Materials Literature
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P-type semiconducting diamonds can be formed at high pressures and temperatures out of mixtures of graphite and catalyst metal (Ni, Fe, etc.) to which small amounts of B, Be, or Al have been added. The crystals may have resistivities of as low as 103 ohm-cm with activation energies for conduction ranging between 0.1 a…
IT IS WELL KNOWN THAT THE ENERGY, DIPOLE MOMENT, AND MANY OTHER PROPERTIES OF AN ATOM OR MOLECULE CAN BE CALCULATED IF THE PAIR DENSITY MATRIX, A FUNCTION OF 12 VARIABLES, IS AVAILABLE. For a system with N electrons and therefore 3N degrees of freedom, this is a great simplification, at least in principle if not yet i…
An investigation of the magnetic structure and properties of Mn${\mathrm{Cr}}_{2}$${\mathrm{O}}_{4}$ has been carried out by means of neutron diffraction and an evaluation of the suitability of various proposed theoretical models has been made. From room-temperature diffraction patterns it is established that Mn${\mat…
Semiconducting crystals of cubic BN may be prepared at high pressures and temperatures by adding small amounts of selected impurities to the synthesis mixture (hexagonal boron nitride plus lithium or magnesium nitride). P-type crystals, blue in color, can be prepared by adding Be; they may have resistivities of about…
Using a simple one-dimensional model of H bonds, vibrational-energy eigenvalues, eigenfunctions, transition moments, and absorption intensities are calculated for a series of symmetric and asymmetric double-minimum (D.M.) potentials. On the basis of the results obtained, the necessary requirements for observing double…
The thermal conductivity from 3\ifmmode^\circ\else\textdegree\fi{} to 300\ifmmode^\circ\else\textdegree\fi{}K of single crystals of the two spinels, diamagnetic Mg${\mathrm{Al}}_{2}$${\mathrm{O}}_{4}$ and paramagnetic ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$, has been measured and analyzed. The heat is transported by pho…
The polarized absorption spectra of Ni2+ and Co2+ in crystals of ZnO, ZnS, and CdS; Ni2+ in crystals of Cs2ZnCl4 and Cs2ZnBr4; and Cu2+ in ZnO have been measured at 4°K, 77°K, and room temperature. The spectra have been interpreted by the use of crystal field theory for the states of the (3d)n configuration acted on b…
The quantum theory of the frequency- and wave-number-dependent dielectric constant in solids is extended in order to study the full dielectric constant tensor and to include local-field effects. Within the framework of the band theory, an explicit expression for the dielectric constant tensor, neglecting local-field e…
Abstract After a brief introduction discussing the basis of molecular-field theories, we introduce a generalization of Anderson’s treatment of antiferromagnetism which enables us to take higher-order exchange interactions into account as well as anisotropy terms. We restrict ourselves to terms quadratic in the spins.…
Abstract X-ray analyses of selected samples from the argillaceous subdivisions of the English Wealden indicate that illite, kaolinite, and mixed-layer structures are present in variable amounts. The clay mineral assemblage is thought to reflect parent material, weathering conditions in the source area, and possibly so…
Browsing in books, review articles and conference reports, one sometimes nowadays comes across pictures like fig. 1. This peculiar object, which might be mistaken for a piece of modern sculpture, is labelled “The Fermi surface of magnesium”. What does it mean, to say that magnesium has a Fermi surface, and how is it d…
Abstract The principle of the new gas‐phase method of polycondensation consists of carrying out the polycondensation reaction of two high reactive compounds at a liquid—gas interface. The gas‐phase method permits the synthesis of polyamides with rapidly hydrolyzing diacid chlorides (e.g., oxalyl chloride), which canno…
Abstract The swelling of cellulose in alkali solutions has been the subject of numerous investigations in the past. However, there still exists a controversy as to whether the reaction with alkali yields a true alcoholate or an addition compound without ionization of the cellulose. This study presents experimental dat…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNitric Acid Dissolution of Uranium-Molybdenum Alloy Reactor FuelsW. W. Schulz, R. E. Burns, and E. M. DukeCite this: Ind. Eng. Chem. Process Des. Dev. 1962, 1, 2, 156–160Publication Date (Print):April 1, 1962Publication History Published online1 May 2002Published inissue 1 April…
Abstract The molecular weight of silk fibroin in several different solvent systems has been measured by light‐scattering techniques. The values obtained lie between 250,000 and 450,000, with a tendency to lie fairly close to 300,000. The difference between this value of the molecular weight and the values obtained by…
Polycrystalline samples of five iron-aluminium solid solutions were subjected to various heat treatments either (i) in a strong magnetic field, or (ii) under tensile stress. For treatment (i) the samples were in the form of cylinders, while in case (ii) they were machined into this form after stress treatment. Torquea…
Determination and refinement of the crystal structures of väyrynenite and euclase show that these minerals have related, but not identical, structures. Väyrynenite contains chains of BeO 2 (OH) 2 and PO 4 tetrahedra linked by Mn-O and hydrogen bonds; euclase contains chains of BeO 3 (OH) and SiO 4 tetrahedra linked by…
The total groove volume is estimated for a short (similar 1 mm) abrasion stroke of silver on dry grade-3 emery paper (mean particle diameter 150 μm) at approximately 1 kg load. This is compared with the mass wear rate, thus giving an estimate of the order of 10% for the proportion of the total groove volume removed as…
Abstract The degrees of crosslinking of three post‐gelation high‐conversion copolymers were measured by γ‐irradiation, extraction, and swelling experiments. The copolymers containing 0.2, 0.5, and 1.0 mole‐% of the crosslinker were prepared by suspension polymerization at 60°C. with a free‐radical catalyst. The degree…
By C. W. Richards London: Chapman and Hall Ltd. Pp. xiv + 546. Price 60s. Assessment of this book is rendered difficult by the lack of any indication of the kind of reader for whom it is intended, and by a rather misleading title. Although some of the topics dealt with in a qualitative manner are quite advanced, the s…