Materials Literature
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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…
[structure: see text] The synthesis, solution redox behavior, EPR, and intramolecular charge transfer properties of novel donor-acceptor diads of TTF-sigma-A type (TTF = substituted tetrathiafulvalene, sigma = saturated spacer, A = polynitrofluorene acceptor) are reported. The HOMO-LUMO gap for compound 6 is as small…
This paper describes the development of an ASPEN PLUS simulation model for a commercial NO x abatement system involving both absorption and selective catalytic reduction (SCR). The model helps identify operator guidelines and retrofit options needed to enable the commercial system to operate efficiently during surges…
Octahedral complexes of transition metal ions with d(2) and d(8) electron configurations have triplet electronic states with identical T(2g), A(2g), T(1g)((3)F), and T(1g)((3)P) symmetry labels. CASSCF and CASPT2 calculations indicate the predominant electronic configurations for each triplet state. The two (3)T(1g) s…
Water diffusion and its role on the proton conduction are discussed in the sol−gel-derived porous P 2 O 5 −SiO 2 glasses. The diffusion coefficient of water in the glass is ∼10 -7 cm 2 /s at room temperature. The electrical conductivity is proportional to the logarithm of the number of water molecules with three separ…
The redox behavior of Y 0.05 Ce 0.1 Zr 0.85 O 2 and Y 0.1 Ce 0.1 Zr 0.8 O 2 doped with copper(II) was studied by means of diffuse reflectance electronic spectra ( DRES), temperature-programmed reduction (TPR), and electron paramagnetic resonance (EPR) techniques. In the absence of copper, it has been demonstrated that…
Selective catalytic reduction (SCR) with NH3 remains as one of the most effective technologies controlling NOx emission from stationary sources. At low temperatures carbon exhibits higher catalytic activity in NOx reduction than conventional catalysts made of metal oxides or zeolites. In the present work, the rate of…
The effect of physical cross-linking in candidate cycloaliphatic and hydrophobic poly(urethane urea) (4,4'-methylenebis(cyclohexylisocyanate), H(12)MDI/hydroxy-terminated polybutadiene, HTPBD/hexamethylenediamine, HDA) and poly(ether urethane urea)s (H(12)MDI/HTPBD-PTMG/HDA) on the in vitro calcification and blood-mat…
The stiffness and plasticity of boron nitride nanotubes are investigated using generalized tight-binding molecular dynamics and ab initio total energy methods. Due to boron nitride (BN) bond rotation effect, compressed zigzag BN nanotubes are found to undergo anisotropic strain release followed by anisotropic plastic…
Copolymerizations of ω-pentadecalactone (PDL) with trimethylene carbonate (TMC) were studied using chemical and enzyme catalysts. By using stannous octanoate, methylaluminoxane (MAO), or aluminum isopropoxide, copolymerizations of PDL with TMC with 1:1 feed ratio resulted in either homo-polyTMC or PDL/TMC block copoly…
The interaction between the antiferroelectric helix and an electric field applied perpendicular to its axis is investigated, both experimentally and theoretically. A two-stage switching process is observed: (i) in the pretransitional regime the helix distorts and then unwinds to form a nonhelical antiferroelectric sta…