Materials Literature
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Cathode rays, accelerated by tens of thousands of volts or more, have had immense scientific and technological value in the hundred years since Joseph John Thomson used them to discover the electron. The most familiar use of these electron beams is in cathode-ray tubes—as used in television sets and computer displays,…
The new d 10 −d 10 dimer Cu 2 (dppm) 2 (O 2 CCH 3 ) + (as a BF 4 - salt) has been prepared and characterized by X-ray crystallography and by 1 H and 31 P NMR, vibrational, and electronic spectroscopy. The compound is luminescent at 77 K but not at room temperature. MO calculations and geometry optimizations have been…
Solid-state postpolymerization of l -lactide was studied by two different ways with 0.1 mol % of stannous 2-ethyl hexanoate as the catalyst. In a two-step method, the ordinary melt polymerization of l -lactide was first performed at temperatures higher than the crystallization temperature ( T c ) of poly( l -lactide)…
The electrical properties of polymers filled with different types of conducting particles are reviewed. Following a theoretical description of a general effective media (GEM) equation, the experimental conductivity–volume fraction data for thermoplastic filled with vanadium oxide particles as well as thermosetting pol…
The tetragonal‐to‐cubic structural phase transition in pollucite (CsAlSi 2 O 6 ) was investigated using low‐temperature X‐ray powder diffraction in the temperature range of 93 to 298 K, and the lattice constants were refined with Rietveld analysis. It was found that CsAlSi 2 O 6 had a tetragonal phase with a space gro…
La croissance et le developpement des couches protectrices d'alumine sur des alliages NiAl et FeCrAl au cours de l'oxydation a 900°C et a 1300°C sont complexes du fait de la transformation de l'alumine metastable―y-Al 2 O 3 et―θ-Al 2 O 3 , en une phase,―α, plus stable. Comme les vitesses de transformation augmentent a…
It is well known that the spectral transmittance and reflectance of a thin film can be influenced by even small inhomogeneities or variations in its complex refractive-index profile. Formulas are derived that describe the theoretical variation of the spectral characteristics for small changes in the refractive index a…
Saturated hydrocarbon polymers may be differentiated by the relative amount and placement of methylene, methyl, methine, and quaternary carbon moieties. While it has been known or suspected for some time that polyolefins of conventional molecular weight (Mw ≈ 100 kg/mol) with dissimilar chemical microstructures are mo…
The synthesis and reactivity of ansa -metallocenes based upon the new ligand system R(Me)SiCp‘‘ 2 2 - (Cp‘‘ = C 5 Me 4 and R = (CH 2 ) n OMe, n = 3−5) is reported. The tethered donor functionality, which is appended via varying chain lengths to the silicon bridge, is introduced to examine possible intramolecular react…
Other| October 01, 1997 Electron-irradiation-induced phase segregation in crystalline and amorphous apatite; a TEM study A. Meldrum; A. Meldrum University of New Mexico, Department of Earth and Planetary Sciences, Albuquerque, NM, United States Search for other works by this author on: GSW Google Scholar L. M. Wang; L…
Barium oxide supported on magnesium oxide (Ba/MgO) exhibits unusual behavior as a catalyst for NO decomposition at Ba loadings of 11 mol % or greater. The catalytic activity is characterized by a sharp decrease in activity when the reaction temperature exceeds a certain value that depends on the partial pressures of N…
Abstract A theoretical model describing the interaction between crystalline swelling and cation exchange selectivity is proposed for expanding 2:1 phyllosilicates. The model is based on the assumption that changes in basal spacing of a clay are phase changes, and that each phase of a clay has a different selectivity c…
A surface science model for the Phillips ethylene polymerization catalyst has been prepared, by impregnating aqueous CrO 3 on a flat silicium (100) substrate covered by amorphous silica. Impregnating in a spin-coating technique offers control over the chromium loading, which was varied between 0.4 and 4.0 Cr/nm 2 . Af…
Isomerically pure α 1 - and α 2 -[Fe(OH 2 )P 2 W 17 O 61 ] 7 - and α 2 [Fe(OH 2 )P 2 Mo 2 W 15 O 61 ] 7 - were synthesized as aqueous-soluble potassium salts. The iron-substituted complexes as well as their immediate lacunary precursors have been characterized by IR, UV−visible, and 31 P NMR spectroscopies. The acid−b…
Static contact angle and dynamic (advancing and receding) contact angles of water on polymeric surfaces were investigated using microscope cover glasses coated with various plasma polymers of trimethylsilane and oxygen. By variation of the mole fraction of the TMS/oxygen mixture, glass surfaces having varying degrees…
The distribution of solvent in block copolymer solutions near their order−disorder transitions is examined experimentally, by small-angle neutron scattering (SANS), and theoretically, by the self-consistent mean-field (SCMF) approach. Three lamellar-forming poly(styrene- b -isoprene) diblocks were employed, in toluene…
This report details an extensive investigation on vanadium−dinitrogen complexes containing the [V(μ-N 2 )V] n + skeleton with a variable oxidation state of the metal and reduction degree of dinitrogen, n varying from 6 → 5 → 4. This skeleton can be associated to alkali cations in ion-separated or ion-pair tight forms.…
The composition of the barrier anodic film formed at 50 A m−2 to 200 V on solution-treated Al-l at.% Cu alloy in ammonium pentaborate electrolyte at 293 K has been investigated by Rutherford backscattering spectroscopy and nuclear reaction analysis. The film contains about 14% more oxygen in comparison with that expec…
We investigate theoretically the chain-length dependence of the electronic and optical properties of molecules representative of the three base forms of polyaniline (PAni), i.e., leucoemeraldine, emeraldine, and pernigraniline. The results establish that the PAni oligomers show a weak evolution of their electronic and…
A model relaxor ferroelectric ${\mathrm{PbMg}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_{3}$ (PMN) in single-crystal form has been studied by Raman scattering with special attention to the low-frequency spectra in the vicinity of both the diffuse ferroelectric transition (\ensuremath{\sim}270 K) and the electric-field-ind…