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Theses

Multi-functional nanocomposites for the mechanical actuation and magnetoelectric conversion

Abstract : Magnetoelectric (ME) interactions in matter correspond to the appearance of magnetization by means of an electric field (direct effect) or the appearance of electric polarization by means of a magnetic field (converse effect). The composite laminates which possess large ME coefficient, have attracted much attention in the field of sensors, modulators, switches and phase inverters. In this thesis, we report on the ME performances of the bi- and tri- layered composites. It is shown that their ME couplings can be achieved by combining magnetostrictive and piezoelectric layers. A model based on a driven damped oscillation is established for the piezoelectric/magnetostrictive laminated composite. It is used to simulate the mechanical coupling between the two layers. In addition, we report that the ME coupling can be achieved without magnetic phase but only with eddy current induced Lorentz forces in the metal electrodes of a piezoelectric material induced by ac magnetic field. The models based on the Lorentz effect inducing ME coupling in PZT unimorph bender, polyvinylidene fluoride (PVDF) film and PZT ceramic disc are thus established. The results show the good sensitivity and linear ME response versus dc magnetic field change. Thus, the room temperature magnetic field detection is achievable using the product property between magnetic forces and piezoelectricity. Besides, we report on the electrostrictive performance of cellular polypropylene electret after high-voltage corona poling. We use the Surface Potential test, Thermal Stimulated Depolarization Current experiment and Differential Scanning Calorimetry experiment to analyse its charge storage mechanism. The result show that the electrostrictive coefficient and relative permittivity of the charged samples increase. Last but not least, in order to explain this phenomenon, a mathematic model based on the charged sample has been established.
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https://tel.archives-ouvertes.fr/tel-00765011
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Submitted on : Friday, December 14, 2012 - 1:01:22 AM
Last modification on : Wednesday, July 8, 2020 - 12:42:14 PM
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  • HAL Id : tel-00765011, version 1

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Jiawei Zhang. Multi-functional nanocomposites for the mechanical actuation and magnetoelectric conversion. Other. INSA de Lyon, 2011. English. ⟨NNT : 2011ISAL0132⟩. ⟨tel-00765011⟩

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