Microstructure and rheology of magnetic hybrid materials

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The goal of the project is the understanding of the magnetorheological behaviour, i.e. the change of the viscous, viscoelastic and elastic behaviour of magnetic hybrid materials (MHM) in a magnetic field on a multi scale level. This requires an investigation of the correlation between changes of the microscopic structure of the material and changes of its material properties. Therefore the project is intended to fill the gap between microstructural and rheological properties, providing the theoretically working groups within the priority programme with data concerning the microstructure as well as with the corresponding magnetic field dependent material properties. The combination of experimental and theoretical results concerning the connection between microstructural changes and an adjustment of material properties by external stimuli will enable new methods for synthesis for tailored magnetic hybrid materials for certain applications. For this purpose the project will combine magnetorheological investigations, i.e. measurements of viscoelastic and elastic properties of the MHM in a magnetic field, with microstructural investigations using X-ray micro tomography. The tomographic examination of the inner structure of the MHM focuses on changes of the structure induced by external magnetic fields and mechanical loads. Since these changes can be detected for micron sized particles on a single particle level, i.e. for each particle changes of geometrical position can be evaluated individually, respective data can be used as benchmark for theoretical investigations. In the actual project phase we intend to focus on combined action of magnetic fields and mechanical loads on the samples. This way it will become possible to gain real multi scale experimental approach for the investigation of magnetorheological effects and their microscopic reasons. In combination with theoretical investigations within the SPP this will become the basis for a deeper multi scale understanding of such effects. By combination of tomographic data for changes in particle position with data for deformation of the matrix in the vicinity of the particles by WG Auernhammer an even deeper validation of the models will become possible. Moreover the rheological data can be used to provide empirical material laws needed by the application oriented groups in the SPP for the design of prototypes.