Materials Literature
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We have devised a reversible set of nonequilibrium molecular dynamics equations of motion to study viscous flow under an applied shear field utilizing a new profile unbiased thermostat (PUT). Based on a modification of the original equations presented by Evans and Morriss [Phys. Rev. Lett. 56, 2172 (1986)], we have ex…
Polymer chains attached by one end to an impenetrable surface at high coverage exemplify a tethered layer of mesoscopic dimensions. At equilibrium, thermal fluctuations of the segment density profile of the brushlike layer reflect the tethered chain dynamics; the probing of these fluctuations by evanescent-wave dynami…
A pressure and temperature dependent Raman study of the vibrational and spin dynamics in CuGeO3 is presented. A new low temperature, high pressure phase has been identified, and a pressure-temperature phase-diagram is proposed for CuGeO3. The pressure dependence of the effective exchange interaction, of the spin-Peier…
Interpenetrating polymer networks (IPNs) with a controlled degree of microphase separation were synthesized from a poly(ether urethane) (PUR) and poly(ethyl methacrylate) (PEMA). The influence of the crosslink density of both networks was investigated in the 70:30 PUR/PEMA IPN. The extent of damping was evaluated by d…
Thermal conductivity and mechanical properties such as tensile strength, elongation at break, and modulus of elasticity of aluminum powder-filled high-density polyethylene composites are investigated experimentally in the range of filler content 0–33% by volume for thermal conductivity and 0–50% by volume for mechanic…
Plasma polymerization is a useful method for depositing thin films on substrates. The films formed are cross-linked, and their character depends on the plasma polymerization process conditions. The influence of power and monomer flow rate on the character of plasma-polymerized hexamethyldisiloxane (PPHMDSO) was invest…
Aqueous cationomeric polyurethanes (ACPU) were synthesized by a multistep reaction process. The alipathic diisocyanate, e.g., hexamethylene diisocyanate (HDI), was reacted with polyol, e.g., polypropylene glycol (PPG400) to form a prepolymer and it was chain-extended by reacting it with N-methyldietanolamine (N-MEDA).…
Poly(vinyl alcohol) (PVA) is soluble only in water and so some important derivatives like esters cannot be prepared from PVA. The 100% conversion of PVA to acetal is also elusive as there is strong intermolecular and intramolecular hydrogen bonding. However, PVA can be dissolved in a nonaqueous medium in the presence…
The most widely accepted method for determining Hansen's three-dimensional solubility parameters (3DSP) for crosslinked polymers entails graphically estimating the center of a spherical region in 3DSP-coordinate space whose boundaries are defined in terms of the extent of swelling by solvents whose 3DSP values are kno…
The cubic-to-orthorhombic structural transition occurring in CsH at a pressure of about 17 GPa is studied by ab initio calculations. The relative stability of the competing structures and the transition pressure are correctly predicted. We show that this pressure-induced first-order transition is intimately related to…
Thermal conductivity and mechanical properties such as tensile strength, elongation at break, and modulus of elasticity of aluminum powder-filled high-density polyethylene composites are investigated experimentally in the range of filler content 0–33% by volume for thermal conductivity and 0–50% by volume for mechanic…
The existence of anharmonic localization of lattice vibrations in a perfect 3-D diatomic ionic crystal is established for the rigid-ion model by molecular dynamics simulations. For a realistic set of NaI potential parameters, an intrinsic localized gap mode vibrating in the [111] direction is observed for fcc and zinc…
We present a systematic study of the effect of crack blunting on subsequent crack propagation and dislocation emission. We show that the stress intensity factor required to propagate the crack is increased as the crack is blunted by up to thirteen atomic layers, but only by a relatively modest amount for a crack with…
In this Brief Report, we present an algorithm for calculating the elastic Lattice Greens Function of a regular lattice, in which defects are created by removing lattice points. The method is computationally efficient, since the required matrix operations are on matrices that scale with the size of the defect subspace,…
In this paper, we present an algorithm for the solution of the von Karman equations of elasticity theory and related problems. Our method of successive reconditioning is able to avoid convergence problems at any ratio of the nonlinear streching and the pure bending energies. We illustrate the power of the method by nu…
The transport properties of an ionic model for liquid silica at high temperatures and pressure are investigated using molecular dynamics simulations. With increasing pressure, a clear change from "strong" to "fragile" behaviour (according to Angell's classification of glass-forming liquids) is observed, albeit only on…
The coalescence of diamond grains grown by microwave plasma chemical vapor deposition was observed at an atomic level using high resolution electron microscopy in combination with scanning electron microscopy. It was shown that large diamond crystals can be grown either by a coalescence of two [001]-oriented grains wh…
Eu2+ ions were incorporated in SiO2 and Al2O3–SiO2 glasses using a sol-gel process of Si(OC2H5)4, Al(OC4H9sec)3, and EuCl3 6H2O. Glasses incorporated with the Eu2+ ions showed the emission with peak at ∼22000 cm−1 due to 4f 6 5d→4f 7(8S7/2) transition of the Eu2+ ions. 1Al2O3⋅99SiO2 (mol %) glass had an intense emissi…
A new class of photodetectors is proposed, based on localized heating of an ultrathin metallic film due to absorption of individual photons. For a 1 eV photon, the transient temperature rise can be of order 10 K or greater in a nonequilibrium ‘‘hotspot’’ on the nm spatial scale and ps timescale. If current is flowing…
Low temperature two-photon fluorescence excitation microscopy was used to obtain fluorescence spectra of single CdSe colloidal nanocrystals or quantum dots. The fluorescence spectra reveal large, 0.02 eV shifts of the peak emission wavelength on times of the order of 100 s were also observed in some instances. We attr…