Materials Literature
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The syntheses, crystal and electronic structures, and linear optical properties of the new orthoborates LiMBO 3 (M = Sr, Ba) are reported here. These compounds, which crystallize in the monoclinic space group P 2 1 / n with cell dimensions a = 6.476(2), b = 6.684(3), c = 6.843(3) Å, β = 109.41(3)°, and Z = 4 for M = S…
Two new bis(ether anhydride)s, 2,2‘-dimethyl-4,4‘-bis[4-(3,4-dicarboxyphenoxy)]biphenyl dianhydride ( 4A ) and bis[4-(3,4-dicarboxy phenoxy)phenyl]diphenylmethane dianhydride ( 4B ), were prepared in three steps starting from nitrodisplacement of 4-nitrophthalonitrile with 2,2‘-dimethylbiphenyl-4,4‘-diol and bis(4-hyd…
A novel biphenylneolignan, 2,6,2',6'-tetramethoxy-4,4'-bis(2,3-epoxy-1-hydroxypropyl)biphenyl (1), and two new glycosides named atratoglaucosides A (2) and B (3), were isolated from the roots of Cynanchum atratum, and their structures were determined on the basis of chemical and spectroscopic evidence. The aglycons of…
Abstract Thermal decomposition kinetics of diglycidyl ether of bisphenol A (DGEBA)/4,4′‐methylene dianiline (MDA) system with rubber‐modified MDA was studied by the methods of Ozawa, Kissinger, and Friedman, and the kinetic parameters were compared. The thermal decomposition data of the cured epoxy resin were analyzed…
Abstract A new isomer of the oxozirconium cluster Zr 4 O 2 (methacrylate) 12 was obtained by reaction of zirconium butoxide with an excess of methacrylic acid. Contrary to the known isomer, the structure is centrosymmetric with a planar, rhombic Zr 4 core. Copolymerization with a 56–207‐fold excess of methylmethacryla…
Abstract The grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission ele…
Abstract A diol‐based refined, bleached, and deodorized (RBD) palm kernel oil polyol was prepared. It was found that the polyurethane foam produced only gives a good compressive strength property at a 45 kg/m 3 molded density. The combination of sorbitol into the polyol system resulted in a better dimensional stabilit…
Abstract The driving forces for the recent development of nanoscale features in conventional ceramic materials for both mechanical and functional reasons are discussed, and the causes of some of the resulting property enhancements are identified. Examples from the technical literature are examined, and the potential f…
Structure factors based on periodic density-functional (DFT) calculations on 25 molecular crystals have been used to evaluate trends in refined values of the kappa and kappa' expansion-contraction parameters of the Hansen-Coppens multipole formalism. As found previously and expected physically, the spherical-valence-s…
Abstract Dispersions of very small metal particles in polymeric matrixes are scientifically and technologically important. Here, poly( N ‐vinylpyrrolidone) (PVP) filled with nanometric silver particles characterized by a narrow size distribution and a controlled average dimension has been obtained using a modification…
Mesoporous and well-mixed Pt/Ru alloys (1:1 atomic ratio) were prepared by co-reduction of metal salts in the hexagonal liquid crystalline phase of a nonionic surfactant. Preliminary data indicate that oxidation of carbon monoxide by the mesoporous alloy is more facile than by a commercial platinum catalyst or by meso…
Ion bombardment of carbon materials is known to cause erosion with energies far below the threshold energy of physical sputtering, as well as at temperatures below the threshold of thermal desorption. Generally regarded as chemical sputtering, this effect, and factors contributing to it, are not well understood. We us…
In this paper we demonstrate, using density-functional tight-binding theory, that certain classes of silicon-based tubular nanostructures are stable and energetically viable. Specifically, we consider silicide and SiH nanotubes. The structures adopted by these nanotubes are very similar to those of previously reported…
We have calculated the low-field magnetic susceptibility $χ$ of a system consisting of non-interacting mono-dispersed nanoparticles using a classical statistical approach. The model makes use of the assumption that the axes of symmetry of all nanoparticles are aligned and oriented at a certain angle $ψ$ with respect t…
Effects of magnetic impurity on the superconductivity has been investigated in Mg1-xMnB2. With increase of Mn concentration x, the lattice constant c (perpendicular to the boron sheet) decreases at a rate of -1.4 % (= dlnc/dx), while a remains nearly unchanged. The transition temperature Tc steeply decreases with $x$…
Metallic single-walled carbon nanotubes have been proposed to be good one-dimensional conductors. However, the finite curvature of the graphene sheet that forms the nanotubes and the broken symmetry due to the local environment may modify their electronic properties. We used low-temperature atomically resolved scannin…
Carbon nanotubes display either metallic or semiconducting properties. Both large, multiwalled nanotubes (MWNTs), with many concentric carbon shells, and bundles or "ropes" of aligned single-walled nanotubes (SWNTs), are complex composite conductors that incorporate many weakly coupled nanotubes that each have a diffe…
A detailed study of the energy-transfer processes in ${\mathrm{Er}}^{3+}:$ flouride glasses with doping concentrations of 0.2--18 mol % is presented. Fluorescence wave forms for 11 erbium transitions were measured under 802-nm, 1.5-\ensuremath{\mu}m, 975-nm, 520-nm, and 403-nm excitation from a high-energy short-pulse…
We report the first direct, quantitative measurements of the shear aligning properties of a main-chain thermotropic liquid crystalline polymer (LCP). We find that a model thermotrope with alternating mesogen and spacer structure is of the shear aligning type throughout its nematic range. The director rotates uniformly…
The synthesis of block copolymers of 1,3-cyclohexadiene (1,3-CHD) and styrene under various conditions is reported. sec -Butyllithium alone can initiate the polymerization of 1,3-CHD but does not yield a living process due to chain transfer and termination reactions. However, certain additives such as tetramethylethyl…