Materials Literature
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The reaction between finely divided SiO2 and SiC at 1270–1430°C was studied. The reaction scheme proposed is: 2SiC+SiO2= 3Sia+2COa 2Sia+CO = SiOa+SiC Sia+SiO2= 2SiOa Sia, SiOa, COa= Sig, SiOg COg. During the first 2–6% of reaction, Si volatilizes; thereafter primarily SiO and CO volatilize. Only the upper layers of th…
Large dislocation loops on the basal plane and rows of prismatic dislocation loops are both observed in quenched magnesium specimens. It was found that by altering the environment in the quenching furnace either type of dislocation defect could be made to predominate. A mechanism for the production of rows of punched…
Copper produces two emission bands in all and all phosphors. Both bands shift monotonically to lower or higher quantum energies, if the Zn/Cd ratio is varied, so that their differences to the also varying energy of the band gap remain constant. In contrast, the positions of the emission bands in , , and depend relativ…
The magnetic susceptibilities of four iron(III) and five ruthenium(III) compounds, all with the low-spin configuration t52g, have been measured in the range 80–300°K. The data are compared with the theory for a 2T2g ground term in the presence of a low-symmetry ligand-field component, and including electron delocalisa…
Pure zinc oxide is active at 200°C in the catalysis of the oxidation of carbon monoxide. Oxygen appears to be adsorbed in an ionic as well as a non-ionic form, while carbon monoxide and carbon dioxide are adsorbed essentially in non-ionic forms. Two surface sites, probably Zn+ ions, are required to fix O2 and also CO2…
In this review a qualitative description is given of the various types of exchange interactions which might be present in metals and insulators and which might lead to co-operative interactions - particularly ferromagnetism. The theory of spin waves is then described and this is extended to include non-linear and temp…
Upon heating black oxygen‐deficient zirconia in oxygen of atmospheric pressure to 450° to 900°C, oxygen is taken up. The increase in the thickness of a white layer of virtually ideal composition with time follows a parabolic rate law, . The rate constant is about two orders of magnitude higher than Tammann's rate cons…
A theoretical and experimental investigation of inhomogeneous CeO(2)-MgF(2) and ZnS-Na(3)AIF(6) anti-reflection coatings for the visible spectrai region has been made. By a proper choice of the refractive index profile, the reflectance may be considerably reduced. In the infrared region, Ge-MgF(2) films on Ge substrat…
The absorption and permeation of electrolytically generated hydrogen through thin platinum foils have been observed directly by an electrochemical method. The diffusion coefficient and the associated apparent energy of activation were determined. The concentration of absorbed hydrogen was obtained, and it was shown th…
A study has been made of the preparation and properties of aluminum oxide films prepared by reactive sputtering. Deposition temperature, rate, oxygen pressure, etching characteristics in , and phase changes of the deposited films as a function of heat‐treatment were investigated. Two phases of deposited alumina could…
On compare les propriétés magnétiques (aimantations, points de Curie et susceptibilités) et les résistivités résiduelles de borures de formules générales M1-xM'xB et (M1-xM'x) 2B où M et M' désignent des métaux de la première série de transition, à celles des alliages métalliques M1-xM'x. Cette comparaison fait ressor…
Silicon nitride has very attractive electrical, physical, and chemical properties which are of great interest for microelectronic devices. Until recently, most methods that have been reported in literature produce silicon nitride in the form of powder, needles, ribbons, or flakes. Recently, Sterling and Swann reported…
Abstract The dislocation distribution in the surface layer of cyclically deformed specimens of polycrystalline copper is studied by means of transmission electron microscopy of thin foils, both parallel and nonparallel to the surface. The distribution within the surface layer and near the persistent slip bands is foun…
Abstract A polyamide amino acid was prepared by the solution condensation of 3,3′‐diaminobenzidine and pyromellitic dianhydride. This polymer was cast as a film and converted to a polybenzoylenebenzimidazole. The gross conversion path was elucidated by spectroscopy and was substantiated by model compound studies. A no…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLewis Basicity of Metals. II. The Interaction of Group VI and VII Transition Metal Cyclopentadienyl Derivatives with BF3, BCl3, and B2H6M. P. Johnson and D. F. ShriverCite this: J. Am. Chem. Soc. 1966, 88, 2, 301–304Publication Date (Print):January 1, 1966Publication History…
Infra-red studies of NH3, HCl, CO, C2H4, and butene adsorbed on transparent aerogels were made to elucidate the surface chemistry of nickel/silica and the nature of adsorbed species. In addition to the hydroxyl band found on silica at 3750 cm–1, most “dry” nickel/silica aerogels exhibited a band near 3620 cm–1, appare…
In recent years the rapid advances in the understanding of the nature of chemical bonds and in the application of quantum mechanics to chemical problems have imparted a great impetus to studies of luminescent materials, studies which have been primarily directed toward the elucidation of the electronic structures of t…
Abstract Two kinds of dielectric absorptions due to motion of carbonate groups in polycarbonate were observed. In the primary transition region near 150°C, the shape of e′ versus log frequency curve is little affected by a temperature change, while it becomes more widely spread when the polymer is partially crystalliz…
Abstract A brief review of the different topographic methods is given in order to attempt a classification of the various types of contrast observed. Depending on whether the image is obtained by a reflection or transmission method, is simple or integrated, dynamic, direct, or intermediary, the contrast and image widt…
Aided by a Post Doctoral Fellowship in Brain Research from the United Cerebral Palsy Research and Educational Foundation. Medical Investigator, Howard Hughes Institute.