Understanding fluid transport through the multiscale pore network of a natural shale

The pore structure of a natural shale is obtained by three imaging means. Micro-tomography results are extended to provide the spatial arrangement of the minerals and pores present at a voxel size of 700 nm (the macroscopic scale). FIB/SEM provides a 3D representation of the porous clay matrix on the so-called mesoscopic scale (10-20 nm); a connected pore network, devoid of cracks, is obtained for two samples out of five, while the pore network is connected through cracks for two other samples out of five. Transmission Electron Microscopy (TEM) is used to visualize the pore space with a typical pixel size of less than 1 nm and a porosity ranging from 0.12 to 0.25. On this scale, in the absence of 3D images, the pore structure is reconstructed by using a classical technique, which is based on truncated Gaussian fields. Permeability calculations are performed with the Lattice Boltzmann Method on the nanoscale, on the mesoscale, and on the combination of the two. Upscaling is finally done (by a finite volume approach) on the bigger macroscopic scale. Calculations show that, in the absence of cracks, the contribution of the nanoscale pore structure on the overall permeability is similar to that of the mesoscale. Complementarily, the macroscopic permeability is measured on a centimetric sample with a neutral fluid (ethanol). The upscaled permeability on the macroscopic scale is in good agreement with the experimental results

Evaluation of hirst-type sampler and PM10 impactor for investigating adhesion of atmospheric particles onto allergenic pollen grains

International audienc

Observations of single pollen grains after ageing under controlled environment

International audienc

Understanding fluid transport through the multiscale pore network of a natural shale

The pore structure of a natural shale is obtained by three imaging means. Micro-tomography results are extended to provide the spatial arrangement of the minerals and pores present at a voxel size of 700 nm (the macroscopic scale). FIB/SEM provides a 3D representation of the porous clay matrix on the so-called mesoscopic scale (10-20 nm); a connected pore network, devoid of cracks, is obtained for two samples out of five, while the pore network is connected through cracks for two other samples out of five. Transmission Electron Microscopy (TEM) is used to visualize the pore space with a typical pixel size of less than 1 nm and a porosity ranging from 0.12 to 0.25. On this scale, in the absence of 3D images, the pore structure is reconstructed by using a classical technique, which is based on truncated Gaussian fields. Permeability calculations are performed with the Lattice Boltzmann Method on the nanoscale, on the mesoscale, and on the combination of the two. Upscaling is finally done (by a finite volume approach) on the bigger macroscopic scale. Calculations show that, in the absence of cracks, the contribution of the nanoscale pore structure on the overall permeability is similar to that of the mesoscale. Complementarily, the macroscopic permeability is measured on a centimetric sample with a neutral fluid (ethanol). The upscaled permeability on the macroscopic scale is in good agreement with the experimental results

Understanding fluid transport through the multiscale pore network of a natural shale

The pore structure of a natural shale is obtained by three imaging means. Micro-tomography results are extended to provide the spatial arrangement of the minerals and pores present at a voxel size of 700 nm (the macroscopic scale). FIB/SEM provides a 3D representation of the porous clay matrix on the so-called mesoscopic scale (10-20 nm); a connected pore network, devoid of cracks, is obtained for two samples out of five, while the pore network is connected through cracks for two other samples out of five. Transmission Electron Microscopy (TEM) is used to visualize the pore space with a typical pixel size of less than 1 nm and a porosity ranging from 0.12 to 0.25. On this scale, in the absence of 3D images, the pore structure is reconstructed by using a classical technique, which is based on truncated Gaussian fields. Permeability calculations are performed with the Lattice Boltzmann Method on the nanoscale, on the mesoscale, and on the combination of the two. Upscaling is finally done (by a finite volume approach) on the bigger macroscopic scale. Calculations show that, in the absence of cracks, the contribution of the nanoscale pore structure on the overall permeability is similar to that of the mesoscale. Complementarily, the macroscopic permeability is measured on a centimetric sample with a neutral fluid (ethanol). The upscaled permeability on the macroscopic scale is in good agreement with the experimental results

Ageing of single pollen grains under controlled environment

International audienc

Experimental investigation of Fe-clay/organic interactions under asteroidal conditions

International audienceCarbonaceous chondrites contain both soluble and insoluble organic materials (SOM and IOM) which may have been produced in different environments via different processes or share possible genetic relationships. The SOM may have been produced from IOM during hydrothermal episodes on asteroids, and vice versa. The potential role played by the mineral matrix during these episodes (clay minerals of variable crystallinity) remains to be constrained. Here, we exposed a mixture of formaldehyde and glycolaldehyde with ammonia-bearing liquid water together with Fe-rich smectitic minerals to hydrothermal conditions mimicking asteroidal conditions. We used both amorphous gel of smectite or crystalline smectites in order to understand the influence of the crystallinity on the evolution of OM. The organo-mineral experimental residues were characterized at a multiple length scales using X-ray diffraction and microscopy/spectroscopic tools. Results evidence that some IOM polymerizes/condenses in the absence of Fe-rich smectites. Yet, the presence of Fe-rich smectites inhibits this production of IOM. Indeed, the interactions between the SOM and clay surfaces (interlayers or edges) reduce the concentration of SOM available for polymerization/condensation reactions, a necessary step for the production of IOM. In addition, the presence of OM disorganizes the crystallization of the Fe-rich amorphous silicates, leading to smaller crystal sized particles exhibiting a lower permanent charge. This might suggests that the smectite permanent charge distribution may help better constraining the origin and evolution of chondritic clay minerals. Altogether, the present study sheds new light on the organo-mineral interactions having occurred during hydrothermal episodes onto/within chondritic asteroids. Indeed, IOM formation from OM-rich aqueous fluids does not occur during the alteration of amorphous silicates. This would mean that IOM is either produced within pockets free of clay minerals or initially accreted as IOM-rich grain. Last, about ∼50 wt.% of the initial C could not be removed from the clay minerals at the end of the experiments using classical solvent extraction protocols, demonstrating that a high fraction of the SOM in carbonaceous chondrites may have been overlooked

K-factor determination for the FEI Titan Themis (Super X four quadrant EDS system) at 300kV

National audienc

Liquid metals for boosting stability of zeolite catalysts in the conversion of methanol to hydrocarbons

Methanol-to-hydrocarbons (MTH) process has been considered one of the most practical approaches for producing value-added products from methanol. However, the commonly used zeolite catalysts suffer from rapid deactivation due to coke deposition and require regular regeneration treatments. We demonstrate that low-melting-point metals, such as Ga, can effectively promote more stable methanol conversion in the MTH process by slowing coke deposition and facilitating the desorption of carbonaceous species from the zeolite. The ZSM-5 zeolite physically mixed with liquid gallium exhibited an enhanced lifetime in the MTH reaction, which increased by a factor of up to ~14 as compared to the parent ZSM-5. These results suggest an alternative route to the design and preparation of deactivation-resistant zeolite catalysts