Materials Literature
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Polycrystalline SrBi2Ta2O9 thin films having a layered-perovskite structure were fabricated by a modified metalorganic solution deposition technique using room temperature processed alkoxidecarboxylate precursor solution. It was possible to obtain a complete perovskite phase at an annealing temperature of 650 °C and n…
Abstract Während der vergangenen drei Jahrzehnte haben sich Oberflächenchemie und ‐physik mit ihren vielfältigen Bezügen auch zur Katalyse kräftig entwickelt. Im Zentrum der Studienaktivitäten standen über lange Zeit Metalloberflächen, auf die man die im Laufe der Zeit entwickelten oberflächenanalytischen Methoden in…
Using La0.5Sr0.5CoO3 (LSCO) or Pt film as a bottom electrode layer, epitaxial Bi4Ti3O12 (BTO) thin films were grown on MgO(001) substrates by pulsed laser deposition. A symmetric Pt/BTO/Pt capacitor structure shows a surprisingly large asymmetric polarization switching behavior, but a Pt/BTO/LSCO structure has a nearl…
A crack-free, transparent monolithic gel composed of 3 and 4 is obtained from silane 1 and carbodiimide 2. This is the first example of the application of the sol–gel process, which has frequently been used for the synthesis of oxidic glasses and ceramics, to nonoxidic systems for the preparation of oxygen-free Si-C-N…
Abstract Spiders have a bad reputation because of their predacious and hidden way of life. Nevertheless, they developed a finely tuned system, based on the use of venom and silk, which enabled them to compete successfully in evolution. Only recently has the mystery of the chemistry of their silk and venom begun to unr…
A new interpretation of the charge storage mechanism of conducting polymers is provided by the results of cyclic voltammetric studies of diphenylpolyenes like 1. For the first time these investigations indicate the formation of σ bonds in the reversible dimerization of radical cations of these conjugated systems. Furt…
Measurements of light scattered off a bubble that is illuminated by a train of short pulses enables one to resolve the strongly supersonic collapse of a sonoluminescing bubble. We find that the collapse is faster than Mach 4 (relative to the ambient speed of sound of the gas in the bubble) and that the flash of sonolu…
Template-controlled syntheses open the way to stable metal complexes of the previously unknown, energy-rich porphyrin structural isomer isoporphycene. The rapid photochemical equilibrium between (Z)- and (E)- octaethylisoporphycene Pd complexes 1 and 2 confirms the prediction that (Z)- and (E)-isoporphycene have simil…
Light diffraction from shear ordered colloidal dispersions is discussed in terms of the scattering power distribution I(l) along Bragg rods of hexagonal layers. For a charge stabilized dispersion the angle dependence of the light scattering intensity is used to determine I(l), from which conclusions on the mutual regi…
Novel photoelectron yield experiments performed with a dynamical range of 8 orders of magnitude reveal a new excitation channel for electron emission on diamond (100) and (111) surfaces with negative electron affinity which is due to defect states 2.0 and 4.1 eV below the conduction band minimum. Analyzing the competi…
Abstract Materials research is an interdisciplinary field in which engineers and physical scientists work together. Since the major binary oxides, nitrides, and carbides, which are currently used as high‐performance ceramics, were discovered in the last century, the role of chemistry in the development of materials ha…
We present a novel surface-controlled bistable nematic liquid crystal display. This black and white device uses simple monostable planar anchorings and a dielectrically positive nematic. The two bistable textures are, respectively, quasiuniform U and almost half-turn twisted T. Short electric pulses break the surface…
Until very recently the Ni and Cu corroles, already described in the sixties, were regarded as the MII complexes 1 (M = Ni, Cu). Some doubt arose about this interpretation after the existence of FeIV corroles demonstrated that corroles can stabilize metals in unusual oxidation states. Thorough physical studies have no…
In extension of our previous study of KNbO_3 by the semiempirical Hartree-Fock method we present parameterization and total-energy results for non-ferroelectric KTaO_3 as a pure crystal (concentrating on the frozen phonon calculations) and that with Li impurities. The magnitudes of off-center Li displacements and the…
We point out that contrary to a recent suggestion by Boero et al. (PRL 78, 887 (1997)) the +1 charge state of the oxygen vacancy in alpha-quartz cannot be invoked as a candidate E' center in alpha-quartz and silica.
A minimum in resistivity as a function of temperature for an as-quenched Au80Co20 ribbon prepared by melt-spinning using a wheel surface speed of 20 m s^{-1} is found at 25 K. No resistivity minimum is found for an as-quenched ribbon using a wheel surface speed of 60 m s^{-1}, however, upon heat treatment of this ribb…
By exploiting the extremely large effective cross sections ( ${10}^{\ensuremath{-}17}--{10}^{\ensuremath{-}16}{\mathrm{cm}}^{2}/\mathrm{molecule}$) available from surface-enhanced Raman scattering (SERS), we achieved the first observation of single molecule Raman scattering. Measured spectra of a single crystal violet…
Abstract. In fenite data books the reversible permeability for small excitation levels is usually given vs. external dc magnetic field for different values of the effective permeability. To determine these curves the incremental permeability has to be measured on cores with different air gaps. Due to the grinding of d…
A simple model for the continuous recycle of mother liquors from a crystallization or precipitation is discussed. It is shown that the impurity profile of the mother liquors, at moderate recycle levels, quickly reaches a steady state according to (1 − x n +1 )/(1 − x ), where n is the number of times the process is op…
The etching of nondiamond carbon present in diamond thin films which were grown using the CVD method has been studied with UV irradiation in air. The etching of nondiamond carbon was accelerated by UV irradiation, and hence the temperature required was lowered from 600 °C to 250 °C. On the other hand, the temperature…