"Supercritical solvothermal flow synthesis of advanced nanostructured materials "

Vous êtes cordialement invités à la conférence « Supercritical solvothermal flow synthesis of advanced nanostructured materials » de Cyril AYMONIER, Institute of Condensed Matter Chemistry of Bordeaux (ICMCB), CNRS, Univ. Bordeaux, organisée par l'IPCMS

Resumé:

The specific properties of supercritical fluids are exploited for more than 35 years to develop breakthrough technologies, especially in the field of the preparation of advanced materials, from organics to inorganics through carbon-based materials. This process of material processing is continuous, fast (few tens of seconds), sustainable and scalable and gives access to high quality nanostructured materials with unique physico-chemical properties, meaning which can not be obtained with other synthetic methods. This presentation proposes to introduce first the the experimental and modelling tools developed by chemists, chemical engineers, physicists, etc, which are today available to process nanostructured materials, while allowing understanding and improving the control of their formation. For instance, a focus will be made on the description of in situ characterization techniques developed to monitor in real time and in situ several phenomena such as fluid dynamics, thermodynamics, chemistry and particle nucleation and growth.
Then the preparation of advanced materials in supercritical solvothermal conditions will be discussed with a chemist prospective. In fact, the history of this synthesis method was first written with the use of water as solvent through the supercritical hydrothermal flow synthesis, which still represents today most of the research activities. In the last 10 years, the use of supercritical water as solvent was extended to other fluids like alcohols, NH3, alkanes,… and mixtures of them. This extension by chemists to other solvents and mixtures of them for the supercritical continuous process has contributed to increase the versatility of this material synthesis approach and brought us to the development of the flow supercritical solvothermal synthesis. The chemistry accessible in most of the aformentionned solvents will be discussed.
After, this presentation will emphasize how the coupling between these chemistries and chemical engineering gives access to the formation of unique and high quality nanostructured materials. For instance, the first proof of the synthesis in few tens of seconds of geominerals, namely talc, in a continuous millifluidic process will be presented. Very interestingly, this synthetic talc exhibits unique properties as its hydrophilicity knowing that naturel talc is hydrophobic.
In this new field of geomineral synthesis, we went one-step forward with the demonstration of the possibility to prepare highly crystalline geominerals in just few seconds again but under thermodynamically metastable conditions with the synthesis of the torbermorite mineral which is not abundant in nature but very interesting in the construction industry. 
The mastering of the chemistry coupled with one pot multi-step processes opens the road towards the continuous design of multifunctional materials as illustrated with functional layer double hydroxides. All these materials can now be produced from laboratory scale for research & development investigations to pilot scale for industrial purposes. This presentation will also demonstrate the added value of the supercritical solvothermal synthesis method in terms of materials. This will be illustrated with different examples in the fields of optics, energy, catalysis and microelectronics. For instance, the integration of these nanomaterials into microsystems will be illustrated with the preparation of Metal-Insulator-Metal (MIM) capacitors with Ba0.6Sr0.4TiO3 (BST) thin films as insulating layers. The benefits of the sub- and supercritical continuous solvothermal route include not only better performances for advanced applications but also environmental issues associated with the synthesis process. This will be emphasized with the studies performed using LCA approaches coupled with risk assessment ones.