By Topic

Journal of Applied Physics

Issue 11 • Date Oct 1969

Filter Results

Displaying Results 1 - 25 of 96
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (183 KB)  
    Freely Available from IEEE
  • Terminal‐Group Association in Carboxy‐ and Carboxylate‐Terminated Polybutadiene

    Page(s): 4221 - 4228
    Save to Project icon | PDF file iconPDF (580 KB)  

    The viscosity of carboxylic‐acid‐terminated polybutadiene increases markedly upon neutralization with mono‐ and divalent bases. These viscosity increases are related to apparent molecular weight, considering the association of the terminal salts as ``polymerizing'' the difunctional prepolymer. For the monovalent alkali‐metal salts, simple end‐group dimerization seems to occur with an average ΔH of ∼-25 kcal/mole. Neutralization with ions of higher valency leads to materials with higher viscosities. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of Hydrostatic Pressure on the Mechanical Behavior of Polyethylene and Polypropylene

    Page(s): 4229 - 4237
    Save to Project icon | PDF file iconPDF (815 KB)  

    An apparatus has been designed and constructed that will allow determination of the mechanical behavior of polymer specimens subject to applied tensile and compressive loading, while the sample is simultaneously subject to a hydrostatic pressure environment. The moduli of high‐density polyethylene and polypropylene determined from compressive tests show a significant increase with pressure. Tensile nominal stress‐strain curves have been obtained at various pressures up to 100 000 psi. These show that the yield stress also increases significantly with increasing pressure for both materials. The nature of yielding and fracture is found to be quite different for the two polymers studied. Polyethylene tends to deform more by shear, and the necked region at high pressures reduces to a fine point before separation. In polypropylene, fracture occurs by plastic tearing across the cross section. An attempt is made to account for the experimental results by use of yield criteria that includes a hydrostatic pressure component. Consideration is also given to the effect of finite deformation theory on the increase in modulus of elasticity under a high pressure environment. The specific nature of the effects produced by the high pressure is found to depend strongly on the molecular structure of the polymer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Plastic Deformation of Polypropylene. III. Small‐Angle X‐Ray Scattering in the Neck Region

    Page(s): 4238 - 4242
    Save to Project icon | PDF file iconPDF (443 KB)  

    The small‐angle x‐ray scattering (SAXS) pattern of polypropylene (PP) drawn at various temperatures (Td = 20°, 100°, and 135°C) was investigated in a range of very closely spaced draw ratio (λ) values through the neck region. In the zone before the neck starts (λ = 1.05–1.1) the uniform diffraction ring due to microspherulitic material with a long period L0 changes into a four‐point diagram superposed onto an elliptical halo. At the beginning of the neck (λ = 1.3–2.5) two meridional maxima arising from a new fibrous structure with a limiting long period LT appear. Irrespective of whether L0≫LT or L0≪LT the transition between L0 and LT is discontinuous. The four‐point pattern reminiscent of the spherulitic structure remains observable up to the end of the neck. In the same manner as in the case of PE, stacks of lamellae exhibiting the most favorable orientation for chain tilt and slip start being plastically deformed and finally break into folded‐chain blocks which are incorporated into microfibrils. The fracture occurs in a thin destruction zone which separates the new microfibrils from the not yet transformed stack of original lamellae. Because of the morphological inhomogeneity of the spherulitic sample, the destruction zones and, hence, the starting points of the microfibrils are rather randomly scattered in the neck region and do not merge into one single layer extending over the whole cross section of the sample. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Brillouin Scattering Near the Glass Transition of Polymethyl Methacrylate

    Page(s): 4243 - 4247
    Save to Project icon | PDF file iconPDF (406 KB)  

    Brillouin scattering of laser light has been used to measure the frequency of hypersonic sound waves in the range of 1010 Hz in PMMA as a function of temperature through the glass‐transition region. A discontinuity in the temperature coefficient of sound velocity is observed at the glass‐transition temperature; this is explained as a consequence of a corresponding discontinuity in the temperature coefficient of the specific volume (thermal expansion coefficient). The ratio of the light scattered by isothermal density fluctuations to that scattered by adiabatic density fluctuations was also measured. This ratio was large and did not change appreciably near the glass‐transition temperature. The value of the Landau‐Placzek ratio is approximately what one would expect from previously observed ultrasonic‐velocity‐dispersion data as a function of temperature well above the glass‐transition temperature. Both the velocity and intensity ratio data indicate that no velocity‐dispersion effects are present for the hypersonic sound waves up to temperatures 35° above the glass‐transition temperature. These results also indicate that the glass transition is not a classical second‐order phase transition. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Infrared Study of Lamellar Linking by Cilia in Polyethylene Single‐Crystal Mats

    Page(s): 4248 - 4253
    Save to Project icon | PDF file iconPDF (483 KB)  

    The infrared spectra of single‐crystal mats of physical mixtures of polyethylene and perdeuteropolyethylene show splittings of CH2 and CD2 bending and rocking modes which are smaller than those for the pure species. This is believed to be a result of the penetration of cilia from the surface of one crystal into the lattice of an adjacent crystal. Calculations of the concentration of cilia are in good agreement with percentages derived from the study of a mixed‐crystal paraffin system, and these concentrations change with crystal thickness as is predicted. Such cilia can account for most of the amorphous component of polyethylene single crystals. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Activation Energy Spectra for Relaxation in Amorphous Materials. I. Volume Relaxation in Polystyrene and Polyvinyl Acetate

    Page(s): 4254 - 4260
    Save to Project icon | PDF file iconPDF (521 KB)  

    A modification of the Primak analysis for activation energy distributions is presented and compared with the well‐known analysis for relaxation time distributions. Mathematical and physical interrelationships between the two analyses are discussed. Activation energy spectra are derived from the data of Kovacs for volume relaxation in polystyrene and polyvinyl acetate. The energy spectra are bell shaped and cover the range from 5 to 20 kcal/mole. The concept of a shift factor is introduced to account for changing structure in the glass transition region. The shapes and locations of the spectra are discussed and compared with previous interpretations of volume relaxation data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Morphology of Polysiloxanes Crystallized from the Melt

    Page(s): 4261 - 4265
    Save to Project icon | PDF file iconPDF (1201 KB)  

    Poly(tetramethyl‐p‐silphenylene siloxanes) fractions ranging in molecular weight from below 104 to above 106, have been crystallized isothermally from the melt. Samples have also been prepared under a wide range of annealing conditions varying from minutes to hundreds of hours. The morphology of these fractured specimens has been studied by electron microscopy. The ease of fracture increases as the molecular weight decreases. The dimension of the lamellar structures ascertained from Pt shadowing and Au decoration techniques increase as the annealing or crystallization temperature is raised. The values are consistent with the crystallite sizes estimated from small‐angle x‐ray measurements made on these same samples, and with the single crystal thickness obtained under comparable crystallization temperatures. The topography of the fracture surfaces depends on the molecular weight and on the annealing conditions. The lower molecular weight samples (below 40 000) exhibit a much higher degree of regularity than the fractions with longer chain lengths. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stress‐Optical Properties of PVC above the Glass Transition

    Page(s): 4266 - 4271
    Save to Project icon | PDF file iconPDF (422 KB)  

    Studies of the photoelastic behavior of a PVC homopolymer film have been carried out in the rubbery state above the glass transition (up to 160°C) to complement studies already carried out in the glassy state. Some measurements were also made on the same samples in the glassy state for completeness. Step‐loading experiments were used, as in previous experiments in the glassy state. The results obtained are somewhat complex, indicating that this polymer is considerably different in nature from a simple amorphous polymer such as polystyrene. There is a progressive shift in the zero load values of birefringence (when the sample is unloaded from increasing stress levels), indicating that a progressive structure change is taking place as load level is increased. This could be a result of progressive plastic yield or breaking and reforming of stress‐sensitive crosslinks. Below the glass transition this shift takes place in two stages, which may be related to the secondary beta transition and major glass transition of the polymer. The stress‐optical coefficient changes from small negative values to large positive values as temperature is increased through the glass transition; a zero value is observed at 80°C. In addition to the abrupt change of SOC at the glass transition, a second abrupt change is observed at 145°C which is the temperature of annealing of the film; annealing conditions may therefore be playing a very important role in determining the solid‐state structure of the polymer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Composite Acoustic Delay Medium with a Zero Temperature Coefficient of Delay

    Page(s): 4272 - 4278
    Save to Project icon | PDF file iconPDF (963 KB)  

    For application in un‐thermostated delay lines a delay medium possessing a low acoustic loss, a zero temperature coefficient of delay and a zero or low aging rate is required. Present isopaustic glasses meet these requirements satisfactorily with the exception of aging which is found to be dependent upon thermal history to a degree that causes difficulty in some applications. This paper reports a new approach to forming a zero temperature coefficient delay medium consisting of the combination in a hot pressed ceramic, with grain size much less than the acoustic wavelength, of two individually stable materials possessing temperature coefficients opposite in sign. Three mixtures have been prepared with different mass ratios of vitreous SiO2 and powdered crystalline MgF2 by pressing at temperatures of 900°–1120°C and at pressures of 7000–20 000 psi. A zero temperature coefficient is found at 41°C for a mixture with a mass ratio (SiO2/MgF2) of 0.360, a positive coefficient is found for a mixture with mass ratio of 0.306 and a negative coefficient for a mass ratio of 0.419. The internal friction of the mixtures near 1.5 MHz is comparable to and even lower than that of typical isopaustic glasses, though the frequency dependence of the loss is higher. For the mixture with mass ratio of 0.360 the attenuation coefficient depends on frequency as f2.3. Tests have shown no measurable room temperature aging over an eight week period following a mild heating to 110°C. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Crossed‐Field Acoustic Amplification in Extrinsic, High‐Mobility, Nondegenerate Semiconductors

    Page(s): 4278 - 4289
    Save to Project icon | PDF file iconPDF (855 KB)  

    A theory, based on Chambers' solution to the classical Boltzmann equation, is developed for the acoustic gain in a high-mobility (μ), nondegenerate, extrinsic semiconductor subjected to crossed dc electric (E0) and magnetic (B0) fields with the wave vector k in the E0×B0 direction. The theory does not restrict the cyclotron radius Rc to a value much less than acoustic wavelength; previous theory based on the phenomenological semiconductor equations requires kRc≪1 for validity. Simple approximations to the general result are developed for the cases of kRc>~1 and kRc≫1, where Rc is the cyclotron radius. The theory is found to explain recent experimental measurements in the regime kRc>~1 where the simpler theory has failed. A lowering of the maximum attainable gain at a given frequency occurs with decreasing B0. Cyclotron resonance peaks in the acoustic gain occur in the regime kRc≫1 when the Doppler-shifted frequency is an integral multiple of the cyclotron frequency. The anomalous behavior in the threshold curve of acoustoelectric current oscillation in InSb is qualitatively explained on the basis of the theory. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Study of Structure and Crystallite Formation in the Glass System Fe2O3·Na2O·B2O3 by Use of the Mössbauer Effect

    Page(s): 4289 - 4293
    Save to Project icon | PDF file iconPDF (393 KB)  

    Mössbauer techniques have been employed to identify crystal formation in the glass system Na2O·B2O3·Fe2O3 containing up to 35 wt% Fe2O3. Glasses in this system exhibit a broadened, quadrupole split doublet with a peak separation of 1.0 mm/sec, a full width at half‐maximum of 0.7 mm/sec, and an isomer shift of 0.3–0.5 mm/sec with respect to Fe in Cr. The formation of crystalline material is correlated qualitatively with sample composition and preparation procedure. The sensitivity of the Mössbauer technique for identification of small amounts of crystalline material is compared with that of x‐ray techniques. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Growth Kinetics of Plate‐Like Precipitates

    Page(s): 4293 - 4300
    Save to Project icon | PDF file iconPDF (771 KB)  

    Different models for the growth kinetics of plate‐like precipitates have been critically reviewed. It is shown that the Zener‐Hillert equation does not properly take into consideration the capillarity effect at the advancing interphase boundary. A mathematical treatment of the diffusion controlled steady‐state growth of plate‐like precipitate is presented for the case in which the variation of concentration along the interface is determined from the theory of capillarity. This variation is assumed to be small so that the steady‐state shape does not deviate appreciably from a parabola. Applicability of the present treatment to the growth of a group of plates is then discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of Deposition Parameters on the Crystallinity of Evaporated Germanium Films

    Page(s): 4301 - 4305
    Save to Project icon | PDF file iconPDF (462 KB)  

    The crystallinity of Ge films deposited on (111) Ge substrates in vacuum ambients ≪10-8 Torr has been investigated as a function of deposition rate, substrate temperature, thermal treatment of substrates, and background oxygen pressure. Polycrystalline and epitaxial films were obtained at temperatures up to 200° lower than reported by previous investigations, and thermal annealing of substrates at 600°C prior to deposition resulted in a minimum epitaxial temperature of 100°C. Oxygen ambients as low as 5×10-9 Torr have been found to impede crystal growth and increase epitaxial temperatures by 50°–75°C. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Branching and Bending of Dislocations in Sodium Chloride Crystals

    Page(s): 4306 - 4312
    Save to Project icon | PDF file iconPDF (1869 KB)  

    Discrepancies arising in the number and positions of the etch pits on the opposite cleavage faces when cleavage takes place at different positions from the branching and bending points have been discussed. Experimental evidence for these discrepancies is presented by the help of a new etchant consisting of methanol as solvent and CdCl2 as poison developed for NaCl crystals. Using this etchant which has the unique property of producing etch pits associated with beaks at the aged dislocations, actual branching of dislocations occurring inside the crystal, shift in the positions of the corresponding etch pits on the opposite cleavage faces due to bending of dislocations near the cleavage plane, etch pits associated with wings, and solution channels arising due to dislocation half‐loops have been recorded. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Diffraction by Faulted Close‐Packed Lattices: An Analytic Solution for Systems Without Long‐Range Correlation of Stacking Symbols

    Page(s): 4313 - 4321
    Save to Project icon | PDF file iconPDF (590 KB)  

    Wilson's method for analysis of diffraction by faulted close‐packed lattices is generalized in a way which eliminates the need for solution of a difference equation. This leads to an analytic solution for the intensity distribution associated with a difference equation of any order. The solution is valid for all systems where there is not a long‐range correlation between the stacking symbols of close‐packed layers (this criterion is reexpressed in terms of properties of the difference equation). The method is used to derive analytic solutions for the intensity distributions which arise from Jagodzinski's two‐parameter model for growth faulting and from fcc crystals with mixtures of intrinsic, extrinsic, and growth faults. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dislocation Dynamics and Steady Plastic Wave Profiles in 6061‐T6 Aluminum

    Page(s): 4321 - 4334
    Save to Project icon | PDF file iconPDF (1081 KB)  

    Under certain conditions, plastic wave profiles in 6061‐T6 aluminum may achieve a constant wave velocity and steady shape within a few millimeters from the impact surface in a plate‐impact experiment. The finite rise time of the steady plastic wave is assumed to be controlled by the motion of dislocations within the solid. The theory of steady‐propagating waves is presented and theoretically determined wave profiles are compared with those measured experimentally by means of laser interferometry. These studies provide information on dislocation velocity and multiplication under conditions of shock‐wave compression. In particular, if the mobile dislocation density is assumed to be a function of plastic strain alone, the dislocation velocity is found to be proportional to (τ-τ0)n, where τ is the applied shear stress, τ0 is a back stress, and n is a constant approximately equal to 2. Thus, it appears that a linear relationship between dislocation velocity and shear stress, which has been found to apply for strain rates less than 10-2 μsec-1 in aluminum, may not be sufficient to describe rate‐dependent behavior at strain rates greater than 10-2 μsec-1, which are achieved in shock‐wave compression. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Pyroelectric Effect in Barium Titanate Ceramic

    Page(s): 4335 - 4340
    Save to Project icon | PDF file iconPDF (488 KB)  

    The pyroelectric coefficient (at constant stress) of a 95 wt% BaTiO3, 5 wt% CaTiO3 ceramic composition (Clevite Ceramic B) was measured over the temperature range from 4.9° to 400°K. Extrema in the pyroelectric coefficient were observed at the rhombohedral‐orthorhombic transition point (150°–170°K), the orthorhombic‐tetragonal transition point (240°–260°K), and the tetragonal‐cubic transition point (Curie point, at 387°K). The pyroelectric coefficient showed no anomalous behavior below 150°K. A spontaneous polarization curve derived from the pyroelectric results is compared with published single‐crystal measurements. The ceramic results can be completely interpreted by means of a model describing switching of domain orientations at phase transitions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization of Piezoelectric Transducers Used in Ultrasonic Devices Operating Above 0.1 GHz

    Page(s): 4341 - 4352
    Save to Project icon | PDF file iconPDF (859 KB)  

    Piezoelectric transducers for ultrasonic devices operating at frequencies above 100 MHz are presently being made either by thin‐film deposition techniques or by bonding thin plates to the substrate and lapping them to the required thickness. In either case the performance of the transducers cannot be evaluated separated from the device, and the evaluation is complicated by the presence of intermediate layers and spurious circuit elements. This paper uses Mason's equivalent circuit to critically appraise the validity of methods used to evaluate transducer performance from loss and admittance measurements made under these circumstances. Computed families of curves are presented, spanning the practically important range of mechanical impedances and coupling factors. Experimental data from a ZnO film and a LiNbO3 thin‐plate transducer on fused quartz substrates are presented to demonstrate the application of equivalent circuit descriptions to obtain the coupling factors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Elastic and Piezoelectric Constants of Ba2NaNb5O15

    Page(s): 4353 - 4356
    Save to Project icon | PDF file iconPDF (271 KB)  

    The elastic, piezoelectric, and dielectric constants of Ba2NaNb5O15 have been measured. The experimental techniques used involve mostly thickness‐mode measurements made on small plate‐shaped samples of various crystallographic orientations. As reported previously, the z‐cut plate has a thickness longitudinal mode coupling factor of 0.57, which makes this material attractive for application as a high‐frequency longitudinal mode transducer. However, from the measured constants and the theory of piezoelectric plate vibrations, it is determined that no crystallographic orientation other than the z‐cut has properties suitable for ultrasonic transducer applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sputter Machining of Piezoelectric Transducers

    Page(s): 4357 - 4361
    Save to Project icon | PDF file iconPDF (416 KB)  

    This paper demonstrates that sputter machining can be used to obtain fundamental mode transducers or resonators for the frequency range above 100 MHz where mechanical methods of thickness reduction have low yields. Material is removed by bombarding the specimen with high‐energy ions drawn from a gaseous plasma. Experimental results are given for the sputter machining of sputter‐deposited zinc oxide, Y‐cut lithium niobate, and Y‐cut quartz. The highest fundamental resonant frequency attained was 1.8 GHz using lithium niobate, corresponding to a thickness of about 2 μ. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of Penetration Data from Grain Boundary Diffusion Experiments

    Page(s): 4361 - 4366
    Save to Project icon | PDF file iconPDF (467 KB)  

    The results from computer solutions to the various mathematical analyses of the grain boundary diffusion problem which have previously been developed are presented in a convenient manner for interpretation of grain boundary diffusion measurements using the penetration depth technique. In particular, the results allow a quantitative assessment of the limitations and applicability of the two approximate solutions due to Fisher and Whipple. The present results also permit the use of Whipple's exact solution for data analysis using a simple graphical technique. Results of several previous grain boundary diffusion investigations are reevaluated by applying the exact solution to the published penetration data. It is concluded that the activation energy for grain boundary diffusion along 〈100〉 symmetrical tilt grain boundaries is independent of grain boundary misorientation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Grain Boundary Self‐Diffusion in Nickel

    Page(s): 4366 - 4373
    Save to Project icon | PDF file iconPDF (765 KB)  

    High‐purity nickel bicrystals with controlled grain boundary misorientations have been grown from the melt using an electron beam floating‐zone technique. These bicrystals have symmetrical tilt grain boundaries with 10° misorientation between {111} planes tilted about a 〈112〉 axis, and 10° twist about a {111} axis. The diffusion of nickel‐63 in these boundaries and similar sintered grain boundaries has been studied over the temperature range 600°–970°C using high‐resolution contact autoradiography. Using the dislocation pipe model for low‐angle grain boundaries, edge and screw dislocations were found to have similar activation energies of 40.7 and 44.9 kcal/mole, respectively. The value for the tilt boundaries is shown to agree well with recent work on isolated edge dislocations in nickel. It is concluded that the low‐angle tilt boundaries are composed of 〈112〉 {111} edge dislocation arrays which exhibit the same diffusion behavior as isolated edge dislocations formed by plastic deformation. Also, the higher value of the activation energy for 〈112〉 tilt boundaries as compared to previously reported results on 〈100〉 tilt grain boundaries in nickel points out a basic difference in the energy required for the mass transport process in the two types of dislocation structures found in 〈100〉 and 〈112〉 tilt boundaries. A theoretical explanation of this activation energy difference is consistent with an assumed vacancy mechanism for dislocation pipe self‐diffusion. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Diffusion of Nickel in Amorphous Silicon Dioxide and Silicon Nitride Films

    Page(s): 4374 - 4376
    Save to Project icon | PDF file iconPDF (235 KB)  

    Nickel‐59 radiotracer has been used to determine nickel diffusion coefficients in amorphous silicon dioxide and silicon nitride films between 1100° and 1490°K. Nickel distribution has been found to be Fickian with the calculated diffusivities obeying Arrhenius equation. Long diffusion times have been found to produce anomalous diffusivities in silicon nitride. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of Large Electric Fields on the Electron Energy Distribution and Ionization Rate in a Cesium Discharge

    Page(s): 4377 - 4383
    Save to Project icon | PDF file iconPDF (454 KB)  

    The Boltzmann equation with the electric field and the collision terms is solved numerically for a spatially uniform, steady‐state, cesium thermionic plasma. The collision terms includes the elastic, inelastic, and electron‐electron Coulomb interactions. The Fokker‐Plank approximation of the Coulomb collision is used in the present study. The effects of non‐Saha population on the electron energy distribution and ionization rate near the emitter are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

Full Aims & Scope

Meet Our Editors

Editor
P. James Viccaro
Argonne National Laboratory