Materials Literature
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We present new evidence that two electron traps observed in polycrystalline zinc oxide can be associated with complex intrinsic defects. One deep level, E1, can be assigned to an oxygen vacancy. The second deep level, E2, could consist of a cluster-type defect associated with oxygen vacancies. The two traps were chara…
Abstract Dissolution kinetics of sepiolite from Eskisehir (Turkey) have been investigated at various temperatures and particle sizes using dilute hydrochloric and nitric acids. Dissolution reaction rate constants were calculated and apparent activation energies were dependent on acid concentration. For both acids, app…
Abstract Mass sorption/desorption and volume dilation/consolidation measurements are reported for tetramethyl and hexafluoro polycarbonate samples in the presence of carbon dioxide pressures up to 900 psia at 35°C. These results are combined with previous results for bisphenol‐A‐polycarbonate. The combined sorption an…
Alumina was joined to Ti‐6AI‐4V alloy by active brazing. High reactivity between the Cu‐40Ag‐5Ti braze alloy and these materials led to the formation of interfacial reaction products. These products were characterized by transmission electron microscopy and electron microprobe analysis. A continuous layer, identified…
Abstract Thermotropic liquid-crystalline polyethylenimines with an ammonium halide moiety and those low-mass model compounds exhibited enantiotropically smectic phases. They were homeotropically aligned with the formation of an ammonium bilayer. The homeotropic structure of the liquid-crystalline polyethylenimine rema…
Photocatalytic activity of TiO2 in the oxidation by oxygen of formic acid is considerably enhanced by the presence of dissolved copper ions. The role of oxygen transfer between the gas phase and the slurry is examined. The kinetic results obtained in the absence of mass transfer limitations lead to a mechanism based u…
SUMMARY The mechanisms of electron beam scattering are examined to evaluate its effect on contrast and resolution in high‐pressure scanning electron microscopy (SEM) techniques reported in the literature, such as moist‐environment ambient‐temperature SEM (MEATSEM) or environmental SEM (ESEM). The elastic and inelastic…
Diluted magnetic semiconductors (DMSs), i.e. semiconducting crystals whose lattice is made up in part of substitutional magnetic ions (e.g. Cd/sub 1-x/Mn/sub x/Te, Hg/sub 1-x/Fe/sub x/Se, Zn/sub 1-x/Co/sub x/S), are reviewed. The focus is on materials of the type A/sub 1-x//sup II/ Mn/sub x/B/sup VI/, which are the mo…
Abstract The quantum yields of the photochromic reaction between (E)- and (Z)-2-[1-(2,5-dimethyl-3-furyl)ethylidene]-3-isopropylidenesuccinic anhydride and the cyclized valence isomer were determined in various solvents and polymers. In both media the ring-opening quantum yield (ΦCE) depended on the dielectric constan…
A laser-driven picosecond time-resolved electron diffraction system operating in ultrahigh vacuum is described. A picosecond laser pulse is split into two beams. The first interacts with the sample under study. The second activates the cathode of an electron gun creating a collimated and focused electron pulse that is…
The crystallization of polyamide 6.12 was investigated by X-ray diffraction and infrared spectroscopy. Similar to polyamide 6.6, there exist a pseudohexagonal γ modification and a triclinic α modification. The characteristic IR absorption bands of each modification were identified and assigned. In the amorphous state,…
We present sample numerical solutions of the equation of motion that governs the dynamics of molecular orientation in ferroelectric liquid crystal cells with chevron layer structure. We show that the chevron structure significantly influences the director field, the chevron interface providing surface stabilization on…
Residual stresses in a SiC‐TiB 2 particulate composite before and after stressing have been measured using X‐ray diffraction. Tensile residual stresses in the TiB 2 drop by 60% after bending stresses of 250 MPa are applied. Likewise, the compressive residual stresses in the Sic phase decrease accordingly. Such behavio…
X-ray photoelectron spectroscopy has been used to monitor the surface chemical changes on DuPont high-modulus pitch-based carbon fiber surfaces brought about by microwave air-plasma treatments for different periods of time. The air-plasma treatment increased the fiber surface functionalities, but extended treatment ca…
Abstract Ferromagnetic spin-coupling between Cu(II) and Gd(III) ions was observed in a binuclear Cu(II)–Gd(III) complex CuGd(fsaen)NO3·4H2O (H4fsaen = N,N′-bis(3-carboxysalicylidene)ethylenediamine). The magnetic behavior was well reproduced by the equation derived from H = −2JSCu·SGd (SCu = 1/2, SGd = 7/2) with g = 2…
Mixed mass‐transport and kinetic control of sodium ion reduction at porous, inert electrodes on sodium beta′ alumina solid electrolyte (BASE) ceramic in a high‐temperature electrochemical cell has been observed and modeled.The high ionic conductivity of BASE and the reversibility of the liquid sodium/BASE anodic half‐…
The properties of polypyrrole (PPy) films synthesized at very low current densities (1–250 μA/cm 2 ) were investigated. Potentiodynamic cycling, in situ FTIR spectroscopy, and in situ differential electrochemical mass spectroscopy were employed. The use of propylene carbonate (PC) based electrolytes for the synthesis…
The thermal behavior of hyperquenched glassy D2O was investigated by differential scanning calorimetry from 103 to 250 K, in order to investigate the isotope effect on the glass→liquid transition and on the liquid to cubic, and cubic to hexagonal ice. For a heating rate of 30 K min−1 the temperatures of the thermal ef…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA general fluorescence assay for enzyme catalyzed polyanion hydrolysis based on template directed excimer formation. Application to heparin and polyglutamateScott A. Van Arman and Anthony W. CzarnikCite this: J. Am. Chem. Soc. 1990, 112, 13, 5376–5377Publication Date (Print)…
Atomic structures of perfect (90° and 60°) and partial (90°) dislocations including total and core energies have been calculated using four different interatomic potentials in silicon, germanium and diamond. The core energies of dislocations do not scale with the magnitudes of Burgers vectors associated with them. How…