Materials Literature
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In a self-consistent semi-empirical numerical approach based on ab-initio-calculations for small samples, we evaluate the GMR effect for disordered (001)-(3--Fe/3--V)$_\infty$ multilayers by means of a Kubo formalism. We consider four different types of disorder arrangements: In case (i) and (ii), the disorder consist…
During epitaxial crystal growth a pattern that has initially been imprinted on a surface approximately reproduces itself after the deposition of an integer number of monolayers. Computer simulations of the one-dimensional case show that the quality of reproduction decays exponentially with a characteristic time which…
Ohne ein Oxidans wie O 2 kann Methan an Fe/H‐ZSM‐5‐Katalysatoren selektiv zu Benzol, Toluol und Naphthalin umgesetzt werden. Methan wird dabei an Eisenoxidclustern aktiviert, und das Primärprodukt Ethylen reagiert in Oligomerisierungen und Cyclisierungen an Brønsted‐sauren Zentren zu den aromatischen Produkten.
The incorporation of pyrrole units was the key to stabilizing the largest annulene from Sondheimer et al., [30]annulene. Of the new aromatic [30]porphyrins 1–3, the 16-phenyl derivative 2 is the most stable.
The synthesis and magnetic properties of have been investigated. The formation of is found to depend strongly on annealing temperature. Pure single-phase compound can be synthesized at ambient pressure when . The main phase of the Laves structure can still be observed up to x = 0.8. The study of crystalline parameters…
A nucleophilic rather than a radical mechanism was recently proposed for the McMurry reaction. Quantum chemical density functional calculations support this hypothesis. An intramolecular and an intermolecular pathway for the CC coupling step are discussed, and the pinacolate complexes 1 and 2 are identified as centra…
We present an x-ray absorption spectroscopy study at the Cu K edge on Cu-doped soda-lime and BK7 glass waveguides obtained by ion exchange under various preparation conditions. The total electron yield and x-ray fluorescence yield collection modes were used to evidence the chemical behavior of surfacial and deep Cu io…
Biexciton and triexciton states in CuCl quantum dots were studied by means of time-resolved size-selective pump-and-probe technique. A clear induced absorption band is observed on the high-energy side of the excitation photon energy. The new induced absorption is assigned to the transition from the exciton ground stat…
We have measured the dielectric relaxation of several low-molecular-weight glass-forming materials for temperatures ranging from 25 K to and for values of the loss tangent down to . For the materials under study (salol, glycerol, N-methyl- -caprolactam, 2-methyltetrahydrofuran, 3-methylpentane, and o-terphenyl) a -rel…
The switching transition of polymer stabilized cholesteric texture liquid crystals is studied via confocal microscopy. This noninvasive probe enables the simultaneous imaging of the polymer network and the liquid crystal domain structure. We find that the two-stage switching often occurring in these systems results fr…
We present a technique to control the length of carbon nanotubes. Individual carbon nanotubes can be locally cut by applying a voltage pulse to the tip of a scanning tunneling microscope (STM). Topographic imaging and STM spectroscopy are subsequently used to investigate the result. The electronic properties of a nano…
We study the two pseudo-cubic perovskite ruthenates and , by means of LSDA electronic structure calculations using the LMTO method for both the idealized cubic and the real orthorhombic structures. The LSDA calculations predict that both orthorhombic structures are ferromagnetic, with magnetic moments of 2.0 and respe…
A new hydrogenation catalyst is formed by thermolysis of the anionic carbonyl cluster [Ag3Ru10C2(CO)28Cl]2− anchored to the mesoporous silicate MCM-41. The cluster was isolated and characterized in MCM-41 both before and after thermal treatment. The picture on the right shows a model, based in particular on EXAFS anal…
We study the kinetic temperature and the localization of cesium atoms in a three dimensional quasiperiodic optical potential created by the interference of five or six laser beams. Bragg scattering experiments show evidence of a quasiperiodic order for the atomic density. Temperature measurements are consistent with t…
A film of well-oriented carbon nanotubes was produced by sublimation decomposition of silicon carbide at 1700 °C by using YAG laser heating in a transmission electron microscope (TEM). The processes of SiC decomposition and the formation of carbon nanotubes were observed successively by high-resolution electron micros…
Cathodoluminescence at 77 K was used to study the optical properties of ion-implanted and annealed natural type IIa diamonds. The substrates were implanted at room temperature with C12+, B11+, P3+, and As75+ -ions with energies of up to 350 keV and doses of up to 13×1013cm−2. After annealing at 1200 °C, the cathodolum…
The effect of Zr addition on the corrosion behavior of the Ni3Al alloy in an aerated 3.5% NaCl solution has been studied by means of electrochemical methods. The results showed that the corrosion potential of Ni3Al first tended to be noble and then became active with an increase in Zr content. The corrosion current de…
Filled and gum compounds of Isobutylene-Isoprene rubber were extruded through a laboratory extruder at various feeding rates, different temperatures and revolutions per minute. The extruded compounds were vulcanized up to their optimum cure times and the mechanical properties of the vulcanizates were determined. The p…
An overview will be given of some recent results of microstructural electron microscopy studies on martensitic systems. The precursor structure observed in a ternary Ni-Mn-Ti alloy and its correlation with the ensuing stacking sequence is presented. New types of materials of a well known alloy, in casu splat-cooled an…
Transmission electron microscopy and scanning force microscopy of negative-stained, carbon-coated replica and mica-adsorbed preparations of 200 microM poly r(A-U) and 50 microM ethidium bromide/200 microM poly r(A-U) have been employed to evaluate ethidium-induced changes in poly r(A-U) topology. Poly r(A-U) alone exh…