Materials Literature
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We present a theoretical approach to study the conformational and thermodynamical properties of grafted polymer layers. The theory is based on the generalization of a mean-field approach previously used to treat chain packing in amphiphilic aggregates. The theory can be used for any chain model, for any mixture of gra…
We present dynamic light scattering data which show that aqueous gelatin gels display a power-law relaxation to a nonergodic background. In the pregel sol this power law is termined by a stretched exponential which restores ergodicity and which has a q dependent characteristic time proportional to the viscosity. The p…
Abstract The solubility of carbon dioxide, methane, and propane in poly(dimethyl silmethylene) [(CH 3 ) 2 SiCH 2 ] x and poly(tetramethyl silhexylene siloxane) [(CH 3 ) 2 Si (CH 2 ) 6 Si (CH 3 ) 2 O] x was measured in the temperature range from 10.0 to 55.0°C and at elevated pressures. The present results are compared…
Abstract The glass transition ( T g ) of thin polystyrene films (ca. 3000 A˚) cast on silicon wafers was determined by a new technique. An ellipsometer was used to determine the refractive index and thickness of the polystyrene films. T g was determined by measuring the temperature dependence of the refractive index.…
High quality, low resistivity (2.6×10−4 Ω cm), 0.32-μm-thick amorphous and polycrystalline, pure and Sn-doped, In2O3 films prepared by high density plasma-assisted electron beam evaporation were used to investigate the effect of Sn doping on the electronic transport properties of this material. Amorphous films with hi…
We report ab initio calculations of the lattice constants and the electronic band structure of the hexagonal wurtzite-structure semiconductors ZnO and ZnS. We employ the local-density approximation and solve the Kohn-Sham equations for nonlocal, separable, and norm-conserving pseudopotentials self-consistently. We use…
Highly supersaturated nanocrystalline FexCu100−x alloys (10≤x≤95) have been prepared by mechanical alloying of elemental crystalline powders. The development of the microstructure is investigated by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The results are compared wit…
The preparation of CeO 2 thin films on sapphire by DC reactive magnetron sputtering of metallic Ce target in an argon-oxygen mixed gas is reported. The resputtering of the film deposited facing the target track was observed. The films deposited far from the sputtering system axis exhibited well-oriented crystalline st…
The effect of sulphur addition on some structural properties of a-Se was studied for compositions up to about 30 at.% S. The sulphur in the binary amorphous semiconductor system Se-S was found to affect the density (d), microhardness (VH), dielectric constant ( in ) and tendency to crystallization (T c -T g ), as well…
Data are reported on the luminescence spectra generated by X-ray and electron irradiation of optical fibres, fibre preforms and silica. The impurities and imperfections in the fibre core have a higher luminescence efficiency than those in the substrate material. The core luminescence provides a major fraction of the t…
The electronic and geometrical structures of exchange-coupled open-shell systems such as bis(methylene) methane and the chromium–methylene cation were investigated by the molecular orbital and its extended methods: RHF, UHF, UNO-CAS, RMP, UMP, PUMP, APUMP, UCCSD(T), UNO-CI and QCISD(T). The fully optimized geometries…
Sputtering of highly oriented pyrolytic graphite (HOPG) by 248-nanometer laser radiation was studied. Neutral carbon atoms and small clusters were ejected with significantly higher translational energies than were expected from a simple model of thermal vaporization in the absence of a potential barrier. The HOPG also…
As diamond-producing catalysts, 12 transition metals such as iron, cobalt, and nickel were first reported by General Electric researchers more than 30 years ago. Since then, no additional elemental catalyst has been reported. An investigation of the catalytic action of group V elements is of great interest from the vi…
Transmission electron microscopy (TEM) observations of graphite tubules (buckytubes) and their derivatives have revealed not only the previously reported buckytube geometries but also additional shapes of the buckytube derivatives. Detailed cross-sectional TEM images reveal the cylindrical cross section of buckytubes…
Very complicated inorganic solids can be self-assembled from structurally simple precursors as illustrated by the hydrothermal synthesis of the vanadium phosphate, [(CH(3))(2)NH(2)]K(4)[V(10)O(10)(H(2)O)(2)(OH)(4)(PO(4))(7)].4H(2)O, 1, which contains chiral double helices formed from interpenetrating spirals of vanadi…
Abstract Starch‐ g ‐poly(methyl acrylate) (S‐ g ‐PMA) copolymers containing 55–60% PMA were prepared from cornstarch, high amylose cornstarch, and waxy cornstarch with ceric ammonium nitrate initiation. Graft copolymers were characterized with respect to % PMA homopolymer, % conversion of monomer to polymer, grafted P…
Abstract The effect of diethylene glycol (DEG) on the crystallization of poly(ethylene terephthalate) (PET) was studied under isothermal and dynamic conditions. The strain‐induced crystallization of PET and its relationship to DEG content was also studied. The samples were isothermally and dynamically crystallized in…
Abstract Sisal fibers (Agave‐Veracruz) have been used as reinforcements in low‐density polyethylene (LDPE). The influence of the processing method and the effect of fiber content, fiber length, and orientation on tensile properties of the composites have been evaluated. The fiber damage that normally occurs during ble…
The angular dependences of the free energy, thickness and stresses are calculated for the antiphase boundaries (APBS) parallel to the tetragonal z axis but otherwise arbitrarily oriented. The general results are applied to Hg 2 Br 2 and KSCN. The APB in the former case is shown to decay into two ferroelastic domain wa…
Abstract The crystal growth behaviour of the important organic nonlinear optical material 2-(a-methylbenzylamino)-5-nitropyridine (MBANP) (space group P21) has been investigated and techniques have been developed for the preparation of large (up to 7 cm x 4 cm x 3 cm) high-quality single crystals suitable for detailed…