| 초록 |
The preparative parameters on the synthesis and physical properties of tetraethoxysilane (TEOS) based silica aerogels prepared by two step (acid-base) sol-gel processes are reported. The formic acid (A)) concentrations were varied from 0 to 0.1 M and concentrations of NH4OH (B) was kept constant at 1M.Monolithic and transparent silica aerogel have been obtained for the values of A=0.001 M and B= 1M. The molar ratio of EtOH/TEOS (S) was varied from 3 to 8 monolithic and transparent aerogels were obtained for an value of 6.7. The highly transparent (~90%) and monolithic aerogels with lower volume shrinkage (＜20%) were obtained for the molar ratio 1:6.7:3.5:2.4 of TEOS:EtOH:acidic(H2O):basic(H2O).The aerogels were characterized by BET, SEM,UV, bulk density, Volume shrinkage. |
