Materials Literature
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The attenuation of longitudinal acoustic phonons up to frequencies nearing 250 GHz is measured in vitreous silica with a picosecond optical technique. Taking advantage of interferences on the probe beam, difficulties encountered in early pioneering experiments are alleviated. Sound damping at 250 GHz and room temperat…
The role of exchange-correlation effects in non-equilibrium quantum transport through molecular junctions is assessed by analyzing the IV curve of a generic two-level model using self-consistent many-body perturbation theory (second Born and GW approximations) on the Keldysh contour. For weak molecule-lead coupling we…
The infrared phonon spectrum of the spinel CdCr2O4 is measured as a function temperature from 6 K to 300K. The triply degenerate Cr phonons soften in the paramagnetic phase as temperature is lowered below 100 K and then split into a singlet and doublet in the low T antiferromagnetic phase which is tetragonally distort…
We analyze recent experiments on the dilute rare-earth compound LiHo_xY_(1-x)F_4 in the context of an effective Ising dipolar model. Using a Monte Carlo method we calculate the low-temperature behavior of the specific heat and linear susceptibility, and compare our results to measurements. In our model the susceptibil…
Hyperfine interactions, magnetic interactions between the spins of electrons and nuclei, in graphene and related carbon nanostructures are studied. By using a combination of accurate first principles calculations on graphene fragments and statistical analysis, I show that both isotropic and dipolar hyperfine interacti…
This letter reports on the growth, structure and luminescent properties of individual multiple quantum well (MQW) AlGaAs nanowires (NWs). The composition modulations (MQWs) are obtained by alternating the elemental flux of Al and Ga during the molecular beam epitaxy growth of the AlGaAs wire on GaAs (111)B substrates.…
In this work, we show strong experimental evidence in favor of a proposed incorporation mechanism of hydrophobic semiconductor nanocrystals (or quantum dots, QDs) in monodisperse silica spheres (diameter ∼35 nm) by a water-in-oil (W/O) reverse microemulsion synthesis. Fluorescence spectroscopy is used to investigate t…
The present study investigated the effects of the method of surface decoration on the wetability of multi-walled carbon nanotubes (MWCNTs) and the mechanical properties of the cement paste incorporating these dispersions. The results showed that stable and homogenous dispersions of MWCNTs in water can be obtained by u…
Sea cucumbers, like other echinoderms, have the ability to rapidly and reversibly alter the stiffness of their inner dermis. It has been proposed that the modulus of this tissue is controlled by regulating the interactions among collagen fibrils, which reinforce a low-modulus matrix. We report on a family of polymer n…
Significant enhancement in mechanical stiffness (10-200%) and fracture strength (approximately 50%) of graphene oxide paper, a novel paperlike material made from individual graphene oxide sheets, can be achieved upon modification with a small amount (less than 1 wt %) of Mg(2+) and Ca(2+). These results can be readily…
Abstract Polyurethanes were prepared from poly(tetramethylene oxide) end‐capped with MDI and PBT extenders. The PBT extenders were random‐disperse in length and their length varied from three to seven repeating units. The structure of the polyurethanes was studied by FT‐IR and AFM, their thermal and thermomechanical r…
The dissociative excitation reactions of BrCN induced by the electron cyclotron resonance (ECR) plasmas of Ar and He were studied based on the electrostatic-probe measurements and on the optical emission spectra of the B 2 Σ + – X 2 Σ + transition of CN radicals. The density, n e , and the temperature, T e , of free e…
A detailed magnetic study has been carried out for the Fe-doped $\mathrm{Gd}\mathrm{Ba}{\mathrm{Co}}_{2\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{O}}_{5.5\ensuremath{-}\ensuremath{\delta}}$ ($x=0$, 0.02, 0.05, 0.10, and 0.20) cobaltites. Fe doping enhances the high-temperature $T$ ferromagnetism present in the Fe-free…
We report an ammonia-evaporation-induced synthetic method for metal (Ni, Cu, Zn, and Cd) hydroxide/oxide nanostructures including hierarchical CuO spheres with radiating nanoplates, densely branched ZnO nanowires, Cd(OH)<sub>2</sub> nanofibers, and Ni(OH)<sub>2</sub> nanoplates. One important f…
Abstract The influence of the main chain stereoregularity on the properties of poly(3‐decylthiophene‐2,5‐diyl) as anticorrosive additive of conventional organic coatings have been examined. For this purpose a small concentration (0.3% w/w) of regiorandom and regioregular conducting polymers were added to alkyd, epoxy,…
Abstract Porous cellulose acetate butyrate foams with a bimodal cell size distribution were produced using supercritical carbon dioxide as a blowing agent. It is demonstrated that the cell size distribution is tunable, due to the semi‐crystalline nature of the polymer. The resulting morphology will either be homogeneo…
We present the details of growth parameters which promote the cationic ordering in multiferroic A2CoMnO6 (A=La or Bi) thin films grown on SrTiO3 (001). Our study manifest that well-ordered Co∕Mn states can be achieved at relatively high temperature and oxygen partial pressure. Structural, magnetic, and magnetodielectr…
Abstract A synthetic route was developed to prepare thermosetting methyl, cyclopentyl, and cyclohexyl substituted polysiloxanes with epoxide or amino end groups. Cycloalkene (cyclopentene or cyclohexene) and dichlorosilane gas were reacted at 180 °C, and at high pressure (2 MPa) to produce dicycloaliphatic dichlorosil…
Highly ordered metallic nanopore membranes are fabricated by direct deposition of nickel on typical porous anodic alumina (PAA) templates. The large-area uniform nanopore arrays of the PAA templates are accurately transferred to the metallic nanopore replicas, depending on the thickness of the deposited metal and the…
Abstract Blown films prepared from starch‐poly(methyl acrylate) graft copolymers plasticized with urea and water display shrinkage at relative humidities greater than 50%. Shrinkage at relative humidities below approximately 75% is strongly correlated with the urea/starch weight ratio, which controls the equilibrium m…