Preparation of Ta₂O₅ aerogels catalyzed by different kinds of acids

Ta2O5 aerogels are prepared by sol-gel technique in the presence of different kinds of acid catalysts such as HCI,HNO3 and H2SO4. The gelation time of H2SO4 system is far less than that of HCI and HNO3 systems. Moreover, the shrinkage and cracking phenomena of Ta2O5 gels in solvent exchnging process and supercritical drying process, which are unavoidable in HCI and HNO3 systems, are obviously inhibited in H2SO4 system. The SEM observations find that the particles of Ta2O5 aerogels catalyzed by H2SO4 are much bigger due to the cluster effect of nano-particles. The BET analysis finds that Ta2O5 aerogels catalyzed by H2SO4 exhibit the BJH surface area of 167 m2/g, which is much lower due to the cluster phenomenon. XPS estimating results reveal that all the S but no CI or N elements remain in Ta2O5 aerogels, indicating that S element is in the Ta-O-Ta crosslinking structure. Due to this particular structure, the shrinkage and cracking phenomena of Ta2O5 aerogels are significantly prevented, and better mechanical properties are achieved.