Materials Literature
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We have heteroepitaxially deposited Ba0.6Sr0.4TiO3 (BST) thin films on (001)-oriented MgO substrates using pulsed-laser deposition. By optimizing the deposition temperature and adjusting the film thickness, we have successfully increased the dielectric nonlinearity and decreased the dielectric loss of BST films. BST t…
The Wiedemann–Franz law for electron transport in metals was historically a linch pin for the free-electron theory of metals; it states that, at moderately low temperatures, the ratio of thermal conductivity K to electrical conductivity σ is proportional to absolute temperature, with a proportionality constant called…
Abstract Carbonate and sulphate scales are the most common types of mineral deposit associated with the recovery and processing of hydrocarbon and associated produced water. In three high temperature fields (>140C) within the North Sea more usual scale types have been observed namely zinc and lead sulphide. Con…
Electron density distributions were obtained using the maximum entropy method with synchrotron radiation powder data. In the metallic Al12Re, metallic bonding was observed for the icosahedral Al12 cluster with central Re atom. In the nonmetallic alpha-AlMnSi 1/1 approximant, covalent bonds were found in the electron d…
We report the first solid state X-ray crystal structure for a Eu(II) chelate, [C(NH2)3]3[Eu(II)(DTPA)(H2O)].8H2O, in comparison with those for the corresponding Sr analogue, [C(NH2)3]3[Sr(DTPA)(H2O).8H2O and for [Sr(ODDA)].8H2O (DTPA5 = diethylenetriamine-N,N,N',N",N"-pentaacetate, ODDA2- =1,4,10,13-tetraoxa-7,16-diaz…
A marked influence on the catalytic epoxidation and hydroxylation of hydrocarbons by aqueous 30 % H2O2 in an aprotic solvent and on the formation of oxoiron(IV) porphyrin intermediates in m-chloroperoxybenzoic acid (m-CPBA) reactions in polar solvent is shown by the anionic axial ligands of an electron-deficient iron(…
Long-range interactions are found in a neutral sheetlike copper compound in which each CuII ion is bridged by alternating end-on and end-to-end azide groups (see picture). Magnetic studies show unusual ferromagnetic interactions between CuII ions through both kinds of azide bridges in this complex (order at Tc=7 K), w…
The chiral ligand 1,1'-bi-2-naphthol (BINOL) has been succesfully immobilized on polystyrene. Several dendritic and non-dendritic BINOL derivatives (3, and 13-17), bearing at least two polymerizable styryl groups, were prepared and fully characterized. Suspension copolymerization of the MOM- or TIPS-protected cross-li…
Drei molekulare Bausteine bilden durch selbstanordnende Zink-Pyridin-Koordination ein stabiles Porphyrinpentamer (siehe Bild). In diesem supramolekularen Komplex wird Energie in Form von Licht von den äußeren Zink-Porphyrinen absorbiert und in 500 Picosekunden an das freie zentrale Porphyrin übertragen.
Three molecular components self-assemble through zinc–pyridine coordination interactions to form a stable porphyrin pentamer (see picture). In this supramolecular complex energy absorbed by the outer zinc porphyrins is transferred to a central free-base porphyrin in 500 picoseconds.
We report the deposition of a-Si:H on thin films of free-standing single crystalline ZnO columns. The ZnO columns have a height of several μm and a diameter between 100 and 200 nm. The ZnO films are prepared in electrodeposition and have considerable potential for use in photoelectric thin film devices. Morphology, el…
Carbon nanotubes aligned perpendicular to a surface are used as electrodes to form novel, conducting polymer–carbon nanotube (CP–NT) composites. The SEM image (see picture) shows the CP–NT coaxial nanowires, in which an appropriate conducting polymer film is electrochemically deposited onto the carbon nanotube arrays…
We propose a new and general method for discovering novel ordered phases of block copolymer melts. The method involves minimizing a free energy functional in an arbitrary unit cell with respect to the composition profile and the dimensions of the unit cell, without any prior assumption of the microphase symmetry. Vary…
Senkrecht auf einer Oberfläche angebrachte Kohlenstoff-Nanoröhren werden als Elektroden für die Bildung leitfähiger Polymer-Kohlenstoff-Nanoröhren (Nanodrähte) verwendet. Die SEM-Aufnahme (siehe Bild) zeigt die Entstehung der Nanodrähte durch Abscheiden des leitfähigen Polymerfilms auf den teilweise in die Elektrolytl…
Carbon nanotubes with junctions are considered to be of potential value in nanoelectronics. A simple pyrolysis procedure for producing Y-junction carbon nanotubes is described. The method involves the pyrolysis of the organometallic precursor, nickelocene, along with thiophene at 1273 K. Tunneling conductance measurem…
High pressure structural distortions of the hexagonal close packed (hcp) element zinc have been a subject of controversy. Earlier experimental results and theory showed a large anomaly in lattice strain with compression in zinc at about 10 GPa which was explained theoretically by a change in Fermi surface topology. La…
Structure factors for $\mathrm{Ca}{}_{x/2}\mathrm{Al}{}_{x}\mathrm{Si}{}_{1\ensuremath{-}x}\mathrm{O}{}_{2}$ glasses $(x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0,0.25,0.5,0.67)$ extended to a wave vector of magnitude $Q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}40\phantom{\rule{0ex}{0ex}}\AA{}{}^{\e…
Half-Heusler alloys (MgAgAs type) with the general formula MNiSn where M is a group IV transition metal (Hf, Zr, or Ti) are currently under investigation for potential thermoelectric materials. These materials exhibit a high negative thermopower (−40 to −250 μV/K) and low electrical resistivity values (0.1–8 mΩ cm) bo…
Electronic transport measurements were performed on Y-junction carbon nanotubes. These novel junctions contain a large diameter tube branched into smaller ones. Independent measurements using good quality contacts on both individual Y junctions and many in parallel show intrinsic nonlinear transport and reproducible r…
Dendrimeric catalysts can present catalytic units in close proximity, thereby inducing useful cooperative effects (see picture). Commercial dendrimers were derivatized with chiral [Co(salen)] complexes and found to display enhanced reactivity relative to monomeric or even dimeric analogues in the hydrolytic kinetic re…