Materials Literature
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Forty-one different polymers are being exposed to the low Earth orbit (LEO) environment on the exterior of the International Space Station (ISS) for one year as part of MISSE (Materials International Space Station Experiment). MISSE is a materials flight experiment sponsored by the Air Force Research Lab/Materials Lab…
In a scanning electron microscope (SEM) top-down secondary electron image, areas within a few tens of nanometers of the line edges are characteristically brighter than the rest of the image. In general, the shape of the secondary electron signal within such edge regions depends upon the energy and spatial distribution…
Tetrahedral complexes with an excited state consisting of two closely lying triplet states are considered. The full interaction Hamiltonian, including ligand field, Jahn-Teller, pseudo-Jahn-Teller, and spin-orbit interactions is constructed. The emission-band shape is numerically calculated within the semiclassical ap…
Abstract The composition effect on morphology of polypropylene/ethylene–propylene–diene terpolymer/polyethylene (PP/EPDM/PE) and polypropylene/ethylene–propylene–diene terpolymer/polystyrene (PP/EPDM/PS) ternary blends has been investigated. In all of the blends, polypropylene as the major phase was blended with two m…
By means of molecular dynamics simulation, the crystallization process of the copolymer (ethylene-co-propene) with different branch distributions is studied at the molecular level. It is shown that subglobules formed at the branch sites along the copolymer chains and subsequently coalesced into a single globule and th…
The T2g4→4A2g luminescence of a 4.1% Cr3+ doped Cs2NaScCl6 crystal is studied as a function of hydrostatic pressure at room temperature and 15 K. The vibrational fine structure observed in the low-temperature variable pressure emission spectra is analyzed with a two configurational coordinate approach, involving the t…
${\mathrm{Sr}}_{0.85}{\mathrm{Bi}}_{2.1}{\mathrm{Ta}}_{2}{\mathrm{O}}_{9}$ 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…