Materials Literature
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There is increasing interest in the measurements of the dielectric absorption of compressed solid powders. A theoretical analysis is reported which highlights the problems which may arise due to “lack of contact” between the material and the electrodes. It is demonstrated, both theoretically and experimentally, that s…
It is observed that a reversible step period rearrangement on clean nickel single-crystal surfaces occurs in the immediate vicinity of the Curie temperature. Reversible carbon segregation is observed on the same crystal surfaces below the Curie point. The segregated carbon is carbidic, not graphitic, and indicates a c…
Magnetic and crystallographic nature of the compounds NiMnGe1−nSin (0 ≦ n ≦ 1) are studied in the temperature range from 80 to 1000 K by X-ray and neutron diffraction, magnetometric and DTA measurements. On the basis of these experimental data, crystallographic and magnetic phase diagram are constructed. The compounds…
A theoretical study of topological excitations (kinks) in a one-dimensional one-third-filled Peierls system is presented. The charges associated with the kinks are found to be fractional $Q=\ifmmode\pm\else\textpm\fi{}\frac{1}{3}e,\ifmmode\pm\else\textpm\fi{}\frac{2}{3}e$. Calculations of the spatial widths and electr…
A theory for geminate electron-hole recombination in amorphous semiconductors is given, which includes the effects of both diffusion and tunneling. The exact solution of the model is obtained neglecting the Coulomb interaction, which is included later in the prescribed diffusion approximation. It is shown that any com…
A comprehensive study of the Rayleigh–Brillouin scattering spectra of o-terphenyl in the liquid and supercooled liquid state has been carried out. Anomalies in the Brillouin frequency and linewidth data are observed at the glass transition temperature (Tg) and at a temperature (TK) about 36 K higher than the melting p…
The gaseous molecules VC, NbC, NbC2, MoC, and MoC2 have been identified in a mass spectrometric study of the Knudsen effusate from the niobium–graphite and vanadium–niobium–molybdenum–graphite systems at high temperatures. Third-law enthalpies of the various reactions involving these species were determined from the e…
We report static magnetization measurements on the compositionally modulated ferromagnetic alloy Cu/Ni, which, contrary to earlier ferromagnetic resonance measurements, show the moment per Ni atom is reduced relative to pure Ni. The low-temperature magnetization is found to vary linearly with modulation amplitude, but…
Sensitivity analysis is considered for kinetics problems defined in the space–time domain. This extends an earlier temporal Green’s function method to handle calculations of elementary functional sensitivities dui/daj where ui is the ith species concentration and aj is the jth system parameter. The system parameters i…
We show that the spontaneous decay of a phonon by anharmonic processes of any order into a set of phonons of higher phase velocity is impossible for both $N$ and $U$ processes. The result is valid for crystals of arbitrary symmetry and anisotropy and in the presence of frequency and angular dispersion. The implication…
Extended-x-ray-absorption-fine-structure (EXAFS) data on the normal and superionic phases of AgI and the cuprous halides have been analyzed using four structural models: harmonic oscillator, displaced site, anharmonic oscillator, and excluded volume. The most satisfactory description is obtained with the last model, b…
Structural defects in glassy ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$ are classified and labeled according to the constituent like-atom bonds and malcoordinated atoms. A selection rule is formulated to reduce the number of allowed Fermi-level pinning reactions. An elementary Bethe-lattice model is introduced as a starti…
The drift velocity of holes in natural diamond is analyzed for a wide range of temperatures $85\ensuremath{\le}T\ensuremath{\le}700$ K and fields ${10}^{2}<E<6\ifmmode\times\else\texttimes\fi{}{10}^{4}$ V/cm applied parallel to $〈100〉$ and $〈110〉$ crystallographic directions. Experiments are carried out with the…
All types of polygranular carbon and graphite materials take advantage of the extremely high strength of sigma -bonds in elemental carbon. Manufacturing processes have been developed during the last century which allow the control and distribution of domains with anisotropic microstructure within the bulk material. Su…
The authors argue that the McCurdy-Rescigno (1978) and Moiseyev-Corcoran (1979) methods used to calculate molecular resonances can be viewed as finite-matrix approximations to the mathematically precise 'exterior coplex scaling' method of Simon (1978).
Abstract Some impact tests are described in which Gc, the fracture toughness, of three polymers was determined over a range of strain rates and temperatures. It was found that at high strain rates there was a substantial variation of Gc with rate. When this was investigated as a function of loading times, it was obs…
Many commercially important catalysts consist of small metal particles dispersed on inorganic oxide surfaces. Although in most cases there is no significant interaction between the metal and the support, strong bonding can be demonstrated in a recently discovered class of supported-metal catalysts. These cases typical…
The decade of the ’80s was ushered in with a new dimension for designers, the availability of, and the meteoric cost increases of key materials. Though cost consciousness has always been a materials selection factor, current rates of increase make selection decisions more critical. Shortages of key metals such as coba…
A half century ago, researchers described foams as disperse structures that contain a colloidal liquid, such as a protein solution, as the dispersion medium and a gas or air as the disperse phase ( 1, 2, 3, 4 ). The factors principally involved in foam formation were surface tension, viscosity, and the character of th…
Abstract The evolution of the diatoms has never been considered in any detail and this paper sets out some of the problems and discusses briefly the fossil evidence, the likelihood of monophyletic versus polyphyletic origin and the possible habitats of the ancestral forms. We assume that diatoms arose at a fairly earl…