Materials Literature
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The infrared spectra of butyl pyridinium chloride/aluminum chloride and 1-methyl 3-ethyl imadazolium chloride/aluminum chloride room temperature molten salts have been examined over a range of mole ratios (acidities). Bands observed in the 4000-630/cm range have been assigned and spectral changes attributed to the for…
Secondary ion mass spectrometry was used to profile the interdiffusion of network oxygen in a Si 16O2-Si 18O2 thin-film structure. The diffusivity from 1200 to 1400 °C can be described by D=2.6 cm2 s−1 exp (−4.7 eV/kT). The diffusivity values are lower, but with a higher activation energy, than those previously report…
Abstract The reduction in molecular dimensions due to the presence of short side chains in otherwise linear polyolefins can very simply by calculated by assuming that the configuration of the main chain is not influenced by the side chains. This enables us to express the intrinsic viscosity–molar mass relationship as…
The biquadratic coupling between the tilt and polarization is added to the usual bilinear coupling in the Landau free energy density expansion describing the SmA - SmC* transition. The effect on the temperature dependence of the tilt, spontaneous polarization and the pitch of the helix is studied. The results agree qu…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBlock copolymers near the microphase separation transition. 2. Linear dynamic mechanical propertiesFrank S. BatesCite this: Macromolecules 1984, 17, 12, 2607–2613Publication Date (Print):December 1, 1984Publication History Published online1 May 2002Published inissue 1 Decemb…
Heterocyclic conducting polymer films are prepared by the oxidative cationic polymerization of thiophene, pyrrole and furan. Electrical and optical properties of these polymer films are similar to those using electrochemically prepared polythiophene, polypyrrole and polyfuran.
A simple method for measuring frictional stresses between the mairix and individual fibers in a ceramic composite is described. A standard microhardness indenter is used to apply a force to the end of the fiber and depress it below the matrix surface. The frictional stress is calculated from measurement of the applied…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe 1- and 2-dimensional tungsten-183 and vanadium-51 NMR characterization of isopolymetalates and heteropolymetalatesPeter J. DomailleCite this: J. Am. Chem. Soc. 1984, 106, 25, 7677–7687Publication Date (Print):December 1, 1984Publication History Published online1 May 2002…
The green primary compound of chloroperoxidase was prepared by freeze-quenching the enzyme after rapid mixing with a 5-fold excess of peracetic acid. The electron paramagnetic resonance (EPR) spectra of these preparations consisted of at least three distinct signals that could be assigned to native enzyme, a free radi…
The growth rate and final size of developing organs is controlled by organ-intrinsic mechanisms as well as by hormones and growth factors that originate outside the target organ. Recent work on Drosophila imagined discs and other regenerating systems has led to the conclusion that the intrinsic growth-control mechanis…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular order in condensed states of semiflexible poly(amic acid) and polyimideNobuyuki Takahashi, Do Y. Yoon, and William ParrishCite this: Macromolecules 1984, 17, 12, 2583–2588Publication Date (Print):December 1, 1984Publication History Published online1 May 2002Publish…
We report the first observation of the modulation doping effect in Si/Ge0.2Si0.8 heterojunctions grown by molecular beam epitaxy. Peak hole mobilities of ∼3300 cm2 V−1 s−1 have been observed at 4.2 K. These values, although nonoptimum, are comparable to the best reported values for holes in Si/SiO2 inversion layers. L…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReentrant phase transition in acrylamide-derivative copolymer gelsSeiji Katayama, Yoshitsugu Hirokawa, and Toyoichi TanakaCite this: Macromolecules 1984, 17, 12, 2641–2643Publication Date (Print):December 1, 1984Publication History Published online1 May 2002Published inissue…
The development of hot‐pressed Sic‐whisker‐reinforced alumina has resulted in composites with fracture toughness values ∼;8.7 MPa·m 112 at 20 vol% SiC. Whisker orientation during processing leads to anisotropy in both fracture toughness and fracture strength. Fracture strengths are also limited by the ability to dispe…
The aim of this work is the study of the U.V. radiations effects on plasticized Poly (vinyl chloride) used as waterproofing membrane in Building and also in Public Works. The ageing fact due to U.V. radiations has been followed for 3.000 hours, checking the changes produced in the composition of the material, on its m…
This work, which follows on from previous ones, studies the development of the solid-stage quantity formed in ASTM D 1141-75 artificial sea-water, in which the series of samples of mortar (1:3), made up of a portland cement resistant to sulfate (cement 2 < > P 450-Y) and the mixtures: cement 2/slag = 85/15, 65/35, 40/…
This theoretical and experimental study on cement or lime and cement mortars brings up to date the contents of Chapter 3: MORTARS, of Norm MV 201-1972 "Resistant brick-work walls" which lost its validity when disappeared portland cement P-250, substituted by portland cement PA-350 with active additions, prescribed in…
In this article, the author has the purpose to give a general view of the applications of the automatic equipment of X ray diffraction purchased by the I.E.T.c.c., quoting the main software programs used by the team in its qualitative, quantitative and crystallographic analysis, as well as to give a simplified account…
Transmission zone plates composed of materials describable by the complex index of refraction n^[n^=(1-δ)+ik] modulate both the amplitude and the phase of the light passing through them. In this paper, a general variational approach to the design of zone-plate profiles that maximize system transfer functions, such as…