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Polydisperse Systems (polydisperse + system)
Selected AbstractsIn-situ small-angle scattering study on the formation of a nanocrystalline soft-magnetic alloyJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000D. R. Dos Santos A detailed study is presented on the nanocrystallization of the amorphous alloy Fe86Zr7Cu 1B6 (indices indicate at. %). Melt-spun ribbons were rapidly annealed by Joule heating, and the electrical resistance showed strong variations during thermal treatment. X-ray diffraction patterns indicate that these variations are related to the nucleation and growth of ,-Fe nanocrystals, and from peak profile analysis we obtained the average grain size and crystalline volume fraction for different annealing currents. The disorder-order transition was studied by in-situ small-angle X-ray scattering during conventional furnace treatments. SAXS intensity evolution for different temperatures, both below and above the crystallization temperature of the alloy, showed that a fast atomic rearrangement leads to the formation of atomic clusters before crystallization. The evolution of the size distribution function of these clusters as a function of time and temperature was obtained assuming a polydisperse system of spherical particles. [source] Micellar solutions of amphipathic copolymers based on carboxymethyl cellulosePOLYMER INTERNATIONAL, Issue 6 2003Ya Cao Abstract A novel family of amphipathic copolymers based on carboxymethyl cellulose (CM-cellulose) has been synthesized through ultrasonic irradiation. Their micellar conformation in aqueous solution was studied by dynamic laser scattering, environmental scanning electron microscopy and gel permeation chromatography. The results show that conformation of copolymer molecules is totally different from that of CM-cellulose because of the introduction of the surface active macromonomers. Due to the influence of hydrophobic character and molecular weight, different amphipathic copolymers have different micellar conformations, such as cylindrical, spheroidal or ellipsoidal micelles. In the range of concentration tested, the normalized first-order autocorrelation function g(1)(,) of a copolymer of CM-cellulose and poly(ethylene oxide) dodecyl ether acrylate does not fit a single-exponential decay, indicating a polydisperse system and the existence of species of different shapes and size. At different concentrations, the hydrodynamic radii of micelles (R) almost distribute into two regions of smaller and larger size. With increasing copolymer concentration, the region of smaller R remains in the range 30,100,nm and is considered to represent monomolecular micelles, while the larger R region increases gradually with concentration, which means that polymolecular micelles increase in size. © 2003 Society of Chemical Industry [source] Fluid-particle drag in inertial polydisperse gas,solid suspensionsAICHE JOURNAL, Issue 8 2010William Holloway Abstract In this article, we extend the low Reynolds number fluid-particle drag relation proposed by Yin and Sundaresan for polydisperse systems to include the effect of moderate fluid inertia. The proposed model captures the fluid-particle drag results obtained from lattice-Boltzmann simulations of bidisperse and ternary suspensions at particle mixture Reynolds numbers ranging from 0 , Remix , 40, over a particle volume fraction range of 0.2 , , , 0.4, volume fraction ratios of 1 , ,i/,j , 3, and particle diameter ratios of 1 , di/dj , 2.5. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] A coupled DEM/CFD analysis of the effect of air on powder flow during die fillingAICHE JOURNAL, Issue 1 2009Y. Guo Abstract Die filling from a stationary shoe in a vacuum and in the presence of air was numerically analyzed using an Eulerian-Lagrangian model, which employs a discrete element method (DEM) for the particles and computational fluid dynamics (CFD) for the air with a two-way air-particle interaction coupling term. Monodisperse and polydisperse powder systems have been simulated to explore the effect of the presence of air on the die filling process. For die filling with monodisperse powders, the influences of particle size and density on the flow behavior were explored. The numerical simulations revealed that the presence of air has a significant impact on the powder flow behavior, especially for systems with smaller and/or lighter particles. Flow has been characterized in terms of a dimensionless mass flow rate, and it has been shown that for die filling in a vacuum this is constant. The flow characteristics for die filling in air can be classified into two regimes. There is an air-inert regime in which the particle size and density are sufficiently large that the effect of air flow becomes negligible, and the dimensionless mass flow rate is essentially identical to that obtained for die filling in a vacuum. There is also an air-sensitive regime, for smaller particle sizes and lower particle densities, in which the dimensionless mass flow rate increases as the particle size and density increase. The effects of particle-size distribution and adhesion on the flow behavior have also been investigated. It was found that, in a vacuum, the dimensionless mass flow rate for polydisperse systems is nearly identical to that for monodisperse systems. In the presence of air, a lower dimensionless mass flow rate is obtained for polydisperse systems compared to monodisperse systems, demonstrating that air effects become more significant. Furthermore, it has been shown that, as expected, the dimensionless mass flow rate decreases as the surface energy increases (i.e., for more cohesive powders). © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Diffraction line profiles from polydisperse crystalline systemsACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2001Paolo Scardi Diffraction patterns for polydisperse systems of crystalline grains of cubic materials were calculated considering some common grain shapes: sphere, cube, tetrahedron and octahedron. Analytical expressions for the Fourier transforms and corresponding column-length distributions were calculated for the various crystal shapes considering two representative examples of size-distribution functions: lognormal and Poisson. Results are illustrated by means of pattern simulations for a f.c.c. material. Line-broadening anisotropy owing to the different crystal shapes is discussed. The proposed approach is quite general and can be used for any given crystallite shape and different distribution functions; moreover, the Fourier transform formalism allows the introduction in the line-profile expression of other contributions to line broadening in a relatively easy and straightforward way. [source] | ||||||||||