Mercury porosimetry applied to porous silica materials: successive buckling and intrusion mechanisms

Some silica low-density xerogels exhibit two successive volume variation me chanisms, compaction and intrusion when submitted to mercury porosimetry. T he position of the pressure of transition P-t between the two mechanisms is characteristic of the tested material and allows to compute the buckling c onstant used to determine the pore size distribution in the compaction part of the experiment. The analysis of the mercury porosimetry data of a low-d ensity xerogel wrapped in a tight membrane by the buckling law (intrusion i s prevented and the sample is crushed during the whole porosimetry experime nt) leads to a continuous unimodal distribution similar to the distribution of the unwrapped sample obtained by applying the buckling law below P-t an d the intrusion law above P-t. This experiment confirms the validity of the use of the buckling law. The behaviour of the low-density xerogels can be related to one of their morphological characteristics. As the size of the a ggregates of silica particles increases, the strength towards crushing incr eases and the change of mechanism from crushing to intrusion takes place at a lower pressure. (C) 2001 Elsevier Science B.V. All rights reserved.