Aggregation and aging in silica gel

Santen, van Ra Rutger; Beelen, Tpm Theo; Garderen, van Hf; Dokter, WH Wim; Pantos, E.

doi:10.1016/0168-583x(95)00194-8

Cited by 14 publications

(11 citation statements)

References 16 publications

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“…The first hydrolysis constants for acid-and copper-catalyzed sols were found to reach 100 and 3.23 L mol À1 h À1 , respectively. These values are in line with those extrapolated (to correlate with the water/TMOS ratio of 10 used in the present study) from data reported by Van Santen et al 25 As already suggested above, the evolution of Q 0 0 species is very similar in the case of basecatalyzed and Na and K-doped samples; only the kinetics differ. The decrease is very fast in the first few minutes but subsequently, a slower regime is entered.…”

supporting

confidence: 93%

“…As a consequence, its rate of emergence would be correlated to the gelation kinetics at the macroscopic scale and can be interpreted as an aging due to a local increase in density. 25 By correlating these observations to percolation-derived 27,28 or ballistic aggregation 29 theories, the present data show that there exist two types of polycondensation. The first one occurs within a given aggregate, which favors stabilization of small oligomers and, hence, stabilizes the sol.…”

supporting

confidence: 55%

“…, Q 0 3 and Q 0 4 species. 24,25 The 550-900 cm À1 range in the Raman spectra of the acidcatalyzed sol (AC, 500 ppm HNO 3 ) (Fig. 2a) evolves rapidly.…”

Section: Resultsmentioning

confidence: 99%

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Correlation between gelation time, structure and texture of low-doped silica gels

Berrier

Courthéoux

Bouazaoui

et al. 2010

Phys. Chem. Chem. Phys.

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It is shown how the properties of a porous silica xerogel prepared using a classical sol-gel synthesis can be fine-tuned by a minor modification of the composition. The addition of a doping cation (Cu(2+), Ca(2+), Na(+)) in trace quantities in the silica sol was found to exert a dramatic effect at all stages of material preparation. An investigation of both liquid and solid phases is presented, making it possible to highlight strong correlations. The time-resolved speciation of Si-containing moieties in the sol was found to be an indication of the structuration of the gel, which was reflected by the porosity and by the molecular structure of the resulting porous material. Based on a careful comparison of several slightly doped silica gels, a model is proposed which makes it possible to predict the structure and the texture of a silica gel from data recorded early in the liquid phase.

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supporting

confidence: 93%

supporting

confidence: 55%

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Correlation between gelation time, structure and texture of low-doped silica gels

Berrier

Courthéoux

Bouazaoui

et al. 2010

Phys. Chem. Chem. Phys.

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show abstract

“…They showed that dissolution and reprecipitation of silica particles (Ostwald ripening) could not explain the simultaneous increase and decrease of the fractal dimension at small and large length scales, respectively, as observed in experimental scattering data of aged silica gels . When small movements of singly connected branches were allowed, however, resulting in multiconnected particles, the calculated SAXS spectra showed both the, small and large length scale properties of experimental SAXS plots [27] .…”

Section: Computer Simulations Of Aggregation Gelation and Agingmentioning

confidence: 90%

Inorganic particle gels

Beelen

1996

Current Opinion in Colloid & Interface Science

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“…In previous studies carried out by our group [3][4][5] the formation of silicas from water glass solutions was investigated at pH 4. Water glass was mixed into the acidic solution, and subsequently the reaction vessel was left unstirred.…”

Section: Introductionmentioning

confidence: 99%