Materials Literature
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In a nematic medium, as a result of the anisotropic distribution of the molecules, the average local electric field is of the form E+ γP, where E is the applied field, P the polarization, and γ is a factor which is different for the directions parallel and perpendicular to the optic axis. For the nematic medium, the N…
X-Ray photoelectron spectroscopy has been used to study the oxidation of uranium metal. The results indicate that even at 1073 K in a residual oxygen partial pressure of less than 1 × 10–8 N m–2 the interdiffusion of pure uranium and the surface oxide film is not sufficiently rapid to produce a completely pure uranium…
Investigations of tris- and tetrakis-hexafluoroacetylacetonato- and trifluoroacetylacetonato-terbium(III) complexes have established that the temperature-dependence of the 5D4 lifetime is caused by thermal depopulation of the ion level to a ligand triplet state. Ligand triplet to ground state deactivation rates, A, ha…
Far infrared reflectivity of Sb2S3, Bi2S3 and Sb2Se3 single crystals in the spectral region 25-400 cm-1 and temperature region 100-400°K were measured in polarized light. The reflectivity spectra were subjected to the Kramers-Kronig analysis to obtain dielectric response functions. The far infrared dispersion is of a…
Salts of the heteropolyanions PCoIIW11O40H25–, AsCoIIW11O40H25–, BCoIIW11O40H27–, BCoIIIW11O40H26–, and PZnW11O40H25– have been prepared. In the case of the first four and of PNiIIW11O40H25– there is spectroscopic evidence that the constitutional water is present as an actual water molecule and is replaceable by, e.g.…
M\"ossbauer absorption spectra have been observed for ${\mathrm{Fe}}_{2}$B from 290 to 1175 \ifmmode^\circ\else\textdegree\fi{}K. A change in the electric quadrupole interaction was observed from 460 to 480 \ifmmode^\circ\else\textdegree\fi{}K and interpreted as a result of the rotation of the easy axis of magnetizati…
Magnetization and magnetic torque measurements were made on single crystals of ErFe2 from 77°K to 329°K. From these measurements the magnetocrystalline anisotropy constants were deduced. At room temperature K1 = −3.3 × 106 ergs/cm3; at 77°K, −K1 > 108 ergs/cm3. Huge magnetic anisotropies are predicted for TbFe2 and Dy…
-We study the hydrodynamic motion induced by the rotation of the molecular axis in a nematic liquid crystal (backflow). This effect can reduce strongly some effective viscosity coefficients.
A dynamic TGA method was used to study the effect of the molecular weight of well-defined polystyrene samples as well as the effect of heating rate and sample weight on the kinetic parameters of the thermal decomposition. It is shown that the maximum rate, the average specific rate, and the activation energy of the de…
Abstract Temperature dependent infrared studies have been carried out on three series of poly‐urethanes previously synthesized and characterized. The repeat units of the three series may be schematically represented as follows: magnified image In each case n varies from 2 to 10. The H and DP series are partially cryst…
A concise compilation of ferroelectric and antiferroelectric materials, known up to 1971, is presented together with the Curie and other transition temperatures. Spontaneous polarization values are given in the case of ferroelectrics.
The usual analysis of thermal-motion parameters, derived from X-ray diffraction data, in terms of rigid-body motions can be extended to include the effect of certain specified internal molecular motions.
Some 50 ternary sulfides of the type were explored, where and . The structure of the compounds, if they were formed, was investigated with x‐ray diffraction techniques using primarily the materials synthesized in powder form. Single crystals were subsequently grown from the powders for several compounds including and…
The i.r. spectrum of the complex pentacarbonyliron, [Fe(CO)5], has been recorded in a number of different low-temperature matrices. U.v. photolysis produces new bands in the C–O stretching region; these bands disappear on exposure to longer-wavelength light and are assigned to the tetracarbonyl fragment [Fe(CO)4] plus…
Pyrolytic films, in thicknesses up to 30,000Aå, were produced by the reaction at 900°C. These films were characterized by use of transmission electron microscopy, electron microprobe analysis, measurement of dielectric, and optical properties. It was found that the films were orthorhombic with a fine grained structure…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTGeneral method for the synthesis of 3- and 3,4-substituted furans. Simple syntheses of perillene and dendrolasinMichael E. Garst and Thomas A. SpencerCite this: J. Am. Chem. Soc. 1973, 95, 1, 250–252Publication Date (Print):January 1, 1973Publication History Published online…
The liquid phase adsorption and reaction of a range of organo-sulfur compounds with ground iron powder were studied in the temperature range 25–170 C. The reactivity of organic disulfides was found to increase along the series: Monosulfides and mercaptans were found to be less reactive than the corresponding disulfide…
The nature of the oxygen species adsorbed on slightly reduced CeO2/SiO2 supported catalysts has been investigated using oxygen enriched with 17O2. The observed hyperfine splitting was found to be associated with the central component of the g tensor; it indicated that the corresponding orbital contained the unpaired e…
Certain compositions within the quaternary lead-lanthanum-titanate-zirconate (PLZT) system exhibit neither a "true" ferroelectric nor a "true" paraelectric behavior and are therefore best characterized as quasi-ferroelectric. The dielectric, hysteresis, and optical properties of quasi-ferroelectric PLZT ceramics have…
A convenient, large-scale method for separation of the aand b series metal-free chlorophyll derivatives is described, utilising the Girard ‘T’ reagent with subsequent chromatography. Efficient procedures for conversion of phaeophytin-a(3) into rhodoporphyrin-XV dimethyl ester (1) and the corresponding 2-vinyl compound…