Abstract
Thermoporometry (TPM) was applied to characterize a series of mesoporous silicas with uniform and cylindrical pores immersed in water by using the model which classified the water confined in the pores into two different types, i.e. freezable pore water which can form a cylindrical ice crystalline in the mesopores, and non-freezable pore water which can not undergo water-ice phase transition due to the strong interaction with pore surfaces. By applying the empirical relation between a size of the ice crystalline and the solidification temperature of the freezable pore water to a freezing thermogram, i.e. a recording of heat flux during the solidification of the freezable pore water, we succeeded in obtaining a size distribution of the ice crystalline formed in the mesopores. The size of the ice crystalline was clearly shown to decrease with the decrease in pore size, and finally the freezing of water confined in the pores whose diameter was smaller than c.a. 2nm could hardly be observed. By adding the thickness of the layer of the non-freezable pore water to the size of the ice crystalline formed in the mesopores, the size distribution, the surface area and the volume of the mesopores could be determined. The porous properties determined by TPM were compared with those measured by applying the non-local density functional theory (NLDFT) to adsorption isotherms of Ar at 87K.
