Materials Literature
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A highly active solid superacid of sulfated tin oxide was prepared from tin oxide gel, which was precipitated by the hydrolysis of SnCl 4 and washed with aqueous ammonium acetate solution, followed by exposure to aqueous sulfuric acid and calcining. Differencial thermal analysis suggested that the acetate ion remainin…
As a first approach to the motion of particles in anisotropic liquids, we study the Stokes drag of spherical particles in three different nematic environments: a uniform director field, the Saturn-ring configuration, and the dipole configuration. Two independent friction coefficients for the respective motion parallel…
We report a detailed study of the magnetic and magnetotransport properties of Sr 2 FeMoO 6 ceramics having a controlled concentration of antisite (AS) defects. It is found that a high-field differential susceptibility exists in all samples, which increases with AS. Similarly, a high-field magnetoresistivity develops a…
The energy levels of CdSe quantum dots are studied by scanning tunneling spectroscopy. By varying the tip−dot distance, we switch from “shell-filling” spectroscopy (where electrons accumulate in the dot and experience mutual repulsion) to “shell-tunneling” spectroscopy (where electrons tunnel, one at a time, through t…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSynthesis of Well-Defined Block Copolymers Tethered to Polysilsesquioxane Nanoparticles and Their Nanoscale Morphology on SurfacesJeffrey Pyun, Krzysztof Matyjaszewski, Tomasz Kowalewski, Daniel Savin, Gary Patterson, Guido Kickelbick, and Nicola HuesingView Author Inf…
Abstract Isoconversional methods, those using only one curve α = α(T) (α is the conversion degree and T is the temperature), and invariant kinetic parameter method were applied to estimate the kinetic parameters from the following nonisothermal data: (1) simulated TG curves for a single reaction; (2) TG curves for the…
The question whether the linear absorption spectra of metal clusters can be interpreted as density oscillations (collective ``plasmons'') or can only be understood as transitions between distinct molecular states is still a matter of debate for clusters with only a few electrons. We calculate the photoabsorption spect…
The statistical properties of failure are studied in a fiber bundle model with thermal noise. We show that the macroscopic failure is produced by a thermal activation of microcracks. Most importantly the effective temperature of the system is amplified by the spatial disorder (heterogeneity) of the fiber bundle. The c…
Doped divalent hexaborides such as $Sr_{1-x}La_xB_6$ exhibit high \tc ferromagnetism. We isolate a degenerate pair of $2p$-orbitals of boron with two valence electrons, invoke electron correlation and Hund coupling, to suggest that the undoped state is better viewed as a spin-1 Mott insulator; it is predicted to be a…
A novel biological method for the synthesis of silver nanoparticles using the fungus Verticillium is reported. Exposure of the fungal biomass to aqueous Ag + ions resulted in the intracellular reduction of the metal ions and formation of silver nanoparticles of dimensions 25 ± 12 nm. Electron microscopy analysis of th…
A semi-infinite sample of a nematic liquid crystal in contact with a flat solid substrate, possessing an alternating stripe pattern of planar and homeotropic anchoring, is studied in the framework of the Frank-Oseen model. The case of strong anchoring on one of the stripes is treated by means of bifurcation analysis,…
We report on the first observation of strongly damped phonon-polariton beats and picosecond carrier relaxation dynamics of ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ near the metal-insulator phase transition. The observed 60 GHz coherent oscillations show clear softening as the temperature approaches…
Abstract In the melt intercalation of cation‐exchange clay, mixtures of montmorillonite and poly(styrene‐ co ‐acrylonitrile) (SAN) with various acrylonitrile contents were studied to examine the effect of specific interaction. When organic molecules with hydroxyl groups were used as intercalants for the clay, the amou…
It is shown that alkane thiol-capped gold nanoparticles can be dissolved in supercritical ethane. Importantly, the solubility was found to be dependent on the core diameter thus allowing separation by size. Nanoparticles with a core diameter less than 1.7 nm were soluble in the supercritical fluid.
The preparation of a wide range of organically functionalized wormhole-motif and hexagonal mesoporous MSU-X silicas was achieved by a one-step synthesis process involving the simultaneous addition of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) to solutions of structure-directing nonionic surf…
Nucleation, clustering, and multilayer growth of metals on oxide surfaces are processes which influence the stability and function of many catalysts. In this work, we have examined initial stages of these processes by means of modeling involving calculations of energies and optimum structures of Co and Ni on a silica…
Abstract The present work is concerned with the effect of processing variables and filler concentration on the electrical conductivity, hardness, and density of composite materials prepared by compression molding of a mixture of zinc powder and nylon 6 powder. The electrical conductivity of the composites is <10 −1…
The 1:1 reaction of 2-NH 2 (4,6-Me 2 pm) with Cp 2 Mn in thf gives the novel heteroleptic imido/amido Mn(II) cage [(η-Cp)Mn{2-NH(4,6-Me 2 pm)}·Mn{2-N(4,6-Me 2 pm)}] 4 ( 1 ), composed of a central Mn(II) imido [Mn 4 {2-N(4,6-Me 2 pm)} 4 ] core coordinated at the periphery by four [(η-Cp)Mn{2-NH(4,6-Me 2 pm)}] monomer u…
Two methods for the addition of pendent dialkyl phosphonate units onto aryloxyphosphazenes, at both the polymeric and cyclic trimer levels, are described. Sodium organophosphites or halogenated organophosphates were used as the phosphonating agents and were allowed to react with bromomethylene- or lithio-functionalize…
Microporous amorphous metallosilicates designated as Mg−Si−O and Al−Si−O, with a very narrow pore size distribution around 6 Å diameter, typical surface areas ranging from 350 to 650 m 2 /g, and loadings of well-dispersed metal oxide (up to about 10 wt % metal) result from the controlled calcination of magnesium and a…