Synchrotron X-ray multiscale tomography: Visualization of heterogeneous microstructures and defects in ceramics

Synchrotron X-ray multiscale tomography is a three-dimensional (3D) imaging method that combines microtomography and nanotomography to perform a high spatial resolution measurement with a wide field of view. We show how this method can be used to track the 3D microstructural evolution at multiple length scales in powder processing, sintering, and microfracture of ceramics. Heterogeneity, complexity, diversity, and hierarchical structure of powder compact lead to various types of defects that control the quality, reliability, and lifetime of products. The elimination and formation of defects are affected by applied stress in spark plasma sintering and by internal stresses generated during differential sintering and constrained sintering. The complex subsurface crack system induced by Vickers indentation demonstrates how heterogeneous microstructures control the toughening mechanisms.