Observation of Metal Micro-Nanoparticles in an Epoxy Matrix during Thermal Annealing Using Synchrotron X-ray Imaging Techniques

We investigated the thermal annealing behavior of Ag-coated Cu nanoparticles in an epoxy matrix by using synchrotron X-ray transmission microscopy, coherent X-ray diffraction imaging, and scanning transmission X-ray microscopy (STXM). We observed thermal-annealing-induced void formation around the metal particles as well as shape changes in the metal particles because of the volume changes in the epoxy matrix. In addition, the density distribution of the metal particles was changed by thermal annealing. Based on the optical density measurements from the X-ray transmittance analysis, we could distinguish between the Cu-dominant region and the Ag-dominant region from the STXM images.