Materials Literature
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Temperature dependences of density, refractive indices, and dielectric constants have been measured for mesogenic compounds of as for some of their cyano-analogues: and . The effects of substituting a phenyl ring by a cyclohexyl ring, as well as of a –CN group by an –NCS group have been analyzed. The results lead to t…
Abstract The three-dimensional order shown by the two-layer hydrates of Na- and Ca-vermiculite, prepared from Mg-vermiculite from Llano, Texas, has enabled clear, two-dimensional Fourier projections of their interlayer structures to be obtained. Structure factor calculations were made in space group C 2 and with unit-…
In the high-temperature polymorph Na2SO4(I) up to 30% cation vacancies can be generated by substitution of Na + by bi- and trivalent ions. Phase diagrams and lattice parameters of these solid solutions are presented. The hexagonal high-temperature form and its monoclinic distortions can be quenched to room temperature…
The oscillator strength of small-polaron absorption is studied for various thin films of tungsten oxide, WOx (x≤3), prepared by rf reactive magnetron sputtering, reactive ion plating, and vacuum evaporation. The oscillator strength greatly varies depending on the procedure of film preparation and treatment. For WOx fi…
The relationship between the twisting power (β) and the molecular structure of the dopant and neraatic solvent are discussed. High values of β are observed whenever two (or more) planar or quasi-planar moieties, chirally distorted one with respect to the other, are present in the dopant. For high twisting powers, the…
The thermal decomposition rate of hydrogen peroxide (H2O2) was measured in the aqueous phase at an elevated temperature. It was shown that the reaction follows first-order kinetics, and the rate constant was determined as a function of temperature. The mechanism of the aqueous phase decomposition is discussed, particu…
Abstract Blends of elastomers with the proper concentration of appropriate low molecular weight resins exhibit performance as pressure sensitive adhesives. Viscoelastic properties, which may be related to adhesive performance, were measured on 1:l blends of rubber and resin using a mechanical spectrometer. Significant…
Raman scattering is observed in MgO microcrystals with three different particle sizes (105, 103, and 102 Å). The second-order Raman lines in the bulk crystals of MgO disappear in all the microcrystals, while new peaks emerge at 280, 446, and 1088 cm−1 except for specimen prepared by grinding a large single crystal. Ra…
Abstract Conceptual differences in two recent versions of the free‐volume theory for self‐diffusion in polymer–solvent systems are identified and discussed. The validity of the assumptions of these two theories is tested using experimental data. In all cases, the experimental evidence favors the Vrentas–Duda free‐volu…
Oxidation of nitric oxide is an important step in NOx absorption. Recent advances namely catalytic oxidation and the use of slrong oxidizing agents have been reviewed. The refinements which have been made in the kinetics of NO oxidation have been discussed. Several liquid phase absorbents have been suggested for the N…
A comprehensive review on the chemistry and mineralogy of nonexchangeable potassium is presented. Forms of soil K, the effect of mineralogy on release of nonexchangeable K, methods of determining nonexchangeable K, and the kinetics of non‐exchangeable ? release are fully discussed.
Abstract The predictive and correlative capabilities of two recent versions of the free‐volume theory for self‐diffusion in polymer–solvent systems are examined by comparisons with experimental data. Neither the Vrentas–Duda free‐volume theory nor the Paul version generally provides satisfactory predictions for the te…
Abstract not Available.
The concepts of interface and interphase inhibition as two different types of corrosion inhibition mechanisms are discussed briefly. Most of the studies reported in the literature have dealt with interface inhibition in acid media. Experimental results of interphase inhibition have been obtained for a 4340 steel rotat…
Various domain-growth mechanisms in phase-separating binary fluids are discussed. A tube hydrodynamic instability for concentrated mixtures is studied through a linear stability analysis. A quantitative discussion of the three-dimensional linear growth law is given. For two-dimensional concentrated mixtures we argue t…
Ellipsometry was used to study the electrodeposition of polymer films formed by oxidation of bipyrazine, polyvinylferrocene, and aniline. For polymeric films of limited thickness displaying good optical characteristics ( i.e. , high reflectivity, uniform coverage, and homogeneity), the film refractive index and thickn…
The mode-coupling theory of the glass transition recently presented by Leutheusser is generalized so that some of the important wave-number dependence neglected in his theory is taken into account. As a consequence the correlation functions which appear in the theory presented here involve a continuous range of relaxa…
We have investigated the magnetic properties of the Nd2(Fe1−xCox)14B system to improve the thermal properties of the Nd-Fe-B magnets. Nd2(Fe1−xCox)14B exists in the tetragonal form in the entire range of 0≤x≤1. In this system, the replacement of Fe by Co significantly increases the Curie temperature. The room-temperat…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDependence of rate constants for photoinduced charge separation and dark charge recombination on the free energy of reaction in restricted-distance porphyrin-quinone moleculesMichael R. Wasielewski, Mark P. Niemczyk, Walter A. Svec, and E. Bradley PewittCite this: J. Am. Che…
We have produced fully oriented highly crystal 1ine trans-(CH)X films, which exhibit dramatic polarization effects for light polarized parallel or perpendicular to the oriented (CH)X-chains. The polarization behavior in the vicinity of the bandgap and of the characteristic IR-modes, including those which are introduce…