendicular to the vapor beam. A ``self‐shadowing'' model is proposed to explain chain growth, i.e., the area behind a crystallite is left vacant because it is in the crystallite's shadow. Oriented crystallite chains are thus caused by a purely geometric process; their existence has also been demonstrated for Au, Pt, W, and Mg. Oriented chains give rise to a number of macroscopic effects: magnetic anisotropy, anisotropic resistance, dichroism, and anisotropic resonance linewidth. Experiments involving the stripping of oblique‐incidence Permalloy films from their substrates indicate the presence of an anisotropic strain which, in conjunction with magnetostriction, gives another contribution to the magnetic anisotropy; this contribution explains the observed compositional dependence of the magnetic ani...
TL;DR: In this article, the effects of inhomogeneities on piezoelectric, galvanomagnetic, and thermocyclic measurements have been investigated and formulas for all the effects are derived which are asymptotically exact in the limit of small fractional fluctuations in the local conductivity.
Abstract: This paper is designed to supplement the existing extensive literature on the conductivity of a randomly inhomogeneous medium, by treating the effects of inhomogeneities on piezoelectric, galvanomagnetic, and thermoelectric measurements. The scale of the inhomogeneities is supposed small compared with the dimensions of the specimen being measured, but large compared with mean free path, Debye length, etc. Formulas for all the effects are derived which are asymptotically exact in the limit of small fractional fluctuations in the local conductivity, etc. Comparison with other approximations and application to various exactly soluble cases show that these formulas are often roughly valid for quite sizable fluctuations. For material which, if uniform, would show a high field saturation of transverse magnetoresistance, the presence of appreciable inhomogeneities in the Hall constant will cause the magnetoresistance to increase indefinitely with field. This effect is due to the current distortions arising from ...
TL;DR: In this article, the influence of inhomogeneities on the saturation of the ferromagnetic resonance is investigated, and it is shown that the spin-wave line width increases with increasing wave number and decreasing angle between propagation direction and dc magnetic field.
Abstract: The influence of inhomogeneities on the saturation of the ferromagnetic resonance is investigated. In the region of moderate power levels, the susceptibility at resonance χ′′ varies linearly with the square of the rf field h. The magnitude of the slope ∂χ′′/∂h2 depends on the nature of the dominant scattering mechanism. If the uniform mode scatters primarily to spin waves of very large wavelength, the slope should be negative. Scattering to spin waves of short wavelength gives a positive contribution to the slope and can lead to a reversal of the sign. The theoretical predictions agree with measurements at X band on various polycrystalline garnets and ferrites.At very high power levels the opening angle of the precessing magnetization vector approaches a limiting value, which is related to the “line width” ΔHk of z directed spin waves having the same frequency as the uniform mode. Experiments on single crystals and polycrystals of rare earth substituted garnets show that ΔHk increases approximately linearly with the rare earth content. The materials investigated contain Gd, Yb, Er, Sm, Dy, Ho, or Tb and for a given ratio of substitution ΔHk increases in that order. The line width ΔHk of z directed spin waves is found to be approximately proportional to the line width ΔH of the uniform mode as measured in single crystals.Experimental results on cobalt and zinc substituted nickel ferrite are reported. ΔHk increases linearly with the cobalt content. For the nickel-zinc ferrites with a large magnetic moment the saturation curve (χ′′ vs h2) measured at X band shows a maximum well below the initial onset of nonlinearity. A theoretical explanation for this extraordinary behavior is given.A new nonlinear effect arising from spin wave instability in a microwave magnetic field applied parallel to the dc field has been observed. Spin waves which propagate in directions perpendicular to the dc field are most susceptible to this instability. The observed variation of the critical rf field strength agrees well with the theoretical predictions. It indicates that the spin-wave line width increases with increasing wave number and decreasing angle between propagation direction and dc magnetic field.
TL;DR: In this paper, the authors investigated the photovoltaic solar energy conversion over a temperature range of 0-400°C using semiconductor materials with band gaps varying from 0.7 to 2.4 ev.
Abstract: Photovoltaic solar energy conversion is investigated theoretically over a temperature range of 0–400°C using semiconductor materials with band gaps varying from 0.7 to 2.4 ev. Three cases are considered. In Case I, the junction current is the ideal current. In Case II, the junction current is the ideal plus a recombination current; and in Case III, a recombination current. The best conversion performance is obtained for the ideal current; the worst, for the recombination current. The maximum conversion efficiency occurs in materials with higher band gap as the temperature is increased. GaAs is close to the optimum material for temperatures below 200°C. Experimental measurements are presented on Si, GaAs, and CdS cells. The measurements on Si and GaAs agree with theoretical expectations as far as the gross behavior is concerned. The CdS cell behaves anomalously as if it were made from a material with band gap of 1.1 ev.
TL;DR: In this paper, a new metastable phase was found, which has a tetragonal structure with lattice constants a'='2.77'A' and c'= '3.57'A and lattice positions 000 and 121212 with a preference of the Mn atoms for one of these positions.
Abstract: During an investigation of the Mn-Al system from 40–100% Mn, a new metastable phase was found, which has a tetragonal structure with lattice constants a = 2.77 A and c = 3.57 A and lattice positions 000 and 121212 with a preference of the Mn atoms for one of these positions. This τ phase, which has the approximate composition Mn1.11 Al0.89, can only be obtained by special heat treatment. It possesses remarkable magnetic properites. From the approach to saturation an anisotropy constant of about 107 ergs/cm3 can be calculated, while the extrapolated value σ∞ amounts to 96 erg/oe g; the latter corresponds to a 4πIs of 6200 G.Particles obtained by grinding the bulk material possess an IHC value of up to 6000 oe. No fixed correlation exists between particle size and the value of IHC; the latter is strongly dependent on the method of pulverization, and the authors are inclined to think that IHC is largely determined by the extent of deformation.The increase of IHC caused by grinding is accompanied by a decreas...
TL;DR: In this paper, the intensity distribution images of the magnetization distribution in thin ferromagnetic films were derived from the Lorentz force acting on an electron passing through the film, and the intensity distributions for some simple domain walls were computed and compared in various ways with experimental observations.
Abstract: Some new developments are reported in the technique of observing magnetization in thin ferromagnetic films by transmission electron microscopy, and the results of some observations are described that contribute to an understanding of the magnetic character of thin films. Two modes of operation of a microscope are explained, one using projector magnification alone, and one using both objective and projector lenses. The intensity distribution images of the magnetization distribution in a thin film is derived from the Lorentz force acting on an electron passing through the film. The intensity distributions for some simple domain walls are computed and compared in various ways with experimental observations. A magnetization ripple model is proposed and justified to explain an intensity texture observed principally when projector magnification alone is used. The texture is shown to be an orthogonal map of the magnetization of the film, and to be of use in interpreting wall structures. High magnification and resolution wall micrographs are obtained using objective magnification, and a direct measurement of the wall thickness and shape can be made in this way. 180° walls in a Fe‐Ni alloy film of about 200 A thickness are found to have a width of 2δ = 1500 A, using the wall model cot−1θ = −sinhx/δ. The effect of finite resolution on the measurements is discussed. It is shown that the magnetization distribution of a wall can be obtained from the measured intensity distribution by inverting the parametric equation solution for the intensity distribution.
TL;DR: In this article, it was shown that metal precipitates can be removed or prevented by ''gettering'' from surface layers, such as metallic coatings and certain glassy oxide layers.
Abstract: Metal precipitates in junctions were found to cause excess reverse current below avalanche breakdown, which is conjectured to be due to Zener tunneling at localized high‐field points. This current varies as Vn where n is between 4 and 7. By a potential plotting method, it was shown that this excess current is not caused by a surface effect. Metal precipitates can be removed or prevented by ``gettering'' from surface layers. Metallic coatings and certain glassy oxide layers were investigated. Results indicate that layers of Ni and Zn have a limited gettering effect. Glassy layers, especially those of boron and phosphorus, have the greatest gettering effect.
TL;DR: In this paper, a reverse bias is applied to an n −p junction at a sufficiently elevated temperature to give either the donor or the acceptor ions appreciable mobility, the ions will drift in the electric field of the junction to produce an intrinsic semiconductor region between the n and p regions.
Abstract: If a reverse bias is applied to an n‐p junction at a sufficiently elevated temperature to give either the donor or the acceptor ions appreciable mobility, the ions will drift in the electric field of the junction to produce an intrinsic semiconductor region between the n and p regions. Such ion drift offers a simple and straightforward method for investigating diffusion constants, as well as chemical interactions within the host lattice which affect this diffusion. Preliminary results indicate its feasibility for measuring the diffusion constant of Li in Si to as low as 10−18 cm2/sec and also for measuring the effect of Li‐oxygen and Li‐acceptor interactions in decreasing the diffusion rate. Intrinsic regions resulting from ion drift have been used to produce diodes with breakdown in excess of 4000 volts from low resistivity silicon. In addition, they can be used to extend the frequency range of devices by virtue of the decrease in junction capacitance associated with such an incorporated intrinsic region...
TL;DR: In this paper, the authors describe magnetic fields in the 10-15 megagauss range by use of high explosives which compress the flux obtained from initial fields of approximately a hundred thousand gauss.
Abstract: Magnetic fields are produced in the 10–15 megagauss range by use of high explosives which compress the flux obtained from initial fields of approximately a hundred thousand gauss. The fields described here occupy a cylindrical volume and are essentially axial. A typical field might have these general characteristics: Peak field 14 megagauss; 2 μsec duration from 10–14 megagauss; field volume around peak, 6 mm diameter, 50 mm estimated length.
TL;DR: In this paper, the authors modified Rayleigh's results by using a different function for potential, and by considering higher terms in the series expression for the potential in the continuous phase, yielding an analytical expression that represents effective conductance satisfactorily in the concentration region approaching close packing.
Abstract: Precise conductivity measurements on models sectioned out from a cubic lattice of spheres in a continuous medium indicate that the effective conductance of such a system deviates from the values predicted by Lord Rayleigh's analytic solution of this potential distribution problem. Deviations become particularly significant when the spheres approach close packing, and when the conductance of spheres is much greater than that of the continuum. By use of a different function for potential, and by consideration of higher terms in the series expression for the potential in the continuous phase, Rayleigh's results are modified, yielding an analytical expression that represents effective conductance satisfactorily in the concentration region approaching close packing.
TL;DR: In this paper, a theoretical basis is provided for the interpretation of photo effects observed in non-uniformly irradiated p−n junctions, and differential equations describing the junction photovoltage are developed through an application of the continuity and diffusion equations.
Abstract: A theoretical basis is provided for the interpretation of photoeffects observed in nonuniformly irradiated p‐n junctions. Differential equations describing the junction photovoltage are developed through an application of the continuity and diffusion equations. Solutions of the small‐signal steady‐state photoeffect equation indicate that the effects of nonuniform irradiation become increasingly important as the ratio of the lateral to the transverse resistance increases. α, a parameter introduced in this paper and designated as the lateral‐fall off parameter, is a measure of this resistance ratio. The lateral photovoltage resulting from nonuniform irradiation can be eliminated by reverse biasing the junction into saturation. Experimental curves in agreement with the predictions of the analysis are presented.
TL;DR: In this paper, the potential distribution of the spreading resistance of cylindrical semiconductor components is analyzed in graphical form for a range of geometrical parameters applicable to many practical situations.
Abstract: For cylindrical semiconductor components, computation of spreading resistance is considered a boundary value problem of the solid circular cylinder. Solutions of this problem may be used, for example, to characterize the thermal spreading resistance within the package of a semiconductor device, the electrical spreading resistance in a mesa type parametric diode, and the extrinsic collector resistance of a mesa transistor. Equations describing the thermal (or electrical) spreading resistance are presented in graphical form for a range of geometrical parameters applicable to many practical situations. Further, examples are given for the potential distribution within each cylindrical structure considered in this analysis.
TL;DR: In this article, the characteristics of molecular beam formed by sources consisting of long tube arrays are measured for several sources and peak beam intensity and beam width are calculated when collisions in the source are taken into account under the assumption that a limited region of Knudsen type flow occurs near the low-pressure end of the source.
Abstract: The characteristics of molecular beams formed by sources consisting of long tube arrays are measured for several sources. The peak beam intensity and the beam width are calculated when collisions in the source are taken into account under the assumption that a limited region of Knudsen type flow occurs near the low‐pressure end of the source. The peak beam intensity and the beam width are calculated to vary as the square root of the total flow rate for source pressures giving useful directivity, in good agreement with the observations. Considerations in the design of sources are discussed.
TL;DR: There are two kinds of antiferromagnetic domain walls, T (twin) and S (spin-rotation) as mentioned in this paper, which are easily displaced by the application of small mechanical stresses or magnetic fields.
Abstract: Antiferromagnetic domains in NiO have been studied by neutron diffraction and optical observation of single crystals. There are two kinds of antiferromagnetic domain walls, T (twin) and S (spin‐rotation). A T wall is produced by rotation of the antiferromagnetic pattern of magnetic moments and an S wall by rotation of the direction of the magnetic moments. The T walls can be observed with polarized light, and both T‐ and S‐type domains can be studied by neutron diffraction. Crystals with simple T‐wall structures are produced by annealing at high temperature. The crystallography of the T walls can be understood in terms of a small rhombohedral deformation which accompanies the antiferromagnetic ordering. The T walls are easily displaced by the application of small mechanical stresses or magnetic fields. A crystal without T walls may still contain S walls, and these S walls also are displaced or rotated by magnetic fields.
TL;DR: In this paper, the average concentration distribution of diffusant in a polycrystalline body is analyzed under the assumption that two interrelated mechanisms consisting of diffusion through the grains and in the boundaries around the grains are dominant in different penetration regions.
Abstract: Diffusion in a polycrystalline body is discussed under the assumption that two interrelated mechanisms consisting of diffusion through the grains and in the boundaries around the grains are dominant in different penetration regions. The general behavior of the average concentration‐distribution of diffusant is described for the separate action of each mechanism, and the effects of their combined action are inferred. A realistic diffusion model for a polycrystalline body and a suitable empirical function to describe the loss of diffusant from the boundaries to the grains form the basis for these computations.Results are specifically applied to the analysis of the usual sectioning technique for measuring the ratio of grain boundary to lattice diffusion constants in a polycrystalline body. It is shown that, in the penetration range most commonly covered in polycrystalline diffusion experiments, the log of the average concentration varies as the 6/5 power of penetration depth contrary to the linear law report...
TL;DR: In this article, the twin-domain walls in large crystals of antiferromagnetic NiO have been observed by specular reflection in optically polished and annealed crystals.
Abstract: Twin‐domain walls in large crystals of antiferromagnetic NiO have been observed by specular reflection in optically polished and annealed crystals These walls can be moved in annealed crystals by small mechanical stresses (<106 d/cm2) or by moderate magnetic fields (<25 000 oe) to yield completely untwinned crystals The ease with which a twin wall moves appears to be limited by a spin‐rotation energy loss Crystallographic measurements of the rhombohedral distortion agree with the x‐ray data, and verify the [111] antiferromagnetic contraction The anisotropy in the magnetic susceptibility vs field has been measured for untwinned crystals, and is compared with earlier work
TL;DR: In this paper, a simple theory concerning the reflection of electrons from solid targets is derived, based on the following assumptions: (1) the primary cause of electron reflection from a solid material is Rutherford scattering through angles greater than 90°; (2) the energy loss of electrons penetrating a solid target is given by the Thomson-Whiddington law, or a modified version of it; (3) no multiple scattering is allowed.
Abstract: A simple theory concerning the reflection of electrons from solid targets is derived, based on the following assumptions: (1) the primary cause of electron reflection from a solid material is Rutherford scattering through angles greater than 90°; (2) the energy loss of electrons penetrating a solid target is given by the Thomson‐Whiddington law, or a modified version of it; (3) no multiple scattering is allowed. An expression for the reflection coefficient r is derived that agrees surprisingly well with experimental data, in view of the above simplifying assumptions. In particular, the correct variation of r with atomic number Z is obtained, and the observed value of the fractional escape energy is calculated in the limit as Z → 0, where the theory is most accurate. A critical discussion of the simplifying assumptions is given, and the range of validity of the theory is estimated. This theory leads to a better understanding of the related phenomena of secondary emission at primary electron energies betwee...
TL;DR: In this article, an average fiber axis orientation in polypropylene film was measured quantitatively from x-ray diffraction determination of orientation of two planes containing this axis, expressed as the average square cosine of the angle between the fiber axis and a chosen reference direction in the sample.
Abstract: An average fiber axis orientation in polypropylene film was measured quantitatively from x‐ray diffraction determination of orientation of two planes containing this axis. This orientation was expressed as the average square cosine of the angle between the fiber axis and a chosen reference direction in the sample. It was necessary to use an indirect method since there are no crystal planes perpendicular to the fiber axis. The nature of the fiber axis orientation thus determined was found to be consistent with birefringence measurements and qualitative deductions from pole figures. Films produced by flat die extrusion showed a double orientation in which the fiber axis is preferentially oriented in the extrusion direction, and the (010) crystal face is parallel to the film surface. Both components of the orientation tended to be of the same magnitude.
TL;DR: The angular distribution of material sputtered under normal Hg+ ion incidence from flat, polycrystalline targets at 100 to 1000 ev was measured and plotted in polar diagrams as mentioned in this paper.
Abstract: The angular distribution of material sputtered under normal Hg+‐ion incidence from flat, polycrystalline targets at 100 to 1000 ev was measured and plotted in polar diagrams. The distribution is ``under cosine,'' approaching a cosine distribution, at higher ion energies. Mo and Fe show a more pronounced tendency to eject to the sides than Ni or Pt. Under oblique ion incidence atoms are sputtered preferentially in the forward direction.
TL;DR: In this article, electrostatic methods have been used to accelerate μ-diam spheres of iron to hypervelocities by using a single impact in vacuum of measured incident velocity, mass, and position.
Abstract: By electrostatic methods, μ‐diam spheres of iron have been accelerated to hypervelocities. Techniques have been developed to give single impacts in vacuum of measured incident velocity, mass, and position.