Materials Literature
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A method of synthesizing bulk amounts of single-walled carbon nanohorns (SWNHs) on a significant low-cost basis is proposed based on the 'arc in water' method with N 2 injection into the arc plasma. It is elucidated that rapid quenching of the carbon vapour in an inert gas environment is necessary to form the delicate…
Trägerfixierte Gold-Nanopartikel sind nicht nur bereits bei niedrigen Temperaturen, sondern zudem auch in Gegenwart von Feuchtigkeit katalytisch hoch aktiv. Feuchtigkeit erhöht ihre katalytische Aktivität bei der Oxidation von CO über Au/TiO2, Au/Al2O3 und Au/SiO2 bei 273 K um bis zu zwei Größenordnungen, und der Effe…
We have prepared a pillared layer magnetic material containing a noncoordinated aromatic molecule, [{MnII(pyrimidine)(H2O)}2{MnII(H2O)2}{WV(CN)8}2](pyrimidine)2.2H2O. This compound has one-dimensional channels (6.2 x 2.1 A) that are occupied by noncoordinated pyrimidine. The magnetization versus temperature plots show…
Two diblock copolymers composed of polystyrene and a liquid crystalline azobenzene-containing polymethacrylate were used as model systems to investigate the confinement effects on the photoalignment, photochemical phase transition, and thermochromic behavior of the azobenzene polymer. The study finds that when confine…
Grafted MCM-41 materials are ordered mesoporous adsorbents suitable for reversed-phase liquid chromatography applications (RP-HPLC): they possess high surface area, which is a great advantage to enhance the thermodynamic behavior of the classical stationary phase by increasing solute retention. Hence, MCM-41s allow th…
The formation of previously unknown hexagonal modifications of orthoferrites RFeO 3 (R = Eu−Lu) was observed on ZrO 2 (Y 2 O 3 ) (111) substrates at 900 °C. XRD and HREM studies reveal epitaxial growth of the hexagonal film. The structure of the hexagonal RFeO 3 was assigned to the ferroelectric space group P 6 3 cm .…
The switching behavior of carbon nanotube field-effect transistors (CNFETs) can be improved by decreasing the gate oxide thickness. However, decreasing the oxide thickness also results in more pronounced ambipolar transistor characteristics and higher off-currents. To achieve high-performance unipolar CNFETs as requir…
In this study, the influence of increasing the Al concentration on the electrical, optical and structural properties of spray-pyrolysis-deposited SnO 2 films has been investigated. The SnO 2 : Al films were deposited at a substrate temperature of 480°C using a hydro-alcoholic solution consisting of tin and aluminium c…
We show some new properties of the acoustic propagation in two-dimensional sonic crystals, formed by parallel rigid cylinders placed in air. The transmission through slabs of sonic crystals and the associated band structures are considered. It is shown that within partial bandgaps, the waves tend to be collimated or g…
We calculate the logarithmic moment of the phonon frequency spectrum at a single density for 29 monatomic liquids using two methods, both suggested by Wallace's theory of liquid dynamics: The first method relies on liquid entropy data, the second on neutron scattering data in the crystal phase. This theory predicts th…
Through the hysteresis loop and magnetization spatial distribution we study and compare two models for surface anisotropy in nanomagnets: a model with transverse anisotropy axes and Néel's model. While surface anisotropy in the transverse model induces several jumps in the hysteresis loop because of the cluster-wise s…
We have investigated the doping dependencies of the basal areas in single-layer high-T_c cuprates La_{2-x}Sr_xCuO_4 and HgBa_2CuO_x, as well as in two-layer Y_{1-y}Ca_yBa_2Cu_3O_x and HgBa_2CaCu_2O_x. The basal areas not only tend to shrink on hole doping, as expected from single electron quantum chemistry, but exhibi…
Magnetischer Schulterschluss: Der ringförmige Riesencluster {Mn84} (Ø ca. 4.2 nm) verhält sich wie ein Einzelmolekülmagnet und kristallisiert in Form stapelförmiger Aggregate. Molekulare (bottom-up) und klassische Ansätze (top-down) zum Aufbau nanoskaliger magnetischer Materialien werden hierdurch kombiniert.
We have designed oxidation-responsive vesicles from synthetic amphiphilic block copolymers ("polymersomes") of ethylene glycol and propylene sulfide. Thioethers in the hydrophobic poly(propylene sulfide) block are converted into the more hydrophilic sulfoxides and sulfones upon exposure to an oxidative environment, ch…
We report the preparation of composite foils consisting of two layers, one solid gold and one nanoporous gold. Tip displacements of several millimeters are observed when the foils are immersed in aqueous electrolytes and the electrochemical potential varied. This suggests that nanoporous metals could be used as the ac…
Supported gold nanoparticles exhibit high catalytic activity not only at low temperatures, but also under the presence of moisture. The effect of moisture on CO oxidation over Au/TiO2, Au/Al2O3, and Au/SiO2 was studied at 273 K. It was found that the catalytic activities are enhanced by moisture by up to two orders of…
A meeting of two magnetic worlds: The giant (ca. 4.2 nm) {Mn84} cluster, shown, has a torus structure and is a single-molecule magnet (SMM). It represents a meeting of the molecular (bottom-up) and classical (top-down) approaches to nanoscale magnetic materials, and it crystallizes as nanotubular stacks.
Abstract The magnetization reversal in nanocomposite two‐phase grains embedded in a soft magnetic matrix is calculated using Brown's equation. The grains are spherical, consisting of a soft core surrounded by a hard shell. The calculation yields nonlinear algebraic expressions whose solutions describe the nucleation f…
Abstract An atomistic calculation of the Peierls stress in Al and Cu is undertaken in order to assess consistency with experiments. The measured yield stress extrapolated to 0 K results at least one order of magnitude smaller than the Peierls stress commonly derived from internal friction data. On the theoretical side…
Evolution von Feststoffkatalysatoren: IR-Thermographie und kombinatorisches Bibliotheksdesign führen in wenigen Generationen zu neuen edelmetallfreien Katalysatoren für die Tieftemperaturoxidation von CO in Luft. Das Bild zeigt das emissivitätskorrigierte IR-Thermogramm einer Katalysatorbibliothek; rote Punkte markier…