Materials Literature
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Vapor densities of magnesium-bearing species over magnesium oxide were determined by the transpiration method. The MgO reacted with water vapor present in the carrier gas to form gaseous Mg(OH)2. The standard free energy of formation in calories per mole is given over the temperature range from 1660° to 2010°K by the…
Thermal conductivity measurements are used to study phonon scattering by $F$ centers in NaF, KCl, KBr, and KI. $F$ centers were produced by additive coloration and by x and $\ensuremath{\gamma}$ irradiation. The total effect on the thermal conductivity is seen to be different for the two methods of preparation. The ad…
Numerical calculations, based on spin wave theory, have been carried out in connection with the magnetic properties of two simple ferromagnetic salts, EuO and EuS, and the antiferromagnetic compound MnF 2 . The resulting predictions regarding magnetization and specific heat have been compared with experiment over as w…
A neutron diffraction study of polycrystalline HCrO 2 and DCrO2 (chromous acid) is described. Intensity data from the two substances were refined together by the lea~t-squares method, with the constraint that the Cr-O distance be the same in the two substances. Estimates of individual contributions to multiple peaks w…
An empirical description of the shape of optical absorption bands due to localized excitons in ionic crystals is proposed. The new formula links a nearly Gaussian description of the band near its maximum with an exponential description of the band on the low-energy tail (Urbach's rule). The applicability of the propos…
Abstract Poly‐β‐hydroxybutyric acid has been isolated from two bacterial sources by two different procedures. Molecular weight and intrinsic viscosity for the two samples were vastly different. This was blamed on degradation occurring during polymer isolation. An optical rotatory dispersion curve for the high molecula…
Numerous advances in the formulation and processing of electrical insulating compounds based on chemically cross-linked polyethylenes have taken place since they were first introduced commercially in 1958. The result has been a new family of polyethylene based insulations covering a wide range of properties. A review…
A Kerr magneto-optic apparatus has been used to observe the effects of tensile stress on the domain structure in grain-oriented 3.25% silicon steel. Unlike the powder pattern technique, the Kerr apparatus reveals the complete surface domain structure without regard to the type of domain wall, and enables observation o…
Summary Nickel carbonate occurs in nature as a hexahydrate (hellyerite) and as a hydroxyhydrate (zaratite), but the anhydrous species is only known as an artificial product. All of the compounds show anomalous properties that have led to confusion in the literature. Only the calcite structure was found for NiCO 3 ; hy…
The influence of milling upon some magnetic properties of the intermetallic compound MnAlGe has been studied. The Curie temperature of the material seems to be independent of particle size and is constant at 245°C. The saturation magnetization σs, which is 55 erg/Oe·g in the annealed state, decreases as the grinding t…
The quenching technique has been used to determine equilibrium relations in the system manganese oxide‐Cr 2 O 3 in air in the temperature range 600° to 1980°C. The following isobaric invariant situations have been determined: At 910°± 5°C tetragonal Mn 3 O 4 solid solution, cubic Mn 3 O 4 solid solution (=spinel), Mn…
An improved counterbalanced sphere viscometer—densitometer was used to obtain density information between 1050° to 1500°C for a series of binary germanate melts containing as much as 60 mole% Li2O, Na2O, K2O, and Rb2O. Densities and the expansion coefficient of molten GeO2 between 1100° to 1400°C were estimated from t…
A study has been made of high-resolution absorption spectra of C 12 S 2 and C 13 S 2 in the region 4300–3300 Å. The spectra are shown to arise from transitions from the ground state to two or more excited electronic states. In the lowest excited state the molecule is not linear, and the following constants have been d…
Molecular iodine was removed from polypyrrole by electrochemical reduction of slurries at a mercury cathode. This method was found to be more effective than the treatment of rigid or packed polymer electrodes. Voltammetric plots indicated that two reductions occurred, at potentials insensitive to pH. The current passa…
Abstract The tensile stress at break (σ b ) and the associated ultimate strain (ϵ b ) of an elastomer depend on (1) the chemical and topological characteristics of the polymeric network, and (2) the test conditions under which rupture is observed. To separate these effects, the ultimate tensile properties can often be…
The effect of a uniform magnetic field on the mechanism, kinetics, and resulting morphology of a spinodally decomposing alloy is investigated. It is shown that the magnetic field is most effective in forming uniformly spaced rods parallel to the magnetization if the aging is carried out just below the intersection (on…
The viscosity of supercooled water has been measured, using a capillary flow technique, down to -23.8 °C. The large supercooling was obtained by removing nearly all suspended particles from the water by an ion exchange column. These results agree with those obtained by White and Twining in 1914, who obtained results d…
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