Materials Literature
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The finite-electron-lifetime expressions for the longitudinal and transverse dielectric functions of a free-electron gas obtained by Lindhard in the self-consistent-field approximation are examined. It is shown that these results are incorrect, and appropriate expressions are developed for the case where the system ca…
The chemical and magnetic structures of the ${\mathrm{Zn}}_{x}{\mathrm{Ni}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ system have been determined using neutron diffraction for $x=0, 0.25, 0.50, \mathrm{and} 0.75$. The data yield a cation distribution (${{\mathrm{Zn}}_{x}}^{2+}{{\mathrm{Fe}}_{1\ensuremath{-}…
A theory of the relationship between curvature strains and electric polarization in liquid crystals is developed in analogy to piezoelectric theory in ordinary crystals. The theory may explain some recently observed phenomena in nematic liquid crystals.
Abstract In the presence of excess air the kinetics of reaction between CaO and PbO to form calcium plumbate are governed by the diffusion process described by Jander's kinetic model. The energy of activation of the process, as calculated from the Arrhenius equation, is 50 kcal/mol. In an air and nitrogen atmosphere (…
The phase diagram of Li 2 SO 4 -K 2 SO 4 has been determined by differential thermal analysis. By making use of ail improved method, the sensitivity of the measurements has been increased and we have found a number of new transitions, especially in the lithium sulphate rich region. We have also detected a new transiti…
Abstract Under experimental conditions in which the interaction between triplet dye and oxygen is an initiating process (D–O mechanism), the photosensitized oxidation of leucofluorescein in the aqueous solution (reaction (1)) has been found to decrease in rate with the increasing oxygen concentration and that the magn…
Abstract The reactivity of scoured Acala 4‐42 cotton before and after treatment with alkaline and acid swelling agents has been assessed by a number of methods. It is shown that the reactivity depends more on the type of swelling, whether it is interfibrillar or intrafibrillar, than on the degree of swelling achieved.…
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…