Facile synthesis of highly porous silica aerogel granules and its burning behavior under radiation

In this paper, alcogel granules were obtained in n-hexane using tetraethoxysilane as the precursor. Solvent exchange and surface modification were processed synchronously, followed by ambient pressure drying. The whole process can be completed within 12 h. To minimize shrinkage during drying process, N,N-Dimethylacetamide (C4H9NO, DMA), acting as drying control chemical additive, was introduced. The critical point of DMA was studied and determined to be at n(TEOS)/n(DMA) = 2. The resulting aerogels have a well-developed mesoporous structure, low tap density (0.086 g/cm(3)), extremely large specific surface area (1267 m(2)/g), super hydrophobicity (aS- = 162A degrees) and uniform pore size distribution. Particularly, the aerogels' burning behavior was studied using cone calorimeter under various radiant heat flux. It's found that when the heat flux reaches to 50 kW/m(2), the aerogel's combustion type turns to flame from smoulder. O-2 depletion and CO2 production rise. Heat relesase rate and total heat release increase significantly. [GRAPHICS] .