Mechanical strengthening of TMOS-based alcogels by aging in silane solutions

It has been shown that aging of tetramethoxysilane (TMOS)-based alcogels in solutions of tetraethoxysilane (TEOS)/methanol (MeOH) provides new monomers to the alcogel and favorably increases the strength and stiffness of the alcogel and hence reduces the shrinkage during the subsequent drying. Load relaxation experiments have been performed to determine the shear modulus (G), Poisson's ratio (ν), and the permeability of wet gel rods as a function of aging time in the TEOS/MeOH solution. The modulus of rupture (MOR) and G have also been obtained from 3-point bending tests. Aging the gels in 70 vol% TEOS/MeOH causes an increase in G from 0.48 MPa to 1.8 MPa and 7.4 MPa after aging for 24 hours and 144 hours, respectively.