Mercury porosimetry of ordered sphere compacts: Investigation of intrusion and extrusion pore size distributions

Intrusion—extrusion hysteresis in mercury porosimetry is thought to be caused either by mercury contact angle hysteresis or by the domination of extrusion by pore bodies and intrusion by throats to the pore network. Mostly, only the information obtained during the intrusion of mercury has been used in the pore structure characterization of materials via mercury porosimetry. The use of the data obtained during extrusion has been the subject of several recent studies in an attempt to reach a more complete picture of pore structure. In this work, the possible use of both intrusion and extrusion for pore structure characterization have been investigated. Submicron monosize spherical particles of silica and yttrium hydroxycarbonate were synthesized and ordered compacts of these powders have been prepared. Mercury porosimetry tests on these high-density compacts (typically 68 – 70% of sphere density) have shown the presence of two pore peaks for intrusion and extrusion with the exception of one compact. Comparisons of intrusion pore sizes with the theoretical sizes of the constrictions for ordered sphere packings have shown reasonable agreements. Similar comparisons between the sizes of cavities in sphere packings and the extrusion pore sizes did not show the same agreement. Results for one sample did not show a distinct extrusion pore size even at very large pore sizes, most probably due to the domination of mercury extrusion by very few large pores present in the sample. For all other samples, the extrusion pore sizes were close to the actual sphere size and the extrusion was most probably dominated by a few vacant sphere sites in the ] ordered structures. The results of this work have shown that the possibility of using extrusion data for pore body size distribution determination is in serious doubt. The presence of very few larger pores in the porous body may dominate the whole extrusion process and can cause the extraction of inaccurate pore size information from the extrusion data.