Synthesis and grafting of silica aerogels

The attack of sand with a solution of sodium hydroxide allows to synthesize a soluble metasilicate. Sodium ions were substituted by ammonium ions in order to synthesize pure silica gel. The obtained silica aerogels were amorphous. The variation of specific area and porous volume with silica concentration in the sol, with the pH of destabilization and the nature of destabilization acid were studied. The obtained aerogels were grafted by different organic molecules and characterized by high resolution solid state NMR. This technique allows to analyze the type and structure of modified silica areas. Products of silanisation used are (trimethylchlorosilane, octylchlorosilane, and ethoxyvinylsilane). They can be mono or polyfonctional, so the nature and number of bonds are different. This is due to bonding between polyfonctional silane grafts.