The Experts below are selected from a list of 46491 Experts worldwide ranked by ideXlab platform
Hamid Kellay - One of the best experts on this subject based on the ideXlab platform.
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Depletion forces induce visco-elasto-capillary thinning of non-Brownian suspensions
EPL - Europhysics Letters, 2017Co-Authors: R. Harich, A Deblais, Antoine Colin, Hamid KellayAbstract:Droplet pinch-off, which occurs when a Drop of Liquid detaches from a capillary, can be strongly modified in the presence of complex fluids such as polymer solutions and suspensions giving rise to long and slender filaments that thin slowly in time. While for polymers, the molecular conformations of the molecules in the filament are responsible for such a behavior, in suspensions the mechanisms at play remain to be deciphered. Here we show, experimentally, that while Liquid bridges of non-Brownian suspensions of moderate concentrations have a thinning behavior very close to that of the solvent, the addition of short-chain polymers inducing depletion attractions between the particles in the suspension changes the thinning dynamics and gives rise to exponential thinning in time. The characteristic time of this dynamics increases with polymer concentration and therefore the intensity of the depletion forces at play. The tunability of this dynamics may be important for injket and 3D printing applications where short rupture times are sought for or in other situations where Drop formation has to be minimized or inhibited.
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Stretching Polymers in Droplet-Pinch-off Experiments
Physical Review X, 2013Co-Authors: François Ingremeau, Hamid KellayAbstract:Droplet pinch off, which occurs when a Drop of Liquid detaches from a capillary, can be strongly modified in the presence of polymers, giving rise to long and slender filaments that thin slowly in time. However, little is known experimentally about the molecular conformations of the polymers in the filament itself. Since the thinning dynamics of these filaments can be used to extract macroscopic quantities of interest such as the elongational viscosity of polymer solutions, which is of importance in a variety of physical processes (electrospinning, spraying, or drag reduction), the link with the molecular scale dynamics would be an important step towards understanding the extensional properties of such solutions. We show here, experimentally, that the polymers are highly extended within this filament region and that the distribution of these extensions is stationary in time. We then determine the elongational viscosity from the full filament dynamics. Such a determination turns out to be consistent with the polymer extensions observed and also consistent with simple models of polymer elongational viscosities. The direct observation of stretched macromolecules within such suspended Liquid filaments suggests that these filaments may be useful for preparing polymeric materials with specific anisotropy or for optical screening of biopolymers such as DNA.
Fernandez J De La Mora - One of the best experts on this subject based on the ideXlab platform.
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a continuum model for ion evaporation from a Drop effect of curvature and charge on ion solvation energy
Analytica Chimica Acta, 2000Co-Authors: M Labowsky, John B Fenn, Fernandez J De La MoraAbstract:A Drop of Liquid is treated as a continuum medium with surface tension and dielectric constant ". The energy 1 (surface C electrostatic) required to extract a solvated ion from the Drop can then be determined as part of a well posed problem as a function of the initial number z C 1 of elementary charges in the Drop and its initial radius R 0 . Instead of a direct numerical attack on the full model, a geometrically simpler situation is analyzed, in which the Drop and the solvated ion are taken to be either spheres or spherical caps after or prior to detachment, respectively. This simplified model is closely related to the full continuous problem when the radius Ri of the solvated ion is small (Ri/R 0 1), and the main Drop is not near the Rayleigh limit. This model problem is solved analytically in the limit " 1. When z D 0 and 1/R 0 D 0 one recovers Born’s result, where 1 D 2.7 eV for monovalent ions in water, which exceeds by some 0.3 eV the experimental value for the alkali ions. In the limit of small ions one recovers the results of Gamero et al. [5], 1 D 1GBorn e 2 [F(z)C]/(4"0R 0 ), though surface tension effects shift the constant from 4/5 to 2/3. The effect of finite ion diameter is determined numerically for the two-spheres model. When the solvation energy at zero curvature and charge is 1Gborn, small ions do not evaporate from water Drops. When this value is reduced to fit available experimental data, a narrow ion evaporation window appears for Drops charged near the Rayleigh limit with z 12 or less. The domain in (z, R 0 ) space leading to ion evaporation is broader for the case of formamide. The micro-hydrodynamic process of escape of a singly charged nanoDrop from a larger Drop requires a large activation energy. It is hence indistinguishable from Iribarne‐Thomson ion evaporation, and radically different from a Coulomb explosion. ©2000 Elsevier Science B.V. All rights reserved.
Houyang Chen - One of the best experts on this subject based on the ideXlab platform.
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a facile and effective sulfur loading method direct Drop of Liquid li2s8 on carbon coated tio2 nanowire arrays as cathode towards commercializing lithium sulfur battery
Energy Storage Materials, 2019Co-Authors: Chenyang Zha, Tikai Zhang, Houyang ChenAbstract:Abstract The development of high performance lithium-sulfur batteries is trapped by the shuttle effect of intermediate polysulfides and the insulating nature of sulfur. To overcome these drawbacks, numerous state-of-the-art encapsulation/wrap of sulfur strategies have been developed. However, most of these methods have challenges to implement in commercializing applications of lithium-sulfur batteries. Herein, a facile and effective sulfur loading method is presented by Droping Liquid Li2S8 into carbon coated TiO2 nanowire arrays without any complex pre-processing. As a result, these electrodes with 2.0 and 4.0 mg/cm2 sulfur have high initial capacities of 1280 and 1240 mAh/g, and maintain 930 and 680 mAh/g after 500 cycles under 3.2 mA, respectively. For a quick-acting cycling, it holds 520 mAh/g after 500 cycles at 5.8 mA with 4.0 mg/cm2 sulfur loading. The facile sulfur loading approach may provide a new opportunity to construct high performance sulfur-based cathodes for their industrial applications.
G Georg Prokert - One of the best experts on this subject based on the ideXlab platform.
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On Stokes flow with variable and degenerate surface tension coefficient
Differential Equations and Applications, 2005Co-Authors: Matthias Günther, G Georg ProkertAbstract:Short-time existence, uniqueness, and regularity results are shown for the moving boundary problem of a free Drop of Liquid governed by the Stokes equations and driven by surface tension. The value of the surface tension coefficient is variable, not necessarily strictly positive, and transported with the flow on the moving surface.
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On Stokes flow with variable and degenerate surface tension coefficient
Nonlinear Differential Equations and Applications NoDEA, 2005Co-Authors: Matthias Günther, G Georg ProkertAbstract:Short-time existence, uniqueness, and regularity results are shown for the moving boundary problem of a free Drop of Liquid governed by the Stokes equations and driven by surface tension. The value of the surface tension coefficient is variable, not necessarily strictly positive, and transported with the flow on the moving surface. By a perturbation of identity approach, the problem is transformed into a nonlinear, nonlocal first order degenerate parabolic evolution equation on a fixed reference manifold. Its solvability is proved by deriving a priori estimates and using Galerkin approximations.
G. Fras - One of the best experts on this subject based on the ideXlab platform.
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Behaviour of spreading molten metal Drops deposited by fusion
Experimental Thermal and Fluid Science, 2013Co-Authors: J. Chapuis, Cyril Bordreuil, Fabien Soulié, G. FrasAbstract:An experimental approach is presented in order to study the evolution of the spreading of a macro-Drop of Liquid metal. The objective of this work is to supply qualitative and quantitative information during the deposit of Liquid metal in static pulsed Gas Metal Arc Welding (P-GMAW). The experimental results are analyzed in the light of dimensionless numbers in order to identify the involved physical mecanisms and appreciate the heat and mass e ects on the behavior of such a macro-Drop.
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Behavior of a spreading macro-Drop of Liquid metal during deposit
2012Co-Authors: J. Chapuis, F. Souli, Cyril Bordreuil, G. FrasAbstract:An experimental approach is presented in order to study the evolution of the spreading of a macro-Drop of Liquid metal. The objective of this work is to supply qualitative and quantitative information during the deposit of Liquid metal in static pulsed Gas Metal Arc Welding (P-GMAW). The experimental results are analyzed in the light of dimensionless numbers in order to identify the involved physical mecanisms and appreciate the heat and mass e ects on the behavior of such a macro-Drop.
