Materials Literature
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The origin of electronic states in two classes of semiconductors is explored: (i) semiconductors containing group-VI elements in twofold coordination, and (ii) tetrahedral semiconductors. In the first case the valence band arises from the unshared electron pair (lone pair) of the group-VI atom. We examine the effects…
Crystals of armalcolite, Mg(0.5)Fe(0.5)Ti(2)O(5), up to several millimeters in length have been grown from a glass initially having the composition of lunar rock 10017. A single-crystal x-ray study has confirmed that the crystals are isomorphous with pseudobrookite and has shown that the cations are strongly ordered,…
Intracellular Biosynthesis of CollagenWork from several laboratories has demonstrated that the biosynthesis of collagen occurs by a series of sequential steps: assembly on ribosomal complexes of a polypeptide precursor of collagen that we have called "protocollagen"; hydroxylation of appropriate Pro and Lys residues i…
The carbothermic reduction in vacuum of thorium oxide with graphite has been studied with the aid of a high temperature thermobalance at temperatures range of 1,300°–1,900°C. The effects of differences in the reaction temperature, molecular ratio of the reactants, and in the state of the reactants such as differences…
Experimental findings of an irradiation enhancement of precipitation in stainless steel under observation in the High Voltage Electron Microscope (HVEM) are presented. The results for the case of electron irradiation are compared with previous studies of precipitation under neutron irradiation in thermal and fast reac…
SUMMARY Among the examples reviewed are volume‐fraction measurements in phase diagram and kinetic studies, properties dependent upon internal surface area, the characterization of phase arrangements by contiguity, proximity and dihedral‐angle measurements. The use of grain boundary and particle spacings in studies of…
<div class="htmlview paragraph">The friction and wear characteristics of automotive friction materials are strongly dependent on the composition and microstructure of the rotor surface. In this study we investigated the compositional and microstructural changes occurring in the surface layers of cast iron brake…
The effect of small-angle multiple scattering on a number of general structural parameters and on the segment distribution function has been studied using a representative correlation function of the type γ = exp (−r/lp). The results show that size parameters can be severely underestimated if the presence of multiple…
The perovskite SrTiO3 can be controllably crystallized in situ in a glass matrix, and the resulting glass-ceramic displays a large peak in the dielectric constant at about 75 K (shifted from 35 K by doping and glass-chemistry techniques) and a T-1 increase in the dielectric constant below 0.1 K. This high degree of di…
A laboratory investigation was conducted to determine the effects of cathodically charged hydrogen on the mechanical properties of MONEL(1) nickel-copper alloy K-500, and to investigate the relationship between material hardness and susceptibility to hydrogen embrittlement. Tensile specimens having hardnesses of 26 to…
Based on early experiments, a simple closed wet cell has been designed to retain volatile material in the vacuum of the transmission electron microscope. A description is given of the procedure for making the triple film windows for retaining liquid in the cell yet permitting good electron beam penetration and the cla…
The nuclear magnetic resonances in metallic perovskite compounds Mn 3 AlC and Mn 3 GaC have been studied. In Mn 3 AlC the Al 27 and Mn 55 resonances are observed at 78 and 140 MHz, respective at 4.2 K. The corresponding hyperfine fields at Mn 55 and Al 27 and 133 and 70 kOe at 0 K, respectively. In Mn 3 GaC three sign…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUnusual metalloporphyrins IX. Preparation of a new (mesoporphyrin IX dimethyl esterato)dinitrosylruthenium(II)T. S. Srivastava, L. Hoffman, and M. TsutsuiCite this: J. Am. Chem. Soc. 1972, 94, 4, 1385–1386Publication Date (Print):February 1, 1972Publication History Published…
Some of the problems of fabricating thin films of mixed oxide ferroelectrics possessing electrical properties comparable to those of the bulk material are discussed. It is shown that crystallographic disorder and non-stoichiometry can lead to anomalous behavior in dielectric properties such as permittivity and loss. I…
Abstract Comprehensive elucidation of optical and magnetic properties of low-spin cobalt(II) complexes of various types has been attempted. The g-values and magnetic susceptibilities of the complexes have been calculated, the necessary numerical data being obtained from the spectral data and reasonable assumptions. Fa…
A FORTRAN IV computer program has been written for the elaboration of X-ray intensities diffracted by liquid, amorphous and microcrystallized substances. The experimental data, corrected for both polarization and absorption, after conversion into absolute units are inverted into radial distribution functions. Various…
An enantiomorphic transition was observed for the first time by observing Airy's spirals of the oppositely polarized ferroelectric 5PbO 3GeO2 single crystals, which were grown by the Czochralski method. Switching time follows an exponential law at moderate field strengths and a power law at higher field strengths.
For Pt. II see ibid., vol. 5, 150 of 1972. The potential distribution inside three equidiameter coaxial cylinders separated by finite distances has been derived and used to calculate the focal lengths, mid focal lengths and spherical aberration coefficients of some triple cylinder lenses having three different voltage…
SUMMARY Scanning electron microscopy (SEM) provides a considerably greater depth of field than optical microscopy at the same magnification. It is therefore particularly suitable for the examination of specimens with irregular surfaces. This review of procedures for quantitative measurements on SEM images falls into t…
The thermal conductivity, electrical resistivity, and absolute thermoelectric power of pure palladium have been determined from 90 to 1300 K in two experimental systems of proven reliability. These properties are compared with the sparse available literature data, and show large deviations from them, particularly for…