抄録
An acid leaching process in the preparation of porous glass membranes from phase-separated glass in the Na2O-CaO-MgO-Al2O3-B2O3-SiO2 system was investigated under various leaching conditions. Whenever colloidal silica was precipitated and the diffusion of reactants was restricted in the pores, the porous glass membrane always cracked during the acid leaching process. Porous glass membrane with a smaller pore size cracked easily. However, when colloidal silica did not deposit in the pores and the overall reaction rate was controlled by leaching at the interface of the acid-soluble glass phase, the membrane did not crack. It was considered that the acid leaching process was composed of interfacial reaction-controlled and/or diffusion-controlled processes. The apparent activation energy of the former was almost constant at 42.2 kJ·mol-1 in spite of different pore sizes, whereas the activation energy of the latter increased from 8.2 kJ·mol-1 with decreasing membrane pore size. Thus, porous glass membranes with uniformly controlled pores of 200 nm or less in diameter were prepared under the interfacial reaction-controlled leaching process, and showed a mechanical strength that was high enough for practical use.
