Relation between microstructure and mechanical behavior of concentrated silica gels

Small-angle static light scattering of concentrated silica suspensions during in situ destabilization

“…The powder is washed by dilution and subsequent centrifugation. After removal of the supernatant, the particles are dried in a drying oven at 120 • C. Finally, a heat treatment is applied to the particles at 300 • C for three h. 1 In an earlier work we characterized the silica particles using electron microscopy [15]. We found no indication of degradation due to the grinding treatment.…”

Microstructures and mechanical properties of dense particle gels: Microstructural characterisation

“…1: Microstructure of coagulated silica suspensions at a volume fraction of 0.4 formed by the ∆pH-(left) and the ∆I-method (right) using the DCC process (particle diameter 0.525 µm). Micrographs obtained by cryogenic scanning electron microscopy [7]. * Electronic address: iwan.schenker@alumni.ethz.ch solution (∆pH-method) resulting in a "homogeneous" microstructure or by increasing the ionic strength (∆I-method) leading to a "heterogeneous" microstructure [7].…”

“…Micrographs obtained by cryogenic scanning electron microscopy [7]. * Electronic address: iwan.schenker@alumni.ethz.ch solution (∆pH-method) resulting in a "homogeneous" microstructure or by increasing the ionic strength (∆I-method) leading to a "heterogeneous" microstructure [7]. Figure 1 shows cryogenic scanning electron microscopy (cryo-SEM) pictures of both microstructures.…”

“…The particles in the ∆pH-coagulated gel present a highly homogeneous microstructure whereas in the ∆I-system inhomogeneities on the length scale of a few particle diameters are observed. This qualitative observation was quantified by the three-dimensional pair-correlation function calculated from stereo cryo-SEM images [7] and by in situ performed diffusing wave spectroscopy (DWS) experiments during destabilization [8]. The structural differences correspond to differences in the heterogeneity: the first peak of the pair-correlation function at r/d = 1 (r being the distance between the particles and d the particle diameter) is higher for the ∆I-system indicating locally denser regions with higher average coordination number.…”

Spatial Correlation Analysis of Isotropic Microvessels: Methodology and Application to Thyroid Capillaries

“…14,26 Quite interesting is that multiple interrelations were found of spatial pattern with functional features of the objects, specifically, with electrical conductance of a polymer matrix composite containing spherical carbon particles, 20 cold crushing strength of aggregate materials, 12 and elastic and yield properties in concentrated alumina and silica gels. 33 However, in all these papers, nonelongated objects were investigated, for which a considerable number of second-order estimators exist.…”