The Influence of Acidic Treatment and Mechanical Grinding on the Structural Characteristics and Morphology of Pores in Iron-Containing Sodium-Borosilicate Porous Glasses

The method of low-temperature equilibrium nitrogen adsorption and desorption has been employed to study the porous structure and morphology of porous glass (PG) with a composition of (wt %) 1.54Na2O·6.02B2O3·82.24SiO2·10.20Fe2O3 as depending on the acidic treatment of initial phase-separated glass and mechanical grinding of PG obtained by the through acidic leaching of phase-separated glass with an interconnected structure. It has been found that all studied PG samples have a polymodal mesopore size distribution and contain micropores. Judging by the desorption isotherms, the main modes of the mouth sizes of the mesopores correspond to 3.6–3.8 and 23–25 nm. The micropores have sizes of 1.1–1.4 nm. The calculated structural coefficient indicates that the mesopores have predominantly cylindrical shapes. The comparison between the modes in the distribution curves obtained from the data on adsorption and desorption has indicated the presence of bottle-shaped and conical pores. Mechanical grinding of PGs to the powdered state does not changes the general pattern of the adsorption-desorption isotherms but enhances the volume of mesopores due to the opening of internal dead-end pores and widens the mode of 24-nm liquation channels. An increase in the duration of the acidic leaching under boiling from 7 to 14 h leads to a rise in the mesopore volume and average mesopore diameter by 35 and 25%, respectively. At the same time, the fraction of the micropores in the total pore volume decreases by nearly 10%, while the 8.0-nm mode increases. The results obtained may be useful for improving the synthesis conditions and widening the application fields of PGs exhibiting magnetic properties.