Materials Literature
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The stability fields of two high‐pressure polymorphs of ZrO 2 (ortho I and ortho II) were determined by both calorimetry and phase equilibrium experiments. Enthalpies of transition were measured by transposed temperature drop calorimetry. The entropies of transition and slopes of phase boundaries were calculated using…
Abstract Aluminium alkoxides, such as Al(O i Pr) 3 or Et 3‐p Al(O (CH 2 ) 2 X) p with 1≤p≤3, are very effective in initiating the polymerization of lactones, e.g.ϵ ‐ca‐prolactone and δ ‐valerolactone, and lactides (D,L‐ or L,L‐ isomers). The ring‐opening polymerization proceeds through a “coordination‐insertion” mecha…
Three series of metal-free phthalocyanines with alkyl, alkoxy, and alkoxymethyl side groups have been studied with X-ray diffraction. The structure of the columnar mesophases was described as a two dimensional (pseudo) hexagonal packing of indefinitely long stacks of phthalocyanine molecules. From the slope of the squ…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDisubstituted tungstosilicates. 2. .gamma.- and .beta.-isomers of tungstovanadosilicate, [SiV2W10O40]6-: syntheses and structure determinations by tungsten-183, vanadium-51 and silicon-29 NMR spectroscopyJacqueline Canny, Rene Thouvenot, Andre Teze, Gilbert Herve, Michele Le…
High-pressure X-ray powder diffraction has been performed on corundum-type αFe 2 O 3 (hematite) in the pressure range up to 65 GPa using synchrotron radiation and a diamond anvil cell. A structural phase transformation has been observed with a transition pressure of about 55 GPa. The high-pressure form of Fe 2 O 3 is…
Frequency dependent second hyperpolarizabilities of N2 and the prototype organic molecule trans-butadiene are reported using generalized time dependent Hartree–Fock (TDHF) theory for several frequencies of applied fields. A monotonic increase of the values (positive dispersion) is observed for every nonlinear optical…
Defects and impurities in diamond films grown by chemical vapor deposition (CVD) were analyzed by high-resolution cathodoluminescence (CL) spectroscopy and imaging in transmission electron microscopy (TEM). The combination of CL and TEM makes it possible to correlate the film microstructure with the electronic structu…
A variety of temperature dependences of helical pitch were found in ferroelectric SmC * and antiferroelectric SmC A * chiral smectic liquid crystals with large spontaneous polarization. In the vicinity of the transition temperatures of the materials showing the second-order SmA-SmC * or SmA-SmC A * phase transition, t…
Just like technical check valves, the function of mechanical heart valve prostheses may presumably also lead to cavitation effects during valve closure. Due to the waterhammer effect, cavitation may primarily occur in the mitral position leading to high mechanical loading of the valve itself and of corpuscular blood e…
Abstract Three bentonites, from Bavaria, Wyoming and Brazil, were separated into various fractions. The layer charge was determined by alkylammonium ion exchange and increases with particle size from 0·25 Eq/(Si, Al) 4 O 10 (<0·06 µ m) to 0·28 Eq/(Si, Al) 4 O 10 (1–10 µ m). The charge density corresponds to an inte…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular engineering of liquid-crystal polymers by living polymerization. 3. Influence of molecular weight on the phase transitions of poly{8-[(4-cyano-4'-biphenyl)oxy]octyl vinyl ether} and of poly{6-[4-cyano-4'-biphenyl)oxy]hexyl vinyl ether}V. Percec and M. LeeCite this:…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSecond-sphere coordination of transition-metal complexes by calix[4]arenesJerry L. Atwood, G. William Orr, Fumio Hamada, Rebecca L. Vincent, Simon G. Bott, and Kerry D. RobinsonCite this: J. Am. Chem. Soc. 1991, 113, 7, 2760–2761Publication Date (Print):March 1, 1991Publicat…
An experimental investigation has been performed of the Rayleigh linewing in glass-forming liquids in the temperature rangefrom the melting point down to the glass-transition point. The so-called boson peak is found to contribute substantially to the Rayleigh linewing, and to determine the spectral profile of the high…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInteractions of nitric oxide and carbon monoxide with palladium and platinum atomsGregory W. Smith and Emily A. CarterCite this: J. Phys. Chem. 1991, 95, 6, 2327–2339Publication Date (Print):March 1, 1991Publication History Published online1 May 2002Published inissue 1 March…
Thin-film nickel-titanium shape memory alloy has been vacuum sputter deposited, characterized by crystallographic, electrical, and mechanical tests, and incorporated as an actuator in miniature devices. The composition and heat treatment of the film are critical as contamination by oxygen and other species affects the…
We consider the statistical mechanics of a system of semiflexible chains, which can represent polymer liquid crystals, long-chain biomolecules, stiff wormlike micelles, or columns of discotic liquid crystals. Semiflexible chains can order in a hexagonal lattice (also called a columnar or canonic phase), and they can f…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIon association and electric field effects on electron hopping in redox polymers. Application to the tris(2,2'-bipyridine)osmium(3+)/tris(2,2'-bipyridine)osmium(2+) couple in NafionFred C. Anson, David N. Blauch, Jean Michel Saveant, and Ching Fong ShuCite this: J. Am. Chem.…
The reaction between nitrogen gas and the series of R2Fe17 intermetallic compounds is studied by thermopiezic analysis on micron-size powders. Nitrogen diffusion in the range 300–550 °C can be represented by an activated interstitial diffusion process D=D0e−Em/kT with D0=1.95×10−10 m2 s−1 and an activation energy Em=0…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectrically conductive polyaniline-poly(vinyl alcohol) composite films: physical properties and morphological structuresShow An Chen and Woei Guwn FangCite this: Macromolecules 1991, 24, 6, 1242–1248Publication Date (Print):March 1, 1991Publication History Published online1…
Fluorescence and site-selective excitation spectra of chromium-activated forsterite at 10 K are reported. It is found that a high-field ${\mathrm{Cr}}^{3+}$ site in inversion symmetry emits sharp ${\mathit{R}}_{1}$ line fluorescence, while a low field ${\mathrm{Cr}}^{3+}$ site in mirror symmetry produces $^{4}$${\math…