Ph. Tordjeman

Institut de Mécanique des Fluides de Toulouse, Tolosa de Llenguadoc, Midi-Pyrénées, France

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Publications (29)54.35 Total impact

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    ABSTRACT: Milli-Particle Image Velocimetry (Milli-PIV), which is an application of the standard PIV has been developed to measure the velocity distribution of complex fluids in a millimetric Hele-Shaw cell. A laser sheet is sent perpendicularly to the cell and the camera observes the PIV images via an internal optical prism. We studied, with Milli-PIV, a structural series of shear thinning xanthan fluids at different injection rates. We determined the velocity profiles in the thickness of the flow cell and discussed the accuracy of measurement. Using an inverse method, we calculated the constitutive parameters and showed that they are similar to those measured by rheology. The pressure gradient characteristic of the couple experimental conditions – fluid were also calculated from modeling the velocity profile.
    Journal of Non-Newtonian Fluid Mechanics 02/2012; 169-170:114–120. · 1.57 Impact Factor
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    ABSTRACT: In this work we present a new AFM based approach to measure the local dielectric response of polymer films at the nanoscale by means of Amplitude Modulation Electrostatic Force Microscopy (AM-EFM). The proposed experimental method is based on the measurement of the tip-sample force via the detection of the second harmonic component of the photosensor signal by means of a lock-in amplifier. This approach allows reaching unprecedented broad frequency range (2-3 × 10(4)Hz) without restrictions on the sample environment. The method was tested on different poly(vinyl acetate) (PVAc) films at several temperatures. Simple analytical models for describing the electric tip-sample interaction semi-quantitatively account for the dependence of the measured local dielectric response on samples with different thicknesses and at several tip-sample distances.
    Ultramicroscopy 07/2011; 111(8):1366-9. · 2.47 Impact Factor
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    ABSTRACT: In order to measure the dielectric permittivity of thin insulting layers, we developed a method based on electrostatic force microscopy (EFM) experiments coupled with numerical simulations. This method allows to characterize the dielectric properties of materials without any restrictions of film thickness, tip radius and tip-sample distance. The EFM experiments consist in the detection of the electric force gradient by means of a double pass method. The numerical simulations, based on the equivalent charge method (ECM), model the electric force gradient between an EFM tip and a sample, and thus, determine from the EFM experiments the relative dielectric permittivity by an inverse approach. This method was validated on a thin SiO2 sample and was used to characterize the dielectric permittivity of ultrathin poly(vinyl acetate) and polystyrene films at two temperatures.
    The European Physical Journal Applied Physics 04/2010; · 0.71 Impact Factor
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    M Chinaud, T Delaunay, Ph Tordjeman
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    ABSTRACT: Ultrasonic speckle velocimetry (USV) is a non-invasive technique that allows the measurement of fluid velocity in flow and also that of powders under sedimentation. To improve the USV method, we studied the sedimentation of polymethyl methacrylate and silica particles in water. Then, we built a sedimentation cell and characterized the diameter distribution of the particles. Subsequently, we carried out a specific study to optimize the USV procedure, the signal processing and data analysis. Space and temporal resolution and USV dynamics are also discussed with regard to the optimization conditions. We found that USV is a useful technique to measure velocities between 10−5 and 1 m s−1, using appropriate ultrasonic transducers. The space resolution is fixed by the length and the percentage of overlapping of the analyzed speckle windows and varies between 48 and 536 µm for the different studied particle families. Furthermore, we found that a 0.1 ns temporal resolution could be obtained after a zero padding signal processing. In the context of our sedimentation experiments, we showed that the velocities measured by USV are in close agreement with those measured by particle image velocimetry and theory.
    Measurement Science and Technology 03/2010; 21(5):055402. · 1.44 Impact Factor
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    ABSTRACT: Dielectric relaxation (DR) has shown to be a very useful technique to study dielectric materials like polymers and other glass formers, giving valuable information about the molecular dynamics of the system at different length and time scales. However, the standard DR techniques have a fundamental limitation: they have no spatial resolution. This is of course not a problem when homogeneous and non-structured systems are analyzed but it becomes an important limitation for studying the local properties of heterogeneous and/or nano-structured materials. To overcome this constrain we have developed a novel approach that allows quantitatively measuring the local dielectric permittivity of thin films at the nanoscale by means of Electrostatic Force Microscopy. The proposed experimental method is based on the detection of the local electric force gradient at different values of the tip-sample distance. The value of the dielectric permittivity is then calculated by fitting the experimental points using the Equivalent Charge Method. Even more interesting, we show how this approach can be extended in order to obtain quantitative dielectric images of insulating thin films with an excellent lateral resolution.
    Ultramicroscopy 02/2010; 110(6):634-8. · 2.47 Impact Factor
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    ABSTRACT: We present a simple method to quantitatively image the dielectric permittivity of soft materials at nanoscale using electrostatic force microscopy (EFM) by means of the double pass method. The EFM experiments are based on the measurement of the frequency shifts of the oscillating tip biased at two different voltages. A numerical treatment based on the equivalent charge method allows extracting the values of the dielectric permittivity at each image point. This method can be applied with no restrictions of film thickness and tip radius. This method has been applied to image the morphology and the nanodielectric properties of a model polymer blend of polystyrene and poly(vinyl acetate).
    Physical Review E 01/2010; 81(1 Pt 1):010801. · 2.31 Impact Factor
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    ABSTRACT: We present a method to determine the local dielectric permittivity of thin insulating layers. The measurement is based on the detection of force gradients in electric force microscopy by means of a double pass method. The proposed experimental protocol is simple to implement and does not need any modification of standard commercial devices. Numerical simulations based on the equivalent charge method make it possible to carry out quantification whatever the thickness of film, the radius of the tip, and the tip-sample distance. This method has been validated on a thin SiO <sub>2</sub> sample for which the dielectric permittivity at the nanoscale has been characterized in the literature. We also show how we can quantitatively measure the local dielectric permittivity for ultrathin polymer film of poly(vinyl acetate) and polystyrene.
    Journal of Applied Physics 08/2009; · 2.21 Impact Factor
  • Ph. Tordjeman, N. Morel, M. Ramonda
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    ABSTRACT: We studied the friction properties of four model silicate materials at the nanoscale and microscale. From nanotribology, we characterized the tribological properties at single asperity contact scale and from microtribology, we characterized the tribological properties at multi asperity contact scale. First, for each material we measured chemical composition by XPS, Young's modulus by acoustical microscopy and roughness σ by atomic force microscopy (AFM). Second, we measured the nanofriction coefficients with an AFM and the microfriction coefficients with a ball probe tribometer, for three hardnesses of the ball probe. We identified one friction mechanism at the nanoscale (sliding friction) and two friction mechanisms at the microscale (sliding friction and yielding friction). Comparison of the nano and microfriction coefficients at the same sliding friction regime shown, that the tribological properties of these materials didn’t depend on roughness.
    Applied Surface Science 01/2009; 255(15):6999-7004. · 2.54 Impact Factor
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    N Morel, Ph Tordjeman, F Augereau, J Attal
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    ABSTRACT: We studied the tribological properties of a structural series of 11 silicate materials to identify the main physical parameters that control the brittle wear of these materials. First, for each material we characterized Young's modulus E by ultrasonic microscopy, roughness σ by atomic force microscopy and crack pressure P c by Hertzian indentation testing. Second, we measured the static and dynamic friction coefficients µ S and µ D , respectively, with a ball probe tribometer for each material and for three hardnesses of the ball probe. The experiments showed that crack density, which quantified the brittle wear of the materials, was controlled by an adimensional number, C r = P c /µ S E. We show in this paper how this number takes into account the combined effects of the mechanical properties, the lubricating coating layer and the residual internal stresses of these materials.
    Journal of Physics D Applied Physics 01/2008; 41:35307-7. · 2.53 Impact Factor
  • N. Morel, M. Ramonda, Ph. Tordjeman
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    ABSTRACT: The lateral force microscope can provide information on frictional properties on surfaces down to the nanometer scale. Reproducible quantitative measurements require an accurate calibration of the mechanical response of cantilever. In this letter, we propose a fast and nondestructive method to determine the normal and lateral cantilever stiffness, kcantileverN and kcantileverL, used to calculate the normal and friction forces.
    Applied Physics Letters 04/2005; 86(16):163103-163103-3. · 3.52 Impact Factor
  • N Morel, Ph Tordjeman, M Ramonda
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    ABSTRACT: Nanotribology with an atomic force microscope (AFM) requires an accurate calibration of the mechanical response of the cantilever. To determine the friction coefficient on the nanoscale, we have developed a new calibration method to determine the normal and lateral cantilever stiffness, and , used to calculate the normal and friction forces, which allow us to calculate the nanofriction coefficient μ. Comparative experiments on a silicon wafer with two cantilevers of different dimensions validate our calibration method. The nanofriction coefficient μ of two materials, one silicate glass and the same glass with a 100 Å SnO2 layer, has been measured by AFM after calibrating the cantilever stiffness. The different values of μ show the lubrication effects of the SnO2 layer on the nanoscale.
    Journal of Physics D Applied Physics 03/2005; 38(6):895. · 2.53 Impact Factor
  • N Morel, Ph Tordjeman, J Duwattez, E Papon
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    ABSTRACT: Two new devices were developed to provide accurate measurements of both the contact area and the tack strength of pressure-sensitive adhesives (PSAs). The first one is the "mechano-optical tack tester" (MOTT), which was designed to apply controlled contact pressure by means of a quartz prism probe, for determined contact times, onto the surfaces of PSA samples. The contact area is measured by the reflection of light at the quartz probe surface, which is in contact with the adhesive. The second device is an "acoustic contact tester" (ACT) that measures the tack strength and the contact area between a silicate glass and an adhesive by the reflection of an acoustic wave. Two ultrasonic sensors of different acoustic wavelengths have been built in order to study the scaling effects of the contact kinetics between an adhesive and the probe. MOTT and ACT experiments on a commercial PSA show that the contact area is the main parameter that governs the tack properties of the PSA. The experiments and the modeling point out that the contact area depends on the compression stress, the roughness, the thickness, and the Young's modulus of the PSA. However, comparison of contact kinetics from MOTT and ACT experiments show that the contact area is a subjective parameter that depends on the wavelength of the reflected beam used for its measurement.
    Journal of Colloid and Interface Science 01/2005; 280(2):374-9. · 3.55 Impact Factor
  • Journal of Rheology 01/2004; 48(1). · 2.80 Impact Factor
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    ABSTRACT: PSA films are obtained by coalescence of latices synthesized by free-radical emulsion polymerization of methyl methacrylate (MMA) and 2-ethylhexyl acrylate (EHA). For the same overall 50/50 molar composition, the polymer particles have well-defined structures when the feed composition and the feed mode (using batch or semicontinuous processes) are adjusted. The characterizations of the film structures by surface (tapping mode AFM) and bulk (DSC, rheology) analyses argue for the conservation of the initial particle structure when coalescence occurs. The influence of the chemical heterogeneity on the tack properties of the films is investigated to extend the study of these original acrylic PSA films up to relevant structure-property correlations.
    Journal of Colloid and Interface Science 01/2004; 268(2):341-7. · 3.55 Impact Factor
  • Ph. Tordjeman, J.Y. Ferrandis
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    ABSTRACT: High temperature viscoelastic properties of two different silicate glass melts have been measured with a new high temperature rheometer between 700 and 900 °C. Our experiments demonstrate that the viscoelastic properties in the terminal zone, a low frequency domain which has never been explored, are very sensitive to the chemical composition of the glass and to the thermal treatment applied during the preparation of the samples. The storage shear modulus G′ and the loss shear modulus G″ were measured at constant temperature between 10−3 and 102 rad/s. The two chosen silicate glass melts have different chemical compositions and moreover one of them was prepared with two thermal treatments during the sample molding. In the experimental range of temperature, the viscoelastic properties of the two glass melts are characteristic of the ultimate rheological behavior at low frequencies called the terminal zone. We tested the possibility of building the rheological master curve of the two liquids over a wide frequency domain. Experiments show that one glass melt has a Maxwell viscoelastic behavior and obeys time–temperature superposition. Its master curve shows that the glass melt follows the Williams–Landel–Ferry equation. On the other hand, the second glass is non-Maxwellian and does not obey time–temperature superposition. In that case, the master curve cannot be built showing a phase transition, or structural change transition, between 700 and 900 °C.
    Journal of Non-Newtonian Fluid Mechanics 01/2004; 117(1):63-70. · 1.57 Impact Factor
  • J. Soullier, P. Tordjeman, P. H. Mutin
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    ABSTRACT: The formation of octadecylphosphonic acid self-assembled monolayers (SAMs) on titanium deposited by cathodic sputtering on planar substrates has been studied by water contact angle measurements and Atomic Force Microscopy (AFM). Dense monolayers were obtained after one week of reaction. Tribological experiments indicated that these monolayers had good lubricating properties, which were maintained after immersion in a 1 M NaOH solution at 65 °C for up to 100 min. The stability in alkaline media of octadecylphosphonic acid SAMs on titanium was ascribed to the high chemical stability of Ti-O-P interfacial bonds.
    MRS Proceedings. 12/2003; 847.
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    Ph. Tordjeman, J. M. Felio, L. Gazagnes
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    ABSTRACT: High-temperature viscoelastic properties of two different silicate glass melts have been measured with a new high-temperature rheometer between 700 °C and 900 °C. Our experiments demonstrate that the viscoelastic properties in the terminal zone, a low-frequency domain which has never been explored, are very sensitive to the chemical composition of the glass and to the thermal treatment applied during the preparation of the samples. The storage shear modulus G′ and the loss shear modulus G″ were measured at constant temperature between 10−3 and 102 rad/s. The two chosen silicate glass melts have different chemical compositions and, moreover, each of them was prepared with two thermal treatments during the sample molding. In the experimental range of temperature, the viscoelastic properties of the two glass melts are characteristic of the ultimate rheological behavior at low frequencies called the terminal zone. We tested the possibility of building the rheological master curve for the two liquids over a wide frequency domain. Experiments show that one quenched glass melt has a Maxwell viscoelastic behavior and obeys time–temperature superposition, while the same glass annealed below the glass transition temperature presents changes in the viscoelastic behavior and does not obey time–temperature superposition. The second glass is non-Maxwellian and does not obey time–temperature superposition for the two thermal conditions of molding showing a phase transition, or a structural change transition, between 700 °C and 900 °C. We observed a great influence of the thermal treatment on the viscoelastic properties in the melted state for the two silicates. © 2003 American Institute of Physics.
    The Journal of Chemical Physics 12/2003; 119(24):13129-13134. · 3.12 Impact Factor
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    ABSTRACT: Free radical emulsion polymerization of methyl methacrylate (MMA) and 2-ethylhexyl acrylate (EHA) results in the synthesis of pressure-sensitive adhesives (PSAs) with good tack properties. Management of both the copolymer composition and the polymerization process allows one to control the behavior of the PSA. Semicontinuous (SC) processes create polymer particles whose instantaneous composition is close to that of the feed particle The SC Mixture process (continuous feeding with comonomer blends) affords nearly homogeneous latex particles and PSA films. The SC Gradient process (separate feedings at inversely varying rates) affords heterogeneous particles and films. The Batch process leads to somewhat heterogeneous films, but the hard (MMA-rich) microdomains are made compatible with their soft (EHA-rich) matrix because of the assumed formation of tapered-type copolymers. Tack measurements indicate the importance of the particle and film structures. Too much hardness or softness leads to unacceptable lacks of adhesion and cohesion, respectively. Homogeneous structures prove adequate, but their tack properties collapse with rising temperature. Heterogeneous structures, with extensive phase segregation, prove unsatisfactory because they lack adhesion and cohesion. Finally, the association of well-balanced composition and compatible heterogeneity is the criterion for suitable PSA behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2749–2756, 2003
    Journal of Applied Polymer Science 06/2003; 89(10):2749 - 2756. · 1.40 Impact Factor
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    T. Tixier, Ph. Tordjeman
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    ABSTRACT: Five model polydimethylsiloxane (PDMS) networks were obtained by hydrosilation of a difunctional vinyl-terminated PDMS prepolymer with a SiH containing crosslinker. Viscoelastic experiments were performed in order to study the influence of molecular parameters on the dynamic properties at the sol–gel threshold. The results suggest that the critical exponents are not universal and depend on the chemical structure of the incipient gels. They show that the fractal dimension calculated from the rheological data in the framework of the viscoelastic mean field theory, is a decreasing function of the ratio functionality/molecular weight of the crosslinker.
    Polymer 01/2003; · 3.77 Impact Factor
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    ABSTRACT: Pressure-sensitive adhesives must develop simultaneously two conflicting properties:  adhesion and cohesion. To fulfill these requirements, it is imaginable to synthesize suitable materials by free-radical emulsion copolymerization of complementary monomers:  methyl methacrylate (MMA) and 2-ethylhexyl acrylate (EHA). The copolymerization kinetics of various MMA/EHA mixtures is studied using a “batch” process. In all cases, the reaction proceeds at a steady-state rate and the copolymer composition (evaluated by 1H NMR analysis) is quite proportional to the conversion degree. The tack properties of films obtained by coalescence of the latexes are evaluated using a “mechano-optical tack tester”, which allows one to determine the tack strength (Ftack), the tack energy (Gtack), and the actual contact area (A) as functions of time. These tack properties are correlated with the copolymers and adhesive film structures.
    Chemistry of Materials - CHEM MATER. 07/2001; 13(8).

Publication Stats

150 Citations
54.35 Total Impact Points

Institutions

  • 2009–2012
    • Institut de Mécanique des Fluides de Toulouse
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2011
    • Universidad del País Vasco / Euskal Herriko Unibertsitatea
      Leioa, Basque Country, Spain
  • 2010
    • Center of Materials Physics
      San Sebastián, Basque Country, Spain
  • 2009–2010
    • French National Centre for Scientific Research
      • Institut d'Electronique du Sud (IES)
      Montpellier, Languedoc-Roussillon, France
  • 2000–2008
    • Université de Montpellier 1
      Montpelhièr, Languedoc-Roussillon, France
  • 2005
    • Université Montpellier 2 Sciences et Techniques
      • Institut d'Electronique du Sud (IES)
      Montpelhièr, Languedoc-Roussillon, France