Materials Literature
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Nanocrystalline silicon carbide that was doped with boron and carbon (B,C‐SiC) and contained 1 wt% boron additive and 3.5 wt% free carbon was fabricated using hot isostatic pressing under an ultrahigh pressure of 980 MPa and a temperature of 1600°C. The average grain size of the material was 200 nm. The tensile deform…
Up to 50 vol% of TiB 2 , TiC 0.5 N 0.5 , TiN, or TiC was added to Y 2 O 3 ‐stabilized tetragonal ZrO 2 polycrystals (Y‐TZP) and hot pressed under vacuum. The influence of the type of secondary phase on the microstructure and mechanical properties was studied, as a function of the hot‐pressing temperature. The influenc…
Atomistic molecular dynamics simulations are performed to analyze the diffusion of phenol molecules in a bisphenol-A-polycarbonate melt in the zero concentration limit for the temperature range from 500 K to 640 K. The transition from a hopping diffusion to a continuous diffusion is observed. Visualization of the diff…
Octaanionic meso -tetra(3,5-dicarboxylatophenyl) porphyrin 1 was adsorbed to gold electrodes at pH 12 and stayed there after repeated washing with 10 - 2 M KOH. The fluorescence on sputtered gold surfaces amounted to 10% of the intensity observed on an organic subphase. Addition of 10 - 6 M aqueous solutions of the ma…
The interwoven and branched, regular, cubic pore structure of the molecular sieve MCM-48makes it of interest for catalytic and separations applications. A new, easy, fast, and flexible preparation method for metal-containing MCM-48is presented and the characteristics of the resulting spherical particles are discussed.…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTFormation and Characterization of a High-Spin Heme-Copper Dioxygen (Peroxo) ComplexReza A. Ghiladi, Telvin D. Ju, Dong-Heon Lee, Pierre Moënne-Loccoz, Susan Kaderli, Yorck-Michael Neuhold, Andreas D. Zuberbühler, Amina S. Woods, Robert J. Cotter, and Kenneth D. KarlinV…
By using molecular dynamics simulations on a large number of hard spheres and the Voronoï tessellation we characterize hard-sphere systems geometrically at any packing fraction eta along the different branches of the phase diagram. Crystallization of disordered packings occurs only for a small range of packing fractio…
A temperature-dependent UV–visible spectrophotometric study on [Eu(DO3A)(H2O)n] proved the presence of a hydration equilibrium (n = 1, 2), strongly shifted towards the bisaqua species [DO3A = 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane]. The thermodynamic parameters and the reaction volume were determined…
Kinetics of direct α/β-Si3N4→α-SiAlON transformations, reverse α′-SiAlON→β′-SiAlON transformation, and the formation of intermediate phases were investigated for SiAlON ceramics with rare earth stabilizing cations. It was determined that smaller cations (Yb), and α-Si3N4 starting powders lead to faster Si3N4→α′-SiAlON…
By using an oxynitride glass composition from the Y‐Mg‐Si‐Al‐O‐N system as a sintering additive, the effect of atmosphere on densification was investigated during the liquid‐phase sintering of SiC, and the resulting microstructure and mechanical properties of the sintered and subsequently annealed materials were inves…
We present magnetic susceptibility, x-ray-diffraction, and electron-spin-resonance (ESR) studies in the series of nonstoichiometric compounds ${\mathrm{LaMnO}}_{3+\mathrm{\ensuremath{\delta}}},$ for $0<~\ensuremath{\delta}<~0.07.$ The measurements were performed in the paramagnetic regime, especially near the te…
In this work we present an octahedral perturbative model to explain the dependence of the crystal-field (CF) and the charge-transfer (CT) energy with respect to structural distortions in Jahn-Teller (JT) ${\mathrm{CuCl}}_{6}^{4\mathrm{\ensuremath{-}}}$ systems. The method provides a simple way to express the variation…
Abstract A method for blending polystyrene and poly(methyl methacrylate), (PMMA), with the addition of supercritical carbon dioxide has been investigated. The first series of blends was a PMMA and polystyrene with similar melt viscosities. The second series of blends was a PMMA and polystyrene with a viscosity ratio (…
The tensile creep rate of most commercial grades of Si 3 N 4 increases strongly with stress. Although the usual power‐law functions can represent the creep data, the data often show curvature and systematic variations of slope with temperature and stress. In this article, we present a new approach to understanding the…
We report here on the synthesis and characterization of several triblock rodcoil molecules containing conformationally rigid and flexible sequences and luminescent chromophores based on phenylene vinylene. The molecules consist of blocks of oligostyrene, oligoisoprene, and a rigid rod block. The synthesis of the rod b…
Abstract Structural Fe 3+ in kaolinites and dickites covering a broad range of disorder was investigated using electron paramagnetic resonance (EPR) spectroscopy at both the X and Q-band frequencies. A procedure based on a numerical diagonalization of the spin Hamiltonian was used to accurately determine the second an…
Amorphous and crystalline Sn 2 P 2 O 7 can be considered as intrinsic P‐doped glasses, similar to the products from the binary solid state reaction between SnO and P 2 O 5 . Amorphous Sn 2 P 2 O 7 was prepared by melt‐quenching the crystalline form. IR spectroscopy and inductively coupled plasma measurements indicated…
A procedure is described for the evaluation of the fracture behaviour of polycyrstalline ceramics using an in-situ stress analysis involving either fluorescence or Raman microprobe spectroscopy. The full details of the experimental set-up, calibration procedures and stress calculations are shown, and their reliability…
Whatever the preferred representation of the frequency dependence of electrical relaxation experimental data, complex conductivity ${\ensuremath{\sigma}}^{*}(\ensuremath{\omega}),$ complex permittivity ${\ensuremath{\varepsilon}}^{*}(\ensuremath{\omega}),$ or complex electric modulus ${M}^{*}(\ensuremath{\omega}),$ th…
We applied the recently developed density-functional (DFT) formulation of the electron paramagnetic resonance (EPR) g-tensor to a series of axially symmetric d1 transition metal complexes (MEX4z−, where M=V, Cr, Mo, W, Tc, and Re; E=O and N; X=F, Cl, and Br). Values for the g-tensor components are determined by an int…