Materials Literature
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Quasicrystals are solids with quasiperiodic atomic structures and symmetries forbidden to ordinary periodic crystals-e.g., 5-fold symmetry axes. A powerful model for understanding their structure and properties has been the two-dimensional Penrose tiling. Recently discovered properties of Penrose tilings suggest a sim…
New ferrocenyl dendritic macromolecules based on flexible poly(propylenimine) dendrimer cores, built up to the fifth generation, containing 4, 8, 16, 32, and 64 peripheral ferrocenyl moieties, have been prepared and characterized. Solution electrochemical studies showed that all the ferrocenyl redox centers attached t…
To demonstrate that crystallographic methods can be applied to index and interpret diffraction patterns from well-ordered quasicrystals that display non-crystallographic 5-fold symmetry, we have characterized the properties of a series of periodic two-dimensional lattices built from pentagons, called Fibonacci pentili…
We study the approach to global breakdown in disordered media driven by increasing external forces. We first analyze the problem by mean-field theory, showing that the failure process can be described as a first-order phase transition, similarly to the case of thermally activated fracture in homogeneous media. Then we…
We study the behavior of fracture in disordered systems close to the breakdown point. We simulate numerically both scalar (resistor network) and vectorial (spring network) models with threshold disorder, driven at constant current and stress rate respectively. We analyze the scaling of the susceptibility and the clust…
It has been recently observed that synthetic materials subjected to an external elastic stress give rise to scaling phenomena in the acoustic emission signal. Motivated by this experimental finding we develop a mesoscopic model in order to clarify the nature of this phenomenon. We model the synthetic material by an ar…
We present an exact calculation to show that an infinite Sierpinski gasket fractal supports an infinite number of extended electron states. We work within the real space renormalization group (RSRG) scheme and show that by analysing the recursion relations for the Hamiltonian parameters one can extract the eigenvalues…
Br K-edge EXAFS spectra of solid and liquid KBr have been performed and analysed using advanced techniques for data analysis (GNXAS). Structural results on solid KBr at room temperature and near melting are compared with molecular dynamics (MD) simulations and diffraction data. The first-neighbour distribution is foun…
The structure, phase transformation and magnetic properties of mechanically alloyed (MA) alloys and have been studied systematically. The compound can be formed within a wide window for the range of composition and annealing temperature. More carbon than the stoichiometric content for is necessary to stabilize the tet…
Low-sulfate seawater (LSSW) technology provides operational and economic benefits for desulfating seawater to control barium sulfate (BaSO{sub 4}) and strontium sulfate (SrSO{sub 4}) scale. This concluding article in a three part series describes, from a scale control perspective, the membrane technology deployed in t…
This Letter describes neutron diffraction measurements of the rocksalt structured phase of AgI at high pressure and temperature and the structural disorder which accompanies its high conductivity. In contrast to the first-order structural phase transition which results in fast-ionic $\ensuremath{\alpha}$-AgI at ambien…
Measurements of isothermal ( ), high-pressure behaviour (up to 270 MPa) of complex electric permittivity in supercooled glycerol are presented. The observed peaks of relaxation in absorption curves show increasing relaxation time with increasing pressure. The behaviour of can be reproduced by the pressure version of a…
The vibrations of boron carbide have been studied by the valence force model. There have been so far several ambiguities in the interpretation of experimental spectra, which made theoretical study difficult. This paper solves the main difficulties, that is, characterization of the highest band and most of the Raman ba…
The key structural factor governing the one-electron bandwidth (W) in (A = Ca, Sr) magnetoresistive oxides has been identified by a neutron study. Reducing the size of the lanthanide, the Mn - O bondlength in octahedra does not change ( ) and hence does not contribute to the narrowing of the conduction bandwidth. In c…
The temperature dependence of the static magnetic susceptibility (5 to 700 K) and that of the electron paramagnetic resonance linewidth (300 to 700 K) measured at 9.25 GHz is reported for bulk polycrystalline samples of and with negative giant magnetoresistance. For both systems, and the product increase linearly with…
By solving a viscoelastic model of polymer solutions in two dimensions, we demonstrate that polymer-rich regions can form a spongelike network in deeply quenched cases. In late stages the velocity field is suppressed because the network supports stress and is rigid. As a result the domain size grows as ${t}^{1/3}$. In…
The negative thermal expansion recently observed over a wide range of temperatures in may be attributed to the existence of low-frequency phonon modes which can propagate with no distortions of the tetrahedra and octahedra, the so-called `rigid unit modes'. Using methods developed for the study of similar modes in sil…
Introduction to Carbon Materials, M.S. Dresselhaus, G. Dresselhaus, P.C. Eklund, R. Saito, and M. Endo From Carbon Fibers to Nanotubes, M. Endo, R. Saito, M.S. Dresselhaus, and G. Dresselhaus Structure and Morphology of Carbon Nanotubes, P.M. Ajayan Production and Purification of Carbon Nanotubes, T.W. Ebbesen Growth…
The Mg(3s3dπ 3DJ)⋅Ar(3Π), Mg(3s3dδ 3DJ)⋅Ar(3Δ), and Mg(3s4pπ 3PJ)⋅Ar(3Π) excited states have been characterized via resonance enhanced two-photon ionization (R2PI) spectroscopy of transitions from the long-lived Mg(3s3pπ 3PJ)⋅Ar(3Π0+,0−) metastable states of the MgAr van der Waals molecule. Because the outer excited M…
Information obtained from optical absorption, excitation, and emission experiments on erbium doped crystalline CsCdBr3 is analyzed, using a semiempirical Hamiltonian, to calculate atomic and crystal-field interaction parameters and electronic state wave functions. A majority of the Er3+ ions substitute at a Cd2+ site…