Structural changes of monolithic silica gel during the gel-to-glass transition

Kawaguchi, T.; Iura, J.; Taneda, N.; Hishikura, H.; Kokubu, Yoshinori

doi:10.1016/0022-3093(86)90110-9

Cited by 46 publications

(15 citation statements)

References 7 publications

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“…8 It has been pointed that most alkoxide-derived gels may not exhibit a CRP since the liquid phase of the gel is a mixture of water and alcohol. 7 Kawaguchi et al 9 found the evaporation rate to be initially constant for large pore silica gel, meanwhile Hench and Wilson 8 did not find a constant rate of loss of weight during drying alkoxide-derived gels, even when normalized to the surface area.…”

Section: Introductionmentioning

confidence: 99%

Small-angle x-ray scattering study of the structural evolution of the drying of sonogels with the liquid phase exchanged by acetone

et al. 2004

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The structural evolution on the drying of wet sonogels of silica with the liquid phase exchanged by acetone, obtained from tetraethoxisilane sonohydrolysis, was studied in situ by small-angle x-ray scattering ͑SAXS͒. The periods associated to the structural evolution as determined by SAXS are in agreement with those classical ones established on basis of the features of the evaporation rate of the liquid phase in the obtaining of xerogels. The wet gel can be described as formed by primary particles ͑microclusters͒, with characteristic length a ϳ0.67 nm and surface which is fractal, linking together to form mass fractal structures with mass fractal dimension Dϭ2.24 in a length scale ϳ6.7 nm. As the network collapses while the liquid/vapor meniscus is kept out of the gel volume, the mass fractal structure becomes more compacted by increasing D and decreasing , with smoothing of the fractal surface of the microclusters. The time evolution of the density of the wet gels was evaluated exclusively from the SAXS parameters , D, and a. The final dried acetone-exchanged gel presents Porod's inhomogeneity length of about 2.8 nm and apparently exhibits an interesting singularity D →3, as determined by the mass fractal modeling used to fit the SAXS intensity data for the obtaining of the parameters and D.

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Section: Introductionmentioning

confidence: 99%

Small-angle x-ray scattering study of the structural evolution of the drying of sonogels with the liquid phase exchanged by acetone

et al. 2004

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“…However, application of this model to strain data obtained on mesoporous glass with dilatometric setups during gas adsorption revealed that Bangham's model alone was only partially able to explain the observed effects [4,5]. The issue of mesopore deformation received renewed attention in the context of drying and characterization of silica aerogels in the 1980's and 90's [6][7][8]. Using in-situ dilatometry measurements Reichenauer and Scherer demonstrated large sorption-induced strains exceeding 40 vol % during the characterization of aerogels with nitrogen sorption at 77 K, which lead to highly erroneous pore size distributions [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Relationship Between Pore Structure and Sorption-Induced Deformation in Hierarchical Silica-Based Monoliths

Balzer

Morak

Erko³

et al. 2015

Zeitschrift Für Physikalische Chemie

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Abstract:Experimental results on sorption-induced deformation during npentane desorption were obtained by in-situ dilatometry and in-situ small angle X-ray scattering (SAXS). The sample investigated was a silica-based monolith with hierarchical pore structure comprising a macroporous network of struts, each strut containing well-defined cylindrical mesopores ordered on a 2D hexagonal lattice. In-situ dilatometry and in-situ SAXS measurements revealed strain isotherms of similar shape, which are qualitatively in good agreement with recent theoretical predictions. From the relative pressure range of the liquid filled mesopores a pore load modulus of 1.5 GPa is determined. The relative pressure region of mono-and multilayer formation, however, reveals differences between the two independent methods. In particular, the net strain at saturation pressure is considerably larger for in-situ dilatometry. We attribute this observation to the different sensitivity of the two methods to anisotropic deformation in the hierarchical solid framework. While in-situ SAXS measures the mesopore lattice strain and is therefore exclusively sensitive to radial deformation of the struts, dilato-*Corresponding authors: Oskar Paris,

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“…The SCC-treated silica samples were polished to remove the surface layers by a set of silicon carbide sandpapers [37,38]: 320-grit first, then 600-grit, 1200-grit, and eventually 2500-grit. Before the SCC treatment, the sample thickness was 10-14 mm; after the calcination, the thickness shrank to 7-9 mm.…”

Section: Sample Processingmentioning

confidence: 99%