Materials Literature
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Abstract Poly‐ε‐caprolactone prepared by a dibutylzinc‐catalyzed bulk polymerization process was fractionated, and the solution properties of the fractions were studied in benzene and in dimethylformamide. In these solvents at 30°C the Mark‐Houwink relations were [η] = 9.94 × 10 −5 M and [η] = 1.91 × 10 −4 M , respect…
Abstract Investigation of the nucleating ability of selected nucleating agents in various commercial types of isolactic polypropylene revealed that the efficiency of individual additives is not equal for all types of polypropylene. As to the nucleation mechanism, it can be supposed that in most cases the added nucleat…
The photoemission threshold of GaAs–Cs–O is explained on the basis of a heterojunction model composed of GaAs and Cs2O. The concepts involved in this model are generalized to an arbitrary heterojunction, leading to the result that it is, in principle, possible to obtain surfaces with work function lower than 0.5 eV. I…
Nuclear Magnetic Resonance (NMR) of Mn 55 associated with the Mn 3+ ion at the octahedral site in its magnetically ordered state has been studied on manganese ferrite of cubic phase. Using a single crystal sample, the large anisotropic hyperfine field of +115 kOe, in addition to the isotropic hyperfine field of -360 k…
The thermoluminescence of ZrO2 samples, both pure and doped with titanium, irradiated with low doses of x rays has been studied. The glow curve of ZrO2(Ti) exhibits, in the temperature range 100° to 350°K, four main peaks all having the same spectral composition. The pure ZrO2 presents a similar glow curve but having…
Abstract It is demonstrated that in a filled polymer the thermal stresses resulting from the difference in the thermal expansion coefficients of the filler and the polymer have significant effect on the apparent coefficient of thermal expansion of the composite. A model is constructed to aid the thermal stress analysi…
The complex amplitude and intensity distributions in the near field of a plane periodic grating are calculated. To assist in the evaluation of various proposals to utilize the periodic behaviour of the diffraction pattern in the direction of the normal to the grating as a basis for spectrometric and metrological instr…
A method of predicting the 6th-harmonic electromagnetic torque of an induction motor arising from a rectifier-inverter power source is presented. This study includes both the effects of harmonic variation rotor speed and inverter voltage. Although only the 6th harmonic is considered, it is shown that this is sufficien…
Abstract Neither the fringed‐micelle, fringed‐fibril or extreme folded‐chain models explain the morphological and mechanical properties of highly drawn polyethylene. The modified folded‐chain model, assuming that a substantial fraction (between 5 and 30 percent) of the molecules do not fold back at the crystal surface…
Self-diffusion coefficients have been measured from the annealing kinetics of spherical voids in 99·999% pure copper. Thin foil specimens containing voids were annealed under conditions where it was possible for voids to shrink by the following three different diffusion mechanisms: (i) bulk diffusion; (ii) dislocation…
The crystal structure of benitoite has been refined on the basis of powder and single-crystal diffractometer data. Zachariasen's original structure has been fully confirmed. For the least-squares refinement, three-dimensional intensity data with l = 2 n + 1 were used. Thus, the Si 3 O 9 part of the structure could be…
Abstract Completeness of exchange of K from muscovite by Ba 2+ ions decreased with particle size below 20 μ . Accompanying K exchange at 120°C, using a repeated batch technique, was a marked loss of Si and the formation of boehmite in the finer fractions. Several possible explanations for the unexpected high K retenti…
Abstract Changes in the Poisson's ratio of natural vulcanized rubber due to elongation were investigated experimentally. The following results were obtained: If infinitesimal deformation at any instant during elongation is considered, it appears to be correct to take the Poisson's ratio at such instants as 0.5. If the…
Corrosion tests were run for periods up to 5000 hrs in borated water at 600 F (316 C) in a high velocity loop on strip, tubes, and weldments of Alloy 600. During the first 1000 to 2000 hrs of exposure, corrosion rate differences depending upon surface preparation and in the case of weld metal on composition were obser…
Glasses resistant to attack by sodium vapor at temperatures up to 700°C were developed from the CaO‐Al 2 O 3 ‐MgO‐BaO‐B 2 O 3 system. The resistance of these glasses decreases sharply above the transformation temperature. The glasses have a high water content, have good wetting properties, and adhere well to materials…
Far-infrared reflectivity spectra of NaNO 2 crystals were measured from 63 to 400 cm -1 over the temperature range from 85°K to 460°K. The results were analysed using a K.K. dispersion relation and the classical oscillator model. Five modes have been observed; the shifts in frequency are linear with temperature, and a…
Abstract The endoskeletal structure supporting the gill‐books of Limulus polyphemus has been investigated by means of light and electron microscopy, chemical analysis and x‐ray diffraction. This tissue is a cartilage which has significant correspondences with both vertebrate cartilage and plant tissues. Morphologicall…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIntramolecular energy transfer and sensitized luminescence in actinide(III) β-diketone chelatesLeonard J. NugentLeonard J. NugentMore by Leonard J. Nugent, J. L. BurnettJ. L. BurnettMore by J. L. Burnett, R. D. BaybarzR. D. BaybarzMore by R. D. Baybarz, George Knoll WernerGe…
The outgassing characteristics of 304 stainless steel with different surface treatments have been measured. The surface treatments investigated were: (1) glass-bead shot blasting; (2) electropolishing with a surface roughness of 20–25 μ in.; (3) electropolishing with a surface roughness of 4–6 μ in.; (4) one of the ab…
The anisotropy of heat conductivity that develops on uniaxial stretching of amorphous high polymers has been examined theoretically and experimentally. Experimental measurements on oriented polystyrenes and polymethylmethacrylates show a linear increase in conductivity (parallel to stretching) with increasing elongati…