Materials Literature
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Abstract Grafting of acrylonitrile onto various radiation peroxidized polymers was used as a technique to investigate the peroxidation mechanism. It was found that in polymers such as polypropylene, poly(vinyl chloride), and polystyrene, a chain hydroperoxidation process only occurs above the glass transition temperat…
An ab-initio cluster calculation of the electronic d-states in VO 2 has been made by using the self-consistent statistical exchange multiple scattering method. A VO8-6 octaedron was used to represent the tetragonal phase, and a V2O12-10 cluster with paired vanadium atoms was used for the monoclinic phase. Our results…
[in Japanese]
Un cryostat à hélium liquide a été adapté sur un goniomètre à rayons X afin de permettre la mesure continue des paramètres cristallins de 4 K à 300 K. Une distorsion quadratique (c/a < 1) est mise en évidence dans plusieurs pérovskites fluorées du cobalt ; elle apparaît à 117 K dans KCoF3, 101 K dans RbCoF 3 et 94 K d…
Declination lines separating regions with opposite twist in a twisted structure of a nematic liquid crystal are studied theoretically and experimentally. A particular study is made of magnetic-field induced motions of the disclination lines. Comparison of theoretical and experimental results leads to an estimate of th…
A systematic study has been made of the valence bands and core-level peaks in X-ray photoelectron spectra of the heavy rare-earth metals and their surface oxides. Multiplet structure observed in the 4d levels is reported here. This structure alters on oxidation, and in addition the 4d peaks broaden and exhibit shifts…
This theoretical and experimental investigation deals with the electromechanical response of a shock−loaded ferroelectric ceramic material. Quartz gauge and voltage−mode techniques were used to characterize the mechanical and electrical responses, respectively, of PZT 65/35 to ≈80 kbar. Below ≈20 kbar the wave propaga…
The pyrolysis of isopropanol has been investigated at temperatures in the range 721–801 K and pressures between 10 and 100 Torr, using a KCl-coated silica reaction vessel. Under these conditions the reactions occurring were essentially homogeneous and, for reaction times corresponding to < 30 % conversion, led to the…
HeI and HeII spectra of clean polycrystalline lead are reported and discussed. The oxidation of this polycrystalline lead foil by both ground-state molecular and microwave-excited oxygen has been studied using UPS and XPS techniques in combination in the same apparatus. Work function changes were also measured. The in…
An anisotropic polycrystalline magnet of a Mn‐Al‐C alloy with (BH) max=6 MG⋅Oe has been successfully produced by extrusion at about 700°C. During the study on this ternary alloy system, a ferromagnetic phase (τ‐phase) single crystal was obtained by annealing a high‐temperature phase (ε‐phase) single crystal containing…
Continuous grinding of CaCO3 does not lead to continuous increases in the surface area, but causes it to pass through successive minima and maxima. In spite of its technological significance, this phenomenon has not yet been interpreted.The present work attempts to clarify this problem. We demonstrate that mechanical…
A modification to the vacuum system of a JSM2 scanning electron microscope has enabled hydrated specimens to be placed inside the specimen chamber of the instrument and to be surronded by water vapour at a pressure up to approximately I 3-kPa (10 Torr). The surface topography was observed by detecting the backscattere…
Full-thickness skin grafts placed on bare rabbit ear cartilage were revascularized, whereas split-skin grafts on the same kinds of areas failed. The contrast is most likely due to differences in the skin graft thickness and the vascular patterns in the grafts. Full-thickness rat skin grafts placed over the same sized…
Hydrostatic pressure has been known for quite some time to affect the physical and mechanical properties, to help create or synthesize new or known materials, and to enhance the formability of various metals and geological materials [1–19]. Although polymeric materials are far more susceptible to hydrostatic pressure…
There are available to the biologist sophisticated methods for the quantitative determination of many structural parameters of tissues; the methds are covered by the term stereology and are based on statistical sampling techniques introduced by geologists and materials scientists. Methods for determining the volume fr…
Abstract The characterization of eight fully aromatic polyamides are described with the procedures required to yield film‐ and fiber‐forming materials. Solutions of these aromatic polyamides in dimethylacetamide were characterized by NMR and the effects of dissolved lithium chloride on these spectra investigated. The…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolymerization of Hexachlorocyclotriphosphazene. The Role of Phosphorus Pentachloride, Water, and Hydrogen ChlorideH. R. Allcock, J. E. Gardner, and Karen M. SmeltzCite this: Macromolecules 1975, 8, 1, 36–42Publication Date (Print):January 1, 1975Publication History Publishe…
The charge carrier transport properties of a wide variety of quartz single crystals and fused silica have been measured by creating electron-hole pairs in the bulk of the samples with high energy x-rays. The very short x-ray pulses (3 nsec) allowed unprecedented time resolution, and in some cases separate measurements…
Abstract
We consider a solid/nematic interface where long range van der Waals torques favor homeotropic alignment, while a direct steric effect tends to induce a planar alignment. Depending on the relative strength of the two contributions, one may find two transitions : planar ↔ conical and conical ↔ homeotropic. This is remi…