Materials Literature
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${\mathrm{Sr}}_{0.85}{\mathrm{Bi}}_{2.1}{\mathrm{Ta}}_{2}{\mathrm{O}}_{9}$ is shown, by Rietveld refinement of powder neutron-diffraction data, to undergo two phase transitions at elevated temperature. The low-temperature ferroelectric phase (space group ${A2}_{1}am)$ transforms to a paraelectric phase (Amam) at ${T}_…
The electronic structure of the newly discovered superconducting perovskite ${\mathrm{MgCNi}}_{3}$ is calculated using the LMTO method. The states near the Fermi energy are found to be dominated by $\mathrm{Ni}\ensuremath{-}d.$ The Stoner factor is low while the electron-phonon coupling constant is estimated to be abo…
Abstract Postpolymerization of dimethylaminoethylmethacrylate‐methyl chloride (DMAEM‐MC) electropolymerization, with Sn +2 /EDTA as initiator, was studied. The factors that affect the stable average molecular weight of the polymer (MW ∞ ) created by postpolymerization were investigated. The results indicate that the m…
Abstract A new class of dimethyl formamide (DMF)– and acetone‐soluble conducting pyrrole–ketonic resin copolymers has been developed. This was accomplished by oxidatively polymerizing pyrrole monomer by Ce(IV) salt in the presence of methyl ethyl ketone formaldehyde resin (MEKF–R). The resulting copolymers were readil…
Abstract Stress‐relaxation experiments on four varieties of Indian silk fiber show that stress relaxation is significantly greater in non‐Mulberry silks than in the Mulberry silk and that the differences among non‐Mulberry silk fibers are relatively small. All the fibers studied also exhibit inverse stress relaxation.…
The low-temperature homogeneous broadening of the electronic transitions of ${\mathrm{Eu}}^{3+}$ and ${\mathrm{Pr}}^{3+}$ rare-earth impurity ions in ${\mathrm{Y}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{LaF}}_{3}$ nanocrystals embedded into amorphous materials (polymer and oxyfluoride glass ceramics) was studied with hole…
The vacuum systems of all scanning electron microscopes (SEMs), even in the so-called clean instruments, have certain hydrocarbon residues that the vacuum pumps do not effectively remove. The cleanliness of the vacuum and the amount and nature of these residual molecules depends on the type of the pumps and also on th…
Aging dynamics in glassy systems is investigated by considering the hopping motion in a rugged energy landscape whose deep minima are characterized by an exponential density of states $\ensuremath{\rho}{(E)=T}_{g}^{\ensuremath{-}1}\mathrm{exp}{(E/T}_{g}),$ $\ensuremath{-}\ensuremath{\infty}<E<~0.$ In particular…
Abstract The melting behavior of syndiotactic polypropylene (s‐PP) after isothermal crystallization from the melt state was studied using differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD) techniques. Three melting endotherms were observed for isothermal crystallization at high degrees of…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTCatalytic Asymmetric Dihydroxylation of Olefins with New Catalysts: The First Example of Heterogenization of OsO42- by Ion-Exchange TechniqueBoyapati M. Choudary, Naidu S. Chowdari, Mannepalli L. Kantam, and Kondapuram V. RaghavanView Author Information Indian Institut…
Results are presented for the structural and thermodynamic properties of the orthorhombic phase of crystalline polyethylene (PE) from detailed atomistic molecular-dynamics (MD) simulations in the NPT statistical ensemble. Two different PE crystal systems have been investigated: (a) paraffins consisting of an odd numbe…
The isothermal crystallization process of poly(ether-ether-ketone) from the glass has been studied in real time by dielectric spectroscopy and x-ray scattering experiments. The combination of these two techniques revealed a complete picture of the crystallization processes from the point of view of both amorphous and…
Iron(II) bis(1,4,7-triazacylononane), Fe(tacn)22+, exhibits 1A1g ⇌ 5T2g spin-crossover behavior in solution. Values of ΔH°se = 23 kJ mol-1 and ΔS°se = 67 J mol-1 K-1 are obtained for the reaction by variable-temperature UV−visible and 1H NMR spectroscopy. The thermodynamic parameters reflect intramolecular structural…
Abstract A sequence of experimental steps was perfected to produce high‐impact modified polypropylene (PP), and to study the influence of particle morphology and rubber content on the reaction kinetics, especially in terms of mass transfer limitations. It was found that after a critical copolymer content at approximat…
Abstract For numerical simulations of the injection‐molding process, an accurate description of the specific volume is needed to predict differential shrinkage during and after molding, which causes thermally induced stresses and controls the dimensional accuracy and long‐term dimensional stability. For amorphous poly…
The electronic properties of gold–silver binary cluster anions (AunAgm−; 2⩽n+m⩽4) were studied by using photoelectron spectroscopy (PES) with a magnetic-bottle-type electron spectrometer. The AunAgm− cluster anions were generated by a laser vaporization of a gold–silver alloy rod. For triatomic AunAg3−n clusters, mono…
Abstract The morphology of some ternary blends was investigated. In all of the blends polypropylene, as the major phase, was blended with two different minor phases, ethylene–propylene–diene terpolymer (EPDM) or ethylene–propylene–rubber (EPR) as the first minor phase and high‐density polyethylene (HDPE) or polystyren…
Low-frequency Raman scattering experiments have been performed on metal nanoparticles embedded in two different thermally treated matrices. In addition to the well-known Raman scattering by the nanoparticle quadrupolar vibrational mode, the spectra measured in the 3–40 cm−1 frequency range exhibit several new bands. T…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTPeriodic Tiling of Pentagons: The First Example of a Two-Dimensional ( )-netBrian Moulton, Jianjiang Lu, and Michael J. ZaworotkoView Author Information Department of Chemistry University of South Florida 4202 East Fowler Avenue (SCA 400) Tampa, Florida 33620 Cite this…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHeterogeneous Seeded Growth: A Potentially General Synthesis of Monodisperse Metallic NanoparticlesHeng Yu, Patrick C. Gibbons, K. F. Kelton, and William E. BuhroView Author Information Departments of Chemistry and Physics Washington University, St. Louis, Missouri 631…