EFFECT OF DIMETHYLFORMAMIDE ON THE GELS STRUCTURE OF SiO2 -gels MATERIALS FROM TMOS AND TEOS

The effect of dimethylformamide (DMF) on
the gelation processes of tetramethoxysilane
(TMOS) and tetraethoxysilane (TEOS) were
investigated by Polarization Microscope. The
hydrolysis and polycondensation reactions are
carried out at 50°C, with ammonium fluoride
catalysts. The sol-gel was investigated on the
SiO2-gels formed using CP MAS29Si NMR
spectroscopy, BET and XRD. The results have
shown that the hydrolysis rate are as a function
of the quantity DMF; the highest concentration
of DMF produces the fastest gelation time[3, 4].
Both products showed the same textural
properties. N adsorption-desorption isotherms
have indicated that at higher quantity DMF an
ncrease in particle sizes and greater increase in
the mean pore size. Micrographs have shown
hat sols are made of primary particles of about
10-20 Å in diameter. These primary structural
units organize to form the secondary particles
with diameter about 40-70 Å at the agglomeration solid.