Materials Literature
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A reactive sodium polysulfide melt provides the one-dimensional compound NaNbS6 at 350°C. It contains anionic chains of condensed NbS9 polyhedra that are separated by Na+ ions (see picture below). NaNbS6 decomposes at about 400°C and transforms into the layered intercalation compound NaNbS2.
We study the electronic eigenstates on two- and three-dimensional quasiperiodic lattices using a tight-binding Hamiltonian in the vertex model. In particular, we analyse how a quasiperiodic lattice influences the decay form and the self-similar structure of the wave functions. The investigation of the earlier-suggeste…
The Loewenstein rule, according to which the AlO4 tetrahedra in aluminum silicates should always be separated by silicon atoms, is apparently not valid for molecular aluminum silicates such as 2, because the linkage of the AlO4 tetrahedra does not change when the four acidic protons of 1 are replaced by lithium atoms.
A new phosphor, (Gd1.54Zn0.46)O3−δ:Eu0.063+, with a photoluminescent quantum efficiency of ≈86% and a superior color chromaticity (x=0.656, y=0.344) compared to the state of art red phosphor Y2O3:Eu3+ was identified using the combinatorial thin film synthesis method. This phosphor may replace Y2O3:Eu3+ in display appl…
Using neutron diffraction at very high pressures (up to 20.5 GPa), we studied magnetic interactions in the model system EuX ( $X\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{S}$, Se, Te) in a wide range of lattice constants. Surprisingly, when interatomic distances decrease, the Curie temperatures increas…
GeO4 tetrahedra and GeO6 octahedra, which form nine-rings (see sketch on the right), feature in the unprecedented structure of the microporous solid, (NH4)2Ge7O15. This compound provides the first evidence that in the GeO2/NH4+ system the cubic (NH4)3HGe7O16⋅n H2O is not the only existing phase, but depending on the G…
Cis/trans isomerization of the alkene in these pyridine-functionalized porphyrins results in a reorganization of the molecular architecture: the polymeric trans form of 1 transforms into the dimeric cis form when irradiated with UV light. A cis/trans mixture of isomers is obtained when the pure compounds are treated w…
The temperature dependence of the dc conductivity \ensuremath{\sigma} of most glass-forming and crystalline ionic conductors is Arrhenius with constant activation energy, ${E}_{\ensuremath{\sigma}}$, at sufficiently low temperatures or conductivity levels. However, \ensuremath{\sigma} becomes non-Arrhenius at high tem…
Danger of collapse! The structure of hydrated high-alumina cement, whose use as a building material was highly controversial after several accidents occurred, was now determined to be CaAl2O4⋅7.8 H2O from X-ray powder diffraction data by applying direct methods. A picture of the structure as viewed along the c axis is…
Time-correlated single-photon counting reveals that the width of flashes of sonoluminescence ranges from under 40 to over 350 ps for mixtures of various gases in water. Flash widths and emission times are independent of wavelength from the ultraviolet to the infrared. These measurements suggest that sonoluminescence o…
Simple transformations of an unbranched parent chain lead to a diverse range of aluminophosphates with 1D chain, 2D porous layer, and 3D open-framework structures. A section of this chain, which has been hydrolyzed in one position leading to ring-opening, is shown schematically below. Reorientation of the chain follow…
The charge release speed and backward phase switching time of lanthanum-doped lead zirconate titanate stannate antiferroelectric thin films were investigated by directly measuring the switching current upon removal of the applied electric field. The backward switching time is about 6 ns. The maximum switching current…
We present ab-initio electronic structure results on the surface of sqr3 adsorbates. In particular, we address the issue of metal-insulator instabilities, charge-density-waves (CDWs) or spin-density-waves (SDWs), driven by partly filled surface states and their 2D Fermi surface, and/or by the onset of magnetic instabi…
Two pyrrole rings participate in the aromatic structure of porphyrin. Hence, a 22 π-electron description is better than the usual [18]annulene representation. The dianion and the metal complex system favor different electronic structures.
We have measured the temperature-dependent thermoelectric power (TEP) of crystalline ropes of single-walled carbon nanotubes. The TEP is large and holelike at high temperatures and approaches zero as $T\ensuremath{\rightarrow}0$. The results argue against the opening of a gap at low temperature in these materials. Whe…
Intralayer antiferromagnetic and ferromagnetic couplings could be correctly predicted by the spin polarization mechanism for the sheetlike polymers [Co(NCS)2(pyz)2]n and [Co(NCS)2(pym)2]n (structure depicted on the right). These structurally characterized compounds and the monomeric complex [Co(NCS)2(pyd)4], which was…
The database LiqCryst 2.1 contains chemical structure and physical properties of about 70000 thermotropic liquid crystals, extracted from 14000 references. Program and data represent a scientific tool which allows statistical analysis of structure-property-relationships and the prediction of phase transition temperatu…
In order to investigate the effect of soaking temperature and annealing atmosphere on magnetic properties of the semi‐processed nonoriented electrical steel containing 0.4 % silicon, customer annealing was carried out at a temperature ranging from 730 to 950 and in different annealing atmospheres. As the soaking tempe…
Key words Skin microcirculation - galvanic stimulation - laser-Doppler-Flowmetry
Abstract A commercial Polystyrene (M w = 2.5 10 5 , MFI =14.80) was extruded repeatedly from one to eight times at 190 °C. The effects of extrusion process on physical and chemical properties of polystyrene were investigated using: ‐Average molecular weight —Izod Impact strength; —Thermal properties (TGA, DTA). The re…