LOW-DENSITY SILICA-GELS AND SOLVENT PERMEABILITY

The aerogel-like properties of rite previously reported lyosils prepar ed by base catalyzed TMOS were further improved by using partially con densed TMOS followed by curing in TEOS. The cur ed and dried gels show ed lower density: < 0.3 g ml(-1), higher BET surface area: 860 m(2) g( -1) and larger pore size. The effectiveness of the curing media were t ested by measuring permeability and wettability of the liquid media. T he permeability values varied over time with a similar trend for metha nol, ethanol and octanol which exhibited decreasing permeability attri butable to re-esterification. Similar trends are grouped together for TEOS and water which exhibited increasing permeability up to similar t o 10 h due to pore coarsening and decreasing values beyond similar to 10 h attributable to the chemisorption of TEOS and silanol condensatio n with water. The curability was consistent more with wettability than permeability of the liquids tested. (C) 1997 Elsevier Science Limited .