Ortho-positronium migration in mesopores of MCM-41, MSF and SBA-3

Three materials: MCM-41, MSF and SBA-3 with a very similar pore diameter but different lengths of cylindrical pores were investigated using the nitrogen sorption method and positron annihilation lifetime spectroscopy. The size of primary pores and interparticle spaces obtained by both methods is similar. However, volume ratios between the discussed kinds of pores found by the above-mentioned methods differ significantly. Such discrepancy is the result of both ortho-positronium migration and the inaccessibility of the pores for nitrogen. Comparing the results of nitrogen sorption and positron annihilation lifetime spectroscopy allows us to estimate that connectivity between the primary pores and the interparticle spaces is the highest in MCM-41 and lowest in SBA-3.