Materials Literature
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The unique properties of ceramics based on silicon carbide and silicon nitride make them prime candidates for use in advanced energy conversion systems. These compounds are the bases for broad families of engineering materials, whose properties are reviewed. The relationships between processing, microstructure, and pr…
Diamond or cubic boron nitride particles can be sintered into strong masses at high temperatures and very high pressures at which these crystalline forms are stable. Most of the desirable physical properties of the sintered masses, such as hardness and thermal conductivity, approach those of large single crystals; the…
Abstract The kinetics of hydrogen peroxide decomposition was followed in the presence of perchloric acid. The reaction was of second order with respect to the initial concentration of hydrogen peroxide and of first order with respect to the concentration of perchloric acid; the determined activation energy was 102.5 k…
Abstract A polyesterimide was prepared by reacting 4,4′‐diaminodiphenylmethane with trimellitic acid anhydride in ethylene glycol, which acts as an esterification reagent as well as a solvent. The solution and thermal behaviour, and a few other properties were studied. The polymer was found to be soluble in highly pol…
The aggregation of nitrogen in type Ib diamond, at 1500 degrees C in vacuo, has been investigated for natural and synthetic samples containing around 50 ppm and 500 ppm isolated substitutional nitrogen respectively. The rate constant for the aggregation process in untreated diamonds is very much less than that reporte…
Experimental results for the low temperature thermally stimulated luminescence of a single crystal ZnS specimen are presented. The analysis of these by conventional methods indicates the inadequacy of the basic single centre model. An extension of this model to include two overlapping states is developed and the exper…
Single crystals and polycrystalline Bi2WO6 samples are used to measure the dielectric constant, loss, and electrical conductivity, over a wide range of temperature, oxygen partial pressure in ambient atmosphere, and frequency of the measuring electric field. Maxima of the dielectric constant are observed at phase tran…
The behaviour of electron and hole quantum efficiencies as well as mobilities are investigated experimentally at high electric fields. The shape of transient small charge drift current as well as the field dependence of contributions of ionized electrons and holes to the quantum efficiency indicate impact interband io…
Measurements of the back scatter coefficient as a function of incident electron energy, angle of incidence, and target atomic number are described. The results are compared with existing theories for normal and non-normal electron incidence. Analytical expressions for the back scatter coefficient, which can be used in…
DC conductivity and dielectric studies of CoxZn1−xFe2O4 (x = 0.32, 0.49, 0.79), BaFe12O19, and Mg0.25Zn0.75Fe2O4 are reported as a function of temperature and frequency. The lattice constant and the existence of a single phase are established from X-ray studies. The dielectric behaviour is attributed to the Maxwell-Wa…
Highly oriented surface layers of lithium disilicate crystals were grown by crystallizing glasses of composition Li2Si2O5 in a temperature gradient. The polar c axes of the crystallites were oriented parallel to the temperature gradient and perpendicular to the sample surface. The pyroelectric response of the glass-ce…
The electrical conductivity in tungsten phosphate glasses of three different compositions (67 mole% of W${\mathrm{O}}_{3}$-33 mole% ${\mathrm{P}}_{2}$${\mathrm{O}}_{5}$, 70 mole% M${\mathrm{O}}_{3}$-30 mole% ${\mathrm{P}}_{2}$${\mathrm{O}}_{5}$, and 81 mole% W${\mathrm{O}}_{3}$-19 mole% ${\mathrm{P}}_{2}$${\mathrm{O}}…
In this paper we consider energy transfer among impurity molecules in disordered systems. We use the result of Gochanour, Andersen, and Fayer [J. Chem. Phys. 70, 4254 (1979)] for the generalized diffusion coefficient D(t) in terms of the decay function Φ(t), in conjunction with separate calculations of Φ(t) in the pai…
The point dipole interaction model for molecular polarizability recently proposed by Applequist, Carl, and Fung is modified by replacing isotropic atomic point dipoles with anisotropic atomic point dipoles. The modified formalism, which is invariant to coordinate transformations, requires an additional empirical param…
Cross sections for Rayleigh and Mie scattering on a roughned conducting surface are given. The Rayleigh scattering is strongly enhanced by roughness. Rayleigh and Mie scattering are found to interfere with each other. The experimental consequences for surface enhanced Raman Scattering (SERS) are discussed. (AIP)
The pyrolysis of organic dianhydrides (e.g., 3,4,9,10-perylenetetracarboxylic dianhydride) in an evacuated system results in the loss of hydrogen, CO, and CO2 and the deposition of a chemically inert, metallic-appearing mirrolike film. The films are highly conducting (σRT250 Ω−1 cm−1) and can evidence either metallic…
A molecule adsorbed on the surface of a conducting prolate ellipsoid will Raman scAtter with an enhanced cross section. The relevance of this fact to the phenomenon of surface enhanced Raman scattering (SERS) is discussed. (AIP)
The newer tetracyclines are defined as those tetracyclines available in the United States but not approved for veterinary use. These include demeclocycline, methacycline, doxycycline, and minocycline. Of these, doxycycline and minocycline appear to offer advantages that would render them useful in certain situations i…
It is shown on the example of the dielectric data for Er-doped CaF 2 that very slight departures from the true Debye response can be assessed very accurately using the analysis of the real part of the susceptibility. Given adequate precision of measurements, this method is far more sensitive than the plotting of the c…
Chemically deposited PbS thin films have been prepared for use as infrared detectors. A systematic and elaborate study using scanning electron microscopy shows that the structure and crystallite size are related to the photosensitivity. Both the role of chemical oxidant influencing the type of conductivity and morphol…