Materials Literature
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Abstract The effect of stearic acid modification on the dispersity of silica nanoparticles and the adhesion between the filler and polymer matrix with stearic acid concentration were investigated. The wettability of silica nanoparticles was improved by the addition of stearic acid. The presence of adsorbed stearic aci…
Phonons are calculated for single wall carbon nanotubes. Eigenvalues and eigenvectors are presented for armchair and zig-zag tubes. The model contains just three adjustable spring constants: two for first and second nearest neighbor directed bonds, and a third for radial bond-bending interactions. There are four low f…
We report an infrared reflection spectroscopy study of La$_{1/2}$Ca$_{1/2}$MnO$_3$ over a broad frequency range and temperature interval which covers the transitions from the high temperature paramagnetic to ferromagnetic and, upon further cooling, to antiferromagnetic phase. The structural phase transition, accompani…
The energetics of Schottky defects in 123 cuprate superconductor series, $\rm REBa_2Cu_3O_7$ (where RE = lanthandies) and $\rm YAE_2Cu_3O_7$ (AE = alkali-earths), were found to have unusual relations if one considers only the volumetric strain. Our calculations reveal the effect of non-uniform changes of interatomic d…
We use first principles methods to study static and dynamical mechanical properties of the ferroelectric polymer Poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoro ethylene (TrFE). We use density functional theory [within the generalized gradient approximation (DFT-GGA)] to calculate structures and ener…
The structure of disordered GaN:O films grown by ion-assisted deposition is investigated using x-ray absorption near-edge spectroscopy and Raman spectroscopy. It is found that between 4 and 21 % of the nitrogen in the films is in the form of molecular N_2 that interacts only weakly with the surrounding matrix. The ani…
Recently we have shown that $YbInCu_4$ and related compounds present a solid state Pomeranchuk effect. These systems have a first order volume transition where a local moment phase coexists with a renormalized Fermi liquid in analogy with $^3He$ at its melting curve. We demonstrate here experimentally that the solid s…
Time dependent STM has been used to evaluate step fluctuations as a function of temperature (300-450 K) on Ag(111) films grown on mica. The temporal correlation function scales as a power law in time, t^1/n with measured values of 1/n varying over a range of 0.19 pm 0.04 to 0.29 pm 0.04 with no dependence on temperatu…
The magnetotransport properties of an ${\mathrm{In}}_{0.95}{\mathrm{Mn}}_{0.05}\mathrm{As}$ thin film grown by metal-organic vapor phase epitaxy were measured. Resistivity was measured over the temperature range of 5 to $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The resistivity decreased with increasing temperature f…
We analyze damage nucleation and localization in the random fuse model with strong disorder using numerical simulations. In the initial stages of the fracture process, damage evolves in an uncorrelated manner, resembling percolation. Subsequently, as the damage starts to accumulate, current enhancement at the tips of…
So similar yet so different: The crystal structures of six alcohol solvates of the title compound (see formula) are found to be very similar at 200 K. In contrast, their spin-transition behavior and their structural phase transitions are quite different. Implications of these observations for crystal engineering are d…
Higher capacity rechargeable batteries can be constructed by using mesoscale nickel hydroxide tubes as the positive-electrode material. The tubes were prepared by deposition of nickel ions and aqueous ammonia in an anodic alumina membrane as the template. The picture shows a high-resolution TEM image of the tubes.
Höhere Kapazitäten als andere Akkumulatoren zeichnen Batterien aus, deren positive Elektroden mesoskalige Nickelhydroxid-Röhren als Material enthalten. Die Röhren entstehen durch Abscheidung von Ni(OH)2 mit Ammoniaklösung, wobei eine Aluminiumoxidmembran als Templat wirkt. Die Abbildung zeigt eine Hochauflösungs-TEM-A…
In a wide variety of applications, including the modelling of the glassy state of dense matter, non-exponential correlation functions in nuclear magnetic resonance, polymer dynamics, and bone and muscle rheology, Kohlrausch functions have proved to be more appropriate in modelling the associated relaxation and decay p…
A new polymorph of SrS(3) was obtained by a reaction of SrS and S with an atomic ratio of Sr:S = 1:5 under a pressure of 5 GPa at 1200 degrees C. It crystallized in a tetragonal unit cell with a = 6.708(1) A, c = 3.942(1) A, and V = 177.36(6) A(3). It was isotypic with BaS(3), and contained S3(2-) polysulfide ions. Th…
Abstract Magnetite iron oxide (Fe3O4) has been found to be an efficient heterogeneous catalyst for the epoxidation of alkenes by molecular oxygen in the absence of a sacrificial reductant among various transition metal oxides. The reaction probably proceeds via a radical mechanism.
Forces across polymer melts are poorly understood despite their importance for adhesion and fabricating composite materials. Using an atomic force microscope (AFM), this interaction was measured for poly(dimethyl siloxane) (PDMS). The structure of the polymer at the surface changed during the first approximately 10 h.…
The variations with temperature of the viscosity, η, and the relaxation times for various low molecular weight, unentangled polystyrenes (PS) are analyzed. We find that the temperature dependence of η does not directly reflect the behavior of the global chain modes. Depending on molecular weight and temperature, η can…
Hybrid composites of PbS nanoparticles embedded in sulfonated polystyrene matrixes were prepared without other added capping agent in the random ionomer. The nanocomposites were found to exhibit photoluminescence in both the near-infrared and visible regions. The infrared luminescence was tunable in the range 1100−150…
Zeolites collapse under modest pressure or temperature, their microporous structures transforming into glasses of conventional density. Using in situ synchrotron radiation diffraction methods we show how pressure and temperature-induced amorphization are equivalent processes and that these are mirrored by changes in t…