Materials Literature
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Abstract Considerable confusion exists in the literature concerning the glass temperature, T g , of many highly crystalline polymers, in particular, linear polyethylene (PE), poly(vinyl fluoride) (PVF), poly(vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), poly(oxymethylene) (POM), and poly(ethylene oxide)…
Abstract Characteristic features of isothermal growth, thickening, and melting behavior of melt grown single crystals of low molecular weight poly (ethylene oxide) fractions are presented and discussed in terms of their relevance to basic concepts of polymer crystal growth. Measurements of growth (G) and thickening ra…
Treatment of crude meso-tetraphenylporphyrin with 2,3-dichloro-5,6-dicyanobenzoquinone affords a high recovery of ‘chlorin-free’meso-tetraphenylporphyrin (1), the excess of quinone and its transformation products being easily removed by adsorption on alumina. This new procedure is also applied to the purification of m…
The oxide films produced by anodic oxidation of gold and platinum have been studied by X-ray photoelectron spectroscopy. The change in the amount of each species present, with electrode potential, has been investigated. It is demonstrated that X-ray reduction occurs for these systems but that it can be minimised by a…
The ultraviolet and visible reflectance spectra (52 000–15 000 cm–1) of high surface area MgO (250–300 m2 g–1) and CaO (100–200 m2 g–1) have been studied in vacuo and in the presence of O2, N2O, CO2 and H2O. The effect of outgassing MgO and CaO at increasing temperatures (773–1073 K) is to develop u.v. absorption band…
New, efficient, vitroceramic hosts for rare earth luminescence are discussed. Their applications to infrared up‐conversion are emphasized. Optimized compositions lead to an efficiency nearly twice as high as commercially available LaF 3 : Yb : Er . As for infrared to blue efficiency, these vitroceramics are among the…
Data on the structure and chemistry of the iron sulphides are collated. Corrosion of ferrous metals by the iron sulphides and soluble sulphide, including corrosion by the sulphate-reducing bacteria, is reviewed. Corrosion mechanisms are discussed.
In the last 10 years an extensive research and development effort has been made to implement the catalytic removal of noxious constituents from automotive exhaust. This effort is finally coming to fruition as this paper is going into print. Vehicles sold in the United States in 1975 will be, in a significant proportio…
The compounds Ce 1 − x Ln x O 2 − x / 2 ( Ln = lanthanoid element ) have been synthesized and the emf and resistivity measurements have been carried out between 400° and 1000°C. It is found that charge carriers of conduction in these compounds are oxygen ions above 600°C; the oxygen transference number being above 0.9…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNitrosylmetalloporphyrins. II. Synthesis and molecular stereochemistry of nitrosyl-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatoiron(II)W. Robert Scheidt and Mark E. FrisseCite this: J. Am. Chem. Soc. 1975, 97, 1, 17–21Publication Date (Print):January 1, 1975Publicati…
The sorption and diffusion of low molecular weight penetrants proceeds almost exclusively through the amorphous component of the semicrystalline polymer solid. The diffusive transport properties and geometrical distribution of the amorphous component are substantially modified by mechanical and thermal treatment. Defo…
The magnetic properties of all known sulfides, selenides, and tellurides of Pr and Tm (as representative of the light and heavy rare earths, respectively) have been studied. In most cases, Pr and Tm compounds exhibit Van Vleck paramgnetism at low temperatures owing to crystal-field singlet ground states. Splittings ha…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConstituent analysis of the potential gradient along a reaction coordinate. Method and an application to methane + tritium reactionKenichi Fukui, Shigeki Kato, and Hiroshi FujimotoCite this: J. Am. Chem. Soc. 1975, 97, 1, 1–7Publication Date (Print):January 1, 1975Publicatio…
The propagation of electromagnetic waves along open periodic, dielectric waveguides is formulated here as a rigorous and exact boundary-value problem. The characteristic field solutions are shown to be of the surface-wave or leaky-wave type, depending on the ratio of periodicity to wavelength (d/lambda). The dispersio…
A new model has been proposed for describing deoxidation kinetics in turbulent melts by /Jostulating that for aluminum deoxidation the coalescence of the inclusion /Jarticles is the mte contloiling mechanism.
The static equilibrium configurations of a dislocation bypassing a periodic row of impenetrable circular obstacles were obtained for various crystals by means of a self-stress method wherein the elastic anisotropy of the crystal and the dislocation self-interaction could be taken into account. A correlation was develo…
Data on the fluorescent yields of tervalent ions of Pr, Sm, Eu, Gd, Tb, Dy, and Tm in H2O and D2O, containing perchlorate ions, and isotope effects on the fluorescence are reported. The results are interpreted in terms of the mechanisms responsible for radiationless processes in solutions of rare earth ions [Y. Haas a…
A substantial fraction of the defects in epitaxial thin films are formed to accommodate part of the misfit between the stress−free lattice parameters of film and substrate. This paper describes some of the complete dislocations, partial dislocations, and cracks that are made for this purpose. Also described are the op…
Since approximately 1950 an increasing portion of experimental solid state physics research has been concerned with studying defects in crystals. This trend might appear to be a rather belated recognition that most of the materials we come into contact with have a random structure. In fact the theoretical understandin…
Earlier observations on the magnitudes of chemical shifts of photoelectron and core-type Auger lines, and the concept of the role of polarizability, have been combined to produce a unified concept of the role of polarization in determining line position. With core-type Auger lines, polarization effects are more import…