Materials Literature
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Aerospace technology has established the demand for thermally stable polymers which retain useful properties at high temperatures. The reliability of a re-entry shield is directly dependent on the performance of the polymers used as ablators. Polymeric ablation materials are sacrificial and are classified as subliming…
Abstract It was found that anthracene (I) was converted to 9,10-anthraquinone (III) and bianthrone (IV) by irradiation via anthracene peroxide (II). The reaction proceeded most effectively in carbon disulfide. Also IV was found to be oxidized to III by oxygen in singlet state.
Abstract As discussed in this paper, melt treatment prior to crystallization, apparently proceeds by the following stages: partial melting; an insensitive region; and at higher temperatures, deactivation of nucleation sites. The deactivation‐region onset temperature is quite dependent on the subsequent crystallization…
The scanning electron microscope can be used to produce, in a way that is not possible with optical techniques or with casts of pore space, a quasi three-dimensional representation of the pore structure of sandstone, making it possible to determine the pore structure of sandstone, making it possible to determine the n…
Collagen extracted from rat skin by neutral-salt solutions contains less aldehydes than the more insoluble collagen fractions. The concentration of aldehydes in collagen is directly related to its capacity to form stable cross-linked gels, which do not redissolve on cooling and become more insoluble in a variety of re…
The reaction of microspheres of UO z with graphite was studied from 1400° to 1756°C. When a spherically symmetrical layer of carbide was produced around the UO 2 core, only UC 2 was formed, and the diffusion of oxygen through this layer was rate‐controlling. The Arrhenius relation for this system is k D = 21.0 exp(−90…
The thin layer lathe sectioning technique was used to measure the self and solute diffusion coefficients of gold in f.c.c. lanthanum. Self-diffusion is given by D = 1.5 exp (− 45100/RT) cm2/sec, and gold solute diffusion by D = 2.2 × 10−2 exp (− 18100/RT) cm2/sec. The activation energy for self-diffusion is in good ag…
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…