Materials Literature
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Scanning electron microscopy, X-ray diffraction, photoelectrochemistry and microphotoelectrochemistry have been used to characterize thin chromia scales, in the micrometer range, grown on pure chromium at 900°C in oxygen and in water vapour. The duplex structure formed, more easily observable in water vapour grows by…
Thermoelectric power was used to elucidate the electrical transport properties of aligned and randomly oriented carbon nanotube systems in the temperature range 77--450 K. A weakly negative thermoelectric power, comparable with that of a graphite flake, was observed for a macroscopic bundle of multiwall carbon nanotub…
Within the local-density approximation, the interlayer binding and the electronic properties of graphite and ``graphitic'' Si have been determined. For graphite, the optimized equilibrium lattice constant agrees well with the experimental value. The role of ${2p}_{z}$ orbitals $(\ensuremath{\pi}$ states) turned out to…
The optical properties of well-aligned multiwalled carbon nanotube bundles are studied within the gradient approximation. The imaginary (real) part of the transverse dielectric function exhibits a special peak (dip) at frequency $\ensuremath{\omega}\ensuremath{\sim}2{\ensuremath{\gamma}}_{0}$ $({\ensuremath{\gamma}}_{…
The electromagnetic response of a zero-order metal grating having a primary deep short-period component and a shallow long-period component is modeled. It is found that such a metal grating has an unusual surface-plasmon-polariton band structure and exhibits strong selective absorption of incident radiation. This open…
Die Veresterung eines repräsentativen redoxaktiven Polyoxometallats (POM), [H4P2V3W15O62]5−, mit Methanol und zwei einfachen Dendrimeren, die jeweils vier Tris(hydroxymethyl)-Endgruppen enthalten, wurde untersucht. Die Tetra(polyoxometallat)dendrimere sind gegen Hydrolyse stabil, und 1 katalysiert die Oxidation von Te…
We present a core level X-ray photoelectron spectroscopy study of ${\mathrm{Ni}}_{x}{\mathrm{Mg}}_{1\ensuremath{-}x}\mathrm{O}$ crystals with $0.03<x<1$. We show that nonlocal effects involving inter-Ni-site fluctuations strongly influence the Ni $2p$ core-level spectra for higher Ni concentrations including NiO…
The absorption edge of hexagonal (NiAs structure) antiferromagnetic MnTe has been measured by means of light transmission experiments carried out at different temperatures in the range 16--420 K $(P=1\mathrm{bar})$ and hydrostatic pressures up to 9 GPa $(T=295\mathrm{K}).$ An indirect band gap has been found, in agree…
A tight-binding parametrization of the band structure, along with a mean-field treatment of the Hund, electron-electron, and electron-lattice couplings, is used to obtain the full optical conductivity tensor of ${\mathrm{LaMnO}}_{3}$ as a function of temperature. We predict striking changes with temperature in the fun…
Quinoidalization results in amazingly intense near-IR absorption in 1 (λmax=1080 nm), whereas the shorter dimer 2 (λmax=780 nm) is less conjugated because steric interactions force it into a contorted geometry. The crystal structure of 1 shows that the 62-atom chromophore is bow-shaped in the solid state.
Dielectric susceptibility, X-ray diffraction and infrared molecular vibrational spectra have been investigated for a charge-transfer complex, tetrathiafulvalene (TTF)-2-bromo-3,5,6-trichloro- p -benzoquinone (QBrCl 3 ) to probe a ferroelectric valence transition at T c =66 K in comparison with the typical first-order…
Epitaxial SrBi2Nb2O9 thin films have been grown with a (103) orientation on (111) SrTiO3 substrates by pulsed-laser deposition. Four-circle x-ray diffraction and transmission electron microscopy reveal nearly phase-pure epitaxial films. Epitaxial (111) SrRuO3 electrodes enabled the electrical properties of these (103)…
Novel elastomeric A-B-A triblock copolymers were successfully synthesized in a new two-step process: controlled ring-opening polymerization of the cyclic ether–ester 1,5-dioxepan-2-one as the amorphous middle block (B-block) followed by addition and polymerization of the two semicrystalline L-lactide blocks (A-block).…
Herein, we describe the design, synthesis, structure, and function of synthetic, supramolecular beta-barrel models. Assembly of octi(p-phenylene)s with complementary -Lys-Leu-Lys-NH2 and Glu-Leu-Glu-NH2 side chains yielded water-soluble rigid-rod beta-barrels of precise length and with flexible diameter. A hydrophobic…
Nineteen commercial high-density polyethylene resins made with different polymerization processes and catalyst types were analyzed by high-temperature size exclusion chromatography and crystallization analysis fractionation. The information obtained with these characterization techniques on the polymer chain structure…
Polarization dependence of soft-x-ray Raman scattering was investigated at the Ti $2p$ absorption edge of ${\mathrm{TiO}}_{2}.$ Strong Raman scattering feature appears about 14 eV below elastic peaks with strong polarization dependence. These Raman scattering structures are charge transfer excitations to the antibondi…
The structural and magnetic characteristics of the recently discovered quantum spin ladders are summarised and the possibilities of supramolecular chemistry for developing such fascinating materials are discussed. The existing examples of molecular spin ladders clearly show that typical supramolecular and crystal engi…
Helium has a decisive effect on the microstructure of silicon carbide materials after implantation and subsequent annealing. A dense population of bubbles and dislocation loops is already observed at relatively low displacement doses after annealing of helium-implanted \ensuremath{\alpha}-SiC, while no visible damage…
Zero-field 57 Fe NMR spectrum has been observed in the 57 Fe-enriched ceramics of BiFeO 3 . The analysis of NMR lineshape confirms the existence in this ferroelectric-antiferromagnetic compound of a long-period cycloidal magnetic structure and enables the first reconstruction of the actual spatial spin distribution al…
We report the dielectric anomaries at the phase transitions of Lu(Fe 2+ Fe 3+ )O 4 , which is considered as a charge and spin frustrated system. Dielectric constant shows a hump, just above the transition from the high temperature two-dimensional to the low temperature three-dimensional charge ordering. A few glassy b…