LES ELECTRONS SECONDAIRES DANS LE PROCESSUS AUGER A LA SURFACE DE L’ALLIAGE Cu-Be

A chaque analyse d’une surface par spectroscopie Auger, il est observé au début du spectre, entre 0 et quelques dizainesd’électrons volts suivant la nature de la surface, un pic d’électrons secondaires très intense par rapport aux pics Auger. Dans cetravail, cette partie du spectre Auger est particulièrement étudiée. La courbe de l’évolution des électrons secondaires vrais aété étudiée et comparée à la littérature. Les surfaces de l’alliage Cu-Be avant et après oxydation à l’oxygène ont étécaractérisées. L’excitation des plasmons de l’alliage, dans le cas de surfaces métallique et oxydé, sont comparées. L’effet dutravail d’extraction sur la forme de la courbe est montré

Mechanical characterization of an electrostrictive polymer for actuation and energy harvesting

Electroactive polymers have been widely used as smart material for actuators in recent years. Electromechanical applications are currently focused on energy harvesting and actuation, including the development of wireless portable electronic equipment autonomous and specific actuators such as artificial muscles. The problem to be solved is to make its devices the most efficient, as possible in terms of harvested energy and action. These two criteria are controlled by the permittivity of the electrostrictive polymer used, the Young\u27s modulus, and their dependence on frequency and level of stress. In the present paper, we presented a model describing the mechanical behaviour of electrostrictive polymers with taking into account the mechanical losses. Young\u27s modulus follows a linear function of strain and stress. However, when the elongation becomes higher, the data obtained from this strain linear trend and significant hysteresis loops appear the reflections on the existence of mechanical losses. In this work, to provide the analysis of the experimental observations, we utilized a theoretical model in order to define a constitutive law implying a representative relationship between stress and strain. After detailing this theoretical model, the simulation results are compared with experimental ones. The results show that hysteresis loss increases with the increase of frequency and strain amplitude. The model used here is in good agreement with the experimental results

Performances analysis of a piezo-pump

Piezo-pumps, in the last decade, have received extensive attention because of their potential applications in biomedical devices, biological and chemical analysis, micro-electronics cooling and space exploration. In this paper an analytical model is developed to analysis the parameters effect on the pump flow. The micro-pump driven by piezostack (PZT alloy multilayer) as actuator is studied as function size and working middle. This one is compared with SCMCP pump actuated by PZT alloy as piezomembrane. The flow change as a function frequency, the chamber diameter and control voltage are analyzed. The simulation results obtained with two different liquids (water and blood) as working middle are discussed and compared with experimental results. The results are satisfactory

Analysis of micro power generator autonomous PZT with use of sliding mode control

International audienceResearch on energy harvesting and related technologies have attracted attention and have shown their potential in a wide range of applications, the portable electronic devices (numerical telephones, diaries, microcomputers, watches, medical prostheses...) accompany us, often in a banal way, in the everyday life; they render very many services to us but, because of their insufficient autonomy, also force us in our desires of mobility and autonomy. Many mechanisms of energy conversion and device designs for vibration-based energy harvesting have been developed and reported in literature, In addition to electromagnetic and electrostatic mechanisms that have been widely applied, many other mechanisms such as electrostrictive and dielectric polymers have also been investigated. The power optimality performance of a piezoelectric energy harvester connected to a resistive load is studied. An analytical solution for the piezoelectric energy harvester based on the piezoelectric constitutive equations and the fundamental mechanics of materials relations is adapted to estimate the optimal power and vibration amplitude. The influence of geometrical parameter on the stack piezoelectric is also investigated. The power harvesting in a pressure-loaded plate depends on several factors. The dominant parameters that affect the performance are the ratio of thickness layer and the area of electrode, a designated power management module for sub mW energy harvester is proposed in this article to increase the energy conversion efficiency and extend the energy storage Life time for small input power, with use sliding mode control The specimen was simulate under tow values ratio of thickness layer and the area 1/0.09 and 0.1/0.01. The measured output voltages for two different ration is 8V and The results indicate that the electricity power output has 2.2 mW