The compaction behavior of the vate

The compaction behavior of the vaterite powder was investigated by performing in-situ X-Ray tomography while the sample was subjected to uniaxial die pressing in a custom-made mechanical tester (Fig. 3a). To enable the visualization of individual agglomerates, this experimental setup was assembled in a synchrotron light source that provides a pixel size of 162.5 nm and temporal resolution of 0.03 Hz (PSI, Villigen). The vaterite powder was pressed inside a custom-made alumina crucible of 0.50 mm inner diameter with walls that are sufficiently thin to minimize X-Ray attenuation but thick enough to enable compression of the sample under uniaxial stress of up to 500 MPa (Fig.3b,c). By rotating the cylindrical sample around its long axis during the measurement, three dimensional reconstructions of the microstructure were first obtained when the targeted pressure was reached. This was followed by tomography measurements 2, 5, 10, 20 and 30 min after the initial scan under external pressure (Fig. 3c). The spatial resolution achieved at the beamline was high enough to visualize the shape of individual particles (Fig. 3d,e).