Materials Literature
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Evidence is presented for the existence of two overlapping dispersions at 20°C in toluene. Resolution of the two dispersions was in terms of separate Debye relaxation processes, with dispersion parameters ε01=2.384, ε∞1=2.269, and τ1=5.80×10−12 sec for the low-frequency process and ε02=2.269, ε∞2=2.222, and τ2=2.0×10−…
An analysis of the experimental evidence in Part I of this paper clearly indicates that for the case of copper crystals, striations in low-amplitude fatigue are suppressed by strong slip on intersecting slip planes, including the cross slip system, but are formed by interactions between dislocations on the primary gli…
The lattice parameter of La 2 Ce 2 O 7 fired at 1 400 °C was found to be 5.5700 ± 7 Å (at 20 ± 2 °C). Its crystal structure was of the disordered fluorite rather than the pyrochlore type. The degree of order in the structure could not be established from the neutron powder diffraction pattern, but it is likely that th…
Reactions between cation vacancies and Cr3+ impurity ions in single crystals of magnesium oxide are studied using optical techniques to determine the concentrations of the reaction components. Several new features of the Cr3+-ion luminescence spectrum are reported. The spectrum of these impurity ions is very sensitive…
New experimental data on the ultraviolet optical properties of single-crystal magnesium oxide are presented in the range 4.0-14.5 eV. Normal-incidence reflectance data exhibit three strong peaks at 7.60, 11.05, and 13.50 eV. The first peak, due to an excition transition at $\ensuremath{\Gamma}$, shows strong temperatu…
The thermal-expansion and room-temperature lattice constants were determined for several phosphates and arsenates isomorphous to KH2PO4. From these data, the lattice constants were calculated at the ferroelectric antiferroelectric temperature. They show a nearly identical c/a ratio for the compounds of any given alkal…
Thermogravimetric (t.g.a.) and differential thermal analyses (d.t.a.) of ϵ-Zn(OH) 2 , Zn 5 (OH) 8 Cl 2 .H 2 O, β-ZnOHCl, and ZnOHF are reported and discussed. The results show that the replacement of a hydroxyl group by a halogen group contributes to greater thermal stability of the hydroxy compound. The thermal stabi…
The elastic constants of single crystals of magnesium and of dilute alloys of magnesium with lithium have been measured at 298\ifmmode^\circ\else\textdegree\fi{}K using the pulse-echo technique. The alloys covered the range of 1.841-2.0 electrons per atom. All fundamental elastic constants decrease with increasing lit…
Impact shear tests of the Kolsky thin-wafer type were used to determine the effect of temperature and strain rate on the critical resolved shear stress for slip in aluminum single crystals at strain rates of 104 sec−1 and in the temperature range 20° to 500°K. The aluminum deformed in a viscous manner in that the flow…
Diamagnetic α-ZnMoO4, the stable phase at STP, is triclinic with lattice constants a=9.625±0.015 Å, b=6.965±0.010 Å, c=8.373±0.015 Å, α=103.28°±0.15°, β=96.30°±0.15°, and γ=106.72±0.15° at 298°K, with six formula weights in the unit cell. The integrated intensities of 6489 reflections in a reciprocal hemisphere with (…
A simple formula in closed form is proposed for the thermal accomodation coefficient from which the accommodation coefficient of a monatomic gas—solid system may be calculated from certain basic parameters of the system. The formula α(T)=1−exp(−T0/T)+α(∞) tanh{[(MT)1/2/α(∞)](a/λ)} exp(−T0/T)is obtained from considerat…
This paper reports measurements of the shift with hydrostatic pressure and uniaxial stress of the temperature for a metal-to-semiconductor transition in ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$; of the change with pressure and uniaxial stress of the resistivity in the metallic phase and the activation energy for condution…
The nucleation of droplets of polyethylene, polyethylene oxide, polyoxymethylene, nylon 6, poly (3,3-bis-chloromethyloxacyclobutane), isotactic polypropylene, and isotactic polystyrene, suspended in silicone oil, has been investigated. Under conditions of slow cooling (0.1°C/min), two different phenomena were observed…
The elastic moduli of hexagonal beryllium oxide, zinc sulfide, and cadmium selenide at 25°C have been determined by measuring ultrasonic wave velocities in the 20- to 50-MHz frequency range. The data are compared with other literature data and discrepancies are discussed. The adiabatic bulk modulus, volume compressibi…
A statistical model for the reflection of scalar plane waves from a rough surface leads to a plane wave in the direction of specular reflection and to a contribution with a finite angular spread about that direction, depending on the tangential correlation of the surface asperities. Based upon on this result, a new se…
The electron Hall mobility has been measured in semiconducting SrTi${\mathrm{O}}_{3}$ over the temperature range from 1.6 to 550\ifmmode^\circ\else\textdegree\fi{}K. Electron concentrations in the range from 1\ifmmode\times\else\texttimes\fi{}${10}^{17}$ to 2.5\ifmmode\times\else\texttimes\fi{}${10}^{19}$ ${\mathrm{cm…
Precision x-ray measurements of the motions of the atoms in LaCo${\mathrm{O}}_{3}$ every 50\ifmmode^\circ\else\textdegree\fi{}C from room temperature to 1000\ifmmode^\circ\else\textdegree\fi{}C indicate that the crystal space group is $R\overline{3}c$ below 375\ifmmode^\circ\else\textdegree\fi{}C and $R\overline{3}$ a…
Results of measurements on the thermoelectric power of pure nickel, pure iron, and four dilute iron alloys are presented. They strongly suggest that, in iron, magnon drag is dominant over a wide temperature range, and provide the first indication of this mechanism in a ferromagnetic metal.
A general investigation into the green luminescence of hexavalent uranium in calcium fluoride has been made in the temperature range 5 to 300\ifmmode^\circ\else\textdegree\fi{}K. Two types of spectra have been found, due to different centers. Absorption spectra for these were also observed. The luminescent spectrum ha…
We have measured the attenuation of 100- and 260-Mc/sec longitudinal acoustic waves in $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ (corundum) containing a few ppm of ${\mathrm{Ni}}^{3+}$, and have compared our data with previous measurements at 2 Mc/sec. The attenuation as a function of temper…