Materials Literature
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We have examined the Raman spectra of violet and infrared emitting Ge+-implanted SiO2 films with special emphasis upon annealing temperature (AT) dependence of Raman scattering. We found that the complete spectrum mainly consists of three bands at 220–280, 300, and 430 cm−1, corresponding to scattering of Ge-related c…
Bubble levitation in an acoustic standing wave is re-examined here for the case of single-bubble sonoluminescence. The equilibrium position of the bubble is calculated by equating the average Bjerknes force with the average buoyancy force. The predicted values, as a function of pressure amplitude, are compared with ex…
Ferroelectric properties and the effect of Li + and Mg 2+ dopants in II–VI semiconductor ZnO were studied. The ferroelectric D – E loops were observed in Zn 1- x (Li 0.02 ·Mg x -0.02 )O, as well as in Zn 1- x Li x O. The transition temperature ( T c ) increases in proportion to the concentration of Mg 2+ ions, while i…
The formation mechanism of the hexagonal, MCM-41, and the lamellar, MCM-50, mesoporous materials, prepared at room temperature with the surfactant cetyltrimethylammonium chloride (CTAC) and tetraethylorthosilicon (TEOS), was studied by in situ EPR spectroscopy using the spin probe 4-( N, N -dimethyl- N -hexadecyl)ammo…
The pressure-temperature phase diagram of tetrathiafulvalene-p-chloranil, prototype for the neutral-to-ionic transition, is determined by neutron diffraction and nuclear quadrupole resonance and discussed in relation to thermally induced charge-transfer (CT) excitations. The respective role of ionicity and dimerizatio…
Simple cobalt porphine, adsorbed on graphite electrodes, catalyzes the direct reduction of O2 to H2O, while most other monomeric cobalt porphyrins do not. The surprising behavior of cobalt porphine suggests possible new strategies for the design of electrocatalysts for the reduction of O2 to H2O using structurally sim…
We report the effect of mixing three rare-earth (RE) elements in the RE site on the superconducting properties of melt-processed , in which RE elements are selected from the group of Nd, Sm, Eu and Gd. The heat treatment profiles for melt processing were determined according to the peritectic decomposition temperature…
The electronic and ionic conduction across grain‐boundary (GB) space‐charge depletion layers in acceptor‐doped SrTiO 3 ceramics have been investigated by admittance analysis in the time domain. The dependence on the acceptor concentration, the oxygen partial pressure during equilibration, and the temperature dependenc…
Scanning force microscopy (SFM) has been used to perform nanoscale studies of domain structures and switching behaviour of (PZT) thin films. An SFM piezoresponse mode, based on the detection of the piezoelectric vibration of a ferroelectric sample, was shown to be suitable for high resolution imaging of ferroelectric…
For a few oxide ceramics, the use of an initial precoarsening step prior to densification (referred to as two‐step sintering) has been observed to produce an improvement in the microstructural homogeneity during subsequent sintering. In the present work, the effect of a precoarsening step (50 h at 800°C) on the subseq…
We followed periphyton succession for 120 d in an artificial stream system to: 1) document an increase in cell densities and associated decrease in irradiance to the base of developing periphyton mats; 2) determine the vertical location of motile and nonmotile diatom species within the mat associated with these change…
Polyethylene oxide (PEO), polymethyl methacrylate (PMMA), and polyacrylonitrile (PAN) based gel electrolytes with a mixture of ethylene carbonate and propylene carbonate as plasticizer and lithium perchlorate were used to fabricate an electric double‐layer capacitor (EDLC). The performance of EDLCs with these gel elec…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTpH-Switchable, Ultrathin Permselective Membranes Prepared from Multilayer Polymer CompositesYuelong Liu, Mingqi Zhao, David E. Bergbreiter, and Richard M. CrooksView Author Information Department of Chemistry, Texas A&M University College Station, Texas 77843-3255 Cite…
Polycarbosilane (PCS) thin films were deposited on silicon (and other) substrates and heat treated under vacuum (∼10 ‐ ‐6>torr)at temperatures in the range of 200°–1200°C. At temperatures in the range of 1000°–1200°C, the initially amorphous PCS films transformed to polycrystalline ß‐silicon carbide (ß‐SiC). Althou…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA Simple Orthogonal Approach to Poly(phenylenevinylene) DendrimersShirshendu K. Deb, Todd M. Maddux, and Luping YuView Author Information Department of Chemistry and The James Frank Institute The University of Chicago 5735 South Ellis Avenue, Chicago, Illinois 60637 Ci…
Abstract The synthesis of hyperbranched methacrylates was achieved by self‐condensing group transfer polymerization of 2‐(2‐methyl‐1‐triethylsiloxy‐1‐propenyloxy)ethyl methacrylate ( 1 ). “Back‐biting” is shown to be the predominant side reaction. In spite of this, the compact nature of the hyperbranched molecules was…
Forming gas annealing causes changes in the remanent polarization (Pr), coercive field (Ec), and leakage current (I) in both PZT [Pb(Zr,Ti)O3] and SBT (SrBi2Ta2O9) samples with a variety of top electrode materials (Pt, Au, Ag, Cu, Ni, and In2O3), and the degree of degradation depends strongly on the top electrode mate…
The reaction of [P 2 W 15 O 56 ] 12- and aqueous Fe 3+ forms two ferric polytungstophosphate derivatives that have been isolated, purified, and characterized by X-ray crystallography and several physical methods. At pH ∼3 and [Na + ] = 2 M, needles of Na 12 [Fe III 4 (H 2 O) 2 (P 2 W 15 O 56 ) 2 ]·58H 2 O, Na- 1, form…
Synthesis and overexpression of a gene encoding Escherichia coli UDP-galactose 4-epimerase and engineered to facilitate cassette mutagenesis are described. General acid-base catalysis at the active site of this epimerase has been studied by kinetic and spectroscopic analysis of the wild-type enzyme and its specificall…
In this paper we study how the steady state morphology during shear of an incompatible blend can be affected by the initial conditions. By means of rheological experiments it is shown that below a critical shear rate multiple steady states can be obtained, the final morphology being then determined by the initial cond…