Materials Literature
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The free volume of a bisphenol-A-type epoxide oligomer (DGEBA) was studied using Williams–Landel–Ferry parameters and thermal expansion coefficients above and below the glass transition temperature (Tg). The values of the free-volume fraction at the Tg are around 0.02 for the DGEBA oligomers having weight-average mole…
The structures and properties of BR/CR/SBS blends were studied by using optical, electron microscopy, FTIR methods, etc. Results showed that the addition of a small amount of SBS to the thermodynamically immiscible blends BR/CR could significantly promote fine and homogeneous dispersion of the system, increase crossli…
We present the results of an experimental and numerical study of the effects of a steady magnetic field on sidewall convection in molten gallium. The magnetic field is applied in a direction which is orthogonal to the main flow which reduces the convection and good agreement is found for the scaling of this effect wit…
This paper reports on the influence of maleated polypropylene (MAPP) on the properties of polypropylene (PP)/newspaper flour (PF) composite, and the compatibilization mechanism was also studied. The results of mechanical tests and scanning electron microscope (SEM) showed that MAPP was a true coupling agent for PP/PF…
The fabrication of near-micrometer-sized close-packed coherent microlens arrays on spheric or aspheric surfaces has been accomplished by use of a compact holographic projector system that was developed for producing multimicrometer down to submicrometer grid patterning on curved surfaces. The microlens arrays, which c…
Modification of polyolefin surfaces is often necessary to achieve improved printability, lamination, etc. Although corona discharge and flame treatments can produce the higher surface energy needed for these applications, the properties of the resulting surfaces are not always optimal. Atmospheric pressure plasma is a…
The coordinate-transformation-based differential method of Chandezon et al. [J. Opt. (Paris) 11, 235 (1980); J. Opt. Soc. Am. 72, 839 (1982)] (the C method) is one of the simplest and most versatile methods for modeling surface-relief gratings. However, to date it has been used by only a small number of people, probab…
Despite occasional references in the older literature to the ability of gold to catalyze certain reactions, the metal has until recently had the reputation of being one of the least catalytically useful. The recent discovery that some supported gold catalysts can affect the oxidation of carbon monoxide at or below amb…
A method is described by which the disulfide dimer of 2,5-dimercapto-1,3,4-thiadiazole (diDMcT, see Scheme 1) can be oxidatively intercalated into the layered structure of a V 2 O 5 xerogel. This intercalation reaction produces a new organic−inorganic composite material with a layer spacing of 13.5 Å, in contrast to t…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTSynthesis of Symmetrical N,N'-Disubstituted Thioureas and Heterocyclic Thiones from Amines and CS2 over a ZnO/Al2O3 Composite as Heterogeneous and Reusable CatalystMarco Ballabeni, Roberto Ballini, Franca Bigi, Raimondo Maggi, Mauro Parrini, Giovanni Predieri, and Giovanni Sart…
The electronic structure of finite-length armchair carbon nanotubes has been studied using several ab-initio and semiempirical quantum computational techniques. The additional confinement of the electrons along the tube axis leads to the opening of a band-gap in short armchair tubes. The value of the band-gap decrease…
The frictional indentation of a semi–infinite dilatant granular mass is examined assuming plane strain conditions. Complete solutions are provided for the problem of indentation by a flat punch and a wedge. Several important results arising from this study include (i) a generalization of Prandtl's solution for the fla…
When an asymmetric bubble collapses it generally produces a well–defined high–velocity jet. This is remarkable because one might expect such a collapse to produce a complex or chaotic flow rather than an ordered one. I present a dimensional argument for the ubiquity of jets from collapsing bubbles, and model the asphe…
We report results from multicanonical simulations of poly-alanine. Homopolymers of up to 30 amino acids were considered and various thermodynamic quantities as a function of temperature calculated. We study the nature of the observed helix–coil transition and present estimates for critical exponents.
Homogeneous electron-transfer kinetics for the oxidation of seven different iron(III) porphyrins using three different oxidants were examined in deaerated acetonitrile, and the resulting data were evaluated in light of the Marcus theory of electron transfer to determine reorganization energies of the rate-determining…
The on–off intermittent behavior of emission from single CdSe/CdS core/shell nanocrystals was investigated as a function of temperature and excitation intensity. Off times were found to be independent of excitation power and the temperature dependence reveals substantial reduction in the number of on–off cycles prior…
Dispersions of colloidal particles in cholesteric liquid crystals form an unusual solid by stabilizing a network of linear defects under tension in the ideal layered structure of the cholesteric. The large length scales of the cholesteric liquid crystals allowed direct observation of the network structure, and its pro…
Three things largely determine the electronic properties of a crystal: the energy levels of the atoms or lattice sites, the coupling between adjacent sites, and the symmetry of the solid. Imagine being able to control each of these properties separately, and therefore being able to “design” a solid with a prescribed s…
Colloidal metal aerogels are composite nanoscale materials that combine the high surface area and porosity of aerogels with the unique optical and physical properties of metal colloids. As such, they are being developed as advanced sensor, catalytic, and electrocatalytic materials. We have prepared colloidal gold−sili…
Ruthenium dioxide is an important electrode material for applications in electrocatalysis and power sources. High surface areas are achieved in hydrous RuO 2 precipitates and in mixed ruthenium oxide−titanium oxide, (Ru−Ti)O x, aerogels (in which nanoscale domains are networked to form a highly porous structure). The…