Porosity of freeze-dried γ-Al2O3 powders

The porosity, inter-particulate and inter-agglomerate, of gamma-Al2O3 nanopowders obtained by the freeze-drying method has been studied. Homogeneous spherical granules with diameters ranging from 1 to 100 mu m have been obtained. These granules are constituted by soft agglomerates of nanoparticles. The pore volume and size distribution are a function of the freezing kinetics and the processing parameters. Mercury intrusion porosimetry results show that the powders exhibit a multimodal porosity. A mesoporosity with mean size of 10 nm, attributed to the interparticulate porosity, is practically constant, whereas the inter-agglomerate porosity (100-600 nm), strongly depends on the salt concentration, freezing rate and thermal treatment of the powders. (c) 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved.