Materials Literature
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By means of dielectric measurements and a Raman-scattering experiment, the uniaxial stress dependence of the ferroelectric and structural phonon modes in SrTi${\mathrm{O}}_{3}$ crystal has been studied at liquid-helium temperature. The ferroelectric phase transitions were induced by a stress normal to the (100) or (11…
We discuss the equilibrium properties of flexible chains adsorbed on a flat surface, assuming that a) adsorption is weak, resulting in large thicknesses D for the adsorption layer, b) the chains are very long, c) the solvent is good, so that excluded volume effects become important (contrary to an early opinion of Hoe…
Papers are presented concerning hydrogen for energy, effects of internal hydrogen, effects of hydrogen-producing environments, effects of external hydrogen, hydrogen transport, hydride-forming materials engineering applications, and hydrogen research. Thirty-six of the papers were individually abstracted. (JRD)
A method was developed to determine the kinetic parameters controlling structural relaxation in the glass transition region from data acquired during continuous heating or cooling. The nonexponential character of the relaxation is accounted for by assuming an equilibrium isothermal relaxation function of the form exp…
The fracture toughness of Al 2 O 3 is considerably increased by the incorporation of fine monoclinic ZrO 2 particles. Hot‐pressed composites containing 15 vol % ZrO 2 yield K lc values of ∼ 10 MN/m 3/2 , twice that of the A1 2 O 3 matrix. It is hypothesized that this increase results from a high density of small matri…
Measurements of the dielectric constant κ in high-purity BaTiO3 ceramics as a function of temperature show that κ is quite dependent on grain size in the ferroelectric state while it is almost independent of grain size in the paraelectric state. In the ferroelectric orthorhombic and rhombohedral phases, κ decreases ra…
BASIC CONCEPTS. One-Dimensional Linear Element. A Finite Element Example. Element Matrices: Galerkin Formulation. Two-Dimensional Elements. Coordinate Systems. FIELD PROBLEMS. Two-Dimensional Field Equation. Torsion of Noncircular Sections. Derivative Boundary Conditions: Point Sources and Sinks. Irrotational Flow. He…
A study of the core-electron X-ray photoelectron (X-p.e.) spectra of the f0 compounds La2O3, LaMO3(M = Fe and Co), CeO2, and BaCeO3 is described. Results on the chelate species [La(tmhd)3] and [Ce(tmhd)4](tmhd = 2,2,6,6-tetramethylheptane-3,5-dionato) are included for comparison. Special precautions have been taken to…
An equation derived by Ritland relating the cooling rate and fictive temperature for glasses without memory is extended to those with memory, i.e. those which exhibit a spectrum of relaxation times. Provided that the spectrum of relaxation times is temperature‐independent, the limiting fictive temperature, T′ f , obta…
Expressions are presented for the moisture distribution and the mois ture content as a function of time of one dimensional homogeneous and composite materials exposed either on one side or on both sides to humid air or to water. The results apply during both moisture absorption and desorption when the moisture content…
The review is devoted to the properties of 7,7,8,8-tetracyanoquinodimethane, one of the strongest of the known organic π acids. Data concerning the methods of synthesis of 7,7,8,8-tetracyanoquinodimethane and its analogues and the physicochemical properties of compounds of this series are surveyed. The addition, subst…
We have deduced from measurements of the neutron elastic cross section that below the N\'eel temperature (${T}_{\mathrm{N}}$) the oxygen atoms in U${\mathrm{O}}_{2}$ are shifted from their ideal fluorite positions. We find quantitative agreement with experiment by assuming a rearrangement (internal shear deformation w…
On the basis of an analysis of data on a large number of compounds exhibiting displacive phase transitions, it is observed (with no known exceptions) that the transition temperature decreases with hydrostatic pressure for those transitions associated with soft zone-center optic phonons and increases for those transiti…
Reflectivity spectra from the basal planes of crystals of 2H-NbSe 2 , 2H-TaSe 2 , 2H-TaS 2 and 1T-TaS 2 have been measured in the energy range 25 meV to 14 eV at room temperature and liquid nitrogen temperature. Using extrapolations of the experimental data to 0 eV and 30 eV, a Kramers-Kronig analysis of the data has…
The velocity of longitudinal and transverse ultrasonic waves has been measured for an Fe50.5Rh49.5 alloy on both sides of the antiferromagnetic-ferromagnetic transition. From these measurements the variation of Young's modulus, shear modulus, and Poisson's ratio with temperature and magnetic field has been calculated.…
The deformation behaviour of tantalum-rhenium, tantalum-niobium, electronbeam melted tantalum, and ultra high vacuum annealed tantalum is studied at temperatures 77 to 293 K. The slip geometry, morphology, and yield stress is determined as function of orientation, temperature, and mode of deformation. Alloying is obse…
Germanium was reacted with N2O, O2, NO2, and NO in a flow system, which produced GeO. Chemiluminescence was observed from three electronic band systems of GeO: A 1Π→X 1Σ+ in the uv, a 3Σ+→X 1Σ+ in the blue, and b 3Π1→X 1Σ+ (a previously unreported system) in the near uv. Vibrational constants and Te values have been o…
The structure of the paraelectric phase of RbHSO 4 has been determined by X-ray and neutron diffraction at T = 23 °C. The structure consists of two crystallographically independent molecules in the asymmetric unit. Each of the independent sulphate tetrahedra is linked to a translationally equivalent sulphate by acentr…
The chemisorption of atomic hydrogen on the silicon (111) 7 \ifmmode\times\else\texttimes\fi{} 7 surface has been studied using ionneutralization spectroscopy and ultraviolet-photoemission spectroscopy with the help of low-energy electron diffraction and work-function measurement. Both spectroscopies showed that the d…
ZnS diodes emitting a stable and bright blue light with forward biases above 5 V are investigated. The external quantum efficiency for the diode is as high as 5×10−4 at room temperature. The presence of a thin high-resistivity ZnS layer on the low-resistivity ZnS is essential for the present diode. The fairly high eff…