Materials Literature
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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…
The direct simulation Monte Carlo (DSMC) method has been modified to deal with the very small degree of ionization that occurs in the early stages of the 'communications blackout' phase of re-entry. The simplified model of the process assumes that the ionization is entirely a consequence of the reaction N + O yields N…
Rapid solidification by twin-roller quenching of iron-neodymium-boron alloys produces flakes which show a strong (00l) texture normal to their surface by x-ray diffraction. The strong crystal orientation is argued to be due to both directional solidification in a thermal gradient and uniaxial deformation of the solid…
The authors report the observation in partially converted precursor-route poly(p-phenylene vinylene) (PPV) of a strong light-induced luminescence fatigue. Increasing the conversion towards the fully conjugated polymer results in a loss of the quenching effect. They discuss exciton annihilation at photoexcited charged…
We have developed a new laser ablation and plasma hybrid technique for depositing thin diamond-like carbon (DLC) films on Si〈100〉 substrates at room temperature and at 110 °C with improved optical and mechanical properties. The technique involves coupling of laser energy (λ=0.308 μm, pulse duration=40 ns, and power 12…
Highly resolved emission, excitation, and absorption spectra of [Os(bpy)3]2+ doped into a single-crystal [Ru(bpy)3]X2 matrix with X = PF6, AsF6, SbF6 are presented for low temperatures (2 ˇ- T ˇ- 16 K). This comprehensive information allows a reliable spectroscopic identification of different sites and several electro…
The single‐crystal elastic moduli of natural samples of grossular (99.0 mol % Ca 3 Al 2 Si 3 O 12 ) and spessartite (94.8 mol % Mn 3 Al 2 Si 3 O 12 ) have been measured by Brillouin spectroscopy under ambient conditions. From these results the adiabatic bulk moduli K s and shear moduli μ are calculated to be K s = 168…
Abstract The effect of tetrabromobisphenol A diallyl ether (TBBA–DAE) on the flame retardancy of high impact‐strength polystyrene (HIPS) was studied and compared with that of tetrabromobisphenol A (TBBA). Experimental results showed that the flame retardancy of TBBA–DAE was superior to that of TBA by thermomixing in t…
The Read-Shockley treatment of small-angle grain boundaries in crystals is generalized to the case of quasicrystals. The dependence of the grain-boundary energy on the angle of mismatch between abutting quasicrystalline grains is calculated. It is found that, even for a symmetric tilt boundary in a quasicrystal, dislo…