Abstract
Porous glass specimens were prepared from a fluorine-containing borosilicate glass and were chemically treated up to ten times repeatedly. During the treatment, the hydrogen fluoride which was generated by the reaction between ammonium fluoride and sulfuric acid in the open pores was allowed to react with the porous glass specimen. The untreated porous glass had the porosity of 28%, the pore volume of 0.179ml/g, and the surface area of 22m2/g. After treated ten times, the porosity and the pore volume increased to 37% and 0.268ml/g, respectively, while the surface area remained almost unchanged. The nitrogen adsorption and Hg intrusion measurements revealed that there exist pores having the diameter of 10-50Å and 300-600Å in the untreated porous glass. The pores having the diameter of 10-30Å completely disappeared after two times of the treatment, which was attributed to the removal of colloidal silica precipitated in the larger pores during the preparation process of porous glass. On the other hand, through the repeated treatments, the amount of pores of 30-300Å and 400-700Å relatively increased, while that of pores of 300-400Å decreased. This change was considered to result from further dissolution of the pore surface. Consequently, the liquid permeability in the porous glass was found to increase considerably by the chemical treatment described above.
