Comparison of methods for the characterisation by image analysis of crystalline agglomerates: The case of gibbsite

Four imaging techniques (light microscopy technique (P-OM), scanning electron microscopy with a secondary electron detector applied to powders (P-SE-SEM), scanning electron microscopy with a backscattered electron detector applied to polished sections of powders embedded in a resin, without chemical etching (S-BS-SEM) and scanning electron microscopy with a secondary electron detector applied to polished sections of powders embedded in a resin, with chemical etching (S-SE-SEM)) have been applied to crystalline agglomerates (gibbsite) to illustrate the possibilities of structural characterisation and comparison based on image analysis procedures. If P-OM can be easily applied in industry, once a suitable immersion liquid has been selected, the information collected from P-SE-SEM on the external structure is more detailed. S-BS-SEM enables the visualisation of larger sets of particles but bias, due to sectioning, should be accepted. It is related to the shape of particles. S-SE-SEM provides information on the external structure as S-BS-SEM and, in addition, on the internal structure, but with a lower output than S-BS-SEM.