Materials Literature
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The structures of NaNb03 in the S phase (480°-520°c) and T1 phase (520°-575°c) have been determined by use of the octahedron tilting schemes of Glazer. Both phases are orthorhombic with unit cell edges approximately twice those of ideal perovskite; their space groups are Pnmm and Ccmm, respectively. An explanation of…
These experiments are a continuation of earlier work on the resistance of diamond to abrasion whilst being polished and ground. The most striking feature of the results is the very great difference in the resistance, or abrasion hardness, observed on the various faces for different directions of abrasion. A discussion…
SrCoO 2.5 with brownmillerite (4CaO·Fe 2 O 3 ·Al 2 O 3 ) type structure is an antiferromagnet with the Néel temperature of 570 K. The magnetic structure as determined from a neutron diffraction study is of G-type and the Co 3+ magnetic moment is 3.3±0.5µ B at liquid nitrogen temperature.
The ternary intermetallic compounds CaBe 2 Ge 2 , BaMg 2 Pb 2 and BaZn 2 Sn 2 have been prepared. Their crystal-structures have been determined. They are isotypic and crystallize in a new variant of the BaAl 4 -type (Space group: P4/nmm — D 4h 7 , lattice parameters: CaBe 2 Ge 2 : a = 4,02 ± 0,02 Å c = 9,92 ± 0,02 Å B…
In the ferrimagnetic rare-earth cobalt compounds, the reciprocal susceptibility obeys a N\'eel-type law. As a function of rare-earth content, the paramagnetic moments of cobalt atoms vary similarly with those deduced from saturation measurements. Particularly, for $R{\mathrm{Co}}_{2}$ ($R=\mathrm{G}\mathrm{d},\phantom…
Samples of the system SrCo 1- x Fe x O 3- y (0≤ x ≤1, 0≤ y ≤0.5) have been prepared under varying oxygen pressure and temperature and their crystal-lographic and magnetic properties have been studied. SrCoO 2.5 with brown-millerite type structure (high temperature phase) is an antiferromagnet with the Néel temperature…
Abstract The formation of junctions between a moving dislocation and the trees of a dislocation forest has been calculated for f.c.c. crystals. In contrast to previous estimates the concept of the orientation‐dependent line energy and a more realistic averaging procedure was used. In a random forest in which the tree…
It was found by microprobe analysis that during corrosion of stainless steel and mild steels in chloride solutions the most susceptible sites for pit nucleation were the inclusions of manganese sulfide. In the case of stainless steels, the corrosion pits were initiated mainly at mixed manganese and iron sulfide inclus…
The crystal structures of realgar, AsS and orpiment, AS 2 S 3 were refined using diffractometer data. The cell dimensions of realgar are: a = 9.325 ±.003 Å, b = 13.571 ± .005 Å, c = 6.587 ± .003 Å, β = 106° 23′ ± 5′, and those of orpiment are: a = 11.475 ± .005 Å, b = 9.577 ± .004 Å, c = 4.256 ± .002 Å, β = 90° 41′ ±…
The polymerization of lactones provides a facile route to polyesters that is unimpeded by the long reaction cycles and elevated temperatures inherent in the condensation of hydroxyl and acid functional groups. Depending on the structure of the lactone monomer, catalyst/initiator systems are known which allow preparati…
The mean-square end-to-end distance and the second virial coefficient are evaluated for stiff chains with excluded volume. The calculation is based on a wire-bead model whose backbone in the unperturbed state obeys wormlike-chain statistics. In order to establish the necessary distribution functions, results derived i…
High‐temperature diffusion kinetics and phase relations between couples of fused SiO 2 or cristobalite and sapphire or mullite were investigated in air and in helium. Subsolidus liquid formation between sapphire and cristobalite indicates the existence of a metastable system without mullite. A liquid phase is consider…
The electrical relaxation associated with alkali diffusion in Na 2 O·3SiO 2 glass was studied from 0.2 Hz to 700 kHz at –1° to 163°C. A formalism for analysis of electrical relaxation in conducting dielectrics which associates the nonexponential decay of the electric field to zero and the dispersions in the dielectric…
A neutron diffraction study was carried out on SrFeO 3 . The results indicate that the magnetic structure is a helical one with the helicoid vector k ; k //<111> and | k |=0.112 a * . The Fe 4+ magnetic moment is 2.7±0.4 µ B at liquid nitrogen temperature.
The X-ray photoelectron spectra of some forty-six copper compounds and complexes have been measured. The chemical shifts obtained from accurate determinations of the binding energies have been qualitatively explained on the basis of the Pauling electronegativity concept using the group electronegatives of Huheey for t…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStable free radicals. X. Nitronyl nitroxide monoradicals and biradicals as possible small molecule spin labelsEdwin F. Ullman, Jeanne H. Osiecki, D. G. B. Boocock, and R. DarcyCite this: J. Am. Chem. Soc. 1972, 94, 20, 7049–7059Publication Date (Print):October 1, 1972Publica…
It is shown that two-step, two-wave mixing makes a substantial contribution to the total three-wave mixing process in a noncentrosymmetric crystal. The efficiency of generating $2{\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}_{2}$ was observed as a function of the difference frequency ${\ensuremath{\omeg…
Foam fractionation is a process whereby dissolved (or colloidal) material is selectively adsorbed on the surfaces of rising bubbles and then is partially segregated by the foam. Even in the absence of foam, a bubble fractionation process may occur in the liquid, the process yielding a concentration gradient therein. B…
Serratia marcescens has been used to demonstrate that bacterial concentrations in jet drops from bursting bubbles can be much higher than the concentration in the water in which the bubbles burst. The ratio of the concentrations is the concentration factor C. A rotating tank was used to study the stripping of bacteria…
The tight-binding approximation has been applied for calculation of the band structure of planar hexagonal crystal layers of graphite and boron nitride. The theoretical width of the valence band of 15.9 eV in graphite and the distance between the centers of $\ensuremath{\pi}$ and $\ensuremath{\sigma}$ band of 5.3 eV a…