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Compression de mélanges liquides et silice 
par chocs générés par laser jusqu’à des conditions thermodynamiques extrêmes 
d’intérêt pour les modèles des intérieurs planétaires

Abstract : Characterising the behaviour of planetary interiors’ components at extreme conditions (megabar pressures, temperatures of a few thousand Kelvin) is essential to build reliable models describing the evolution and structure of planets. In this thesis, we investigated various components on a wide set of conditions using laser-driven shock compression techniques at the LULI2000 (France) and GEKKO XII (Japan) facilities.Single decaying shocks were employed to study high-pressure / high-temperature states. To reach moderate-temperature conditions, closer to planetary interior profiles, we employed static and dynamic pre-compression techniques coupling Diamond Anvil Cells to shock compression and generating double shocks, respectively.We studied the equation of state of water-ethanol-ammonia mixtures and of pure liquid water and ammonia, of interest for icy giant structure models. Pure ammonia measurements have been particularly challenging due to cell design complexity in reason of its reactivity; we provide the first data obtained with laser shocks, in a pressure domain up to now unexplored. Mixtures data are in agreement with recent ab initio calculations based on the linear mixing approximation.We measured the optical reflectivity of liquid mixtures and silica, a key component of rocky planets’ interiors. From reflectivity data we estimated the electrical conductivity of such components — a crucial parameter for modelling the generation of planetary magnetic fields in the interiors via a dynamo mechanism.Water, ammonia, and water-ethanol-ammonia mixtures exhibit different reflectivity (hence conductivity) behaviours as a function of pressure and temperature. This suggests that pure water should not be used in dynamo models as representative of the icy mixtures.Moreover, we provide the first experimental confirmation of recent ab initio studies showing that the conductivity of silica along isothermal lines is not monotonic at moderate temperatures. Our data provide experimental support for the calculations predicting a dynamo action to occur in super-Earths’ and early Earth’s magma oceans.
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  • HAL Id : tel-02439675, version 1

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Marco Guarguaglini. Compression de mélanges liquides et silice 
par chocs générés par laser jusqu’à des conditions thermodynamiques extrêmes 
d’intérêt pour les modèles des intérieurs planétaires. Condensed Matter [cond-mat]. Université Paris Saclay (COmUE), 2019. English. ⟨NNT : 2019SACLX075⟩. ⟨tel-02439675⟩

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