Materials Literature
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Abstract It has recently been postulated that viscous flow, or plastic deformation, occurs near the tip of an advancing crack in glassy amorphous polymers such as Plexiglas, and this results in molecular orientation at the fracture surface. The evidence for this has been the appearance of colors on fresh fracture surf…
By use of electron microbeam probe analysis on quenched samples, the concentration distribution of CaO, A1 2 O 3 , and SiO 2 was determined across the boundary layer between molten calcium aluminum silicates and dissolving or growing sapphire and fused silica. A definite shift in the concentration ratios of the solven…
Co${\mathrm{F}}_{2}$ is a simple two-sublattice antiferromagnet and has a rutile crystal structure. Each ${\mathrm{Co}}^{++}$ ion is surrounded by a rhombically distorted octahedron of fluorine anions and the crystal-field parameters are known from an analysis of infrared absorption measurements. A good description of…
A polarization technique for the measurement of electronic and ionic transference numbers in mixed conductors is described; also a discussion of the conditions governing its applicability. The application of this technique is demonstrated by measurements on the solid solution Zr0.85 Ca0.15 O1.85, which is shown to be…
Accurate values of the parallel and perpendicular components of g-factor and hyperfine coupling tensor were determined for [CrOCln]—(n−3) where n=4 and 5, by the ESR line shape analysis. It was shown by a molecular orbital treatment that these magnetic parameters can be explained consistently by taking into account of…
The crystal structures at 298°K of MnCl2·2H2O and FeCl2·2H2O have been refined by means of three-dimensional differential syntheses using diffractometer single-crystal x-ray-intensity data. The crystal structures of these isomorphic compounds consist of polymeric chains of metal and chlorine ions arranged in a near-sq…
Abstract The viscoelastic properties and thermal expansion properties of bisphenol A polycarbonate have been studied in the neighborhood of the major glass transition temperature. A discussion is given of the possible relation of these properties to the unusual impact resistance of this polymer in the glassy state.
Population of luminescent levels of rare-earth ions in solution has been accomplished through energy transfer from excited, nonchelated organic molecules. Twenty-one aromatic aldehydes and ketones have been shown to be capable of transferring energy to Tb3+ or to Eu3+. It is suggested that a diffusion-controlled proce…
A scanning electron microscope using three magnetic electron lenses and a thermionic electron source has been developed to give an electron probe size of 50 Å and a resolution in reflection of 100 Å. This experimental result agrees with the theoretical limit on electron probe size and current found by consideration of…
The interaction between two neighboring localized magnetic moments in the transition metals and alloys in studied by using the Anderson model generalized to the case of five-fold degenerate d-orbitals. The effective exchange energy and the change of the localized moments due to the d-d covalent admixture are calculate…
Abstract The linear thermal expansion of molded PTFE samples of various crystallinities was measured in the vicinity of the transition at about 400°K. In the plot of length of the specimen versus temperature, an inflection of the straight line was observed in the temperature range from 388 to 402°K., the mean value be…
Abstract Heats and entropies of fusion of polymers are customarily evaluated through melting point depression measurements with the assumption that the observed and thermodynamic melting points are nearly identical. However, it has recently become evident that the crystal surface free energy is not negligible, so that…
Optical absorption, fluorescence, and paramagnetic-resonance experiments on single crystals of $\ensuremath{\beta}$-${\mathrm{Ga}}_{2}$${\mathrm{O}}_{3}$ doped with chromium were performed from room temperature down to a few degrees Kelvin. All the important low-lying energy levels have been identified from the optica…
Wavelength and intensities are reported for the Al K series using primary excitation. Included in the tabulation are the diagram lines α1α2 and β1, and the nondiagram lines α′, α3, α4, α5, α6, β′, β″, and β″′. Spectra are shown and line positions and intensities are detailed using both aluminum metal and aluminum oxid…
Intersecting faults on basal (0001) and prismatic (1210) planes in A1N (hexagonal, wurtzite structure) have been studied by diffraction contrast with the electron microscope. The faults on (1210) had fault vectors 3/2 p + 1/2 c=½[1011], as deduced from the observed vanishing conditions. The expected stair-rod dislocat…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMacrocyclic PolydimethylsiloxanesJohn F. Brown Jr. and George M. J. SlusarczukCite this: J. Am. Chem. Soc. 1965, 87, 4, 931–932Publication Date (Print):February 1, 1965Publication History Published online1 May 2002Published inissue 1 February 1965https://pubs.acs.org/doi/10.…
Abstract The conventional “string‐of‐beads” statistical model for flexible chain polymers is modified for derivation of configurational and thermodynamic properties of long‐chain ring molecules (i.e., flexible linear chains with ends joined) in dilute solution near the Flory temperature. The effect of the intramolecul…
The suggested phase diagrams for the system B 2 O 3 ‐SiO 2 as drawn from the findings of previous investigators are presented. These diagrams show the wide controversy regarding this system. The principal difficulties in obtaining reliable equilibrium data are the volatilization of B 2 O 3 , the hydration of B 2 O 3 ‐…
Measurements of thermal conductivity for the range 3° to 300°K are reported for both pure and heavily doped n- and p-type GaAs single crystals, and n-type heavily doped polycrystalline GaAs1−xPx crystals with six compositions between x=0 and x=0.5. The alloy ingots have much lower K values due to alloy scattering, wit…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Effect of Molecular Weight on the Melting Temperature and Fusion of Polyethylene1J. G. Fatou and L. MandelkernCite this: J. Phys. Chem. 1965, 69, 2, 417–428Publication Date (Print):February 1, 1965Publication History Published online1 May 2002Published inissue 1 February…