Materials Literature
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Abstract Microstructural features of semicrystalline polymers are reviewed, as are the roles of chain properties and thermal history in their development. Experimental results relating failure properties to microstructural detail are described. General models to explain inter‐ and intra‐spherulitic failure behavior ar…
Richard Zallen 1983 Chichester: John Wiley xi + 304 pp price £30.95 ISBN 0 471 01968 2 As the author points out, solid state physics has traditionally meant crystal physics, where crystal-lattice periodicity assists the formulation of the mathematical descriptions which predict the properties of the solid. In recent y…
The action of basic catalysts such as KH on the ammonolysis products of CH 3 SiHCl 2 , (CH 3 SiHNH) n , results information of polysilazanes of intermediate molecular weight (600 to 1800). Pyrolysis of these polysilazanes gives ceramic materials, which appear to be mixtures of Si 3 N 4 , SiC, and C, in yields of 80 to…
An earlier report [Acta Cryst. (1977), A33, 681-684] by a joint IUCr-IMA committee on the nomenclature of polytypism has been revised and extended. Two kinds of symbolism are recommended for use with either simple or complicated polytypic structures. The first consists of 'indicative symbols' in a modified Gard notati…
Abstract Extremely small colloidal ZnS particles (diameter ∼ 1.7 nm) were made by either photo‐degradation of 3 nm particles or rapid precipitation in phosphate containing solution at pH = 7‐−8. The absorption spectra of these particles are different from that of macrocrystalline ZnS, and the changes are regarded as a…
Abstract Infrared spectra in conjunction with calorimetric measurements have been used to follow the crystallization process and microstructural changes of poly(ethylene oxide) (PEO) in poly(ethylene oxide) and poly(methyl methacrylate) (PMMA) blends. We have given particular attention to compositions containing low P…
The diffractive properties of constant-thickness zone plates composed of arbitrary materials are presently well known. Less well known, however, is the fact that the constant-thickness zone plate is the best possible profile that can be created for maximizing the throughput diffraction efficiency of a zone plate syste…
The cubic Laves phase of YCo 2 is near a transition from a paramagnetic to a magnetically ordered state. Self-consistent energy-band calculations yield the total energy and the magnetic moment as functions of volume. The new fixed spin-moment (FSM) method, which allows one to calculate the total energy as an explicit…
Rigorous expressions for the exchange parameters and the spin-wave stiffness constant of ferromagnetic metals are obtained using a local spin-density functional formalism and the muffin-tin potential model. The calculated results for ferromagnetic iron are given as an example of the approach.
Narayanaswamy's model of structural relaxation has been shown to provide an excellent description of the behavior of a variety of glasses. In the standard formulation, the relaxation time, τ is represented by the Arrhenius equation, with the activation energy partitioned between the temperature and Active temperature.…
We discuss the behavior of a liquid partially wetting a solid surface, when the contact angle at equilibrium θ0 is small, but finite. The solid is assumed to be either flat, but chemically heterogeneous (this in turn modulating the interfacial tensions), or rough. For weak heterogeneities, we expect no hysteresis, but…
A simple form of multi-ion interaction has been constructed for the purpose of atomistic simulation of transition metals. The model energy consists of a bonding term, which is the square-root of a site density ρi, summed over atoms i, and a repulsive pairwise term of the form The site density ρi is defined as sum over…
Brillouin scattering from $a$-Si${\mathrm{O}}_{2}$ up to 17 GPa shows that an irreversible change in the longitudinal sound velocity takes place between 10 and 17 GPa and that this change is stable at atmospheric pressure. Raman spectra of the retrieved sample indicate that it is also amorphous but differ noticeably f…
Measurement of the fractal dimension, $D$, of colloidal aggregates of small silica particles is reported. We observe power-law decay of the structure factor $[S(k)\ensuremath{\sim}{k}^{\ensuremath{-}D}]$ by both light and x-ray scattering showing that the aggregates are fractal. $D$ is found to be 2.12\ifmmode\pm\else…
The new tetrachalcogenide compounds have a one-dimensional structure and two of these show transport properties which are characteristic of this type of conductor. The authors electron microscopy study permits them to show clearly and characterise the charge density waves which appear at 263 and 285K in (TaSe 4 ) 2 I…
We have used the theory developed in the previous paper to study the induced orientational order at simple models of a solid-liquid crystal (LC) interface. The LC is modelled by a Maier-Saupe type of anisotropic pairwise potential while the solid is modelled by an impenetrable wall which exerts an anisotropic external…
Molecular simulation calculations lead to strongly correlated data sequences for which the normal method of estimating the errors may lead to serious underestimates. The nature of the correlations are examined and superior methods of error estimation are identified.
By means of Penning-ionization electron spectroscopy the outermost surface layer of a pentacene film on a graphite substrate (cleavage plane) was selectively observed. Ultraviolet photoelectron spectroscopy was also applied to observe several layers from the surface. From the analyses of the two types of spectra the s…
Subharmonic steps in the dc $I\ensuremath{-}V$ characteristics are reported in the model compound Nb${\mathrm{Se}}_{3}$, when subjected to combined dc and ac drives. The steps occur at currents which correspond to frequencies ${\ensuremath{\omega}}_{\mathrm{int}}=(\frac{p}{q}){\ensuremath{\omega}}_{\mathrm{ext}}$, wit…
A series of twenty homogeneous ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}\mathrm{Ti}{\mathrm{O}}_{3}$ mixed crystals has been measured dielectrically between 4.2 and 300 K. In the tetragonal phase, the dielectric constant perpendicular to the $c$ axis becomes peaked above ${x}_{c}=0.0018$, the quantum mechanic…