MULTIDIMENSIONALLY RESOLVED PORE-SIZE DISTRIBUTIONS

A novel method of determining median pore size and pore size distribut ions as a function of spatial position inside a porous sample is descr ibed. Pore sizes have been measured with 1-, 2- and 3-dimensional spat ial resolution, using NMR cryoporometry in conjunction with magnetic r esonance imaging techniques. The method is suitable for pore diameters in the range of 30 Angstrom to over 2000 Angstrom pore diameter, and is based on the technique of freezing a liquid in the pores and measur ing the melting temperature by nuclear magnetic resonance. Since the m elting point is depressed for crystals of small size, the melting poin t depression gives a measurement of pore size.