The crystal structure of NbAs (comments)
SrBeO4.4HeO forms
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Thermal Decomposition of Europium Hydroxide
The thermal decomposition of europium hydroxide in an air atmosphere was investigated by means of weight‐loss measurements, infrared spectroscopy, X‐ray diffraction analysis, and electron microscopy. These studies showed that EU(OH)° decomposed at temperatures between 225° and 300°C into EuOOH, which was stable up to…
Aspherical atomic scattering factors in crystal structure refinement. I. Coordinate and thermal motion effects in a model centrosymmetric system
The consequences of ]-refinement procedures on atoms whose charge distributions are intrinsically non-centrosymmetric are examined in terms of a simple hypothetical structure consisting of two sp a hybrid valence 'prepared' state nitrogen atoms which are centrosymmetrically disposed in a unit cell and asstuned to be v…
Correlation of optical absorption and thermoluminescence curves for single crystals of magnesium oxide
Optical absorption and thermoluminescence measurements on untreated crystals of magnesium oxide have shown that the crystals can be divided into two groups. X irradiation of the crystals induces an optical absorption peak at 2.3 ev in group I crystals and at 2.3 and 3.0 ev in group II crystals. Thermoluminescence curv…
Dielectric Breakdown of Polycrystalline BaTiO3
The temperature dependence of breakdown field, distribution of time lag. and dielectric constant in high electric field were studied on polycrystalline BaTiO 3 . The d. c. breakdown field is nearly constant in the temperature range 20 to 150°C, on the other band the pulse breakdown field changes markedly near the Curi…
Flame-Contact Studies
This paper is composed of three parts: 1 Apparatus and method for determination of heat transfer through fabric during flame contact; 2 experimental validation of mathematical analysis and heat flow; 3 application to determination of thermal properties of materials in thin layers.
Phase Diagram of the Partial System of MnSi-Si
A phase diagram of the system MnSi-Si containing Si in the range from 45.00 to 57.00 wt% is determined by the methods of X-ray, metallographic and thermal analyses and also by the electrical measurements. It is found that the intermetallic compound in this system is MnSi 1.72 . This compound has the maximum melting po…
Mechanical Relaxations and Transitions in Polytetrafluoroethylene
Thermal expansion, ultrasonic and creep behavior of polytetrafluoroethylene are studied in temperatures from -100° to 180°C. The glass transition and primary dispersion of this polymer observed. The assignments of relaxations and transitions described in what follows are found to be quite compatible with experimental…
The stress-fields around groups of dislocations in face-centred cubic metals
The various components of the stress-fields of piled-up groups of screw and edge dislocations are calculated by replacing the array of discrete dislocations by a continuous distribution. The stress-fields are resolved onto each of the eleven secondary systems of the face-centred cubic lattice; by mapping out the stres…
Stress Corrosion Cracking Susceptibility Of Stainless Steels and Nickel-Base Alloys In Polythionic Acids and Acid Copper Sulfate Solution
Intergranular cracking tendencies of fourteen stainless steels and two high-nickel alloys have been evaluated by exposing numerous specimens to polythionic acid and standard acid copper sulfate solutions. The sensitization curves for solution-annealed wrought stainless steels, which had been held for varying times at…
Dislocation Structure and Growth Mechanism of Cadmium Sulfide Crystals
Crystals, needles, ribbons, and platelets, grown from pure and impurity-added CdS vapor, have been studied morphologically. Needles grow parallel to the [0001], [101̄0], and [21̄1̄0] axes of the hexagonal system. Ribbons grow parallel to the [101̄0] and [21̄1̄0] axes and their surfaces are parallel to the (12̄10) and…
Dislocation Multipoles and Their Role in Strain-Hardening
The stress fields of edge dislocation dipoles are able to trap other edge dislocations that pass nearby. The configurations, energies, and trapping stresses of the resulting tripoles are discussed here in some detail. Dipoles may also interact dynamically with approaching dislocations because they cause fluctuating st…
Single-Crystal X-Ray Diffraction Studies of α-N2 and β-N2
The structure of α-N2 is cubic in the space group P213 with four molecules per unit cell. A total of 49 independent observed single-crystal x-ray diffraction maxima yield R=Σ ‖Fo|−|Fc ‖ /Σ|Fo|=0.13. Two faint reflections, (501) and (520), violate the space group Pa3, which yields R=0.21. Molecular centers are displace…
Viscosity of amorphous polymers
Abstract An amorphous polymer is characterized as a homogeneous array of N identical, n ‐center polymer segments which can be described in terms of four molecular constants. A mechanism for viscous flow (or self diffusion) is visualized as a positional exchange of two adjacent polymer segments in a hole the size of a…
The Redox Reaction of 1-Ethoxy-n-heptyl Hydroperoxide
Abstract 1) The reaction of 1-ethoxy-n-heptyl hydroperoxide with ferrous sulfate has given ethyl formate, n-heptanal, ethyl heptanoate and n-dodecane, while the reaction with a mixture of cuprous and cupric chlorides has given ethyl formate, n-hexyl chloride, n-heptanal and ethyl heptanoate. 2) The formation of n-hept…
Procedure for Stripping Anodic Oxide Films from Tantalum and Niobium
Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation R. E. Pawel; Procedure for Stripping Anodic Oxide Films from Tantalum and Niobium. Rev Sci Instru…
X-ray evidence for CrCO3, VBO3and TiBO2with calcite structure
The borates were prepd. by heating the metal oxides, halides, and H3BO3 in a sealed quartz tube. Structures were deduced from x-ray powder diagrams.
Conduction—Ionic or Electronic—in BaTiO3
Conduction in single crystal and ceramic BaTiO3 has been investigated using a concentration cell and activation analysis. Ionic conduction occurs near 100°C in single crystals containing Fe2O3 while electronic conduction predominates in ``pure'' crystals from 100° to 600°C. Ceramic samples conduct predominately ionica…
The theory of Raman scattering from crystals
e theory of the Raman scattering by crystals is discussed and detailed calculations made of the spectra from sodium iodide and potassium bromide. Expressions for the dependence of the optical polarizability on the normal modes of vibration are obtained by using the shell model with anharmonic interactions between the…
Morphology of polyethylene crystallized from the melt under pressure
Abstract The morphology of linear polyethylene crystallized under pressures up to 5300 atm. has been investigated. Electron micrographs of fracture surfaces obtained from these samples show that the majority of the polymer, at the highest pressures, crystallizes in the form of extended chain lamellae which can be as t…