Alain Ponton

French National Centre for Scientific Research | CNRS

In this paper we investigate the rheological complex behavior of a vase of Fergoug dam which is located in the region Perregaux (Western Algeria) as a function of aging time, shear rate, and temperature. The modified Herschel-Bulkley model is used to fit the stationary flow curves of vase as a function of aging time and the generalized model of Kel...

In order to get better knowledge of mechanical properties from microscopic to macroscopic scale of biopolymers, viscoelastic bulk properties of aqueous solutions of sodium alginate were studied at different scales by combining macroscopic shear rheology (Hz), diffusing-wave spectroscopy microrheology (kHz-MHz) and Brillouin spectroscopy (GHz). Stru...

Nanocomposite hydrogels were elaborated by the addition of citrated magnetic nanoparticles (MNPs) in sodium alginate aqueous solutions ionically crosslinked by in situ release of calcium ions from calcium carbonate (CaCO3) with gradual hydrolysis of d-glucono-δ lactone (GDL). The sol-gel transition was studied by time-resolved mechanical spectrosco...

Absorption process of different PVA/GO composites Conclusions  Synthesis of aqueous GO dispersions through modified Hummer's method and elaboration of PVA/GO composites  Improved viscoelastic properties of PVA/GO composites by increasing PVA or GO concentration and freezing-thawing cycles  GO is the main factor in absorption behavior, which is r...

The aim of the present work is first to synthesis a magnetic chitosan hydrogel (chitosan ferrogel) using the blending method and second to study it rheological behavior. Magnetic components ( maghemite particles γ-Fe2O3 ) were synthesized via a simple chemical co-precipitation route also called Massart's procedure. Before being dispersed in chitosa...

This study investigated the steady shear flow and viscoelastic properties of composite materials elaborated by introduction of positively charged polyol-made maghemite nanoparticles (NPs) in aqueous solutions of negatively charged sodium alginate polymers. Two different ligands were covalently attached to the particle surface, the 3-aminopropyl tri...

We propose a complete viscoelastic characterisation of aqueous networks of biopolymers, from individual polymer chains to three-dimensional networks. In the dilute regime, the intrinsic viscosity and persistence length of the macromolecular chains were deduced from macroscopic rheology measurements. In the semi-dilute and concentrated regimes, the...

In the polymer-surfactant system, increasing the concentration of surfactant leads to structural changes in surfactant micelles. This is expected to influence the polymer conformation in the dilute regime where polymer chains are singles and in the entangled regime where the polymer system is described by the blob concept. In this report, the effec...

Viscosity measurements were performed in water/AOT (sodium bis(2-ethylhexyl) sulfoccinate)/isooctane microemulsions as a function of temperature between 25 C and 55 C, molar ratio Wo = water/AOT ranging from 3 to 45 and three values of AOT/isooctane volume fractions (Φm = 0.1, 0.15, and 0.2). It was shown that microemulsions behaved as Newtonian fl...

We present a study of the structural and thermomechanical properties of lyotropic phase in the quasi ternary system made of Cetylpyridinium chloride (CPCl)/hexanol/salt water (0.9 % by mass) with and without cobalt microparticles. Phase transition temperatures of the structural sequence isotropic L 1/nematic calamitic Nc,/hexagonal H have been dete...

The sol-gel transition of homogeneous biocomposites synthesized using tetraethyl-orthosilicate alkoxide, calcium nitrate tetra hydrate and di-ammonium hydrogen phosphate salts as reagents are investigated at the macroscopic scale by small amplitude oscillatory shear measurements and probed locally by passive microrheology at 37 °C. Structural evolu...

The developments of albumin-based nanocarriers, which are nontoxic, biocompatible and biodegradable, have been extensively studied for seeking new alternatives of the treatment for numerous diseases. The most relevant characteristic of these protein-based systems are its capacity of the selectively achieve the target cells within of the brain. Thes...

This study investigated a methodology based on image processing and statistics to characterize and model the deformation upon controlled and uniform magnetic field and the relaxation under zero field of droplets observed in aqueous solutions of sodium alginate incorporating magnetic maghemite nanoparticles stabilized by adsorption of citrate ions....

In this paper we investigate the rheological complex behavior of a vase of Fergoug dam which is located in the region Perregaux (Western Algeria) as a function of aging time, shear rate, and temperature. The modified Herschel-Bulkley model is used to fit the stationary flow curves of vase as a function of aging time and the generalized model of Kel...

A new magnetorheological cell is implemented to perform measurements of temperature-controlled flows and determine viscoelastic properties in magnetic complex fluids under applied continuous magnetic fields. The flow properties of water-based and oil-based ferrofluids with volume fractions up to 10 % are investigated here in various situations of i...

We present a structural and a multi-scale rheophysical investigation of magneto-sensitive materials based on biopolymers, namely aqueous solutions of sodium alginate incorporating magnetic maghemite nanoparticles, functionalized with adsorbed negative citrate ions. The large alginate ionic strength impacts the structure and the rheology of these na...

We propose the elaboration and study of rheological properties under continuous magnetic field of magnetic sensitive biopolymer-based nanocomposites. Magnetic iron oxide (maghemite) nanoparticles were synthesized by the polyol process and then functionalized by grafting organic bifunctional ligand for establishing electrostatic bonds between the so...

It has been shown that introducing carbon nanotubes (CNT) into a polymer matrix has a beneficial effect on thermal stability of composites. While the specific effects noted differ depending on many parameters, the general trend is an increase in the degradation temperature and reduction in the degradation rate, quantified as the mass decline over t...

We have measured, by a rotational concentric cylinder viscometer, the viscosity of the AOT / water / isooctane reverse micelle [1] as a function of the volume fraction of the dispersed phase at 25°C-55°C temperature range.��The results are interpreted with several equations based on the hard sphere model. According to Vand equation [2], the shape f...

Calcium pyrophosphate nanocrystals incorporated in an amorphous silica based matrix were obtained by sol-gel process followed by heat treatment applied at 550 °C. The resulted nanocomposite was characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrosc...

In this work we describe the effects of heat treatment and of the addition of hydrogen peroxide on the physicochemical and rheological behavior of activated sludge produced in a water purification plant. An increase in temperature and dosing with H2O2 both induce a reduction in Chemical Oxygen Demand (COD) of the sludge. At the same time they cause...

The temperature and shear rate effects on rheological behavior of residual sludge from wastewater treatment plant was investigated in this work. The model of Herschel–Bulkley was used to fit the shear rate dependence of the shear stress. The temperature increase induced not only an increase in the yield stress and the flow index of sludge but also...

Mechanical properties of the extracellular matrix (ECM) play a key role in tissue organization and morphogenesis. Rheological properties of jellyfish ECM (mesoglea) were measured in vivo at the cellular scale by passive microrheology techniques: microbeads were injected in jellyfish ECM and their Brownian motion was recorded to determine the mechan...

The wastewater resulting from various urban activities cannot be directly released back to natural environment because they contain various pollutants, including organics and minerals causing potential various types of diseases. Instead, wastewater must be purified prior to its release, which leads the production of waste sludge. A large quantity i...

Reçu le 3 mai 2011-Version finale acceptée le 16 novembre 2011-Résumé : nous présentons une étude des propriétés structurales et thermomécaniques d'une phase nématique calami-tique dans laquelle sont introduites des microparticules de cobalt. Les températures de transition de phase ont été déterminées par microcalorimétrie différentielle à balayage...

We have studied the formation of three-dimensional silicon alkoxide-based network resulting from an inorganic polycondensation based on hydrolysis and condensation reactions. Using mechanical spectroscopy, small-angle X-ray scattering, and penetration measurements, we have shown that viscoelastic and morphological properties of gelling soft matter...

The local structure and the viscoelastic properties of semi-interpenetrated biopolymer networks based on cross-linked chitosan and poly(ethylene oxide) (PEO) were investigated by Small Angle Neutron Scattering and rheological measurements. The specific viscosity and the entanglement concentration of chitosan were first determined, respectively, by...

L’évolution temporelle du comportement de matériaux complexes, c'est-à-dire de matériaux à structure multi-échelle, peut être associée soit à leur structuration/déstructuration, réversible sous cisaillement, soit à la formation d’un réseau tri-dimensionnel élastique ayant la capacité de gonfler. L’étude de leurs propriétés rhéologiques nécessite la...

The mutual influence of the mineral and biological components of a specific bio-hybrid system consisting of diatom cells entrapped in a silica gel was studied by rheological methods. Small amplitude shear stress oscillatory measurements indicate that the culture medium alone has a strong impact on the silica network formation and viscoelastic prope...

The diffusion properties of caffeine and dextran within chitosan networks with controlled structure were investigated using a gel−gel method and fluorescence recovery after photobleaching (FRAP) by fringe pattern. The center of mass diffusion was studied by varying the molecular weight of dextran macromolecules labeled with fluorescein isothiocyana...

Micelle formation was followed by micro-DSC and rheology for aqueous solutions of two copolymers of PEO-PPO-PEO, the Pluronic F127 (from BASF) and the EG56 (from PolymerExpert), a branched copolymer built with three chains of F127 type. It is shown that micellization is endothermic and that, for both polymers, the enthalpy of formation/melting is p...

The water treatment, which it about production of drinking water where of waste water purification of urban or industrial origin, always leads to the sludge formation which one separates and of treated water. This sludge arises to the exit of the purification plant like a liquid with strong water content. High percentage of polluting substance gene...

We propose to analyse power law shear stress relaxation modulus observed at the sol–gel transition (SGT) in many gelling systems in terms of fractional calculus. We show that the critical gel (gel at SGT) can be associated to a single fractional element and the gel in the post-SGT state to a fractional Kelvin–Voigt model. In this case, it is possib...

A strong hysteretic behaviour has been observed for the self-focusing of a c.w. laser beam focused in a four-component micellar phase near a sponge phase in the phase diagram. All data demonstrate that the laser wave induces a structural change from the micellar phase towards a phase of droplets the nature of which is discussed. The recorded limit...

Conférence orale présentée par Alain Ponton

Regeneration of thixotropic gels resulting from aggregation of positively charged magnetic nanoparticles is here investigated by mechanical spectroscopy. The frequency independence of the ratio ( and being respectively the viscous and the elastic moduli) at the gel point seen as a liquid–solid transition allows the determination of the gelation tim...

Viscoelastic characterization of titania-based sol–gel materials are investigated. Small amplitude oscillatory measurements are used to determine the gelation time tg and the critical exponent of the frequency dependence of the loss and storage moduli. The scaling exponent is analyzed in order to estimate a fractal dimension at tg. Hydrolysis molar...

The viscoelastic properties of silica alkoxide gel during the sol-gel transition (SGT) are analysed using an extended shear relaxation modulus expression with a functional form based on a product of power law and Debye-Maxwell relaxation kernels. The dynamic properties are probed by small-amplitude oscillatory shear measurements in three viscoelast...

The study of the sol to gel transition of silicon based materials obtained from alkoxide precursor Si(OCH3)4, catalyzed by a nucleophilic activator (DiMethylAminoPyridin, DMAP) in methanol has been performed by rheological measurements and sound propagation in an audible range. Different samples obtained by varying the initial monomer concentration...

The flow birefringence and the rheological properties of four viscoelastic solutions having nearly the same zero shear viscosity and subjected to shear flows are investigated in the linear and non-linear domains. The surfactant used for the samples is the cetyltrimethylammonium chloride in water at the concentration of 100 mmol/l with an organic sa...

An experimental method based on the rotational dynamics of a magnetic probe is reported to measure the local viscoelasticity of soft materials on microscopic scales. The technique is based on the alignment of dipolar chains of submicrometer magnetic particles in the direction of an applied magnetic field. On one hand, light scattering is used to de...

The sol–gel transition of thixotropic magnetic gels is studied at macroscopic and mesoscopic scales by rheology and dynamic birefringence. Gelation times are, respectively, determined from small amplitude shear oscillatory measurements in the framework of Winter's model and from relaxation dynamic birefringence. A fractal dimension of the thixotrop...

We present an experimental method allowing a direct measurement of the local rheological behavior of complex fluids. A magnetic probe is inserted into the bulk of the fluid and submitted to a controlled magnetic force or torque, which induces a mechanical perturbation of the fluid. The geometry of the perturbation can be varied using two kinds of p...

The sol-gel transition of the system tetramethylorthosilicate-water-methanol under basic conditions has been studied by rheological measurements. The gelation time t(g) has been determined from the measurements of the elastic G' and viscous G'' moduli as a function of time at different frequencies according to Winter's criterion. At gelation time t...

The gelation of silicon oxide and titanium oxide based materials obtained from the sol–gel process at room temperature was studied through rheological measurements. The determination of the gelation time tg was investigated by the variation of the storage and loss shear moduli as a function of time at several frequencies using Winter’s criterion. T...

The rheological behavior of cosmetic concentrated water-in-oil emulsions has been investigated in relation to their microstructure. Oscillatory measurements and droplet-size distribution have been performed as a function of the dispersed phase percentage. The elastic shear modulus is shown to exhibit a universal dependence on the volume fraction Ph...

The gelation of silicon oxide and titanium oxide based materials obtained from the sol–gel process at room temperature was studied through rheological measurements. The determination of the gelation time t g was investigated by the variation of the storage and loss shear moduli as a function of time at several frequencies using Winter's criterion....

The gelation of hydrolysed alcoholic solutions of acetylacetone complexed titanium butoxide was studied through rheological measurements. The gelation time was determined through the evolution of the storage and the loss moduli versus time at several frequencies using the Winters criteria. Fractal dimensions determined from rheological measurements...

We present experimental results on the linear and non-linear rheology of elongated flexible micelles with salt. Steady shear experiments were carried out on aqueous surfactant solutions made of cetylpyridinium chloride and sodium salicylate in 0.5 M brine. The isotropic phase of entangled micelles was investigated for total surfactant mass fraction...

The motivation of this study is a recent work of Porte et al. (1997) on shear induced inhomogeneous flows of solutions of giant micelles. The authors proposed a phenomenological analysis based on a effective potential that accounts for the free energy stored in a viscoelastic material under steady shear conditions. In such a scheme, mechanical flow...

Aqueous solutions of cationic surfactant with binding counterions exhibit a transition under shear. In this paper the steady shear properties of semidilute aqueous micellar solutions (cetylpyridinium chloride and sodium salicylate in brine) are presented as a function of concentration and temperature. The shear thinning behavior of this system coul...

Rheological measurements of both electrostatically and sterically stabilized silica suspensions are analyzed on the basis of the hard sphere approximation.For electrostatically stabilized suspensions, non-Newtonian viscosity is related to an effective pairwise interaction potential. It is shown that the shear rate dependence of viscosity can be pre...

The non-Newtonian viscosity of colloidal dispersions at low electrolyte concentration is analyzed with an effective interaction potential proposed by Buscall. Experimental data at several volume fractions are compared to the model in order to first obtain interaction potentials versus surface-to-surface distance between particles, and then viscosi...

Extensive dielectric measurements in the frequency range 100 kHz–15 GHz have been performed at 25 °C on two oil-continuous microemulsion systems composed of water, n-dodecane, 1-pentanol, sodium dodecylsulfate and water, toluene, 1-butanol, sodium dodecylsulfate. It was found that in the above mentioned systems, the micellar phases display broad di...

Measurements of the electrical conductivity and the complex permittivity near a percolation threshold in the ternary microemulsion system composed of water, iso-octane, and AOT are reported. It is shown that the electrical conductivity, which implies charge transfer process, is well described by a dynamic percolation model. The frequency dependence...

We analyze in this paper, the static and dynamic properties of the laser beam self-focussing induced by a thermodiffusive (or Soret) effect in particle suspensions. We show theoretically that the beam radius exhibits oscillations along the propagation axis at the steady state, or at a given point during the transit time. These characteristics resul...

We propose a theoretical study of the nonlinear propagation of a Gaussian laser beam in a mixture of two liquids. Retaining electrostriction (dipole radiation forces), thermal expansion, and thermodiffusion (Soret effect) as the major mechanisms in the perturbation of the medium by the field, we analyze their relative importances in the nonlinear r...