Materials Literature
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A study has been made of the stress-strain behaviour, secondary slip geometry and slip line morphology of niobium single crystals purified by annealing in ultra-high vacuum. Within favourable limits of orientation, temperature and strain rate the stress—strain curves exhibit well-defined three-stage hardening. The pri…
Studies of the x-ray diffraction pattern from different potassium graphites have shown that intercalation of graphite by potassium is accompanied by an expansion of the carbon layers. This expansion is uniform within a single layer and is constant for all n carbon layers separating successive intercalate layers in the…
SUMMARY In order to obtain data comparable to those of B iscaye (1965) on the Atlantic Ocean, the authors carried out quantitative X‐ray determinations of clay minerals in the sediments of the Indian and Pacific oceans using the Biscayemethod.
Abstract Polyethylene, polypropylene, poly(vinyl fluoride) (Tedlar), polystyrene, nylon 6, poly(ethylene terephthalate) (Mylar), polycarbonate, cellulose acetate butyrate, and a poly(oxymethylene) copolymer were treated with activated helium and with activated oxygen. Mechanical strengths of adhesive‐bonded specimens…
An apparatus has been designed and constructed that will allow determination of the mechanical behavior of polymer specimens subject to applied tensile and compressive loading, while the sample is simultaneously subject to a hydrostatic pressure environment. The moduli of high-density polyethylene and polypropylene de…
The six lowest excited states of benzene have been investigated in the gas-phase free molecule at low pressure by electron-impact spectroscopy. Incident electron energies of 13.6 and 20.0 eV and scattering angles from 9° to 80° were used. Three singlet–singlet transitions at 5.0, 6.2, and 6.9 eV were identified. These…
Abstract Most thermoplastics far below their glass transition give a brittle fracture when de‐formed in uniaxial tension. Bisphenol‐A polycarbonates are an exception and deform in a ductile manner. However, it has been observed in Izod impact studies of notched samples that the mode of failure changes from a ductile t…
Abstract The glass transition temperature, dynamic shear moduli, and bulk viscosities of Phenoxy PKHH (a thermoplastic polymer made from bisphenol‐A and epichlorohydrin) filled with glass beads and Attapulgite clay were investigated. The glass temperature of the polymer increased with increasing filler concentration a…
Abstract Thermogravimetric Analysis (TGA) is finding increasing utility in investigations of the pyrolysis and combustion behavior of materials. Although a theoretical treatment of the TGA behavior of an idealized reaction is relatively straight‐forward, major complications can be introduced when the reactions are com…
A new study of the structure of vitreous silica has been made under greatly improved conditions. Using Rh Kα radiation with the method of fluorescence excitation, reliable intensity values were measured to 4π sinθ/λ = 20. The interpretation was in terms of pair functions, thereby eliminating the approximations in earl…
Abstract Der Einfluß einer Temperung auf den Zustand von technischem Polyvinylchlorid wird zunächst durch kalorimetrische Messungen untersucht. Eine Temperung unterhalb der Glastemperatur führt infolge von Enthalpie‐Relaxation zu Zustandsänderungen, die nicht eine Erhöhung der Ordnung der amorphen Bereiche im Sinne zu…
Exact analytic solutions to the linearized Boltzmann equation for combined electron-electron electron-impurity scattering have been obtained. For the usual two-band model of a transition metal, these make possible a precise theoretical consideration of the experimentally important question as to the additivity of the…
A theoretical analysis is made of crystal stability and of low-temperature deviations from the Cauchy relations between elastic constants of ionic crystals with $\mathrm{AX}$ composition and with cubic or hexagonal structure. The Born-Mayer model is used as a basis, extended to take into account short-range three-ion…
A general expression for the electric field gradient (EFG) at the positive ion nucleus in an ionic crystal with polyatomic negative ions has been derived in the frameworks of the LCAO–MO approximation and the multipole expansion theorem of the electrostatic potential. The contribution to the field gradient in the pres…
Cadmium pyrophosphate forms crystals having triclinic symmetry with the unit cell parameters a = 6.672(8) Å, b = 6.623(8) Å, c = 6.858(7) Å, α = 95.80(10)°, β = 115.38(8)°, and γ = 82.38(8)°. The space group is [Formula: see text] and there are two molecules per unit cell. The structure was refined by least squares me…
Measurements of acoustic attenuation in SrTi${\mathrm{O}}_{3}$ reveal critical scattering behavior near the structural phase transition at ${T}_{a}\ensuremath{\cong}105$ K. Power laws for the frequency and temperature dependences have been found. By these measurements the behavior of the soft mode frequencies could be…
The hydrostatic-pressure dependence of the electronic properties of V${\mathrm{O}}_{2}$ near the semiconductor-metal transition to a pressure of 40 kbar is described. The temperature dependence of the V${\mathrm{O}}_{2}$ resistivity from 0\ifmmode^\circ\else\textdegree\fi{}C through the semiconductor-metal transition…
The absorption spectrum of Pr3+ in LaF3, LaCl3, CaF2, Pr(Y)Cl3·6H2O, and Pr2(SO4)3·8H2O was investigated. Evidence for the S01 level in Pr3+:LaF3 at 46 986 cm−1 is presented; this level was not observed directly in absorption in any of the other matrices studied. An analysis of the 13 observed levels in Pr3+:LaF3, bas…
The specific heats of $n$-type bismuth telluride with carrier concentrations ranging between 2.2\ifmmode\times\else\texttimes\fi{}${10}^{18}$ and 8.3\ifmmode\times\else\texttimes\fi{}${10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, $p$-type ${\mathrm{Bi}}_{2}$${\mathrm{Te}}_{3}$ with a carrier concentration of 1.3\ifmmo…
Intramolecular energy transfer in lanthanide chelates can occur through different paths depending on the nature of the chelate. Contrary to prevailing notions, it is shown that energy transfer does not require the participation of the lowest triplet level of the chelate. The experimental results from a study of soluti…