Materials Literature
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A nucleation model was proposed for a carbon nanotube enclosing a Ni bar which was grown by chemical vapor deposition (CVD) at 700 °C using round Ni particles. At an early stage of CVD, each round Ni particle with a diameter of about 30 nm is covered with graphite layers. The graphite-covered Ni particle is considered…
Military fighter aircraft occasionally suffer highspeed collisions with birds, posing a threat to pilot safety and to the structural integrity of the aircraft. An explicit three-dimensional finite element code for transient dynamic analysis, named X3D, has been developed at the University of Dayton Research Institute…
This paper presents an experimental investigation of the effect of surface charge upon the impulse flash-over of metallic-particle-contaminated insulators, which were clamped between two parallel planar electrodes, in at 1.0 bar. The results show that the accumulated surface charge greatly affects the impulse flash-ov…
High resolution x-ray emission spectroscopy is shown to reveal unprecedented details of the chemical bond formed between a molecule and a transition metal surface. An atom and symmetry projected view of the bonding orbitals is obtained. We find that all outer and inner valence orbitals of the molecule change due to th…
Hysteresis, the lag between the force and the response, is often associated with noisy, jerky motion which have recently been called ``avalanches''. The interesting question is why the avalanches come in such a variety of sizes: naively one would expect either all small events or one large one. Power-law distributions…
A suitable in situ monitoring technique for growth of thin films is reflection high energy electron diffraction (RHEED). Deposition techniques, like pulsed laser deposition (PLD) and sputter deposition, used for fabrication of complex oxide thin films use relatively high oxygen pressures (up to 100 Pa) and are, theref…
Topology related changes in the local density of states near the ends of closed carbon nanotubes are investigated using spatially resolved scanning tunneling spectroscopy and tight binding calculations. Sharp resonant valence band states are observed in the experiment at the tube ends, dominating the valence band edge…
The high-temperature properties of the Al(111) surface are studied by molecular-dynamics simulation. This surface does not melt below the bulk melting point, but can be superheated. Superheating of metal surfaces has been recently observed in several experiments. A molecular-dynamics study of the structural properties…
Reactive functional thermoplastic poly(arylene ether) toughness modifiers were demonstrated to enhance toughness of brittle thermosetting cyanate ester networks and also allowed retention of a highly desirable stability to solvent stress cracking and a moderately high modulus. Careful control of the heterophase morpho…
The basic mode of relaxation in polymer molecules involves the rotation of a conformer, with a time scale of the order of picoseconds. This fast relaxation process, however, cannot take place easily in the condensed state crowded by densely packed conformers, necessitating the intermolecular cooperativity among them.…
The cure of a technical-grade TGDDM (N,N,N′N′-tetraglycidyl-4,4′-diaminodiphenylmethane) with two different anhydride hardeners (hexahydrophthalic anhydride [HHPA] and tetrahydrophthalic anhydride [THPA]) is reported. The reaction was followed by differential scanning calorimetry (DSC), in situ infrared spectroscopy (…
A review on the synthesis of unsaturated polyester (UP) prepolymers showed that Ordelt saturation (reaction of hydroxyl groups with double bonds) is the major effect that may cause formation of chain branches and then result in an uncertainty of chain end number or functionality. A model has been derived in this work…
At the core, at the core and at the surface, within the cascade structure, or within the cascade structure and at the surface are different ways in which the dendrimers described here can be selectively alkylated. These phosphorus-containing dendrimers have generations of different constitution (example depicted on th…
The hydrolysis of a cyanate ester network made from the monomer 2,2′-bis(4-cyanatophenyl) isopropylidene (bisphenol A dicyanate homopolymer) was studied. Hydrolysis reactions were performed isothermally at temperatures from 150 to 180°C under conditions of excess water. The kinetics of the reaction were characterized…
The differential scanning calorimetry glass transition (DSC Tg), measured by ASTM test method E-1356, and the dynamic mechanical analysis glass transition (DMA Tg), measured using a new definition of the DMA Tg, generally agree within ±4°C for a wide variety of commercially available polymers. The DMA Tg is defined as…
Introduction to Dielectric Guides Analysis of Dielectric Integrated Guides: Approximate Methods Analysis of Dielectric Integrated Guides: Rigorous Methods Image-, Insular Image-, Trapped Image- and other Variant Guides Semiconductor and Planar Optical Guides Non-Radiative Dielectric Guide Non-Planar Dielectric Guides…
An equation, based on thermodynamic considerations to relate the glass transition temperature, Tg, to compositional variation of a polymer system, is adapted in this article for modeling the Tg vs. fractional conversion (x) relationship of reactive thermosetting systems. Agreement between the adapted equation and expe…
The reaction of SiCl4 with bis(trimethylsilyl)carbodiimide in a 1:2 molar ratio followed by annealing at temperatures above 400 or 900°C provides the first crystalline ternary Si-C-N solids, namely silicon dicarbodiimide (SiC2N4) and silicon (carbodiimide)nitride (Si2CN4), in near quantitative yields. The anti-cuprite…
A combination of classical density-functional theory and thermodynamic perturbation theory is applied to a survey of finite-temperature trends in the relative stabilities of one-component crystals and quasicrystals interacting via effective metallic pair potentials derived from pseudopotential theory. Comparing the fr…
Hydrogen molybdenum bronzes, H0.21MoO3 (type I) and H0.91MoO3 (type II) were characterized by Mo K-edge XAFS spectroscopy. XANES spectra showed that type I has an axially symmetric MoO6 unit which is mainly conncted to each other with vertices sharing and a MoO6 unit in type II are similar to that in MoO2. EXAFS spect…