bluuebunny/crossref_metadata_2025 huggingface dataset:
Defects in Polyethylene Crystals
Authors: Slichter W. P.
Published: April 2005

Nuclear magnetic resonance measurements have been made of the development of chain motion in linear polyethylene and polymethylene crystallized from solution. It is shown that segmental mobility is produced at room temperature when the compounds are heated below the melting point. The changes are rapid and irreversible, and are independent of crystallization temperature and concentration, except at high concentration. The effects are ascribed to the development of defects in the crystalline structure.
Effect of Reactor Irradiation on the Tensile Strength of Uniaxially Oriented Polyethylene Terephthalate
Authors: Hsiao C. C. , Chow S. T.
Published: April 2005

A series of uniaxially oriented polyethylene terephthalate fibers irradiated in a nuclear reactor have been investigated. On the basis of tensile studies the ultimate tensile strength is found to decrease as the dose of reactor irradiation increases. However, the ultimate tensile strength is found to increase when the degree of molecular orientation increases. But after the samples have received a relatively high dose of irradiation the tensile strength approaches practically zero. The x-ray diffraction scans of the nonirradiated samples with low degrees of orientation indicate very little crystallinity, whereas the very definite diffraction peaks associated with the irradiated and oriented samples indicate a definite trend toward crystallinity.
Stress as a Reduced Variable: Stress Relaxation of SBR Rubber at Large Strains
Authors: Landel Robert F. , Stedry Paul J.
Published: April 2005

Stress relaxation measurements on SBR were carried out at temperatures from −5 to +60°C and at initial strains of up to 550%. The effects of strain and time were found to be factorable, so that the isochronal stress-strain curve may be written as a modified Hooke's law with a time dependent modulus: S = E(t)ef(α), where f(α) is an appropriate function of the strain. By defining a strain-reduced stress S* = S / f(α), i.e., a strain-reduced modulus E*(t) = E(t)f(α), it can be shown that Ferry's method of reduced variables may be extended to large deformations. An appropriate strain function was obtained from the empirical Martin-Roth-Stiehler equation [Trans. Inst. Rubber Ind. 32, 189 (1956)] as f(α) = α−2 expA (α−α−1) with A =0.40. Although it cannot yet be certain that A is truly a constant and the same for all elastomers, this equation has the advantage of being valid right out to the breaking strain.
A Theoretical Calculation of the Briefringence of Polypropylene Crystals
Authors: Keedy D. A. , Powers J. , Stein R. S.
Published: April 2005

In the course of some investigations on the effect of carbon-carbon and carbon-hydrogen bond polarizabilities on the optical properties of hydrocarbon polymers, a theoretical calculation of the polypropylene chain principal polarizabilities was performed. The polypropylene chain model given by Natta was used. Results were expressed in terms of carbon-carbon and carbon-hydrogen bond polarizabilities. Two sets of values of bond polarizabilities, one given by Denbigh, the other by Bunn and Daubeny, were substituted into the polarizability equation. Values of chain principal polarizabilities were then used to calculate the refractive index and birefringence using the Lorentz-Lorenz equation. Better agreement was found between experimental and theoretical birefringence values using Denbigh's data. Three explanations are suggested which might account for the differences between the two sets of bond polarizabilities.
Morphology of Polymer Single Crystals
Authors: Reneker D. H. , Geil P. H.
Published: April 2005

Evidence is presented indicating that polyethylene crystals grow in the form of hollow pyramids as well as lamellar crystals. Modes of packing the folded molecules consistent with the nonplanar structure are proposed. Observed electron diffraction patterns and dark-field micrographs are related to the pyramidal morphology. Various sources are described for the screw dislocations which result in spiral growths on crystals of polyethylene and polyoxymethylene.
Effect of Random Inhomogeneities on Electrical and Galvanomagnetic Measurements
Authors: Herring Conyers
Published: April 2005

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 the large and fluctuating Hall fields. For the special case of an isolated inclusion, these distortions are shown to extend, at high fields, to distances in the direction of the magnetic field which are many times the diameter of the inclusion. Under some conditions it appears that even the random distribution of impurities in a semiconductor can give rise to perceptible fluctuations on a scale large enough for concepts of macroscopic conduction to be applicable. Since fluctuations of even smaller scale are still larger, the total effect of fluctuations cannot be properly treated by the present methods; however, when the macroscopic part of the fluctuations is large, conventional impurity-scattering theories must be inadequate. Applications to polycrystalline metals and semiconductors are discussed briefly.
A Structural Study of the Compound AgSbTe2
Authors: Armstrong R. W. , Faust J. W. , Tiller W. A.
Published: April 2005

X-ray, optical and electron microscope, and chemical etching techniques have been used to investigate a striated microstructure observed in zone refined single crystals of the AgSbTe2 structure. This microstructure, originally thought to be fine twin lamellas, has been identified as a Widmanstatten precipitate of Sb2Te3 upon the {111} planes of the matrix face-centered cubic material. In addition, the evidence obtained from all the measurements made on this material indicates that the ternary compound of the AgSbTe2 type does not melt congruently.
Transformation Studies of Gray Tin Single Crystals
Authors: Wolfson R. G. , Fine M. E. , Ewald A. W.
Published: April 2005

Measurements of the linear growth rate of white tin into thin single-crystal wafers of gray tin, over the temperature range 24.2° to 46.5°C, are presented. The rate is not a single-valued function of the temperature. Imposed upon the strong temperature dependence of the average rate is a variation which is well defined at a given temperature; the spread in the observed values decreases sharply with increasing temperature. The variation is attributed to two observed stress-relaxation processes: cleavage in the gray tin and plastic deformation, accompanied by recrystallization, in the white tin.
Conservation Laws of Uniform Linear Homogeneous Systems
Authors: Pease M. C.
Published: April 2005

A generalized linear homogeneous system is analyzed for the quadratic forms that are invariant under it. Such forms lead to conservation laws that are properties of the system. If the system has n degrees of freedom, it will have at least n such conservation laws which together determine the ``type'' of the system. The analysis may be viewed as the determination of the metrics under which the operator becomes rotational. In such a metric, the square of the length of a vector is invariant. A conservation law is expressible as its appropriate metric. The Manley-Rowe relations for parametric devices, and Chu's kinetic power theorem for electron-beam devices are examples.

The analysis is related both to the system operator and to a possible system matrix differential equation. In the latter case, this allows a direct connection between the conservation laws and the physical construction of the system. The converse problem in which two metrics are specified is also considered. The range of possible matrix differential equations of a given type, and of system operators, is determined. Application is made to a uniform parametric line with ``ideal forward coupling.'' Such a device will be stable in the sense that it avoids internal feedback. If it is matched either on the input or output side, it will not oscillate regardless of its gain or electrical length. The necessary and sufficient conditions for this ideal behavior are obtained by considering the invariant forms—the conservation laws—that it should obey.
Orientation-Dependent Dissolution of Germanium
Authors: Frank F. C. , Ives M. B.
Published: April 2005

The dissolution of single crystals of undoped germanium in Superoxol etchant is shown to be very closely completely orientation-dependent by the applicability of recent theorems on crystal dissolution shapes. The results of the theory are outlined, and the method of application is described in detail.
Neutron and Optical Studies of Domains in NiO
Authors: Roth W. L.
Published: April 2005

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.
Adiabatic Collapse of a Relativistic Electron Beam
Authors: Godlove T. F. , DePackh D. C.
Published: April 2005

Differential equations are derived and two computer solutions presented for the case of a relativistic electron beam injected into neutral gas. Processes included are ionization, scattering of electrons on atoms and ions, charge exchange, supply of neutrals to the beam by diffusion, and incoherent radiation by the electrons. A longitudinal electric field is assumed. The main restrictive assumptions are those of uniform densities and hydrodynamic stability. Solutions are given for an 1100-amp, 0.77-Mev, externally-focused beam injected into H2 at pressures of 10−6 and 2×10−5 mm Hg. The beam contracts from an initial radius of 1.73 cm to an equilibrium radius of 7×10−4 cm in 3 and 0.5 msec, respectively. It is found in these cases that neutrality of the beam does not occur until after the radiation-scattering equilibrium, which was first studied by Budker, has occurred. Several difficulties connected with a neutralized beam are discussed. It is shown that a space-charge-limited beam of high phase-space density is the type most suitable for obtaining a small beam diameter in the shortest time. An approximate solution is derived which applies after a specified time near equilibrium and allows calculation of several parameters of interest without the necessity of computer integration.
Effect of Neutron Bombardment on the Magnetic Properties of Very High Permeability Iron
Authors: Biorci G. , Ferro A. , Montalenti G.
Published: April 2005

Rings of iron with permeability of about 150 000, after neutron bombardment (1×1018 nvt), show lower permeability and higher coercive force. This effect can be interpreted as due to large defects giving long range internal stresses, or as due to anisotropic defects interacting with the magnetization vector at each point of the specimen.
In What Sense Do Slow Waves Carry Negative Energy?
Authors: Sturrock P. A.
Published: April 2005

It has been found in the theory of electron tubes that, according to the ``small-amplitude power theorem,'' the fast and slow space-charge waves carry positive and negative energy, respectively. Similar analysis of different systems leads to similar results, leading one to conjecture that there is some sense in which one might assert that, for a wide class of dynamical systems, slow waves carry negative energy. In a one-dimensional model, ``slow'' and ``fast'' waves in a moving propagating medium refer to waves of which the phase velocity does or does not change sign, respectively, on transforming from the moving frame to the stationary frame. Small-amplitude disturbances of any dynamical system may be described by a quadratic Lagrangian function, from which one may form the canonical stress-tensor, elements of which are quadratic functions of the variables which appear in the linearized equations of motion. For any pure wave in this system, the energy density E and the momentum density P, as they appear in the canonical stress tensor, are related to the frequency ω and wave number κ by E=Jω, P=Jκ, where 2πJ is the action density. The rules for Galilean transformation now show that the energy densities, as measured in the stationary frame, of fast and slow waves have positive and negative sign, respectively, if (as is usually the case) the energy densities of both waves are positive in the moving frame. Similar arguments explain the signs of the energy density of the two ``synchronous'' waves which arise in the analysis of transverse disturbances of an electron beam in a magnetic field.
Nonlinear Effects of Crystalline Anisotropy on Ferrimagnetic Resonance
Authors: Gottlieb Peter
Published: April 2005

The crystalline anisotropy of a ferrimagnetic solid will cause the magnetic resonance frequency to depend upon the angle of precession. It is shown that the resonance frequency depends quadratically upon the precession amplitude to lowest order. It is also shown that the dependence of this quadratic term upon the magnetic field orientation with respect to the crystal axis is the same as dependence of the usual zero-order resonance term upon orientation of the magnetic field. It is shown that the quadratic nonlinear term can cause a foldover of the resonance line, even in a spherical sample which is usually considered to have no foldover. The necessary conditions for the onset of this foldover are discussed, and some experimental results are mentioned.
Experimental Investigation in Lead of the Whipple ``Meteor Bumper''
Authors: Olshaker Arnold E.
Published: April 2005

Experimental results are presented to indicate the effects of a thin protective shield on reducing the penetration of simulated meteoroids. The study is mainly of lead impacting lead at 2.5 km/sec. The effects of thickness and separation of the shield are investigated. It is shown that a shield of thickness slightly less than half the projectile diameter at a separation of about five projectile diameters reduces the penetration of shield plus target to approximately one-third the depth of the unshielded crater. This shield is also effective against hardened steel ball bearings. Based on the assumption that the ``fluid impact'' penetration mechanism of lead at this velocity is qualitatively similar to that of structural materials at meteor velocities, it is concluded that the weight saving potential of ``bumper'' construction will make its use mandatory for space structures designed by the penetration condition.
Magnetic Viscosity Due to Solute Atom Pairs. Part I. Theory of the Effect
Authors: Biorci G. , Ferro A. , Montalenti G.
Published: April 2005

It is shown that solute atom pairs in ferromagnetic alloys, as well as the interstitial atoms in iron, can give magnetic viscosity.

The viscosity field of the alloys vs wall displacement is determined for various crystal structures. The maximum value of the viscosity field is related to the anisotropy energy induced in the same materials by heat treating in a magnetic field.
Electron Optical Study of Basal Dislocations in Graphite
Authors: Amelinckx S. , Delavignette P.
Published: April 2005

Dislocations having a Burgers vector in the basal plane and lying in this plane, have been studied in graphite by the use of thin foil transmission electron microscopy. The dislocations are dissociated into ribbons consisting of two partials separated by a stacking fault. Specific models for these dislocations are presented. Hexagonal networks contain extended and contracted nodes. The presence of two types of stacking faults gives rise to singularities which are analyzed in terms of experimentally determined Burgers vectors. The dislocations and even the networks are very mobile along the basal plane. The stacking fault energy is determined as 3 to 5×10−2 ergs/cm2.
Study of Initial Conditions in Constant Velocity Impact
Authors: Bell James F.
Published: April 2005

Diffraction grating measurements are made of dynamic plastic strain within a few thousandths of an inch from the impact face of 1-in. diameter, annealed aluminum specimens in free flight undergoing constant velocity impact. From these data it has been established that initial nondispersive shock fronts are present, even in low-velocity impact. This initial nondispersive front develops in the first ¼ diameter in two sections, each involving ½ the initial kinetic energy; the first section is that of the deviatoric, or shear, component, and the second is associated with the hydrostatic stress. It is shown that the dynamic stress-strain curves obtained experimentally in annealed aluminum and copper may be computed directly from the theory, using information supplied by the static stress-strain curve. The von Karman critical velocity for annealed aluminum is found to be a dividing point between two types of initial wave development.
Some Effects Occurring in Dislocated Tellurium
Authors: Blakemore J. S. , Schultz J. W. , Nomura K. C.
Published: April 2005

Dislocation densities as small as 1000 cm−2 are sometimes found in carefully produced single crystals of tellurium, but since the material is very soft a quite mild stress can introduce 106 dislocations/cm2 or more. Dislocation etch pits of sharply geometric shape can be developed on the cleavage (101̄0) planes by the slow attack of sulphuric acid; their planar surfaces correspond to (11̄00), (101̄3), (011̄1), and (01̄11̄) faces. Effects are noted on faces exposed by cleavage at 77°K which suggest that even at this temperature the material can suffer localized plastic damage, for brief etching of such faces produces small flat-bottomed pits; these may be interpreted by supposing that the mild stress of cleavage at 77°K generates shallow dislocation loops. The flat-bottomed pits disappear when a surface layer ≥25 μ is etched away. A marked increase in electron-hole recombination rate is noted in plastically deformed crystals. If the additional recombination occurs through the dislocations themselves, then each has a capture radius of some 4×10−8 cm at 300°K. Dislocated crystals also show more prominent trapping effects at low temperatures than structurally pure samples, and contain additional readily ionizable acceptor sites; these may be derived from the dislocations themselves or from other defects created or activated by plastic flow.
Filled and Empty Dangling Bonds in III-V Compounds
Authors: Holt D. B.
Published: April 2005

It is pointed out that the model of dangling bonds from the {111} and {1̄11} surfaces of III-V compounds proposed by Gatos, Moody, and Lavine is open to serious objection. The idea of resonance is introduced in order to develop a model which is not subject to the same difficulties. Certain implications of this model for dislocation theory are discussed.
Mechanism of Photoconductivity in Microcrystalline Powders
Authors: Bube Richard H.
Published: April 2005

Measurements on a variety of cadmium sulfide powder cells show that there are four different regions encountered as the applied voltage is varied. At low voltages an ohmic region is found in which barrier breakdown does not occur. At intermediate voltages a region is found in which barrier breakdown by a Process I occurs. At still higher voltages a region is found in which barrier breakdown by another Process II occurs in addition to that associated with Process I. At very high voltages another ohmic region is found where all barrier limitations have been removed. It is proposed, on the basis of the data, that Processes I and II are associated either with tunneling of electrons through interparticle barriers or with a reduction in barrier height assisted by the localized trapping of photo-excited or field-excited holes. A model constructed along these lines is applied to a variety of observations such as current-voltage curves, photocurrent lag after periods of no applied voltage or of opposite-polarity applied voltage, the existence of a semipermanent polarized set, ac properties of powders, and the hysteresis or storage effect.
Subsidiary Resonance in the Coincidence Region in Yttrium Iron Garnet
Authors: Rossol F. C.
Published: April 2005

The measurement of hcrit, the threshold rf field for subsidiary resonance, as a function of frequency throughout the coincidence region, and the behavior of μ″max at rf fields exceeding hcrit are presented for a single-crystal yttrium iron garnet sphere at room temperature. The sphere has a linewidth of 480 moe measured at 3000 Mc. The hcrit curve obtained was quite flat at approximately 0.3 moe from 2000 Mc to 3300 Mc and increased by more than a factor of 6 within 150 Mc of either end; a much more sudden increase than was the case for previously measured spheres of wider linewidth. The measured curve is compared to a curve computed from Suhl's theory of subsidiary resonance at high power levels, and the effects of the linewidths ΔH and ΔHk on the shape of the curve are considered. The variation of μ″max with rf power above the threshold followed Suhl's P−½ law rather closely for frequencies above 2700 Mc but exhibited fine structure and a slower fall-off for frequencies below.
Gold-Induced Climb of Dislocations in Silicon
Authors: Dash W. C.
Published: April 2005

Studies were made of the climb of dislocations in silicon crystals induced by the diffusion of gold in the temperature range from 1000°C to 1300°C. For some studies, dislocations were introduced into previously dislocation-free crystals by indentation at room temperature and deformation at about 900°C in order to predetermine both Burgers vector and the direction of deformation. It was possible in this way to introduce left-handed screw dislocations in small concentrations. The left-handed screw dislocations were found to form right-handed helices upon the diffusion of gold during subsequent heat treatment at temperatures above 1000°C. This observation is shown to be consistent with the idea that gold diffuses as an interstitial atom and causes a vacancy deficiency in the neighborhood of dislocations. Further evidence of the structure sensitivity of the diffusion of gold is shown by autoradiographic techniques. Studies were made of the effect of heat-treatment times and quenching rates upon the diameter of helices. The diameter of the helices increases with time at a given temperature, and increases with temperature during a given time of heat treatment. Variation of the cooling time by a factor of 103 has no apparent effect on the diameter. Therefore, the helices form as a result of a gradient in the concentration of gold rather than by a quenching process. Impurities introduced by heat treatment at 900°C strongly modify climb in crystals which are relatively free from oxygen. Precipitates believed to be formed during this heat treatment act as nucleation sites for the formation of prismatic loops. Crystals grown from quartz crucibles and thus containing about 10+5 atom fraction of oxygen have complicated climb mechanisms believed to be associated with the pinning effect of the oxygen on the dislocations. Modified Bardeen-Herring sources have been found in these cases.
Development of Facets, Spirals, and Etch Pits on Copper Crystals by Heating to High Temperatures in High Vacua
Authors: Young F. W. , Gwathmey A. T.
Published: April 2005

Single crystal spheres of OFHC and 99.999% copper were heated to temperatures of 950 to 1075° in high vacua. In the case of the OFHC copper, facets parallel to the (111), (110), and (100) planes were formed over relatively large areas centered at the respective poles, and with some of these crystals spiral facets were formed around the (111) pole. When an OFHC crystal was heated in a copper cup, an appreciable number of pits were formed. In the case of the 99.999% copper, facets parallel to the (111) and (100) planes were formed in small areas around the respective poles, and at certain temperatures etch pits were formed. An attempt was made to interpret the difference in the size of the facets formed on the two types of crystals in terms of the influence of impurities on the rates of evaporation. It was proposed that the etch pits formed at dislocations in the crystal, although there was not a one-to-one correspondence between pits and dislocations.
Factors Affecting the Ductility and Strength of NaCl Single Crystals Tested in Flexure
Authors: Stearns C. A. , Pack A. E. , Lad R. A.
Published: April 2005

An experimental investigation has revealed that the initial deformation of NaCl single crystals is anelastic rather than Hookean. This anelastic deformation is manifested by a low slope foot in the load-deflection curve. The magnitude of the foot is dictated by the pretreatment given the specimen. Treatments which increase or decrease the fresh dislocation density respectively increase or decrease the length of the initial anelastic foot.

The order of increasing ductility and strength with specimen pretreatment was found to be (1) heated at 135°C, (2) as cleaved, (3) coated with silver, (4) heated at 135°C and then water polished, (5) water polished and then coated with silver, (6) water polished, (7) water polished and then heated at 135°C, (8) annealed at 700°C, and (9) annealed at 700°C and then water polished.

The experimental results have been discussed in terms of the role played in deformation and fracture by surface cracks, grown-in dislocations, and fresh dislocations.
Torsion Induced Recrystallization of Molybdenum and Tungsten Filaments
Authors: Gifford F. E. , Coomes E. A.
Published: April 2005

When an optimum amount of permanent twist is introduced in 3- to 10-mil filaments of molybdenum or tungsten, single crystals up to 15 cm in length grow by either the moving gradient or Robinson techniques. About 5 turns per inch for W at 2500°K or for Mo at 1650°K was favorable. Although there is evidence of perfection in the volume of the crystals, the twist leaves a threadlike surface imperfection which remains even after severe heat treatment at evaporation temperatures.
Determination of Magnetization Distribution in Thin Films Using Electron Microscopy
Authors: Fuller Harrison W. , Hale Murray E.
Published: April 2005

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.
Submillimeter Wave Maser
Authors: Bergmann Saul M.
Published: April 2005

It is shown that coherent emission between the levels 32P32−32P12 for Na atoms enclosed in a resonant cavity should occur at a rate greater than in free space where transition probabilities are very low. It is therefore proposed to operate a maser at the submillimeter wavelengths corresponding to these transitions (ν = 5.18×1011sec−1) using a dielectric tube resonator as the cavity. An input and output coupling scheme is discussed.
Propagation of Large Amplitude Waves in Annealed Aluminum
Authors: Bell James F.
Published: April 2005

An experimental study of large amplitude compression waves in annealed aluminum for the case of constant velocity impact has given a close agreement with the strain rate independent theory of one-dimensional plastic wave propagation. Radial effects in the first diameter are observed and calculations of Poisson's ratio indicate the presence of relatively large dilatation. Propagation velocities, maximum strain, and energy considerations are in agreement with predictions from the slopes of the static stress-strain curve. These data were obtained using the author's diffraction grating technique for measuring strain and surface angle.
Ion Drift in an n-p Junction
Authors: Pell E. M.
Published: April 2005

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. Ion drift has also been used for the fabrication of analog transistors, an early unit having an input impedance of 6 megohms, a power gain of 17 db and a voltage gain of 4.
Diffusion of Boron into Silicon
Authors: Kurtz A. D. , Yee R.
Published: April 2005

The diffusion of boron into silicon has been investigated over a temperature range of 1050°C to 1350°C using an open-tube vapor-solid diffusion technique at atmospheric pressure. A p-n junction method of measuring the diffused layer was used to determine the diffusion constant. Lower diffusivities and a somewhat lower activation energy, (ΔH=81 kcal) were obtained than those reported previously.

The difference is attributed to variation of diffusivity with surface concentration and is discussed on the basis of field-aided diffusion theory.
Rolling Friction of Polymeric Materials. I. Elastomers
Authors: Flom Donald G.
Published: April 2005

Coefficients of friction for the rolling of steel balls on butyl, silicone and Neoprene elastomers have been measured in the temperature range of 25 to 100°C. For equivalent amounts of deformation rolling friction is directly proportional to dynamic mechanical losses measured by a rebound method. In addition, the coefficients of friction vary directly with (load)⅓ and inversely with (ball radius)⅔. These results are in agreement with recent theoretical predictions.

The high mechanical losses and rolling friction for the butyl elastomer at 25°C drop sharply on increasing the temperature to 100°C. For the silicone and the Neoprene the losses and the friction decrease only slightly with increase in temperature.
Effect of the Polarity of the III-V Intermetallic Compounds on Etching
Authors: Faust J. W. , Sagar A.
Published: April 2005

For the III-V intermetallic compounds, the <111> directions are polar axes. The shape of etch pits bounded by crystallographic planes and the presence or absence of pits at dislocations are influenced by the effect of the polar axes on the etch rates. Studies of these effects are reported for several etches on InSb, InAs, GaSb, and GaAs. Correlation of these studies with published x-ray investigations shows that these etches reveal dislocations and truncated pyramidal pits only on {111} surfaces that are at the group III end of the polar axis. A difference in the shape of the pits on opposite {100} surfaces was found and is explained by means of the polar axes.
Theory of Fast-Wave Parametric Amplification
Authors: Johnson Curtis C.
Published: April 2005

A new type of low-noise beam-type parametric amplifier has recently been introduced by Adler, Hrbek, and Wade. This device is characterized by its use of the fast-cyclotron wave for amplification purposes instead of the conventionally used slow space-charge wave. The fast-cyclotron wave is selected because it can be made relatively noiseless by appropriate coupling processes. Since the input beam noise is the principal source of noise in beam-type tubes, a very great reduction in noise figure is obtained. Amplification of the fast-cyclotron wave is achieved by use of the parametric principle.

An analytical description of the device is presented which includes a discussion of parametric amplification of the fast-cyclotron wave. A method of coupling to cyclotron waves is investigated, and design procedures for establishing optimum low-noise characteristics are outlined.
Mobility of Edge Dislocations in Silicon-Iron Crystals
Authors: Stein Dale F. , Low J. R.
Published: April 2005

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 experiments on pinned dislocations suggest that there may also be an effect of temperature on the strength of pinning by impurities which would be superimposed on the increase in lattice resistance with decreasing temperature.
Method for the Detection of Flaws in Yttrium Iron Garnet Crystals
Authors: Buehler E. , Tanenbaum M.
Published: April 2005

Infrared techniques similar to those used in examining silicon crystals have been applied to the examination of yttrium iron garnet crystals. Photographic results for both flux grown and sintered crystals are given.
Ion Energies in a Cold Cathode Discharge in a Magnetic Field
Authors: Backus John , Huston Norman E.
Published: April 2005

A cold cathode discharge in a strong magnetic field was studied by means of a pulsing technique. The discharge was run at pressures of a few microns with magnetic fields of 2400 gauss and currents of the order of half an ampere. By means of a multivibrator and amplifier the discharge was pulsed off for 300 μsec at 1000 μsec intervals. During the off period the current flow to the cathodes was observed. Analysis of the current flow shows an approximately Maxwellian distribution of velocities at the cathodes with a temperature of about 0.5 ev. This gives an ion density in the discharge of approximately 20%.
Structure in Vitreous Silicate Fibers as Shown by Small-Angle Scattering of X-Rays
Authors: Statton W. O. , Hoffman L. C.
Published: April 2005

The relation of the x-ray diagram at small angles to the preparation conditions of glass fibers from molten silicates is studied. The composition Na2O·MgO·3SiO2 is studied extensively, and fibers are also studied in which K2O replaces Na2O, and CuO and PbO replace MgO.

Most of the diagrams are characterized by very intense, shaped, diffuse scattering. Also, fibers which had certain thermal histories show intense, unshaped diffraction maxima.

The diffuse scattering is interpreted as due to voids which are elongated by the spinning process. The discrete diffraction corresponds to a Bragg spacing of about 30 A but is not associated with short-range order. It is concentrated on the surface or accessible to liquid penetration from the surface. It is either frozen in by quenching, produced by quenching, or produced by a combination of quenching and reaction with the atmosphere. No interpretation of the structure responsible for it is given.
Precision Lattice Parameter Measurements of Cold-Worked Metals
Authors: Asimow Robert
Published: April 2005

A technique is developed for precise measurement of interplanar spacings under conditions such that both crystal imperfections and the finite x-ray spectrum contribute significantly to the broadening of the diffraction peaks. This is accomplished by considering the variation of the interference function in the neighborhood of a reciprocal lattice point. A weighted average value of sinθ, which corresponds to the interference function centroid, is calculated from the usual intensity versus angle data for a diffraction peak. Comparison of this measurement, with that obtained by using the position of maximum intensity, indicates that errors greater than 0.1% may be expected with the latter technique depending on the shape of the diffraction peak.
Absorption and Reflection Spectrum of a Plasma
Authors: Hershberger W. D.
Published: April 2005

A series of absorption and reflection peaks for plasmas, cylindrical in form, and occurring at electron densities lower than that required for the conventional plasma frequency, has been reported by various workers such as Tonks, Rommel, and Dattner. This paper describes experiments at a wavelength of 10 cm in which the multiple resonances are observed both within a wave guide and in free space. The electric field of the incident microwave is perpendicular to the axis of the plasma column. The positions of the absorption peaks are given by the interference-dispersion relationship, 2n/(2n+1)=[1−(f0/f)2]12. The mode spectrum is found by assigning integral values, including zero, to n. When n=0, we obtain the conventional plasma frequency f0, but for n>0, the frequencies, and electron densities for higher order modes are obtained. The relationship identifies a distinctive set of ratios between the phase velocity of a plasma wave and the rms velocity of the electrons such that simultaneously the conditions are met for the existence of a standing plasma wave and a stationary pattern of electron motion. Application of the relationship to radar echoes from meteor trails is indicated.
On the Nonconservation of Noise Parameters in Multivelocity Beams
Authors: Berghammer J. , Bloom S.
Published: April 2005

Macroscopic equations for conservation of charge, momentum, and energy, as derived from the Boltzmann equation, are applied to an electron stream having a velocity spread. For small velocity spreads, these equations are simple to treat. The noise parameters, S and Π, which determine the minimum noise figure of a beam-type microwave tube, lose their invariance in the presence of velocity spread; they become functions of position. The changes of S and Π are such as to lower the minimum noise figure. These results are in agreement with a detailed numerical solution of the Boltzmann equation as previously reported by others.
Molecular Beam Formation by Long Parallel Tubes
Authors: Giordmaine J. A. , Wang T. C.
Published: April 2005

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.
Creep of Al2O3 Single Crystals
Authors: Chang Roger
Published: April 2005

The ``steady-state'' creep of Al2O3 single crystals was investigated. The experimental data are analyzed according to three mechanisms: the dislocation climb mechanism, the micro-creep mechanism, and the Peierls stress mechanism. It is shown that the dislocation climb mechanism fits experimental data best. The expectation that Peierls stress mechanism is rate controlling in the ``steady-state'' creep of Al2O3 is ungrounded.
Low-Temperature Transport Properties of Commercial Metals and Alloys. III. Gold-Cobalt
Authors: Powell Robert L. , Bunch M. D. , Gibson Edward F.
Published: April 2005

The thermal conductivity, electrical resistivity, and Lorenz number are given in the temperature range 4–100°K for the widely used thermocouple wire, gold-2.1 atomic percent cobalt alloy. The total thermal conductivity is relatively low: from 0.01 watt/cm°K at 4°K to 0.23 at 100°K. The lattice contribution to the total thermal conductivity is larger than the electronic contribution. The electrical resistivity is nearly independent of temperature, but does have a definite minimum of about 1.20×10−5 ohm-cm at 30°K. Because of the relatively large contribution of the lattice term to the total thermal conductivity, the Lorenz number is considerably above the electronic Sommerfeld value, 2.44×10−8 watt-ohm/°K2.
Noise and Signal Response in Lead Sulfide Photoconductive Films
Authors: Spencer H. E.
Published: April 2005

Experimental noise and signal response data of two lead sulfide photoconductive films have been obtained as a function of frequency and radiation wavelength at temperatures ranging from about 25°C to −173°C. Good agreement between experiment and a theory proposed by Petritz is found. The theory is used in such a way that correlations between noise and response may be made independent of the temperature. The measured time constants enter into the correlations only indirectly; they are necessary only to extrapolate data measured at a given frequency to some lower frequency. Generation-recombination (G-R) noise predominates at all temperatures. Time constants measured by noise and by response agree. The role of absorbed ambient photons is described. These photons are important at the lower temperatures. The concentrations of the majority carriers (holes) and their mobility as derived from signal data are listed.
Ultimate and Secondary Electron Energies in the Negative Glow of a Cold-Cathode Discharge in Helium
Authors: Anderson J. M.
Published: April 2005

The ``ultimate'' electron density in the negative glow plasma of a cold-cathode discharge in helium at gas pressures 3–12 mm Hg has been determined by simultaneous Langmuir probe and microwave transmission methods. A correlation is obtained at densities above ∼4×1011/cm3 when the influence of positive ion scattering of the electrons diffusing to the probe is considered. The ultimate electron temperature in the helium negative glow was measured by the metallic probe to be quite low, ∼400°K, and the ``secondary'' electron temperature was found to be ∼50 000°K. These probe indications are substantiated by measurement of the microwave noise power radiated from the plasma which is found to correspond to an effective temperature varying from 300 to ∼1000°K.
Charged Sphere in Cylinder
Authors: Smythe W. R.
Published: April 2005

The method first used to solve the problem of a freely charged right circular cylinder in J. Appl. Phys. 27, 917 (1956), is applied to the case of a charged conducting sphere enclosed by a coaxial circular conducting cylinder. The charge density on the sphere, the potential between it and the cylinder and the capacitance are given for sphere to cylinder radius ratios of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 0.95. All results are accurate to one part in 107 or better. An approximate formula for the capacitance of a sphere in a cylindrical box is given.
Flow of Polyethylene into a Capillary
Authors: Bagley E. B. , Birks A. M.
Published: April 2005

The flow of polyethylene from a reservoir into a capillary has been studied visually using a new technique for observing the flow patterns. Various patterns observed with different polyethylenes are shown, both below and above the critical shearing stress at which the extrudate becomes distorted. The technique is readily adaptable to observe directly the elastic energy stored in the melt above the capillary entrance and the rate at which this energy can be dissipated on the cessation of the steady flow into the capillary.
Alloying Behavior of Thin Bimetal Films, Simultaneously or Successively Deposited
Authors: Belser Richard B.
Published: April 2005

Studies of the alloying of thin bimetal films of 20 metal pairs have been conducted by measurement of changes in the properties of the films before and after heating to successively higher temperatures in vacuo. Films consisted of layers of about 1000 angstroms of each metal consecutively deposited or of a single layer of 2000 angstroms formed of two metals deposited simultaneously. Techniques of study included visual examination of color changes, measurements of changes in electrical resistivity and temperature coefficient of resistance, metallography, x-ray diffraction, electron microscopy and diffraction, and measurement of frequency changes of piezoelectric resonators coated with a metal pair. Regardless of the method of coating, i.e., evaporation, sputtering, or electroplating, films were found to interdiffuse or alloy at or below the temperature of recrystallization of the metal of higher melting point. The order of deposition of the films affected their subsequent behavior. Films of aluminum formed an oxide coating during a few minutes storage in vacuo; the oxide appreciably retarded diffusion between the layers until a temperature of about 400°C was reached. Simultaneous evaporation produced films which alloyed readily at relatively low temperatures or, in the absence of intrinsic alloying affinities of the metal pair, films of highly imperfect structure. The imperfection of the latter was exhibited by reductions of up to 90% in the electrical resistance of the films upon annealing. By the methods outlined valuable studies of the properties of metals can be conducted with microquantities of the metals at temperatures below 0.40°Km (melting point °K); and alloys unavailable commercially can be prepared in the laboratory at minimum expense.