Materials Literature
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Coiled carbon nanotubes were produced catalytically by thermal decomposition of hydrocarbon gas. After deposition on a silicon substrate, the three-dimensional structure of the helix-shaped multiwalled nanotubes can be visualized with atomic force microscopy. Helical structures of both chiralities are present in the n…
Raman spectra of single-wall carbon nanotubes (SWCNTs) were measured at different temperatures by varying the incident laser power. The elevated temperature of the SWCNTs and multiwall carbon nanotubes (MWCNTs) is confirmed to be due to the presence of impurities, defects, and disorder. The temperature coefficient of…
We propose using blue cooperative upconversion of ytterbium (Yb3+) ions produced by a one-color one-beam pumping scheme for a three-dimensional fluorescence display. The results are presented using a diode laser as a pump source emitting at 973 nm, and the sample used was a multicomponent sol-gel-processed silica glas…
Pressure-induced structural transformation in cubic silicon carbide is studied with the isothermal-isobaric molecular-dynamics method using a new interatomic potential scheme. The reversible transformation between the fourfold coordinated zinc-blende structure and the sixfold coordinated rocksalt structure is successf…
Time resolved magnetization measurements have been performed on a spin 1/2 molecular complex, so-called V15. Despite the absence of a barrier, magnetic hysteresis is observed over a time scale of several seconds. A detailed analysis in terms of a dissipative two-level model is given, in which fluctuations and splittin…
Decoherence mechanisms in crystals of weakly anisotropic magnetic molecules, such as V15, are studied. We show that an important decohering factor is the rapid thermal fluctuation of dipolar interactions between magnetic molecules. A model is proposed to describe the influence of this source of decoherence. Based on t…
Electronic transport properties through junctions in nanographite ribbons are investigated using the Landauer approach. In the low-energy regime ribbons with zigzag boundary have a single conducting channel of edge states. The conductance as a function of the chemical potential shows a rich structure with sharp dips o…
Surface enhancement factors of at least 10(12) for the Raman scattering of single-walled carbon nanotubes in contact with fractal silver colloidal clusters result in measuring very narrow Raman bands corresponding to the homogeneous linewidth of the tangential C-C stretching mode in semiconducting nanotubes. Normal an…
The reconstructed anatase ${\mathrm{TiO}}_{2}(001)$ surface has been investigated by low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), and angle-resolved mass spectroscopy of recoiled ions (AR-MSRI). Prior investigations have observed or considered only a $(1\ifmmode\times\else\texttimes\…
The investigation of the field emission (FE) properties of carbon nanotube (CNT) films by a scanning anode FE apparatus, reveals a strong dependence on the density and morphology of the CNT deposit. Large differences between the microscopic and macroscopic current and emission site densities are observed, and explaine…
Ordered semiconductor ZnO nanowire arrays embedded in anodic alumina membranes (AAM) were fabricated by generating alumina templates with nanochannels, electrodepositing Zn in them, and then oxidizing the Zn nanowire arrays. The polycrystalline ZnO nanowires with the diameters ranging from 15 to 90 nm were uniformly a…
Using highly sensitive Moiré interference technology, the full deformation around the austenite-martensite (A-M) interface during stress-induced martensitic transformation of polycrystal NiTi shape memory alloys (SMA) thin strips are recorded; and the deformation features of the A-M interface are revealed. The nominal…
How, in principle, could one solve the atomic structure of a quasicrystal, modeled as a random tiling decorated by atoms, and what techniques are available to do it? One path is to solve the phase problem first, obtaining the density in a higher dimensional space which yields the_averaged_ scattering density in 3-dime…
To test whether distances derived from paramagnetic broadening of (15)N heteronuclear single quantum coherence (HSQC) resonances could be used to determine the global fold of a large, perdeuterated protein, we used site-directed spin-labeling of 5 amino acids on the surface of (15)N-labeled eukaryotic translation init…
The solubility of sodium gluconate in water and in aqueous ethanol and methanol solutions was measured, over the temperature range 10 °C to 50 °C. The measurements were performed with ethanol solutions of (0 to 1.2) g of ethanol/g of water and with methanol solutions of (0 to 1.4) g of methanol/g of water. An equation…
Transient electric birefringence decay studies of the rotation of rodlike polymers in solutions with spherical particles have been performed as a function of the sphere volume fraction. The rodlike polymers are helical poly-γ-benzyl, α-L-glutamates of several lengths. The spheres are coated silica particles and the so…
The work is motivated by the experimental observation of B. Chu et al. [Macromolecules 28, 180 (1995)] which suggests that, while polymer globules in dilute solution in poor solvent are supposed to be very sticky, in actuality they collide many hundreds of times before merging and before aggregation starts. We argue t…
The method of calculating distributed polarizabilities is extended to the first and second dipole hyperpolarizabilities, in order to describe more accurately the molecular response to strong and inhomogeneous external time-dependent electric fields. The dipolar response is expressed in terms of both potential related…
The AM1 scheme extended to d orbitals, AM1/d, has been parametrized for molybdenum. Computational results on structures and energetics of a series of molybdenum compounds are compared with experimental data. The mean absolute error of bond lengths is 0.044 Å (83 comparisons) and that of X−Mo−Y angles is 3.3° (65 compa…
A series of experiments and simulations that vary the texture and microstructure simultaneously are used to establish the role of the microstructure in texture formation in FCC metals. The stacking fault energy (SFE) of the metal, which is known to have a strong impact on texture and microstructure, is the vital param…