Materials Literature
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Abstract Many problems—from soil research to ceramics—require a reliable characterization of the clay minerals involved. This can be done using four clay-organic reactions: (i) staining tests and dye adsorption; (ii) glycerol and glycol adsorption; (iii) intercalation; (iv) alkylammonium ion exchange. Dye adsorption (…
The slip band formed in a grain on the material surface is a preferential site for crack initiation during low strain fatigue of polycrystalline metals. The forward and reverse plastic flow within the slip band is modeled in the present study by dislocations with different signs moving on two closely located layers, a…
Calorimetric, thermal expansion and optical measurements as well as optical observations confirm the sequence of structural phase transitions D 4h 17 (I) to D 2h 18 (II) to D 2h 12 (III) in the perovskite layer compound (C 2 H 5 NH 3 ) 2 CuCl 4 . For the I to II change the results show second-order character together…
Abstract Durch Erhitzen von Dicyano‐cobyrinsäure‐heptamethylester unter bestimmten Bedingungen wird zwischen den C‐Atomen 7 und 8 unter formaler Abspaltung von Essigsäure‐methylester eine neue Doppelbindung gebildet.
Experiments are presented which show that surface imperfections can give rise to a larger linear magnetoresistance than previously supposed; in fact, large enough to explain many hitherto-unexplained published results. A theoretical model, which takes into account both the finite width of the sample and the Hall field…
The incommensurate adsorbed solid is found to become unstable to dislocations when the lattice period approaches that of a sufficiently low-order commensurate phase such as a 2\ifmmode\times\else\texttimes\fi{}1 rectangular overlayer or the $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\te…
Abstract Nitrogen occurs in most natural diamonds in concentrations of up to 0.3 at. %. In about 0.1% of diamonds, the nitrogen occurs as single substitutional atoms but in most diamonds aggregates of two or more nitrogen atoms occur. The various types of aggregate have been identified by detailed study of optical abs…
Abstract Poly(ethylene terephthalate) fibres grafted with poly(vinyl acetate) by γ‐radiation were hydrolysed under alkaline and acidic conditions in order to obtain poly(ethylene terephthalate)‐graft‐poly(vinyl alcohol) fibres. In alkaline media poly(ethylene terephthalate) degraded without appreciable conversion of a…
The analogy between the ray-optical (Eikonal) theory of X-ray diffraction in distorted crystals and mechanics gives the possibility to explain qualitatively the contrast in section topographs of crystals containing one-directional varying lattice-plane distances. The formation of topographic contrasts is discussed for…
Measurements of the directional coefficient of backscattered electrons are carried out in the incidence plane of the beam. Samples of C, Al, Cu, Ag, Au, and U are investigated with primary energies 5, 10, 20, and 30 keV for normal incidence and for the incidence angles 30°, 60°, and 80°. The analysis of the obtained r…
Dielectric, thermal, electrocaloric, elastic, optical, and electromechanical properties of three ferroelectrics with diffuse phase transition (PLZT 8/65/35 ceramics, lead magnesium niobate and strontium barium niobate single crystals) are investigated in dependence on temperature and electric field strength. It is sho…
Apart from Fuchs-Kliewer surface phonons, conduction-band surface plasmons and probably intraband single-particle scattering contribute to the electron-energy-loss spectra (primary energy \ensuremath{\sim}5 eV, resolution 10 meV) measured on clean, UHV-cleaved, $n$-type GaAs(110) surfaces. Coupling between surface pho…
The luminescence of pure single crystals of CdWO4 is reported. Two emission bands are observed. Their decay times are measured and discussed.
A simple model for the depinning and dynamics of a sliding charge-density wave is presented. The model consists of viscously damped motion in a periodic potential and accounts for the main features of the nonlinear conductivity, noise, and ac-dc coupling in the charge-density-wave state of Nb${\mathrm{Se}}_{3}$ at low…
The two photon excited fluorescence excitation spectrum of UF6 has been observed in the region 410 to 315 nm. The spectrum is virtually indistinguishable from the one photon absorption in this region. No vibronic structure was observed in absorption or dispersed emission. These data indicate a high density of u and g…
The results of Raman scattering measurements on the mixed-crystal system $1T\ensuremath{-}\mathrm{T}\mathrm{a}{\mathrm{S}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ in the commensurate charge-density-wave state are reported. In the pure compounds, our measurements indicate that a strong LA-TA phonon interaction at the dist…
A set of polarized low-energy-electron diffraction (PLEED) data from a W(100) surface measured using a polarized electron beam is presented. The data include conventional LEED profiles $I(E,\ensuremath{\theta})$ as well as $S(E,\ensuremath{\theta})$ profiles which measure the spin dependence of the scattering. These p…
The compound ${\mathrm{Fe}}_{x}{\mathrm{Nb}}_{1\ensuremath{-}x}{\mathrm{Se}}_{3}$, which has been prepared in the form of single crystals and powders, only forms in a narrow range of stoichiometry near $x=\frac{1}{4}$. The crystal structure of Nb${\mathrm{Se}}_{3}$ is radically modified by the addition of iron and con…
We have found exact limits on the validity of the Flory–Huggins approximate treatment of stiff chains on a lattice for small values of g, the fraction of gauche bonds, by obtaining lower bounds for the total number of Hamilton walks WH(g) as a limiting case of the lattice model. The Flory–Huggins approximation underes…
The silver halide crystals have many peculiarities in their physical properties which are uncommon among the simple ionic solids. The different theoretical models used to calculate the properties of this group of solids have concentrated on explaining one or the other of them. But these calculations have one major dif…