Materials Literature
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Using a realistic many-body potential, we have simulated the properties of double-walled carbon nanotubes with the aim of investigating the role of lip-lip interactions on nanotube growth. Surprisingly, the lip-lip interaction by itself does not stabilize open-ended growth, but rather facilitates tube closure by media…
Neutron and high-resolution synchrotron x-ray diffraction measurements have indicated a tetragonal zirconia phase with both an axial ratio of unity and internal shear deformation: The oxygen displacements from ideal fluorite positions of 0.088 and 0.078 Å are observed for 65 and 70 mol % CeO2–ZrO2 samples, respectivel…
A continuum-space bead-spring model is used to study the phase behavior of binary blends of homopolymers and the structure of the interface between the two immiscible phases. Results of numerical simulations using molecular dynamics supplemented by Monte Carlo exchanges are presented. The structure of the interface is…
The single quasicrystal elastic moduli ${c}_{\mathrm{ij}}$ of decagonal Al-Ni-Co were determined using resonant ultrasound spectroscopy at selected fixed temperatures in the range between 5 and 290 K. Decagonal Al-Ni-Co is found to be transversely elastically isotropic to $(0.02\ifmmode\pm\else\textpm\fi{}0.04)%$. The…
The optical and physical properties of a low-voltage phosphor, SrGa2S4:Eu2+, are reviewed. This phosphor has excellent chromaticity and high luminous efficiency at excitation voltages <3 kV and at high drive current (∼100 μA/cm2). At high current densities this phosphor was found to have superior saturation pro…
Concentrations of defects in amorphous ${\mathrm{SiO}}_{2}$ created by implantation of 10 MeV protons were examined. The depth profile of Si-Si bonds, ${E}^{\ensuremath{'}}$ centers, or peroxy radicals (PORs) was close to that of electronic energy loss. Interstitial ${\mathrm{O}}_{2}$ molecules were identified and the…
Mössbauer spectra have been recorded in fields of up to 13 T from a single crystal of cut perpendicular to the [111] axis. The spectra were best fitted with five magnetic components complementing studies on a crystal cut normal to a [100] axis. One component corresponds to situated on the tetrahedral A sites of the in…
Single cavitation bubble luminescence is investigated. The cavitation bubbles are produced by focused laser light and collapse under the action of the ambient pressure. Both spherical and aspherical collapse is studied. Luminescence is observed in both cases, but only up to a mildly aspherical collapse.
We present a simple and direct proof that the exchange-correlation hole, and therefore the exchange-correlation energy, in a polarized insulator is not determined by the bulk density alone. It is uniquely characterized by the density and the macroscopic electric polarization of the dielectric medium.
A matching algorithm for the identification of backbones in percolation problems is introduced. Using this procedure, percolation backbones are studied in two- to five-dimensional systems containing 1.7x10^7 sites, two orders of magnitude larger than was previously possible using burning algorithms.
Using a combination of first-principles total energies, a cluster expansion technique, and Monte Carlo simulations, we have studied the Li/Co ordering in LiCoO_2 and Li-vacancy/Co ordering in CoO_2. We find: (i) A ground state search of the space of substitutional cation configurations yields the (layered) CuPt struct…
We report the observation of single nanotube fragmentation, under tensile stresses, using nanotube-containing thin polymeric films. Similar fragmentation tests with single fibers instead of nanotubes are routinely performed to study the fiber-matrix stress transfer ability in fiber composite materials, and thus the ef…
The explanation is presented for the temperature dependence of the fourfold intensity peak splitting found recently in diffuse scattering from the disordered Cu3Au alloy. The wavevector and temperature dependence of the self-energy is identified as the origin of the observed behaviour. Two approaches for the calculati…
The relationship between the type of activator and the morphology of polycaproamide (PCA) powders was investigated. The powders were prepared by anionic polymerization of caprolactam in ethylbenzene using sodium caprolactamate as initiator and CO2, diisopropylcarbodiimide, and dicyclohexylcarbodiimide as activators. T…
Meltblown is one of the fastest growing processes for nonwoven production. The design of the coat-hanger geometry of a die is very important for meltblown technology. In this article, melt rheological properties were studied based on capillary rheometry, followed by analysis and simulation of the melt flow in the die…
Effects of catalyst acidity and the restricted reaction volume afforded by HZSM-5 on the catalytic cracking of polypropylene are described. Polypropylene cracking by silica—alumina and HZSM-5 catalysts yields olefins as primary volatile products. In addition, HZSM-5 channels restrict carbenium ion rearrangements and f…
(1,2-Naphthalocyaninato)lutetium(III), bis(1,2-naphthalocyaninato)lutetium(III), and tris(1,2-naphthalocyaninato)dilutetium(III) have been synthesized in good yields. These complexes were characterized by UV-visible, (1)H NMR, and mass spectroscopies and by electrochemical techniques. Bis(1,2-naphthalocyaninato)luteti…
The structures and electrical properties of four NASICON compositions, Na 1.4 M 1.6 In 0.4 (PO 4 ) 3 (M = Ti, Sn, Hf, Zr), have been determined and compared. Rietveld refinement of powder X-ray diffraction data confirmed the basic rhombohedral NASICON structure with random occupancy of the octahedral In/M sites, full…
The success of the "Cluster Variation Method" (CVM) in reproducing quite accurately the free energies of Monte Carlo (MC) calculations on Ising models is explained in terms of identifying a cancellation of errors: We show that the CVM produces correlation functions that are too close to zero, which leads to an overest…
As part of a series of studies on energy transfer processes between optical centers in condensed matter, an analysis is made of the problem of a crystalline system made up by a majority of regular optical centers and small amounts of defective optical centers. Within the conceptual framework of the crystal model, anal…