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HAADF-STEM images of gold nano particles immobilized on MCM41. In cooperation with Z. Li and R. Richards, International University Bremen.

Erwachsene Weiß Schwarz Schwarz Radsportschuhe Whisper Catlike Road Unisex 2016 HAADF-STEM images of gold nano particles immobilized on MCM41. In cooperation with Z. Li and R. Richards, International University Bremen.

Classical heterogeneous catalysts consist of a nano crystalline porous support material covered by a high density of nano particles providing the active catalyst sites. In addition to the size and shape distribution of the active catalyst particles, the quality of a catalyst is crucially affected by the shape, pore size distribution and permeability of the support material as well as the distribution of the active catalyst on the support material. Using electron microscopy, it is possible to image and analyze the distribution and composition of the catalytic material. Figure 1-2 shows an example of gold nano particles immobilized on a MCM41 zeolite. The HAADF-STEM images clearly show the hexagonal pore structure of the zeolite and the average gold loading of the support material.

However, simple 2D projections mainly reveal information about the average particle density in the projected area, but the shape and pore size of the support material are difficult to interpret accurately. Furthermore, especially for thick samples, it can be difficult to unambiguously identify the catalyst particles themselves.
In contrast, the 3D volume reconstructed by electron tomography reveals significantly more details of the material's structure. Using a commercial oil refining catalyst as an example (Figure 3 and 4), it can be seen that the support material consists of nano sheets with a thickness of 4-5 nm randomly distributed in 3D, forming pores of different size and shape. Furthermore, the 3D distribution of the catalyst particles can be visualized.

Weiß Erwachsene 2016 Radsportschuhe Unisex Schwarz Catlike Schwarz Road Whisper 3-D visualization of a commercial oil-refining catalyst: the structure and pores of the alumina support and the distribution of the catalyst nanoparticles can be recognized. C. Kübel, A. Voigt, R. Schoenmakers, M. Otten, D. Su, T.-C. Lee, A. Carlsson, J. Bradley, Microscopy and Microanalysis, 2005, 11(5), 378-400; 'Recent Advances in Electron Tomography: TEM and HAADF-STEM Tomography for Materials Science and Semiconductor Applications'. Copyright 2005 Cambridge University Press.

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Surface rendering showing the detailed structure of an isolated alumina support sheet. C. Kübel, A. Voigt, R. Schoenmakers, M. Otten, D. Su, T.-C. Lee, A. Carlsson, J. Bradley, Microscopy and Microanalysis, 2005, 11(5), 378-400; 'Recent Advances in Electron Tomography: TEM and HAADF-STEM Tomography for Materials Science and Semiconductor Applications'. Copyright 2005 Cambridge University Press.

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