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Mesure de tension de surface de particules microniques et submicroniques : application à la formation des nuages

Abstract : Clouds have an important impact on the Earth system, especially by rain fall and the radiative forcing and on the Climate. The cloud formation stays none well understood physical phenomena, many questions about their physics and chemistry still without answers. The formation of droplets constituents of clouds was for the first time theorized by Köhler in 1936. In this model the key parameters for the existence of a stable droplet are the size and the chemistry of the particle who act has nucleation center. In the chemistry parameter, the surface tension of the droplet plays a significant role for the smallest droplet. Since this theory, a lot of works have done to improve the model and reach a realistic one. Nevertheless, most of these semi-empirical models underestimate the surface tension parameter of the droplet and fix it to the value of pure water 72,8 mJ.m-2. Recent studies have shown the presence of surfactants in aerosol reducing the surface tension of the droplet. These studies have been done on an aerosol’s population; measures of surface tension of these aerosols are averaged on all the population. The surface tension measurements of aerosol particle to particle have been recently reached by optical Tweezer or by AFM. Particle to particle analyzed can also be done by using an ESEM, it’s a versatile tool for following the evolution of a unique particle, like hygroscopic proprieties, at relative humility from 0 to 100%. This dynamic analysis allows following the evolution of the contact angle and growth factor of water drops in presence or not of surfactants. The impacts of the nature hydrophilic or hydrophobic of the surface of the dynamic contact angle of microscopic drops have been investigated by ESEM. Development of tools for direct measurement of surface tension in ESEM has been done; measure is performed by a resistive piézo. This tool allows the direct surface tension measure of droplets with a range size 500 nm up to hundreds of micrometres. Measures have been performed by nano metallic synthesized probes, metallic nanowires with a diameter between 80 nm and 300 nm have also been used. Surface tension of known liquid and of aerosol droplet has been done with this new tool.
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Submitted on : Thursday, June 23, 2022 - 12:44:11 PM
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  • HAL Id : tel-03702765, version 1

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Clément Chatre. Mesure de tension de surface de particules microniques et submicroniques : application à la formation des nuages. Génie chimique. Université de Lyon, 2021. Français. ⟨NNT : 2021LYSE1272⟩. ⟨tel-03702765⟩

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