Materials Literature
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Standard microcanonical rate-constant theory can be cast in a form which closely resembles and, in the case of a sufficiently large medium, reduces to that of the canonical ensemble. This relation permits a new understanding of the role of an activation energy in a chemical reaction. A facile methodology is also propo…
The quasiparticle excitation spectrum is calculated for the nearly-free-electron metals Li, Na, and Al by evaluation of the electron self-energy operator within the GW approximation and a generalized plasmon-pole model. The calculated quasiparticle energies for Na and Al are in excellent agreement with angle-resolved…
Multiple-scattering effects of electrons traveling along atomic chains are shown to be important and useful for surface structure determination, especially in the medium-energy range (200--1000 eV). This applies to techniques based on diffraction of elastic electrons, such as medium-energy electron diffraction, as wel…
The unfavorable effect of La on the magnetic properties of R-Fe-B permanent magnets is shown to be related closely to remarkable changes in microstructure due to excessive oxidation of La-containing R-rich phases in the alloys. Ce and Al are found to be effective in promoting the sintering process of La-containing all…
A thermodynamic theory is presented to model the phase transitions and properties of lead zirconate. The free energy ΔG is expressed as a power series in terms of the ferroelectric polarization (Pi=Pai+Pbi) and antiferroelectric polarization (pi=Pai−Pbi) including all possible terms up to the sixth power, but only fir…
The room-temperature cation distributions in bulk CoFe2O4 samples, cooled at rates between <10−2 and ∼103 °C s−1, have been determined using Mössbauer spectroscopy in an 80-kOe magnetic field. With increasing cooling rate, the quenched structure departs increasingly from the mostly ordered cation distribution o…
A complete set of transverse and longitudinal phonon branches in each of the three principal directions (〈100〉, 〈110〉, and 〈111〉) and polarizations have been measured up to 60 meV in the cubic perovskite ${\mathrm{KTaO}}_{3}$. Results were obtained at 296 K and at several other temperatures between 4 and 1220 K. The d…
This paper describes the application of the numerical solution of the Percus–Yevick approximation for a multicomponent system of sticky hard spheres to small angle x-ray scattering experiments. The effect of polydispersity on the pair correlation function is quantitatively described, thus enabling the analysis of expe…
Extensive characterization of the hole mobilities \ensuremath{\mu} in dispersions of p-diethylamino- benzaldehyde-diphenyl hydrazone (DEH) in polycarbonate has been carried out. We report the effect of varying the electric field E, temperature T, and spacing between DEH molecules \ensuremath{\rho} on \ensuremath{\mu}.…
X-ray photoelectron spectroscopy (the deconvoluted high-resolution N 1s core-level spectrum in particular) was used for the quantitative determination of the proportion of benzoid amine, quinoid imine, and protonated units in chemically synthesized polyaniline. This method allows the tracking of structural changes dur…
The near-infrared fluorescence of pure and doped KTaO 3 samples is studied. In the neighbourhood of 14570 cm -1 , 11 peaks are observed at 16 K and are associated with the fluorescence of a Ta 3+ ion near an O vacancy. In the ferroelectric KTa 0.982 Nb 0.0l8 O 3 crystal the fluorescence is not affected below T c appro…
The dynamics of the interface between an ordered phase, characterized by an order parameter, \ensuremath{\psi}, and a disordered phase where \ensuremath{\psi}=0 provide a promising, powerful tool to distinguish between continuous or second-order and weakly first-order phase transitions. We apply this idea to the nemat…
The stopping power for antiprotons has been measured for the first time. The antiproton stopping power of silicon is found to be 3%--19% lower than for equivelocity protons over the energy range 3.01 to 0.538 MeV. The ``${Z}_{1}^{3}$ contribution'' to the stopping power (the Barkas effect) is deduced by comparing the…
H2 and DH release was investigated in a pulsed deuterium discharge over a carbon thin-film deposited wall. A large quantity of hydrogen was desorbed by 300 eV D+2 irradiation from hydrogenated amorphous carbon (a-C:H) deposited by a hydrogen-admixed methane discharge. On the other hand, a strong pumping effect was obs…
We have found that encapsulated thin Si films, adjacent to SiO2, are dissolved at elevated temperatures by a reaction: Si+SiO2→2SiO, with SiO diffusing through the silica network. The presence of SiO in SiO2 in a concentration ≤3 at. % has a profound effect on thermomigration of dopant impurities in the oxide. We prop…
Two infrared local vibrational mode (LVM) absorption lines occurring at 715 and 845 cm−1 shift to 679 and 802 cm−1 in gallium arsenide doped with 18O, proving that the lines arise from the vibrations of oxygen impurities. The 715 cm−1 line exhibits a triplet 69,71Ga isotope fine structure consistent with that expected…
The solubility and the diffusion coefficient of hydrogen were determined in the austenitic (cubic) high-temperature phase of the shape-memory alloy NiTi. The measurements were made between 500 and 950 degrees C, with hydrogen gas pressures of up to 1.3 bar, and with hydrogen-to-NiTi ratios of up to 0.027. The hydrogen…
Abstract The method of matched asymptotic expansions is used to describe solutions of the nonlinear Cahn-Hilliard equation for phase separation in N > 1 space dimensions. The expansion is formally valid when the thickness of internal transition layers is small compared with the distance separating layers and wi…
Although the concept of an artificial photosynthetic reaction center that mimics natural electron-and energy-transfer processes is an old one, in recent years major advances have occurred. In this review, some relatively simple molecular dyads that mimic certain aspects of photosynthetic electron transfer and singlet…
Shape memory alloy (SMA) reinforced composites is a class of materials that have the ability to change their material properties, induce large internal distributed forces in a structure, can modify the stress and strain distribution within a structure, alter its geometric configuration, and do so all in a controlled m…