References of "Lumay, Geoffroy"
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See detailStatics and dynamics of magnetocapillary bonds
Lagubeau, Guillaume; Grosjean, Galien ULg; Darras, Alexis ULg et al

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2016), 93

When ferromagnetic particles are suspended at an interface under magnetic fields, dipole-dipole interactions compete with capillary attraction. This combination of forces has recently given promising ... [more ▼]

When ferromagnetic particles are suspended at an interface under magnetic fields, dipole-dipole interactions compete with capillary attraction. This combination of forces has recently given promising results towards controllable self-assemblies as well as low-Reynolds-number swimming systems. The elementary unit of these assemblies is a pair of particles. Although equilibrium properties of this interaction are well described, the dynamics remain unclear. In this paper, the properties of magnetocapillary bonds are determined by probing them with magnetic perturbations. Two deformation modes are evidenced and discussed. These modes exhibit resonances whose frequencies can be detuned to generate nonreciprocal motion. A model is proposed that can become the basis for elaborate collective behaviors. [less ▲]

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See detailRemote control of self-assembled microswimmers
Grosjean, Galien ULg; Lagubeau, Guillaume ULg; Darras, Alexis ULg et al

in Scientific Reports (2015)

Floating magnetic particles can self-assemble into structures. These structures are periodically deformed in a non reciprocal way using magnetic fields, which leads to controllable low Reynolds number ... [more ▼]

Floating magnetic particles can self-assemble into structures. These structures are periodically deformed in a non reciprocal way using magnetic fields, which leads to controllable low Reynolds number locomotion. [less ▲]

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See detailQuantitatively mimicking wet colloidal suspensions with dry granular media
Messina, René; Aljawhari, Sarah; Bécu, Lydiane et al

in Scientific Reports (2015)

Athermal two-dimensional granular systems are exposed to external mechanical noise leading to Brownian-like motion. Using tunable repulsive interparticle interaction, it is shown that the same ... [more ▼]

Athermal two-dimensional granular systems are exposed to external mechanical noise leading to Brownian-like motion. Using tunable repulsive interparticle interaction, it is shown that the same microstructure as that observed in colloidal suspensions can be quantitatively recovered at a macroscopic scale. To that end, experiments on granular and colloidal systems made up of magnetized particles as well as computer simulations are performed and compared. Excellent agreement throughout the range of the magnetic coupling parameter Γ is found for the pair distribution as well as the bond-orientational correlation functions. This finding opens new ways to efficiently and very conveniently explore phase transitions, crystallization, nucleation, etc in confined geometries. [less ▲]

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See detailRheological behavior of β-Ti and NiTi powders produced by atomization for SLM production of open porous orthopedic implants
Yablokova, G.; Speirs, M.; Van Humbeeck, J. et al

in Powder Technology (2015)

The growing interest for Selective Laser Melting (SLM) in orthopedic implant manufacturing is accompanied by the introduction of novel Ti alloys, in particular β-Ti for their excellent corrosion ... [more ▼]

The growing interest for Selective Laser Melting (SLM) in orthopedic implant manufacturing is accompanied by the introduction of novel Ti alloys, in particular β-Ti for their excellent corrosion resistance as well as favorable combination of high mechanical strength, fatigue resistance and relatively low elastic modulus. As part of the SLM process for producing quality β-Ti parts powder flowability is essential to achieve uniform thickness of powder layers. In this work the flowability of different gas atomized β-Ti, including NiTi, powders has been studied. Their rheological properties were compared to those of commercially available plasma-atomized Ti–6Al–4V powder using a newly developed semi-automatic experimental set-up. Not only the particle size, shape and size distribution of the powders display a large influence on the powder flowability but also particle surface properties such as roughness, chemical composition and the presence of liquid on the surface of the particles. It was found that plasma or gas atomization production techniques for SLM powder have a considerable effect on the particle topography. Among the powders studied regarding SLM applicability only rheological properties of the fine size fraction (25–45 μm) of Ti–45Nb didn't conform to SLM processing requirements. To improve flowability of the Ti–45Nb powder itwas annealed both in air and argon atmosphere at 600 °C during 1 h, resulting in an improved rheological behavior suitable for SLM processing. [less ▲]

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See detailLinking flowability and granulometry of lactose powders
Boschini, Frédéric ULg; Delaval, Vincent ULg; Traina, Karl et al

in International Journal of Pharmaceutics (2015)

The flowing properties of 10 lactose powders commonly used in pharmaceutical industries have been analyzed with three recently improved measurement methods. The first method is based on the heap shape ... [more ▼]

The flowing properties of 10 lactose powders commonly used in pharmaceutical industries have been analyzed with three recently improved measurement methods. The first method is based on the heap shape measurement. This straightforward measurement method provides two physical parameters (angle of repose αr and static cohesive index σr) allowing to make a first screening of the powder properties. The second method allows to estimate the rheological properties of a powder by analyzing the powder flow in a rotating drum. This more advanced method gives a large set of physical parameters (flowing angle αf, dynamic cohesive index σf, angle of first avalanche αa and powder aeration %ae) leading to deeper interpretations. The third method is an improvement of the classical bulk and tapped density measurements. In addition to the improvement of the measurement precision, the densification dynamics of the powder bulk submitted to taps is analyzed. The link between the macroscopic physical parameters obtained with these methods and the powder granulometry is analyzed. Moreover, the correlations between the different flowability indexes are discussed. Finally, the link between grain shape and flowability is discussed qualitatively. [less ▲]

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See detailFlow of magnetic repelling grains in a two-dimensional silo
Lumay, Geoffroy ULg; Schockmel, Julien ULg; Henandez-Enriquez, D. et al

in Papers in Physics (2015)

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See detailBernal random loose packing through freeze-thaw cycling
Ludewig, François ULg; Vandewalle, Nicolas ULg; Dorbolo, Stéphane ULg et al

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2015)

We study the effect of freeze-thaw cycling on the packing fraction of equal spheres immersed in water. The water located between the grains experiences a dilatation during freezing and a contraction ... [more ▼]

We study the effect of freeze-thaw cycling on the packing fraction of equal spheres immersed in water. The water located between the grains experiences a dilatation during freezing and a contraction during melting. After several cycles, the packing fraction converges to a particular value η∞ = 0.595 independently of its initial value η0. This behavior is well reproduced by numerical simulations. Moreover, the numerical results allow one to analyze the packing structural configuration. With a Vorono ̈ı partition analysis, we show that the piles are fully random during the whole process and are characterized by two parameters: the average Vorono ̈ı volume μv (related to the packing fractionη)andthestandarddeviationσv ofVorono ̈ıvolumes.Thefreeze-thawdrivingmodifythevolumestandard deviation σv to converge to a particular disordered state with a packing fraction corresponding to the random loose packing fraction ηBRLP obtained by Bernal during his pioneering experimental work. Therefore, freeze-thaw cycling is found to be a soft and spatially homogeneous driving method for disordered granular materials. [less ▲]

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See detailProgramming self assembly by designing the 3D shape of floating objects
Poty, Martin ULg; Lagubeau, Guillaume ULg; Lumay, Geoffroy ULg et al

Conference (2014, November 25)

Self-assembly of floating particles driven by capillary forces at some liquid-air interface leads to the formation of two-dimensionnal structures. Using a 3d printer, milimeter scale objets are produced ... [more ▼]

Self-assembly of floating particles driven by capillary forces at some liquid-air interface leads to the formation of two-dimensionnal structures. Using a 3d printer, milimeter scale objets are produced. Their 3d shape is chosen in order to create capillary multipoles. The capillary interactions between these components can be either attractive or repulsive depending on the interface local deformations along the liquid-air interface. In order to understand how the shape of an object deforms the interface, we developed an original profilometry method. The measurements show that specific structures can be programmed by selecting the 3d branched shapes. [less ▲]

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See detailInteractions between particles in a magnetocapillary self-assembly
Lagubeau, Guillaume ULg; Darras, Alexis; Grosjean, Galien ULg et al

Conference (2014, November 24)

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See detailRemote control of self-assembled microswimmers
Vandewalle, Nicolas ULg; Grosjean, Galien ULg; Darras, alexis et al

Conference (2014, November 24)

Physics governing the locomotion of microorganisms and other microsystems is dominated by viscous damping. An effective swimming strategy involves the non-reciprocal and periodic deformations of the ... [more ▼]

Physics governing the locomotion of microorganisms and other microsystems is dominated by viscous damping. An effective swimming strategy involves the non-reciprocal and periodic deformations of the considered body. Herein, we show that a magnetocapillary-driven self-assembly, composed of three soft-ferromagnetic beads, is able to swim along a liquid-air interface when driven by an external magnetic field. Moreover, the system can be fully controled, opening ways to explore low Reynolds number swimming and to create micromanipulators in various applications. [less ▲]

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See detailCustomizing mesoscale self-assembly with three-dimensional printing
Poty, Martin ULg; Lumay, Geoffroy ULg; Vandewalle, Nicolas ULg

in New Journal of Physics (2014)

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See detailMelting of a confined monolayer of magnetized beads
Schockmel, Julien ULg; Mersch, Eric; Vandewalle, Nicolas ULg et al

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2013)

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See detailFlow abilities of powders and granular materials evidenced from dynamical tap density measurement
Traina, Karl; Cloots, Rudi ULg; Bontempi, Sébastien ULg et al

in Powder Technology (2013), 235

This paper offers an overview of the flow properties of granular systems, including voids, granular porosity and random packing characteristics. For the purposes of the study, the notion of additional ... [more ▼]

This paper offers an overview of the flow properties of granular systems, including voids, granular porosity and random packing characteristics. For the purposes of the study, the notion of additional porous volume is intro-duced. This volume is defined as the additional air volume added to the optimal granular packing. It represents the difference between the volume of the bulk powder bed and that of the same powder but when ideally packed. It appears as the volume of additional air (or voids) trapped/stored between the grains when the powder passes from a dynamical state to a static state (during the filling of a container or the formation of a powder heap, for example). Therefore, if the powder bed traps air, it is then able to restore air partially or completely or not at all, depending on the intergranular cohesion level. This mechanism of the storing and releasing of air can be analysed from the measurement of compressibility curves. If the powder is non-cohesive or free flowing, it traps a small amount of air in its static state. Conversely, if the powder is cohesive, it traps more air. These data can be related to the flow properties of granular materials. Indeed, the compressibility curves obtained for gran-ular materials provide information such as additional porosity, a kinetic parameter which characterizes the com-pressibility dynamics, a granular relaxation index which predicts how far a powder is from its optimal packing state and an index which gauges the de-areation speed of the powder. Measurement of such properties provides a better understanding of the nature of granular materials. Measurements of dynamical compressibility were car-ried out on five granular materials (two different lactose powders, hydrated lime Ca(OH)2, yttrium stabilized zir-conia balls and polystyrene balls). The overall results are presented using a radar graph. The use of this tool and its advantages are discussed in relation to the measurement and characterization of powder flow properties. [less ▲]

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See detailInfluence of the gravity on the discharge of a silo
Dorbolo, Stéphane ULg; Maquet, Laurent ULg; Brandenbourger, Martin ULg et al

in Granular Matter (2013), 15

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See detailMesoscale structures from magnetocapillary self-assembly
Vandewalle, Nicolas ULg; Obara, Noriko; Lumay, Geoffroy ULg

in European Physical Journal E -- Soft Matter (2013), 36

When identical soft ferromagnetic particles are suspended at some water-air interface, capillary attraction is balanced by magnetic repulsion induced by a vertical magnetic field. By adjusting the ... [more ▼]

When identical soft ferromagnetic particles are suspended at some water-air interface, capillary attraction is balanced by magnetic repulsion induced by a vertical magnetic field. By adjusting the magnetic field strength, the equilibrium interdistance between particles can be tuned. The aim of this paper is to study the ordering of particles for large assemblies. We have found an upper size limit above which the assembly collapses due to capillary effects. Before reaching this critical number of particles, defects are always present and limit the perfect ordering expected for that system. This is due to the curvature of the interface induced by the weight of the self-assembly. [less ▲]

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See detailCascade of granular flows for characterizing segregation
Lumay, Geoffroy ULg; Boschini, Frédéric ULg; Cloots, Rudi ULg et al

in Powder Technology (2013)

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See detailSelf-assembled magnetocapillary swimmers
Lumay, Geoffroy ULg; Obara, Noriko; Weyer, Floriane et al

in Soft Matter (2013)

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See detailExperimental study of a vertical column of grains submitted to a series of impulses
Lumay, Geoffroy ULg; Dorbolo, Stéphane ULg; Gerasimov, Oleg et al

in European Physical Journal E -- Soft Matter (2013), 36

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See detailMeasuring the flowing properties of powders and grains
Lumay, Geoffroy ULg; Boschini, Frédéric ULg; traina, Karl et al

in Powder Technology (2012), 224

A granular material is a complex system which exhibits non-trivial transitions between the static, the quasi-static and the dynamical states. Indeed, an assembly of grains can behave like a solid or a ... [more ▼]

A granular material is a complex system which exhibits non-trivial transitions between the static, the quasi-static and the dynamical states. Indeed, an assembly of grains can behave like a solid or a fluid according to the applied stress. In between solid and fluid granular states, very slow dynamics are observed. When a complete macroscopic characterization of a powder is needed, all these granular states have to be precisely analyzed. In this paper, we show how three measurement techniques can be used to measure the physical properties of a powder. The measurements are based on classical tests modified to meet the recent fundamental researches on granular materials. The static properties of the powder are analyzed through the shape of a heap. The quasi-static behavior is studied with the analysis of the compaction dynamics. Finally, the dynamical regime is monitored through the flow in a rotating drum. In order to illustrate how these measurements can be used in practical cases, analyses are performed with three types of granular materials: silicon carbide abrasives, flours and rice. These selected materials allow to show the influence of the different parameters (grain size, grain size distribution, grain shape) on the macroscopic properties of the assembly. Moreover, these studies show the pertinence of the parameters obtained with the proposed techniques for the rheological characterization of powders and grains. [less ▲]

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