Materials Literature
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The ohmic conductivity of the sol-gel derived Pb1+y(Zr0.3Ti0.7)O3 thin films (with the excess lead y=0.0 to 0.4) are investigated using low frequency small signal alternate current (AC) and direct current (DC) methods. Its temperature dependence shows two activation energies of 0.26 and 0.12 eV depending on temperatur…
Despite the fact that Josephson Junction Arrays (JAA) have been actively studied for decades, they continue to contribute to the variety of intriguing and peculiar phenomena (both fundamental and important for potential applications) providing at the same time a useful tool for testing new theoretical ideas. To give j…
Bulk textured MgB_2 material of nearly full density showing a weak c-axis alignment of the hexagonal MgB_2 grains parallel to the pressure direction was obtained by hot deformation of a stoichiometric MgB_2 pellet prepared by a gas-solid reaction. The texture of the material was verified by comparing the x-ray diffrac…
The ability of the cornea to transmit light while being mechanically resilient is directly attributable to the formation of an extracellular matrix containing orthogonal sheets of collagen fibrils. The detailed structure of the fibrils and how this structure underpins the mechanical properties and organization of the…
We describe the synthesis of water-soluble semiconductor nanoparticles and discuss and characterize their properties. Hydrophobic CdSe/ZnS core/shell nanocrystals with a core size between 2 and 5 nm are embedded in a siloxane shell and functionalized with thiol and/or amine groups. Structural characterization by AFM i…
This paper summaries two sets of tension-tension fatigue results. The first set corresponds to low R ratio (0.1) and low frequency (1Hz), whereas the second set covers high R ratio (0.9) and high frequency (10Hz). For the former, detailed analysis of stress strain loops is conducted in connection with the underlying m…
Local structure around Ge in Si/Ge superlattices containing the “inverted hut” nanocrystals has been investigated by using the extended x-ray absorption fine structure (EXAFS) technique. In contrast to the usual nanometer-sized Ge “hut clusters” commonly grown on top of Si layers using the conventional Stranski–Krasta…
The aim of this work is to investigate the performance of Internal Reforming Solid Oxide Fuel Cell (IRSOFC) and Gas Turbine (GT) combined cycles. A mathematical model of the IRSOFC steady-state operation was presented in Part A of this work (Massardo and Lubelli, 1998), coupled to the thermodynamic analysis of a numbe…
Abstract To control molecular mobility and study its effects on mechanical properties, we synthesized two series of poly(ester carbonate) and polycarbonate copolymers with different linkages: (B x t) n ( x = 3, 5, 7, 9) and (B x T) n ( x = 1, 3, 5, 7, 9), where t represents the terephthalate, T represents the tetramet…
Carbon-nanotube tips are plastically deformed during field emission. High-resolution transmission electron microscopy and structural simulations suggest that the deformed structure of the closed nanotube is explained by heterogeneous nucleation of the pentagonal and heptagonal carbon ring pairs, and that of the opened…
The exchange interactions in polycrystalline samples of Ca1-xLaxMnO3 (0.00< or =x< or =0.05) are studied by means of Raman scattering and electron paramagnetic resonance. Dramatic reductions in the spin-phonon interactions and magnetic correlations are observed for La doping levels as small as approximately 2%-3%. The…
We have used an atomic-force microscope tip to mechanically buckle single-walled carbon nanotubes. The resistance of the induced defects ranged from 10 to 100 kΩ and varied with the local Fermi level, as determined by scanned-gate microscopy. By forming two closely spaced defects on metallic nanotubes, we defined quan…
Adsorption of lithium and hydrogen onto carbon nanotubes has been modeled using a neglect of diatomic differential overlap semiempirical calculation. Our results predict that lithium can be adsorbed on zig-zag nanotubes with a charge transfer, an adsorption energy, and a vibration frequency which depend on the tube ra…
Finite element modeling of bird impacts has been developed and calibrated using the 3-D impact analysis code MSC/DYTRAN. These modeling efforts have shown that the Arbitrary Lagrange Euler (ALE) formulation within MSC/DYTRAN is capable of capturing the physics of the bird impact problem, producing impact pressures and…
A photoluminescent porous silicon microcavity is exposed to saturated vapor of ethanol. The ethanol substitutes the air inside the pores giving rise to a progressive monotonic redshift of the interference pattern of the photoluminescence spectrum. On the other hand, the photoluminescence intensity of the cavity peak o…
The electronic structure of a single pentagon in a hexagonal carbon lattice has been revealed on an atomic scale by scanning tunneling microscopy. The pentagon is located at the apex of the conical protuberance of the graphitic particle. The enhanced charge density localized at each carbon atom in the pentagon is iden…
The electronic and optical properties of the new cubic spinel nitrides $c\ensuremath{-}{\mathrm{Si}}_{3}{\mathrm{N}}_{4},$ $c\ensuremath{-}{\mathrm{Ge}}_{3}{\mathrm{N}}_{4},$ and that of the predicted double nitrides $c\ensuremath{-}{\mathrm{SiGe}}_{2}{\mathrm{N}}_{4}$ and $c\ensuremath{-}{\mathrm{GeSi}}_{2}{\mathrm{N…
Ultrabright ultrasmall (∼1 nm) blue luminescent Si29 nanoparticles are chlorinated by reaction with Cl2 gas. A Si–N linkage is formed by the reaction of the chlorinated particles with the functional amine group in butylamine. Fourier transform infrared spectroscopy and x-ray photospectroscopy measurements confirm the…
We study theoretically the spin dynamics of antiferromagnetic molecular rings, such as the ferric wheel Fe10. For a single nuclear or impurity spin coupled to one of the electron spins of the ring, we calculate nuclear and electronic spin correlation functions and show that nuclear magnetic resonance (NMR) and electro…
Monocrystalline ZnO columns grown in electrodeposition were converted to ZnS using ion exchange reactions in H2S or S vapor. At ∼400 °C the reaction with H2S only affects a thin layer of 10–30 nm thickness at the surface of the ZnO crystallites, and ZnS-coated ZnO columns are produced. Exploiting the large difference…