Materials Literature
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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…
The surface loss probabilities of hydrocarbon radicals on the surface of amorphous hydrogenated carbon (C:H) films are investigated by depositing films inside a cavity with walls made from silicon substrates. This cavity is exposed to a discharge using different hydrocarbon source gases, and particles from the plasma…
We recently proposed a concentration fluctuation model to describe the segmental dynamics of miscible polymer blends [Kumar et al., J. Chem. Phys. 105, 3777 (1996)]. This model assumes the existence of a cooperative volume, similar to that in the Adam-Gibbs picture of the glass transition, over which segments have to…
The luminescence spectra and extended x-ray-absorption fine-structure (EXAFS) measurements of a series of ${\mathrm{Eu}}^{3+}$-based organic/inorganic xerogels were reported and related to the local coordination of the lanthanide cations. The hybrid matrix of these organically modified silicates, classed as $U(2000)$…
Continuous porous polymer monoliths that take on the shape of the reaction vessel are described. These materials are generated by polymerizing crosslinking monomers such as trimethylolpropane trimethacrylate (TRM, see Figure) in supercritical CO2. It is demonstrated that the pore size distribution can be fine-tuned wi…
A powder mixture of α‐Si 3 N 4 , Y 2 O 3 , and SiO 2 was heat‐treated in a loose powder state in the temperature range of 1750°–1900°C for 2 h; then, the mixture was acid‐rinsed to remove the glassy phase. The widths and lengths of the resulting β‐Si 3 N 4 crystals were analyzed quantitatively. The width–aspect‐ratio…
Abstract The purpose of the presented research was the investigation of the stability and differences of degradation of polyolefines during various recycling processes. In modeling the recycling process during melting, extrusion with a one‐screw extruder was used. Recycling through selective dissolution was modulated…
Two commercial Si 3 N 4 powders were coated with sintering aids by coprecipitation. Lanthanum and yttrium nitrates were used as sintering aid precursors. Electrokinetic sonic amplitude measurements and X‐ray photoemission spectroscopy analysis were used to investigate electrokinetic behavior and surface properties, re…
Experimental solubilities are reported at 25.0°C for biphenyl dissolved in 26 different alkane, dialkyl ether, and alcohol solvents. Results of these measurements, combined with previously published biphenyl solubility data, are used to test the applications and limitations of expressions derived from Mobile Order the…
The bulk amorphous-like (a-) semiconductor, a-ZnIn2Te4, is prepared by the melt-quench technique. The pseudodielectric-function spectra, 〈ε(E)〉=〈ε1(E)〉+i〈ε2(E)〉, of a-ZnIn2Te4 are measured by spectroscopic ellipsometry in the 1.2–5.3 eV photon-energy range at room temperature. The measured 〈ε(E)〉 spectra strongly rese…
Abstract Poly(3‐hydroxybutyrate) (PHB) and ist 3‐hydroxyvalerate containing copolymers form a family of fully biodegradable polyesters with many potential applications. In this work, the results obtained in our laboratory concerning carbon dioxide, water and organic solvent transport through PHB and three low 3‐hydrox…
The formation of ettringite (3CaO·Al 2 O 3 ·3CaSO 4 ·32H 2 O) from monosulfate (3CaO·Al 2 O 3 ·CaSO 4 ·12H 2 O) and gypsum (CaSO 4 ·2H 2 O) was investigated by isothermal calorimetry and X‐ray diffraction (XRD) analyses. Hydration was carried out at constant temperatures from 30° to 80°C using deionized water and 0.2…