gamma radiolyzed amorphous silica: a study with 29Si CP-MAS NMR spectroscopy

Precipitated amorphous silica has been gamma radiolyzed at 333, 666 and 1000 kGy in air. The structural changes undergone during irradiation have been studied by Si-29 CP-MAS NMR spectroscopy. The spectra suggest that silica looses the hydrogen atoms attached to the silanol groups and the resulting silanol radicals undergo a crosslinking reaction by forming peroxysiloxane groups or by reacting with E' centres yielding siloxane groups.