3D Quantitative Characterization of Local Structure and Properties of Contact Materials

The characterization of spatial distribution of different phases in materials provides understanding of structural influence on the properties and allows making physically well-grounded correlations. The FIB/SEM nanotomography opens new possibilities for the target microstructure characterization oil the scales from 10 nm to 100 mu m. It is based on the automatic serial sectioning by the focused ion beam (FIB). Scanning electron microscope (SEM) in high resolution mode can be used for the imaging of nanostructured materials. Afterwards a detailed three dimensional (3D) image analysis enables the comprehensive quantitative evaluation of local microstructure. The possibilities of these techniques will be presented on the example of silver-composite contact materials which were analyzed using FIB nanotomography before and after exposure to plasma discharge. Significant changes in the spatial distribution of the oxide particles within the switched zone induce among other effects the changes in the local electric and thermal properties. These cause eventually the failure of the contact material. Advanced methods of image analysis allow characterization of inhomogeneous distribution of oxide particles in silver contact materials. Quantitative parameters characterizing the agglomeration of oxide inclusions and accumulation of pores can be derived from the results of distance transformations and morphological operations. The additional consideration of the connectivity allows the quantification of homogeneous and inhomogeneous states with high sensitivity and confidence level. Local thermal and electrical properties were estimated using simulation software on the real tomographic data. The combination of FIB microstructure tomography with modern 3D analysis and simulation techniques provides new prospects for targeted characterization and thus understanding of the microstructure formation and local effect associated with e.g. electro-erosion phenomena [1], [2]. First correlations between 3D microstructure parameters and resulting properties will be discussed.