Materials Literature
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The structural and electronic properties of the complex tetrahedral structures B-8 (or ``BC8,'' bcc with 8 atoms per cell) and T-12 (or ``ST12,'' simple tetragonal with 12 atoms per cell) phases of silicon and carbon are computed with ab initio density-functional calculations of the energy, pressure, and enthalpy. For…
ac impedance techniques have been used to characterize ceramic samples of LiTaO3 and the solid solutions Li1−5xTa1+xO3 as a function of temperature in the range 350–800 °C. LiTaO3 has a low conductivity and the principal charge carriers appear to be electrons. At temperatures well removed from its ferroelectric Curie…
A simple, universal model for structural properties of sp-bonded semiconductors and insulators is presented. The model elucidates the physical mechanisms determining the chemical trends and predicts semiquantitatively the stable crystal structures, bond lengths, bulk moduli, transition pressures of structural phase tr…
Using the Stillinger-Weber potential we explored the liquid, crystal, and amorphous phase diagram of silicon by molecular dynamics. We obtain the chemical potential of the crystal by following the crystal-vapor coexistence curve from the T=0 harmonic solid up to the melting point. The liquid free energy is found by re…
Recently, nanometer-sized crystalline materials have been proposed to represent a new solid-state structure which exhibits neither long-range order (like crystals) nor short-range order (like glasses). It was the purpose of this study to test this idea by x-ray diffraction experiments. Nanometer-sized crystalline mate…
We present the results of a study of the room-temperature polarized reflectance of (1:2) 1,1'-dimethylferrocenium ditetracyanoquinodimethanide [(${\mathrm{Me}}_{2}$Fc)(TCNQ${)}_{2}$] over the range between the far infrared and the near ultraviolet. Kramers-Kronig analysis of the reflectance is used to determine the op…
The optical properties of glasses containing a small amount of thermally developed CdSexS1−x microcrystalline phase are studied with emphasis on quantum confinement effects exhibited at small crystallite size. Optical absorption, photoluminescence, x-ray diffraction, and transmission electron microscopy are used to ex…
In order to account for the differences observed between low and high temperature deformation textures, the influence of slip or cross‐slip on planes other than the {111} is considered in FCC metals. The first set of possible new slip systems treated is the {100}〈110〉. The dual single crystal yield surface is construc…
A method of polarization ray tracing for calculating the instrumental polarization function of an optical system using the Jones calculus is presented. Polarization ray tracing supplements the equations of ray tracing to include amplitude, phase, polarization and retardance effects of thin films, polarization elements…
Intracavity nearly degenerate four-wave mixing has been used together with transmission measurements to evidence the important role played by Auger recombination in the relaxation rate of electron-hole pairs in semiconductor-doped glasses pumped by high laser intensities. Results show a shortening by a factor of 100 o…
The goal of the triagency SP-100 Program is to develop long-lived, compact, lightweight, survivable nuclear reactor space power systems for application to the power range 50 KWe to 1MWe. The successful development of these systems should enable or significantly enhance many of the future NASA civil and commercial miss…
A 1.8-A resolution x-ray crystallographic restrained least squares refinement has been carried out on the phenylethane boronic acid (PEBA) complex of alpha-chymotrypsin dimer (alpha-CHT), and it has been compared to the 1.67-A resolution structure of the native enzyme. PEBA has a high binding affinity for alpha-CHT, a…
Solute exclusion was used to determine the pore volume and micropore size distribution of wet cellulosic materials. Glucose, cellobiose, and polyethylene glycol (PEG) (8 to 130 A in diameter) were used as molecular probes. Four replicates of cellulosic samples, with each sample being analyzed 4 to 8 times, gave the co…
A viable chemical surrogate for monitoring the effectiveness of hazardous waste incinerators must include high thermal stability and low toxicity among its characteristics. The relationship between sulfur hexafluoride (SF6) and hazardous constituent thermal stability for a mixture of chlorinated hydrocarbons indicates…
Abstract Single crystals of LHP (Lead Hydrogen Phosphate) have been grown using the controlled reaction between lead nitrate and orthophosphoric acid solution by diffusion process in silica gel medium. Transparent crystals upto 6 × 4 × 3 mm 3 in size have been grown at room temperature. The d.c. electrical conductivit…
From more than one hundred Nickel-Aluminium (Ni-Al) bronze sand cast ship propellers, the effect of thickness on the properties of the material has been investigated. For this purpose the mechanical and corrosion fatigue properties have been measured
Abstract Measurements of electrochemical photocapacitance spectroscopy (EPS) of ZnSe were carried out with the aim of studying the effect of photoelectrochemical etching. A new transition is observed that can be assigned to a shallow acceptor state. The observation of that transition is explained by the etching‐out of…
The oxidation states of chromium dissolved in binary sodium silicate glasses were analyzed by X‐ray photoelectron spectroscopy (XPS). The measured “equilibrium” Cr 6+ fractions in glasses with varying Na 2 O contents are shown to be in good agreement with results obtained by other techniques reported in the literature…
Abstract Defect Sites of CdO, Reducibility, Analysis Three procedures of chemical analysis are proposed for the direct determination of excess Cd in CdO: a spectrophotometric, a titrimetric and a gravimetric one, for 0-1500 ppm, 500-50,000 ppm and above 5%, respectively. The good reproducibility and reliability is ill…
Solid mixtures containing initially uniform dilute concentrations of impurity elements may, upon the application of mechanical and thermal loading, develop regions of high impurity concentration that could result in local degradation of material properties. To address these degradation processes, a fully coupled therm…