Elaboration of Monophasic and Biphasic Calcium Phosphate Coatings on Ti6Al4V Substrate by Pulsed Electrodeposition Current

Calcium phosphate coatings on Ti6Al4V substrates are elaborated by pulsed electrodeposition. The surface morphology and chemical composition of the coatings are characterized by SEM–EDS. The obtained results are systematically confirmed at the nanometre scale using TEM. Moreover, XRD is performed in order to identify the coatings phases. The results show that pulsed electrodeposition allows uniform coatings to be obtained without the holes and craters usually observed with classical electrodeposition. After appropriate heat treatment, these coatings have a biphasic composition of stoichiometric hydroxyapatite and β‐tricalcium phosphate. Moreover, the addition of 9% H₂O₂ to the electrolyte leads to monophasic coatings made of stoichiometric hydroxyapatite. As an indication of the passive nature of the electrodeposited coating, electrochemical potentiodynamic tests are performed in physiological solution in order to determine the corrosion behaviour of these coatings.     

Raman spectroscopic study of the ternary system Sb2S3-As2S3-Tl2S

Raman spectroscopy has been used to study the local structure in glassy compositions of the ternary system As₂S₃-Sb₂S₃-Tl₂S. The evolution of the positions and shapes of the bands observed is attributed to modifications in the environment of arsenic and antimony corresponding to structural changes as the composition is varied.     

Building energy consumption flatness-based control using algebraic on-line estimation

A new model-based on-line control of building energy consumption with no drawbacks related to the thermal model or the unplanned changes (occupation, exterior temperature, …) is presented in this paper. The main theoretical tools of this method are the flatness-based control and the recent new setting of numerical differentiation for fast and on-line parameter estimation. Indeed the estimation techniques form an added value in terms of the reliability of the thermal model. Furthermore, the main advantage of using the differential flatness control scheme is that the system behavior can be described by the trajectory of a so-called flat output and a number of its successive time derivatives. This leads to a simple design of the control strategy without the integration of any differential equations. Numerical simulations as well as comparative studies with a classical PID (proportional-integral-derivative) controller are provided to demonstrate the relevance of the proposed approach.     

In situ monitoring of the volume change and cracking of a MgTi hydride electrode

Metastable MgTi–10 wt% Pd alloy was synthesized by high-energy ball milling and evaluated as metal hydride electrode for Ni–MH batteries. In situ acoustic emission and generated/relaxed force measurements were performed to monitor the particle cracking and volume expansion/contraction of the electrode occurring during electrochemical charge–discharge cycling. On the basis on these measurements, it was shown that the electrochemical hydrogenation of the MgTi alloy occurs first by an irreversible hydrogenation (corresponding to a charge capacity of 500 mA h g⁻¹) followed by a reversible hydrogenation (resulting in a discharge capacity of 370 mA h g⁻¹). This second step induces MgTi particle cracking and electrode collapse. During the subsequent cycles, a more reversible volume expansion/contraction is observed and the particle cracking becomes progressively less intensive and originates from the hydrogen evolution reaction rather than to the hydrogen absorption reaction.     

Viscous dissipation effects on the asymptotic behaviour of laminar forced convection for Bingham plastics in circular ducts

The present study concentrates on the effects of viscous dissipation and the yield shear stress on the asymptotic behaviour of the laminar forced convection in a circular duct for a Bingham fluid. It is supposed that the physical properties are constant and the axial conduction is negligible. The asymptotic temperature profile and the asymptotic Nusselt number are determined for various axial distributions of wall heat flux which yield a thermally developed region. It is shown that if the asymptotic value of wall heat flux distribution is vanishes, the asymptotic value of the Nusselt number is zero. The case of the asymptotic wall heat flux distribution non-vanishing giving a value of the Nusselt number dependent on the Brinkman number and on the dimensionless radius of the plug flow region was also analysed. For an infinite asymptotic value of wall heat flux distributions, the asymptotic value of the Nusselt number depends on the dimensionless radius of the plug flow region and on the dimensionless parameter which depends on the asymptotic behaviour of the wall heat flux. The condition of uniform wall temperature and convection with an external isothermal fluid were also considered. The comparison with other existing solutions in the literature in the Newtonian case is analysed.     

Étude du couplage d’une onde électromagnétique externe et d’une ligne de transmission aérienne non uniforme

In this paper, a flexible and efficient method for analyzing the electromagnetic field to nonuniform multiwire aerial lines coupling is proposed. This analysis in based upon the finite- difference time- domain (fdtd) algorithm. The transient responses of nonuniform lines excited by different waves obtained by this method are compared with those of Spice and literature. The good agreement between all the simulation results validates the proposed approach.     

Characterisation of iron inclusion during the formation of calcium sulfoaluminate phase

The iron distribution among the sulfoaluminate clinker phases and its ability to enter the calcium sulfoaluminate lattice in solid solution can have a significant influence on manufacturing process and reactivity of calcium sulfoaluminate (CSA) cements. X-ray diffraction (XRD) analysis, Mössbauer spectroscopy, scanning electron microscopy (SEM) equipped with an energy dispersive X-ray analysis system (EDAX) and infrared spectroscopy were used to identify the mineralogical conditions of iron inclusion during the formation of calcium sulfoaluminate (C₄A₃S) phase from different mixtures in the CaO-Al₂O₃-Fe₂O₃-SO₃ system. The mixtures, heated in a laboratory electric oven, contained stoichiometric amounts of reagent grade CaCO₃, Al₂O₃, Fe₂O₃ and CaSO₄·2H₂O for the synthesis of Ca₄Al_(6 − 2x)Fe_2xSO₁₆, where x, comprised between 0 and 3, is the mole number of Al₂O₃ substituted by Fe₂O₃. With x increasing from 0 to 1.5, both the iron content of C₄A₃S phase and the amounts of side components such as C₂F and CS increased. For x values included in the range of 1.5-3.0, at temperatures higher than 1200 °C, melting phenomena were observed and, instead of the C₄A₃S solid solution, ferritic phases and anhydrite were formed.     

High strength-ductility of thin nanocrystalline palladium films with nanoscale twins: On-chip testing and grain aggregate model

The mechanical behaviour of thin nanocrystalline palladium films with an ∼30 nm in plane grain size has been characterized on chip under uniaxial tension. The films exhibit a large strain hardening capacity and a significant increase in the strength with decreasing thickness. Transmission electron microscopy has revealed the presence of a moderate density of growth nanotwins interacting with dislocations. A semi-analytical grain aggregate model is proposed to investigate the impact of different contributions to the flow behaviour, involving the effect of twins, of grain size and of the presence of a thin surface layer. This model provides guidelines to optimizing the strength/ductility ratio of the films.