Materials Literature
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Silicones have become established in a wide variety of applications ranging from electronics to personal care products. It has been estimated recently that there are approximately 3000 commercial silicone products. These are made up from silicone fluids, elastomers and resins. Many hybrid materials also exist whereby…
The freezing-in phenomena that occurred in some orientationally disordered crystals and liquid crystals, either in the metastable or in the stable state, are described in comparison with those in liquids. These observations indicate clearly that the glass transitions observed exclusively in liquids are just one exampl…
Potassium-functionalised alumina (6 wt.% K–Al2O3) was obtained by calcination at 973 K of pure alumina particles (Al2O3) impregnated with an aqueous solution of K2CO3. Both Al2O3 and K–Al2O3 were, then, impregnated with aqueous RhCl3·3H2O, dried at 393 K, and in situ reduced in H2 atmosphere to obtain 1 wt.% Rh/Al2O3…
Powder samples of the magnetically diluted cubic perovskite phases Sr2Fe1 − xGaxTaO6 have been prepared by high temperature ceramic methods. X-Ray powder diffraction data show that the cations occupying the 6-coordinate site are chemically disordered in the range 0.10 ≤ x ≤ 0.40 and that increasing the Ga3+ concentrat…
Microporous hexagonal niobium phosphate synthesized using neutral surfactants of molecular length, C6 to C10 hydrocarbons, by a supramolecular templating mechanism (S0I0) possesses strong hydrophilic character, which leads to high selectivity for catechol formation (95.3%) in the presence of protic solvent (MeOH) in t…
The techniques which allow the numerical evaluation of the statistical properties of the potential energy landscape for models of simple liquids are reviewed and critically discussed. Expressions for the liquid free energy and its vibrational and configurational components are reported. Finally, a possible model for t…
There is a growing belief that the mode coupling theory is the proper microscopic theory for the dynamics of the undercooled liquid above and around a critical temperature T c . In addition, there is some evidence that the system leaves the saddle points of the energy landscape to settle in the valleys at this critica…
We propose that the concept of liquids characterized by a given locally preferred structure (LPS) could help in understanding the observed phenomenon of polyamorphism. 'True polyamorphism' would involve the competition between two (or more) distinct LPSs, one favoured at low pressure because of its low energy and one…
“Picotubes”: A chiral tube is formed in the surprisingly clean Friedel–Crafts alkylation of a fully conjugated tubelike structure. Unlike helical carbon nanotubes synthesized at high temperatures, this chemically modified picotube is chiral by substitution. The two enantiomers were separated by chromatography on a chi…
The rheological behaviour of soft glassy materials results essentially from the interplay between shearing forces and an intrinsic slow dynamics. This competition can be described by a microscopic theory, which can be viewed as a nonequilibrium schematic mode-coupling theory. This statistical mechanics approach to rhe…
We show that the phonon–saddle transition in the ensemble of generalized inherent structures (minima and saddles) happens at the same point as the dynamical phase transition in glasses, that has been studied in the framework of the mode coupling approximation. The boson peak observed in glasses at low temperature is a…
We present structural and dynamical results of molecular dynamics simulation of vitreous silica undergoing a hydrostatic compression and decompression cycle at room temperature. Structural results as a function of density compare fairly well with experiments as well as with the longitudinal and transverse sound veloci…
Photolysis of perfluoroazooctane with diamond powders led to chemical modification of the surface with the introduction of perfluorooctyl ester and ether functional groups, the presence of which was confirmed by means of FT-IR, XPS and 19F NMR measurements.
In this work, we review, extend and discuss low-temperature specific-heat experiments, that we have conducted on different molecular (hydrogen-bonded) solids both in crystalline and glassy (either amorphous or orientationally disordered) phases. In particular, we have measured the low-temperature specific heat C p for…
RTV siloxane rubbers have been thermally aged in inert gas atmospheres and in the presence of moisture at temperatures up to 190°C. Toluene extractable matter measurements showed an increase in the levels of non-network fragments with age for those samples aged in sealed containers. Samples aged open to air did not sh…
Linear and Fourier-transform rheology were used to study the influence of the oscillatory shear amplitude, γ 0 , on the isothermal crystallization at 140 ° C of three commercial isotactic polypropylenes. The development of the crystallization was monitored through the time dependence of the dynamic storage modulus, G…
The dynamical behaviours of glass-forming liquids have been analysed extensively via computer simulations of model liquids, among which the Kob–Andersen binary Lennard-Jones mixture has been a widely studied system. Typically, studies of this model have been restricted to temperatures above the mode coupling temperatu…
The ageing of various glass forming materials (polycarbonate, polystyrene, polyvinyl acetate and triphenylethene) has been studied by differential scanning calorimetry. The variation of the relaxation enthalpy Δ H with the ageing time measured in a large domain of time is compared to the variation of volume Δ V report…
Newtonian viscosities of 19 multicomponent natural and synthetic silicate liquids, with variable contents of SiO 2 (41–79 wt%), Al 2 O 3 (10–19 wt%), TiO 2 (0–3 wt%), FeO tot (0–11 wt%); alkali oxides (5–17 wt%), alkaline-earth oxides (0–35 wt%), and minor oxides, obtained at ambient pressure using the high-temperatur…
Superconducting ${\mathrm{LaGe}}_{5}$ was synthesized by the reaction of La and Ge mixtures under a pressure of 5 GPa at 1200 \ifmmode^\circ\else\textdegree\fi{}C. It crystallized in the orthorhombic space group Immm (No. 71) with $a=4.0290(6),$ $b=6.307(1),$ and $c=9.978(2)\AA{},$ $V=253.54(6){\AA{}}^{3},$ and $Z=2.$…