Characterisation of Defects in Dry-Pressed Green Bodies

The influence of shaping parameters on microstructural defects (porosity gradients, residual granule structures) in dry-pressed green cylinders were investigated by three-dimensional X-ray computed tomography (3D-XRCT), liquid immersion technique (LIT) and confocal laser microscopy (CLM). The non-destructive 3D-XRCT method enables the comprehensive quantitative determination of macro porosity gradients mainly caused by friction between powder particles and die wall. The liquid immersion technique and the confocal microscopy were successfully used for the detailed characterisation of micro inhomogeneities. So the residues of the spray-dried granules and resulting small flaws in the green samples were detected and the influence of the pressing conditions on the development of such defects was assessed. (Example material: alumina.)