Materials Literature
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Density functional calculations have been performed for many isomers of neutral carbon clusters Cn (4⩽n⩽32, n even) using both local spin density (LSD) and gradient-corrected (Becke–Perdew) approximations to the exchange-correlation energy. The stable isomers include chains, rings, cages, and graphitic (“plate ” and “…
We present the first successful attempt at calculating cluster full-potential x-ray absorption near-edge structure (XANES) spectra, based on the finite difference method. By fitting XANES simulations onto experimental spectra we are able to perform electron population analysis. The method is tested in the case of Ti $…
We study hydrogen-bond dynamics in liquid water at low temperatures using molecular dynamics simulations, and find results supporting the hypothesized continuity of dynamic functions between the liquid and glassy states of water. We find that average bond lifetime $(\ensuremath{\sim}1\mathrm{ps})$ has Arrhenius temper…
We present a detailed study of the electronic properties of CdSe nanocrystals in the absence and presence of a dielectric medium. The electronic structure of the nanocrystal is modeled within the framework of the empirical pseudopotential method. We use a real-space grid representation of the wave function, and obtain…
The shear viscosity of liquid ${\mathrm{Zr}}_{41.2}{\mathrm{Ti}}_{13.8}{\mathrm{Cu}}_{12.5}{\mathrm{Ni}}_{10.0}{\mathrm{Be}}_{22.5}$ has been measured. At the liquidus temperature we find an extremely high viscosity of 2.5 Pa s, favoring glass formation. At deep supercooling the time scales for the diffusion of small…
We have investigated the effects of nanometer-sized silver particles on the optical properties of Eu3+ ions in SiO2 glass. Glass samples were prepared by the sol-gel method. The mean particle size and volume fraction of silver particles, which were estimated from UV-VIS absorption spectra using Mie-Drude theory modifi…
The electronic structure of various nickel oxides with nickel valence varying from 1+ to 3+ was investigated with the aim to find similarities and differences to the isoelectronic cuprates. Only if the Ni ions are forced into a planar coordination with the O ions can a $S=1/2$ magnetic insulator be realized with the d…
We present measurements of the lattice thermal conductivity ${\ensuremath{\kappa}}_{\ensuremath{\perp}}$ normal to the interfaces of $(\mathrm{GaAs}{)}_{n}/(\mathrm{AlAs}{)}_{n}$ superlattices with n between 1 and 40 monolayers. The conductivity was measured by an optical pump-and-probe technique in the temperature ra…
Electronic and magnetic properties of ribbon-shaped nanographite systems with zigzag and armchair edges in a magnetic field are investigated by using a tight-binding model. One of the most remarkable features of these systems is the appearance of edge states, strongly localized near zigzag edges. The edge state in a m…
An advanced heat-resistant fiber (trade name Ekonol) spun from a nematic liquid crystalline melt of thermotropic wholly aromatic poly(p-oxybenzoate-p,p′-biphenylene terephthalate) has been subjected to a dynamic thermogravimetry in nitrogen and air. The thermostability of the Ekonol fiber has been studied in detail. T…
The thermal degradation and kinetics of poly(2,6-dimethylphenylene oxide) (PPO) were studied by high-resolution thermogravimetry. The thermogravimetry measurements were conducted at an initial heating rate of 50°C min−1, resolution 4.0, and sensitivity 1.0 in both nitrogen and air from room temperature to 900°C. A two…
Using thermomechanical spectroscopy, the molecular-weight distribution and relaxation transitions have been investigated in commercial LDPE and grafted by itaconic acid (LDPE-g-IA). This grafting in the molten LDPE was done by reactive extrusion with varied content of reactants in the blend under alternating of a shea…
Molecular weight determination of 83% degree of deacetylation (DD) chitosan with non-Gaussian and broad molecular weight distribution by high-performance size exclusion chromatography (HPSEC) and by capillary viscometry were proposed. The relationships between weight average retention volumes (RVw) of HPSEC and intrin…
The chain extension reaction in poly(butylene terephthalate) (PBT) melt was studied in detail. A high-reactivity diepoxy, diglycidyl tetrahydrophthalate, was used as a chain extender that can react with the hydroxyl and carboxyl end groups of PBT at a very fast reaction rate and a relatively high temperature. A Haake…
Polymerization of ethylene in a CSTR using a combined metallocene catalyst system (combination of an open-face catalyst, such as Constrained Geometry Catalyst, and a conventional metallocene catalyst) was studied. Using the model developed by Soares and Hamielec, and expanded by Beigzadeh et al., a steady-state simula…
The thermal decomposition of polycarbonate (PC), PC containing resorcinol bis(diphenyl phosphate) (RDP), and PC—acrylonitrile–butadiene–styrene (PC–ABS) blend containing RDP was studied by thermogravimetry. Volatile and solid products of thermal decomposition were collected at different steps of thermal decomposition…
The tensile drawing behavior of quenched and annealed films of isotactic polypropylene is investigated as a function of draw temperature and strain rate. A strain-induced structural change from the smectic to the monoclinic form is observed for the quenched films. A kinetic interpretation is proposed for the phenomeno…
New nanocomposites are processed with a plasticized poly(vinyl chloride) matrix reinforced by cellulose whiskers whose characteristics are a high aspect ratio and a large interface area. Dynamic mechanical analysis performed on samples reinforced with a filler fraction of up to 12.4 vol % gives the viscoelastic proper…
Experimental solubilities are reported for anthracene dissolved in ternary 2-butoxyethanol + 1-propanol + 1-butanol, 2-butoxyethanol + 1-propanol + 2-butanol, 2-butoxyethanol + 2-propanol + 1-butanol, and 2-butoxyethanol + 2-propanol + 2-butanol solvent mixtures at 25 °C and atmospheric pressure. For each of the four…
A series of codoped nanocrystalline ceria compositions, Ce 1 - x M x Bi 0.4 O 2.6 - x (M = Ca, Sr, and Ba; x = 0.01−0.15) were hydrothermally synthesized at 240 °C and characterized by powder X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. All as-made Ce 1 - x M x Bi 0.4…