Materials Literature
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Results of self-consistent ab initio band-structure calculations using the augmented--spherical-wave method are presented for the stable intermetallic compounds ${\mathrm{Y}}_{2}$${\mathrm{Fe}}_{17}$, ${\mathrm{Y}}_{6}$${\mathrm{Fe}}_{23}$, ${\mathrm{YFe}}_{3}$, and ${\mathrm{YFe}}_{2}$ and for the hypothetical compou…
The diffraction by two planar slanted fringe gratings superposed in the same volume of an anisotropic medium is treated using rigorous 3-D vector coupled wave analysis. Arbitrary angle of incidence and polarization are included. Both phase and/or amplitude slanted gratings in anisotropic media are treated in the analy…
Preliminary studies were conducted on the laser processing of SiC/A356-Al alloy metal matrix composite (MMC) for such applications as welding/joining and cutting. The SiC/A356-Al MMC was processed using several different laser specific energies. Microstructural observations after laser processing revealed that the ext…
The oxygen-carbon luminescence defects with no-phonon emission at 0.767 eV (``P line'') and 0.79 eV (``C line'') created in pulled silicon after 450 \ifmmode^\circ\else\textdegree\fi{}C thermal annealing or electron irradiation, respectively, are investigated in a comparative study. This includes investigation of all…
Alloys with the composition RE2Fe17 and RE2Fe15X2 (X=Al,Ga) have been synthesized by the arc-melting technique followed by an 125-h anneal at 900–1000 °C in evacuated silica capsules. The new compound Nd2Fe15Ga2 is unstable below 800 °C, and is only obtained by quenching from above 900 °C. From x-ray powder diffractio…
We present for the first time a comparative vibrational study of polythiophene, polypyrrole, and polyisothianaphthene. The calculation is performed at k=0 in the plane of the chains for both aromatic-like and quinoid-like structures. The Ag species which are present in the Raman spectra are more particularly investiga…
Pseudomorphic Si/Si-Ge strained layer superlattices are metastable and will relax to lower-energy, less strained, states on thermal annealing. Such relaxation may occur by the generation of misfit dislocation or by compositional homogenization of the superlattice. The particular mechanism adopted is shown to depend on…
We calculate the contribution to the thermal conductivity, \ensuremath{\kappa}, in amorphous solids of the hopping of localized vibrational modes coupled to phonons via the anharmonic interaction. This contribution is generally important for temperatures above the plateau region in \ensuremath{\kappa}. The temperature…
Point defects, impurities, and defect-impurity complexes in diamond particles and polycrystalline films were investigated by cathodoluminescence (CL) imaging and spectroscopy in a scanning electron microscope. The diamond films and particles were grown by hot-filament methane-hydrogen chemical-vapor deposition at seve…
A high density of microvoids could cause inhomogeneous distribution of deep localized states in amorphous germanium. The electronic transport in such media is no longer dominated by Mott variable-range hopping. The dc conductivity is proportional to ${T}^{n}$ with n\ensuremath{\simeq}6, suggesting that the transport i…
The physical properties of carbon-boron nitride (C-BN) prepared from mixtures of BCl3, NH3, and selected hydrocarbons by codeposition methods have been investigated using x-ray diffraction, electron diffraction, transmission electron spectroscopy, x-ray photoelectron spectroscopy, Raman scattering, optical reflectivit…
Under static conditions, the macroscopic contact angle θ between a (partially wetting) liquid, a solid, and air, lies between two limiting values θr (receding) and θa (advancing). If we go beyond these limits (e.g., θ=θa+ε, ε>0) the contact line moves with a certain macroscopic velocity U(ε). In the present pap…
Conformational disorder plays an important role in determining the electronic properties of conjugated polymers. To obtain a better theoretical description of the role and extent of conformational disorder, we derive the π electron correlation length and the bond correlation length in terms of the effective torsional…
The nature of excess oxygen in as-manufactured and γ-irradiated high-purity synthetic silicas is investigated. Electron-spin-resonance measurements suggest that peroxy radicals ( 3/4 SiOO⋅) could be produced either by the cleavage of peroxy linkages ( 3/4 SiOOSi 3/4 ) or by the reaction of E’centers ( 3/4 Si⋅) with ox…
The effect of hydrogen addition on growth of diamond films under the conditions of chemical vapor deposition was investigated computationally. A detailed chemical kinetic mechanism was composed to describe the evolution of reaction species in pyrolysis of hydrogen- and argon-diluted methane mixtures with imposed tempe…
We distinguish between two classes of the emeraldine form of polyaniline. Class I consists of materials prepared in the conducting, doped emeraldine salt (ES) form. They form substantially crystalline salts ES-I with the Pauli susceptibility, ${\ensuremath{\chi}}^{P}$, of a polaron lattice. Dedoping leads to an amorph…
We report the preparation of hard nitrogenated amorphous carbon films doped with as much as 20 at. % nitrogen. The nitrogen groups created by doping do not dramatically affect the film structure, but are found to break symmetry in ${\mathrm{sp}}^{2}$ domains causing the Raman-active G (``graphitic'') and D (``disorder…
Abstract The dye‐sensitized photo‐oxygenation of 3‐hydroxyestra‐1,3,5(10), 9(11)‐tetraen‐17‐one ( 8 ) gives a complex mixture from which only the 1,4‐endo‐peroxide 10 can be isolated in low yield. In contrast, the 3‐methoxy derivative 9 yields the C‐seco‐aldehyde 11 as a major product, suggesting that 1,2‐dioxetane is…
Single crystals of potassium hydrogen phthalate, commonly known as potassium acid phthalate (KAP) have been grown from aqueous solutions. The dielectric constant, loss tangent, specific heat and pyroelectric coefficient were determined as a function of temperature. Frequency response of the dielectric constant and tan…
Ba 0.9 Ca 0.1 TiO 3 ceramics have been fabricated using powders obtained by calcining mixtures of (i) BaCO 3 , CaCO 3 and TiO 2 and (ii) Ba 0.9 Ca 0.1 CO 3 and TiO 2 . The precursor Ba 0.9 Ca 0.1 CO 3 was prepared by a wet technique to ensure homogeneous mixing of Ba and Ca ions at the atomic level. DTA analysis of so…