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Machine thermique nano-électro-mécanique

Abstract : The purpose of this work is the study of energy transfer and dissipation at the mesoscopic scale, through the study of nanotubes, nanowires, or sharp tips for example. Our interest for energy dissipation will lead us to dive into Nano Electro Mechanical Systems (NEMS) and their quality factor. Energy transfers will be studied with small scale thermodynamics and stochastic heat engines which use those energy transfers to produce useful work (mechanical, electrical…). This work is focused in a first time on the energy dissipation and particularly on the quality factor of single wall carbon nanotubes at room temperature and the ways to improve it by applying an electrical voltage. This voltage induces a strong pulling on the nanotube and the resulting vibrating shape modification changes the dissipation. This phenomenon, coupled with a clamping modification (tunable soft clamping) also stemming from the voltage, drastically reduces the dissipation. We can then achieve record high quality factors. In a second time we take interest in heat engines: a stochastic cyclic heat engine and a continuous electrical heat engine. The stochastic heat engine is realized with a vibrating nanowire under high vacuum. The stochastic thermodynamics allow us to redefine work and heat for an object that stores energies of the order of magnitude of thermal fluctuations in the thermal bath it interacts with. The aim is to build a Carnot cycle and achieve the corresponding yield, out of reach for macroscopic engines. Concerning the continuous heat engine we study numerically a prototype for an electrical heat engine based on resonant tunneling which could be an improvement of the thermionic heat engines. Allowing the thermal reservoirs to exchange electrons through tunneling allows in principle to reduce the temperature of the hot source because overcoming the work function of both electrodes is not necessary anymore. The resonances in the tunnel effect, obtained through confinement of one dimension, is useful for filtering the energy of the electrons tunneling from one reservoir to another, thus increasing the yield of the heat engine
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https://tel.archives-ouvertes.fr/tel-02387011
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Submitted on : Friday, November 29, 2019 - 3:26:15 PM
Last modification on : Thursday, October 15, 2020 - 8:54:04 AM

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TH2019DESCOMBINALEXIS.pdf
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  • HAL Id : tel-02387011, version 1

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Alexis Descombin. Machine thermique nano-électro-mécanique. Thermique [physics.class-ph]. Université de Lyon, 2019. Français. ⟨NNT : 2019LYSE1193⟩. ⟨tel-02387011⟩

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