Materials Literature
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The basic mode of relaxation in polymer molecules involves the rotation of a conformer, with a time scale of the order of picoseconds. This fast relaxation process, however, cannot take place easily in the condensed state crowded by densely packed conformers, necessitating the intermolecular cooperativity among them.…
The cure of a technical-grade TGDDM (N,N,N′N′-tetraglycidyl-4,4′-diaminodiphenylmethane) with two different anhydride hardeners (hexahydrophthalic anhydride [HHPA] and tetrahydrophthalic anhydride [THPA]) is reported. The reaction was followed by differential scanning calorimetry (DSC), in situ infrared spectroscopy (…
A review on the synthesis of unsaturated polyester (UP) prepolymers showed that Ordelt saturation (reaction of hydroxyl groups with double bonds) is the major effect that may cause formation of chain branches and then result in an uncertainty of chain end number or functionality. A model has been derived in this work…
At the core, at the core and at the surface, within the cascade structure, or within the cascade structure and at the surface are different ways in which the dendrimers described here can be selectively alkylated. These phosphorus-containing dendrimers have generations of different constitution (example depicted on th…
The hydrolysis of a cyanate ester network made from the monomer 2,2′-bis(4-cyanatophenyl) isopropylidene (bisphenol A dicyanate homopolymer) was studied. Hydrolysis reactions were performed isothermally at temperatures from 150 to 180°C under conditions of excess water. The kinetics of the reaction were characterized…
The differential scanning calorimetry glass transition (DSC Tg), measured by ASTM test method E-1356, and the dynamic mechanical analysis glass transition (DMA Tg), measured using a new definition of the DMA Tg, generally agree within ±4°C for a wide variety of commercially available polymers. The DMA Tg is defined as…
Introduction to Dielectric Guides Analysis of Dielectric Integrated Guides: Approximate Methods Analysis of Dielectric Integrated Guides: Rigorous Methods Image-, Insular Image-, Trapped Image- and other Variant Guides Semiconductor and Planar Optical Guides Non-Radiative Dielectric Guide Non-Planar Dielectric Guides…
An equation, based on thermodynamic considerations to relate the glass transition temperature, Tg, to compositional variation of a polymer system, is adapted in this article for modeling the Tg vs. fractional conversion (x) relationship of reactive thermosetting systems. Agreement between the adapted equation and expe…
The reaction of SiCl4 with bis(trimethylsilyl)carbodiimide in a 1:2 molar ratio followed by annealing at temperatures above 400 or 900°C provides the first crystalline ternary Si-C-N solids, namely silicon dicarbodiimide (SiC2N4) and silicon (carbodiimide)nitride (Si2CN4), in near quantitative yields. The anti-cuprite…
A combination of classical density-functional theory and thermodynamic perturbation theory is applied to a survey of finite-temperature trends in the relative stabilities of one-component crystals and quasicrystals interacting via effective metallic pair potentials derived from pseudopotential theory. Comparing the fr…
Hydrogen molybdenum bronzes, H0.21MoO3 (type I) and H0.91MoO3 (type II) were characterized by Mo K-edge XAFS spectroscopy. XANES spectra showed that type I has an axially symmetric MoO6 unit which is mainly conncted to each other with vertices sharing and a MoO6 unit in type II are similar to that in MoO2. EXAFS spect…
A design procedure for two aberration-corrected spherical concave gratings operating in the spectral range 91–103 nm (extreme-ultraviolet) is presented. The first configuration is a Rowland circle mount whereas the second is based on the conditions of stationarity with respect to wavelength for the second-order aberra…
According to diffraction measurements of the average structure, V2O3 changes on heating from monoclinic to trigonal, accompanied by a 1.4% volume decrease, where some V - V distances decrease by about 0.11 Å, favoring the Mott - Hubbard mechanism of the phase transition from insulator to metal. Our polarized XAFS meas…
Studies of local atomic structure in the zinc-blende Zn 1 _ x F e x S (x = 0.11-0.50) diluted magnetic semiconductors with the use of the EXAFS technique are reported for the first time. They include the Kedge EXAFS measurements for both cationic elements (Zn, Fe). The experiment was carried out at room temperature in…
The dissolution rates of silicon nitride (Si 3 N 4 ) ceramics into CaOAl 2 O 3 SiO 2 slags were investigated by using a rotating specimen method in the temperature range of 1773–1873 K. Dissolution rates in the present study increased as the revolution speed and temperature increased and decreased as the SiO 2 content…
Abstract The corrosion behaviour of nickel‐aluminium alloys with aluminium contents of 2‐50%, in molten carbonate has been investigated with electrochemical techniques in combination with post‐test analysis of quenched specimens. For the 2 to 10% aluminium alloys a type of aluminium oxide is formed along the grain bou…
The phenomenon of hysteresis in magnetic materials has been widely studied for many decades and several models have been proposed to find good approximations for this phenomenon. The simulation presented in this paper describes hysteresis in a cylindrical type II superconductor of small aspect ratio. A fundamental app…
It is shown that in a layered medium consisting of a magnetic metal (Co) and a nonmagnetic insulator (TiO 2 ), the layer thickness being less than the wavelength of the light, a fundamental change occurs in the character of the Faraday-effect spectra if the number of layers is sufficiently large. When the number of pa…
This article discusses different natural and man-made foams, with particular emphasis on the different modes of formation and stability. Natural foams, such as those produced on the sea or by numerous creatures for nests, are generally stabilised by dissolved organic carbon (DOC) molecules or proteins. In addition to…
A laboratory investigation of the geotechnical properties of a marine clay saturated with a series of monovalent, divalent, and trivalent cations revealed large differences in behavior which depend on the exchangeable cations. The exchangeable cations employed in this study are sodium (Na), potassium (K), ammonium (NH…