Scientific activities

Team "Supercritical Fluids"

The group’s “Supercritical Fluids” is structured around a central theme that relates to the review of thermo-hydro-chemical mechanisms (THC) in fluid media reagents through a multidisciplinary approach to the interface between chemistry , physical and processes. This central theme also includes fundamental studies of the phenomena of critical points and critical boiling subject of experiments in the CNES-DECLIC instrument aboard the International Space Station, in collaboration with NASA (http: //smsc.cnes.fr/DECLIC/index.htm). Our knowledge of near-critical or supercritical THC process requirements can be used for the development of sustainable technologies in the fields of the environment, on the one hand, and materials on the other.
The research axis “environment” includes activities on thermochemical conversion of biomass, the process of hydrothermal oxidation, the geological storage of CO2 and recycling of materials.
The axis “materials” is interested in the development of advanced specific and unique properties nanostructured materials. This contract has fully exploited the technological breakthrough created with the implementation of supercritical microfluidic tool.

thèmes de recherche du groupe Fluides Supercritiques
Thèmes de recherche du groupe Fluides Supercritiques

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Some representative research work over the 2009-2014 period:

Development and use of supercritical microfluidic tools . These new tools for studying basic processes THC used to open the black box which conventionally was supercritical reactors used until 2009 Their main originality combines (i) the integration of microfabrication techniques to ICMCB for achieve internally supercritical microreactors and (ii) the construction and development of experimental setups coupled with several in situ characterization techniques (optical diagnostics, UV-visible spectroscopy and Raman).
Their use limitation, (i) the determination of the critical points of complex mixtures in wide ranges of temperatures and pressures, (ii) the visual analysis of hydrodynamics in fluid mixtures, including CO2 / water confined in sub and supercritical conditions. This activity is directly related to the problems related to geological storage of CO2. Our microfluidic tools are at the advanced base significant in understanding the processes involved in the development of materials in supercritical fluid media.

 

Microfluidique
Microfluidique

Geological Laboratories on-chip for the study of mechanisms related to deep storage of CO2. Dedicated mainly to the study of issues related to geological storage Duco 2 – to create real geological laboratories on a chip (GLoCs Geological Labs on Chips) This new business aims. Indeed, GLoCs are particularly innovative in geosciences because they can “simulate” real conditions in aqueous media representative lithospheric fluids as observed, for example, in natural fluid inclusions.
A new method for quantifying the solubility of CO2 in water or brine in wide ranges of pressure and temperature has been developed. The interest of our GLoCs was also demonstrated for the study of drainage process and reactions CO2 – brine – minerals in a 2D porous network storage conditions.

Phenomena of critical points and critical boiling . HTI inserts and ALI, used since 2009 in DECLIC instrument on the International Space Station (ISS) in collaboration with the CCIA, JPL-Caltech and NASA-GRC, are dedicated to the study of properties of universality of critical phenomena , studies of the boiling crisis, and studies of water-salt mixtures under supercritical conditions.

Mesure de la vitesse de déplacement de la ligne triple de contact solide-gaz-liquide pour l'étude de la crise d'ébullition en microgravité
Mesure de la vitesse de déplacement de la ligne triple de contact solide-gaz-liquide pour l’étude de la crise d’ébullition en microgravité

Coupling of chemistry and processes in supercritical fluid media to the development of unique nanostructures. The synthetic route in supercritical fluid media reagents for the development of advanced nanostructured materials has been extensively validated over the last five years, particularly through studies of the chemical reactivity and germination & growth in supercritical fluid media (CO2, H2O, alcohols, and mixtures thereof). Nanocrystals (NCs) of ZnO, virtually no defects, was highlighted by the mere presence of free exciton (at low temperatures) have a kind exciton luminescence. This unique optical behavior can be explained by the formation mechanism of the ZnO NCs.

 

Luminescence de type excitonique de nanocristaux de ZnO
Luminescence de type excitonique de nanocristaux de ZnO

 

 

In general, nanomaterials very low default rates are achieved through this synthetic route. The crystalline quality of the nanoparticles obtained by supercritical fluid media decouples the effects of intrinsic size of extrinsic contributions about both the electronic properties and the properties of the network (if the TSB for example). These studies of the properties of the materials are made ​​in the context of close collaboration with our colleagues ICMCB materials scientists involved. This “process” approach also allows us to take advantage of the good control of hydrodynamics in our continuous reactors, in particular, to strengthen the size distributions of nanostructures (σ <5%). A new concept of a supercritical reactor coaxial injection separates germination stages of growth & functionalization steps nanostructures; This new concept is the origin of “design” unique and multifunctional nanostructures.