Materials Literature
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The effects of an insoluble surfactant on the motion of a drop or bubble as it is driven by a pressure gradient through a capillary tube is investigated numerically. We find that a drop in a straight capillary tube can either approach a steady-state shape or develop a re-entrant cavity at its rear. For a gas bubble mo…
Composites of a polypyrrole (PPy) and poly(vinyl chloride-vinyl acetate) copolymer (PVC-PVA) were prepared both chemically and electrochemically. An insulating polymer was retained in the blend and the thermal stability of the polymer was enhanced by polymerizing pyrrole into the host matrix in both cases. The composi…
The dynamics of a spreading liquid body are dictated by the interface shape and flow field very near the moving contact line. The interface shape and flow field have been described by asymptotic models in the limit of small capillary number, Ca . Previous work established the validity and limitations of these models o…
Unmodified blends of two thermoplastic polyurethanes (TPU) and six polyolefines were used to study the influence of the component viscosities on the blend morphology and mechanical properties. Blends were produced by melt mixing using a twin screw extruder. Interactions between the blend components could not be detect…
A series of eight thermoplastic polyurethane elastomers were synthesized from 4,4′-methylene diphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) chain extender, with poly(hexamethylene oxide) (PHMO) macrodiol soft segments. The PHMO molecular weights employed ranged from 433 g/mol to 1180 g/mol. All materials contain…
We report a novel practical method to determine exchange parameters by using experimental susceptibility data in a relatively narrow temperature region and a low order high-temperature-expansion equation. This method is applied to a square lattice and a CaV_4O_9-type lattice, and its accuracy is discussed.
In this paper, we develop a rigorous formulation of the local stress field. This approach can be used in conjuction with any first-principles method to study stress fields in complex bonded systems. In particular we investigate the induced stress fields resulting from homogeneous deformations for tetragonal PbTiO_3 an…
The strong corrugation of the V4O9 layer in the spin gap system CaV4O9 is examined for its impact on the exchange coupling constants between the spin 1/2 V ions. Local spin density (LSD) calculations show that the V spin occupies a d(x^2-y^2) orbital (x and y are the V-V directions). The Kanamori-Goodenough superexcha…
We have contrasted the quantum confinement of (i) multiple quantum wells of flat GaAs and AlAs layers, i.e. $(\GaAs)_{m}/(\AlAs)_n/(\GaAs)_p/(\AlAs)_q$, with (ii) ``cylindrical Russian Dolls'' -- an equivalent sequence of wells and barriers arranged as concentric wires. Using a pseudopotential plane-wave calculation,…
The present paper deals with some mathematical aspects of generalized time-dependent Ginzburg–Landau theories for the numerical simulation of mesoscale phase separation kinetics of copolymer melts. We shortly discuss the underlying theory and introduce an expansion of the external potential, to be used in the dynamics…
We develop here a highly efficient variant of the Monte Carlo method for direct evaluation of the partition function, free energy, and other configurational dependent physical properties for long polymer chains. This method (CC–BB) combines continuous configurational biased sampling with Boltzmann factor biased enrich…
We use a recently developed density-functional perturbation theory, which has been applied successfully to predict phase diagrams of systems of attractive particles, to describe the phase diagram of particles interacting via repulsive potentials. We consider potentials composed of a hard-sphere core plus a repulsive t…
Using the bond-fluctuation-algorithm we perform dynamic Monte Carlo simulations on dense symmetric copolymer melts. We cover structures from homogeneous melts to strongly separated regimes. We confirm the scaling laws found in previous simulations for the static properties of the chains and extend these laws into the…
The phase diagram of fluids of hard biaxial ellipsoids with c/a=10 and b/a∈{1,10}, where a, b, and c are the semi-axes, has been studied using computer simulation. Four homogeneous phases are in evidence: isotropic (I), nematic (N+), discotic (N−) and biaxial (B). First-order isotropic-nematic and isotropic-discotic c…
We critically discuss relaxation experiments in magnetic systems that can be characterized in terms of an energy barrier distribution, showing that proper normalization of the relaxation data is needed whenever curves corresponding to different temperatures are to be compared. We show how these normalization factors c…
An experimental study of the origin and hitherto unexplored structure of the pressure - tension cycles accompanying the cavitation of liquids under dynamic stressing by tension is presented. The results of this study are relevant to certain problems in engineering and medicine, and the potential for application of the…
Although the low-threshold emission from polycrystalline diamond heavily doped with nitrogen has been proposed in our previous report, this is the first report on a practical diamond cold cathode, having pyramidal-shape array structure, promising for battery-driven flat panel displays. We have used urea [(NH3)2CO] as…
Synthesis of the perovskite solid solution that forms between metallic SrRuO3 and insulating SrSnO3 is reported. This material is proposed as a conducting thin-film electrode/epitaxial-substrate material. While the bulk solid solution could not be formed, thin films of single-phase SrRu0.5Sn0.5O3 were grown on (001) K…
Thermoluminescence glow peaks are calculated numerically for a one-trap-one-recombination-centre model using a generalized approach. Except in extreme cases the peaks are seen to change in position and shape with a change in dose. These glow peaks are fitted to the general-order kinetics model and the values of the ki…
We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe nanocrystals, 33 and 42 Å in diameter, embedded in a ZnS matrix. The thin-film quantum dot composites were synthesized by electrospray organometallic chemical vapor deposition. Cathodoluminescence and phot…