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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.

The harvesting energy with electrostrictive polymers has great potential for remote applications such as invivo sensors, embedded micro-electro-mechanical systems devices, and distributed network instruments. A majority of current research activities in this field refers to classical piezoelectric ceramics, but electrostrictive polymers offer promise of energy harvesting with few moving parts; power can be produced by simply stretching and contracting a relatively low-cost rubbery material. The use of such polymers for energy harvesting is a growing field, which has great potential from an energy density viewpoint. The output power is inversely proportional to the harvester's frequency bandwidth. Consequently, it is much harder to efficiently harvest power from low-frequency sources with a large frequency band response and with a very small system size than from a stabilized high-frequency vibration source. This paper presents a new structure that is able to predict mechanical frequency excitation in order to increase power-harvesting capabilities of electrostrictive polymers. An equivalent structure scheme has been developed by using current and electrical schemes models. With a transverse strain of 0.5% and a bias field of 10 V/μm, such a process rendered it possible to increase the converted power by 80% with a low-frequency mechanical excitation. This study contributes to provide a framework for developing an innovative energy-harvesting technology that collects vibrations from the environment and converts them into electricity to power a variety of sensors. [ABSTRACT FROM AUTHOR]

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's 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's 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. [ABSTRACT FROM AUTHOR]

Polyvinyl chloride (PVC) is widely used as insulator in electrical engineering especially as cable insulation sheaths. In order to improve the dielectric properties, polymers are mixed with ceramics. In this paper, PVC composites with different weight percentages 2 wt.%, 5 wt.%, 8 wt.% and 10 wt.% were prepared and investigated. Loss index () and dielectric constant () have been measured using an impedance analyzer RLC. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) have been used as characterization techniques. The incorporation of BaTiO3 does not modify the crystallinity and the morphology of the PVC but reduces the space charges, therefore the dielectric losses. The frequency response analysis has been followed in the frequency ranges (20-140 Hz and 115-1 MHz). Relaxation frequencies have been evaluated in each frequency range. Experimental measurements have been validated using Cole-Cole's model. Experimental results show well that BaTiO3 as a filler improves the dielectric properties of PVC. [ABSTRACT FROM AUTHOR]

Abstract: Auger Electron spectroscopy (AES) has been used to study lithium segregation on Al-3.49wt%-Li alloy surface. In this work, the surface atomic composition as a function of temperature was followed. In our previous works, the activation energy of Li segregation has been determined experimentally being in agreement with the resulted theoretical value. In this paper, one showed that the segregation energy of Li on the surface depends of the crystalline structure and of the Li content in the Al-Li alloy matrix. -AlLi phase on the alloy surface, used in the power sources for the propulsion of electrical vehicles and for stocking energy, is obtained by progressive heating. We showed that the segregated lithium on the alloy surface is reversible as a function of decreasing temperature and consequently -AlLi phase is converted in -AlLi phase. On the other hand, the brutal heating of the sample drives to the conversion of the -AlLi phase to -AlLi phase and stabilizes the surface towards other segregation; therefore the conversion of -AlLi phase to -AlLi phase is irreversible. [Copyright &y& Elsevier]

Auger electron spectroscopy (AES) has been used to study Be segregation on Cu-4%at. Be alloy surface. In this work, the surface atomic composition was followed as a function of temperature at the surface, in hydrogen atmosphere. The activation energy of Be segregation has been experimentally determined. The result is in agreement with the theoretical value. It has been found that in hydrogen atmosphere, the segregation energy of Be decreases and molecular adsorption occurs at the oxidized Cu-Be alloy surface. Hydrogen and oxygen effects are discussed in terms of formation heats of Be (OH)2, Cu (OH)2, BeH, BeH2 and CuH chemical components in the alloy matrix. [ABSTRACT FROM AUTHOR]

Auger electron spectroscopy (AES) has been used to study the Be segregation on the Cu-4%at.Be alloy surface. This segregation has been studied in the presence of both chemisorbed oxygen and carbon impurity. The layer of Be formed, on the surface, by Gibbsian segregation has been followed. Its thickness has been found close to that of a monolayer. The activation energy of Be segregation has been determined experimentally and the value found is in agreement with the resulted theoretical one. [ABSTRACT FROM AUTHOR]