Materials Literature
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Abstract Polypropylene/clay (PP/clay) nanocomposites were synthesized via intercalative polymerization. The nanostructure of the composites was investigated by wide‐angle X‐ray diffractometry (WAXD) and transmission electron microscopy (TEM). The WAXD patterns of the PP/clay nanocomposites indicated that the character…
Raman spectra of the MgB2 ceramic samples were measured as a function of pressure up to 32 GPa at room temperature. The spectrum at normal conditions contains a very broad peak at ~590 cm-1 related to the E2g phonon mode. The frequency of this mode exhibits a strong linear dependence in the pressure region from 5 to 1…
The question addressed in this paper is that of the influence of the density of dislocations on the spin tunneling in Mn12 clusters. We have determined the variation in the mosaicity of the crystal structure of fresh and thermally treated single crystals of Mn12 by analyzing the widening of low angle X-ray diffraction…
The Kohn-Luttinger envelope-function method is generalized to the case of heterostructures with atomically sharp heterojunctions based on lattice-matched layers of related semiconductors with zinc-blende symmetry. For electron states near the Γpoint in (001) heterostructures the single-band effective-mass equation is…
The van der Waals liquid ortho -terphenyl has long been used as a model system in the study of the glass transition. Motivated by mode-coupling theory, extensive experiments have been undertaken to monitor the onset of structural relaxation on microscopic time- and lengthscales. Using in particular quasielastic neutro…
A ferroelectric monoclinic phase of space group Cm ${(M}_{A}$ type) has been discovered in $0.65{\mathrm{P}\mathrm{b}(\mathrm{M}\mathrm{g}}_{1/3}{\mathrm{Nb}}_{2/3}{)\mathrm{O}}_{3}{\ensuremath{-}0.35\mathrm{}\mathrm{PbTiO}}_{3}$ by means of high-resolution synchrotron x-ray diffraction. It appears at room temperature…
The thermal reaction of single-wall carbon nanotubes with in situ generated aryl diazonium compounds is described and is compared to a previously reported, electrochemically induced reaction with preformed aryl diazonium salts.
Optimal co-doping concentrations and dynamics of energy transfer processes for Tm3+-Tb3+ and Tm3+-Eu3+ in LiYF4 crystal hosts, J T Vega-Durán, L A Díaz-Torres, M A Meneses-Nava, J L Maldonado-Rivera, O Barbosa-García
Fluorescence upconversion experiments were performed on monomer solutions of a number of structurally similar thiacarbocyanine dyes. The results from these time-resolved experiments combined with the data obtained from steady-state absorption and emission and 1 H NMR spectra allowed us to assign the components with di…
Spontaneous pattern formation in hybrid nematic liquid-crystal films on glycerol was studied with both polarized transmission and unpolarized monochromatic reflected light microscopy. These observations reveal that the patterns that are found in 1 to 10-microm-thick films are due to a combination of film topography, g…
Polyaniline (PANI) zeolite composites have been prepared by oxidative polymerization of anilinein the presence of zeolite 13X, producing composite materials with PANI/zeolite weight ratios from about 0.5 to 55. The DC conductivity of the composite materials decreased exponentially with zeolite weight fraction. Pure PA…
The influence of the solvent (water, acetone, and ethanol) used during alumina impregnation on the properties of Pt/Al 2 O 3 and Pt−Sn/Al 2 O 3 catalysts was studied. Catalysts were characterized by H 2 chemisorption, TEM, temperature-programmed reduction, ammonia temperature-programmed desorption, UV−vis spectroscopy…
Short-wavelength visual pigments (SWS1) have lambda(max) values that range from the ultraviolet to the blue. Like all visual pigments, this class has an 11-cis-retinal chromophore attached through a Schiff base linkage to a lysine residue of opsin apoprotein. We have characterized a series of site-specific mutants at…
Atomistically detailed models of free-standing thin films and the bulk structure of amorphous atactic polystyrene have been produced by reverse mapping from equilibrated coarse-grained models. The bridging technique employed in the simulation allows the generation of a moderate sized atomistic system (six independent…
The electronic band structure of the Peierls compound NbSe3 has been explored for its symmetries with microspot synchrotron photoemission. The Fermi level crossings and deviations from one-dimensional behavior are identified. Density-functional calculations of the Fermi surfaces confirm the nesting conditions relevant…
Arrays of polypyrrole (Ppy) dots (80−180 nm diameter) have been prepared in a highly parallel fashion. This process is achieved by templating Ppy growth on a 2D surface micelle array, initially formed by the Langmuir−Blodgett (LB) technique. Ppy growth on self-assembled (SA)-based surface micelles produces more comple…
There exists a need to synthesize PMOs with bridging organic groups beyond the few that are accessible from commercially available bis(triethoxysilyl)organic precursors. To fulfill this need, three new periodic mesoporous arylsilicas, aromatic PMOs, having bridging aromatic organic groups as an integral part of the fr…
We report ab initio quantum mechanical calculations on LnIII(NO3−)n (n = 1–3) and Ln(NO3)3(H2O)m (m = 4–6) complexes to compare the monodentate s. bidentate binding mode of nitrate anions to trivalent lanthanide cations (LaIII, EuIII and LuIII) in the gas phase. In all LnIII(NO3−)n complexes studied, bidentate coordin…
A two-dimensional model has been developed to simulate heat transfer and solidification phenomena of squeeze cast magnesium alloy (AZ91D). The model was based on the control-volume finite-difference approach and on the enthalpy method. The computation was carried out to understand the effect of varying processing para…
Abstract The thermal oxidation of poly(bismaleimide) of the F655‐2 type, supplied by Hexcel‐Genin, was studied by isothermal gravimetry at 180, 210, and 240°C and various oxygen pressures ranging from 0 to 1.2 bar. Comparison of various sample thicknesses and visible microscopy observations on bulk aged samples shows…