CNRS Research Scientist
Topics of Research
Composite materials, composed of at least two components, are particularly promising systems for the novel properties arising, such as optical, photonic or mechanical properties. Within the LSFC, we are interested in the synthesis and the shaping of textured composite ceramics, so-called “artificial nacres”. Indeed, organisation within the composite is a crucial parameter to promote the desired effect. For example, natural nacre, formed by a “brick and mortar” organisation of Aragonite platelets in an organic matrix, is a material that presents a toughness more than 10 times higher than the expected toughness from a homogeneous mixing of its components. For a long time, we have been interested in organisation of alumina platelets in a glass phase (works of Sylvain Deville, CNRS Research Director, and his team). Now, we are developing novel anisotropic metal-oxide particles to be used as bricks, and we study the effect of the matrix (polymer or inorganic). We use several shaping methods for the material, such as ice-templating or 3D-printing..
Synthesis of anisotropic particles
Via diverse synthesis protocols, we study the formation of micron-sized metal-oxide particles with a well-defined morphology to be used as bricks in the fabrication of artificial nacres. We have for example synthesised silica particles with diverse morphologies (platelets, rice shape, short or long rods, donuts). To understand the synthesis mechanisms and do rational design, we use small angle x-ray/neutron scattering (and associated techniques) via beamtime applications at large-scale facilities (Soleil, ISIS, ILL, ESRF…). We currently study diverse metal-oxides, to create high-toughness ceramics or even conductive ceramics for example.
SEM micrographs of silica particles, from 
Organisation of anisotropic objects
One of the aim to form artificial nacres is to tailor the arrangement of the anisotropic bricks within the material, notably by controlling their orientation. We study diverse methods to orient µm-sized or nm-sized particles in suspensions or gels: use of an electric field, effect of shear, ice-templating or 3D-printing methodologies. We hence have to develop tools and methods to study and quantify this orientation (SEM imaging, SAXS/USAXS etc).
 Schmitt, J. et al, Anisotropic mesoporous silica/microgel core–shell responsive particles, RSC Advances (2020), 10, 25393-25401. DOI: 10.1039/D0RA02278K
 Schmitt, J. et al, Mesoporous silica formation mechanisms probed using combined Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) and Small Angle Neutron Scattering (SANS), ACS Applied Materials and Interfaces (2020), 12 (25), 28461–28473. DOI: 10.1021/acsami.0c03287
 Schmitt, J. et al, Outset of the Morphology of Nanostructured Silica Particles during Nucleation followed by Ultra Small Angle X-ray Scattering, Langmuir (2016), 32 (20), 5162–5172. DOI: 10.1021/acs.langmuir.6b00572
|Julien Schmitt||CNRS Research Scientist||Julien.Schmitt@saint-gobain.com|
|Baptiste Rouchié||M2 Intern|