Materials Literature
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The distribution of gallium/germanium in the type-I clathrates Sr8Ga16Ge30 and Sr4Eu4Ga16Ge30 over the three crystallographically distinct framework sites has been determined by resonant diffraction. The analyses indicate a strong preference for the occupation of the 6c site by gallium. This is consistent with theoret…
In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local m…
To understand and improve the applications of titanium-oxide nanoparticles, it is extremely important to perform a detailed investigation of the surface and the interior structural properties of nanocrystalline materials, such as rutile and anatase with diameter of few nanometers. Here, x-ray absorption spectroscopy h…
Two molecular triads consisting of a porphyrin (P) covalently linked to a fullerene electron acceptor (C60) and a π-extended tetrathiafulvalene electron donor (TTF) have been synthesized. Time resolved spectroscopic investigations of the triad featuring a free base porphyrin moiety (TTF–P2H–C60) show that in 2-methylt…
A new Monte Carlo algorithm is implemented for simulation of the density of states of free-standing polymer films. The algorithm combines the original idea of conducting a random walk in energy space with advanced trial moves such as configurational bias and end-bridging. Excellent agreement is found between the resul…
White electroluminescence (EL) was observed from hydrogenated amorphous-SiNx-based light-emitting device. Silicon nitride thin films were deposited on the indium-tin-oxide (ITO)-coated glass substrate by plasma enhanced chemical vapor deposition method with a mixture of Ar-diluted 5% SiH4 and pure N2 gases, in the rat…
We study the equilibrium behavior and dynamics of a polymer collapse transition for a system composed of a short Lennard-Jones (LJ) chain immersed in a LJ solvent for solvent densities in the range of ρ=0.6–0.9 (in LJ reduced units). The monomer hydrophobicity is quantified by a parameter λ∈[0,1] which gives a measure…
The kinetic interplay between crystal superstructure growth and late-stage liquid phase coarsening in a polymer blend has been examined. By controlling the relative quench depths for liquid–liquid phase separation and crystallization, the growth kinetics of the characteristic length scales of the simultaneous ordering…
A mode-coupling theory for dense polymeric systems is developed which unifyingly incorporates the segmental cage effect relevant for structural slowing down and polymer chain conformational degrees of freedom. An ideal glass transition of polymer melts is predicted which becomes molecular-weight independent for large…
We use dynamical low-energy electron diffraction (LEED) to determine the surface structure of $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}(0001).$ Sapphire surfaces are prepared in three different ways, and the diffraction results are analyzed using an exhaustive search of possible models. For a…
Surfaced-enhanced Ramon scattering (SERS) spectra of pyrazine are analyzed on the basis of the properties of the electronic states of the metal-adsorbate surface complex. Ab initio CIS calculations have been carried out for the Ag2-pyrazine complex, which have enabled us to find two excited singlets, namely CT0;1B1 an…
Carbon nanostructures of different kinds have been synthesized by chemical vapor deposition. By modifying the deposition temperature, the catalyst material, and the hydrocarbon, nanofibers with herringbone structure, multi-walled nanotubes with tubular structure, and single-walled nanotubes were deposited. The nanostr…
We have studied the oxygen-isotope effects on T_{c} and in-plane penetration depth λ_{ab}(0) in an optimally doped 3-layer cuprate Bi_{1.6}Pb_{0.4}Sr_{2}Ca_{2}Cu_{3}O_{10+y} (T_{c} \sim 107 K). We find a small oxygen-isotope effect on T_{c} (α_{O} = 0.019), and a substantial effect on λ_{ab} (0) (Δλ_{ab} (0)/λ_{ab} (0…
We recently have shown that a negative streamer in a sufficiently high homogeneous field can branch spontaneously due to a Laplacian instability, rather than approach a stationary mode of propagation with fixed radius. In our previous simulations, the streamer started from a wide initial ionization seed on the cathode…
A method for incorporating electromagnetic fields into empirical tight-binding theory is derived from the principle of local gauge symmetry. Gauge invariance is shown to be incompatible with empirical tight-binding theory unless a representation exists in which the coordinate operator is diagonal. The present approach…
We review various isotope effects in the high-T_c cuprate superconductors to assess the role of the electron-phonon interaction in the basic physics of these materials. Of particular interest are the unconventional isotope effects on the supercarrier mass, on the charge-stripe formation temperature, on the pseudogap f…
Quantitatively-unexplained stationary waves or ridges often encircle icicles. Such waves form when roughly 0.1 mm-thick layers of water flow down the icicle. These waves typically have a wavelength of 1cm approximately independent of external temperature, icicle thickness, and the volumetric rate of water flow. In thi…
A pulse-modulated plasma irradiation technique was applied to hydrogenation of ZnO. Three kinds of ZnO samples were employed to investigate the electronic state of hydrogen in ZnO. Secondary-ion-mass-spectroscopy analysis using isotope tracer revealed that the surface layer to 100 nm was doped with hydrogen after the…
Preface.Introduction, Safety and Instrumentation. The Chemical Dissolution of Silicon. The Semiconductor--Electrolyte Junction. The Electrochemical Dissolution of Silicon. Anodic Oxidation. Electrochemical Pore Formation. Microporous Silicon. Mesoporous Silicon. Macroporous Silicon. Applications.AppendicesSupplier Ref…
Polymer Science and Technology, Chonbuk National University, Chonju, Chonbuk 561-756, KoreaDepartment of Chemistry, Kunsan National University, Kunsan, Chonbuk 573-701, KoreaReceived November 27, 2001Keywords : Raman, Liquid crystal, Intermolecular interaction, Coil effect, Hydrogen bonding.IntroductionLiquid crystall…