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Résumé |
We assist nowadays at the continuous development of materials and methods employed for the synthesis of nanomaterials exhibiting sometimes unexpected properties. In order to understand their origin and to explain the subsequent materials behavior upon applications, one needs to find the close correlation between the synthesis methods and materials fundamental physical and chemical characteristics. Though the Transmission Electron Microscopy (TEM) allows the access to the atom scale morphological, structural and chemical characteristics, it has been shown that only a 2D approach is from time to time not enough to explain the behavior of complex systems under given conditions. Therefore, the scientific community turned its attention to the electron tomography (ET), a powerful tool that allows the passage to the 3rd dimension. In principle, the volume is reconstructed by using a series of images acquired by specimen tilting over an angular range as wide as possible. When combined to different working modes, one can access specimen morphology, i.e. shape porosity, identify facets within crystalline nanostructures, assess for the short and long order characteristics, etc. A particular place is actually attributed to the “analytical” tomography, which adds another “dimension” to the 3D reconstructed volumes, the chemical composition. This is a doubly selective technique as it combines the electron tomography with the filtered imaging and gives a 3d chemical apprehension of complex morphologies. The power of electron tomography as applied to different systems and under different working modes will be highlighted, by focusing on suggestive examples. The benefits of 3D electron microscopy as performed under different modes and conditions, together with the technique complementarity with other methods employed in materials research will be exposed. Finally, the use of different TEM based methodologies as applied to complex systems will be exposed in order to get deep insights on materials behavior under well defined conditions. |
