Multi-fractal imaging and structural investigation of silica hydrogels and aerogels

Abstract

In this work, we report on the preparation of TEOS gels by means of the sol-gel method employing different TEOS/ethanol/water ratios at room temperature. Small-angle X-ray scattering (SAXS) measurements provide the first-generation structural parameters, which indicate that particle size and fractal dimension are synthesis and depth dependent. These results are supported by the second-and third-generation aggregates observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The fiber-like first-generation clusters aggregate as spherical second-generation particles which, in turn, in the third generation rearrange into complex structures.

Colloidal aggregation phenomena: Spatial structuring of TEOS-derived silica aerogels

“…The synthesis conditions were identical to those used in our previous work [13]. The silica alcosols were transferred into 13-mm-length and 45-mm-diameter test tubes and were tightly covered.…”

“…In our previous work [13], we have experimentally shown the specific spatial structuring of TEOS silica aerogels. Briefly, the combination of small-angle X-ray scattering (SAXS) experiments with direct visualization techniques such as atomic force microscopy (AFM) and scanning electron microscopy (SEM), has indicated that the morphology, particle size, and fractal dimension of the TEOS aerogels depend on their position between the surface and the internal part of the corresponding wet gels.…”

Preparation of super hydrophobic silica aerogel and study on its fractal structure

“…Table 2 shows that the volume fractal dimension of DMF-modified aerogel is bigger than unmodified one. The fractal dimension (D) represented the degree of connectivity of a polymeric network [18], therefore the network of the aerogel without DMF (D = 1.44) was more open compared with the sample with DMF (D = 1.75) and the DMF-modified aerogel possessed uniform and smaller particles and PSDs, which could also be seen from their SEM photographs (Fig. 6).…”

Sol–gel simulation—I: Scattering response

“…Region 1 corresponds to a structure in critical percolation regime that spans the simulation box being modeled with Eq. (15), and region 2 corresponds to isolated clusters modeled with Eq. (24).…”

“…This technology uses colloidal aggregation [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], which after the removal of the liquid phase leaves a solid ceramic structure [28,12]. Extracting the liquid phase of the colloid gently, e.g.…”