Materials Literature
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A theoretical model is proposed for describing the polar biaxial and uniaxial nematic phases observed in thermotropic liquid crystals formed from rodlike polyester molecules. The polarity and biaxiality are shown to result from the same molecular mechanism, i.e., they are associated with the same critical order parame…
A simple and completely non-lithographic route to free-standing nanostructured polymeric films with a close-packed hexagonal array of nanoembossments or nanorods is presented in which electrochemically prepared textured aluminum sheets or nanoporous anodic alumimum oxide are used. The Figure shows an polystyrene/PMMA…
Using a geometry-based density functional theory we investigate the free interface between demixed bulk fluid phases of a colloidal mixture of hard spheres and vanishingly thin needles. Results are presented for the spatial and orientational density distributions of the particles, as well as for the interface tension.…
The pressure dependences of the elastic constants and the sound velocities are calculated from first principles for $3C\ensuremath{-}\mathrm{SiC}$ in the range 0--100 GPa. The sound velocities are found to decrease with increasing pressure for the lowest transverse acoustic (TA) branches for the [110] and [111] sound…
An ordered mesoporous silica with novel cubic structure (space group Fd3m) has been synthesized by using tri-head group quaternary ammonium surfactants [CmH2m + 1N+(CH3)2CH2CH2N+(CH3)2CH2CH2CH2N+(-)(CH3)(3).3Br-] (Cm-2-3-1, m = 14, 16, 18) as the structure-directing agents under basic conditions at low temperature.
Isothermal magnetization curves up to 23 T have been measured in ${\mathrm{Gd}}_{5}{\mathrm{Si}}_{1.8}{\mathrm{Ge}}_{2.2}.$ We show that the values of the entropy change at the first-order magnetostructural transition, obtained from the Clausius-Clapeyron equation and the Maxwell relation, are coincident, provided the…
The existence of spin polarized sub-bands, a half-semiconducting state in which the electron spins in “valence” and “conduction” bands are oppositely polarized, has been derived for the vanadium-organyl-based “soft” ferrimagnet V(TCNE)x by measurements of its electrical and magnetic resistance at different temperature…
The formation of Ni(OH)2 nanorods within an anodic oxide template via hydrothermal synthesis, followed by their subsequent liberation to form discrete NiO nanorods, is presented. The carbon can effectively be removed to form this uniform rod-like product. The Figure shows a schematic illustration of the synthesis.
From in situ stress measurements, we have observed that a large component of the precoalescence compressive stress that develops during Volmer-Weber growth of polycrystalline Cu films relaxes reversibly. This phenomenon is similar to the reversible stress relaxation previously observed in the postcoalescence regime. W…
Highly ordered arrays of antimony nanowires have been fabricated reproducibly by pulsed electrodeposition in anodic alumina membranes. The nanowires are shown to be single crystalline, metallic, and have a diameter of 40 nm. The field emission microscopy image (see Figure) shows the degree of filling of the template a…
We determine the depletion-induced phase-behavior of hard-sphere colloids and interacting polymers by large-scale Monte Carlo simulations using very accurate coarse-graining techniques. A comparison with standard Asakura-Oosawa model theories and simulations shows that including excluded-volume interactions between po…
We demonstrate by both experiments and phase-field simulations that lamellar eutectic growth can be stable for a wide range of spacings below the point of minimum undercooling at low velocity, contrary to what is predicted by existing stability analyses. This overstabilization can be explained by relaxing Cahn's assum…
Different phases of solid boron under high pressure are studied by first principles calculations. The $\ensuremath{\alpha}\ensuremath{-}{\mathrm{B}}_{12}$ structure is found to be stable up to 270 GPa. Its semiconductor band gap (1.72 eV) decreases continuously to zero around 160 GPa, where the material transforms to…
Gold nanorods have been prepared in aqueous solution using a seed-mediated growth approach in the presence of surfactant. We observe the formation of liquid crystalline phases in concentrated solutions of high aspect ratio (13–18) gold nanorods by polarizing microscopy, transmission electron microscopy, and small angl…
Diluted ferromagnetic III-V semiconductors typically show a high degree of compensation. Compensation is connected to the presence of comparable densities of charged defects of either sign. This naturally leads to the development of strong correlations between defect positions during growth and annealing. We show that…
A new model of localized highly frustrated ferromagnetism is presented: kagome spin ice. By use of analytical and Monte Carlo calculations its massive groundstate entropy is evaluated. Monte Carlo calculations are also used to explore the phases in the presence of further-neighbor interactions and applied fields. The…
A new type of crystalline trititanate nanotube (see Figure and inside front cover for a 3D drawing) has been synthesized in a single alkali treatment. Novel formation mechanisms of the nanotubes are proposed based on a series of experiments. In the process, NaOH can be regarded as a catalyst and a reusable source. The…
New Thin Crystal Film (TCF) polarizers and retarders are produced by deposition of water based lyotropic liquid crystals formed by supramolecules of dichroic dyes. The supramolecules have an aspect ratio of more than 100 with a "spaghetti-like" structure. The supramolecules are formed by disk-shaped aromatic molecules…
The local structure of amorphous As–Se films prepared by thermal evaporation in a vacuum and by RF ion-plasma sputtering, two techniques strongly differing in the conditions of substance vaporization and condensation of atoms on a substrate, was studied by Raman spectroscopy. It was found that the local structure of t…
Das ehrgeizige Ziel der Nanobiowissenschaften ist die Kombination der Funktionalität und Stabilität nanostrukturierter anorganischer Festkörper mit der strukturellen Vielfalt und den selbstorganisierenden Fähigkeiten biochemischer Moleküle. Wie die Ligandenhülle der Nanopartikel aufgebaut sein muss, damit eine stabile…