A small-angle X-ray scattering study of aggregation and gelation of colloidal silica

Zackrisson, Anna; Pedersen, Jan Skov; Bergenholtz, Johan

doi:10.1016/j.colsurfa.2007.07.004

Cited by 11 publications

(10 citation statements)

References 43 publications

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“…NH 4 + ions). Furthermore, as observed in the experiments, chemical accelerators can result in heterogeneous gel formation due to the non-uniform distribution of ions during aggregation (Schantz Zackrisson et al, 2008). No aggregations or clumping were observed in any of the bacterially induced gels.…”

Section: Discussionsupporting

confidence: 54%

Use of bacterial ureolysis for improved gelation of silica sol in rock grouting

MacLachlan¹,

Mountassir²,

Lunn³

2013

Géotechnique Letters

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Low pH silica-based grouts suitable for penetrating fine aperture fractures are increasingly being developed for use in engineering applications. Silica sol has an initial low viscosity and mixing with an accelerator destabilises the suspension producing a gel. The influence of sodium, calcium and ammonium chloride accelerators on gel time, rate of gelation and shear strength of the resulting gel were investigated in this study. For the first time the potential use of bacterial ureolysis as an accelerator for the destabilisation of silica sol was also explored. This study demonstrates that bacterial ureolysis can be used to control the gelation of silica sol. The rate of ureolysis increases with increasing bacterial density, resulting in faster gel times and higher rates of gelation. In addition, for grouts with similar gel times, using bacterial ureolysis to induce destabilisation results in a higher rate of gelation, a higher final shear strength and a more uniform gel than direct addition of the corresponding chemical accelerator. These results suggest that bacterial ureolysis could potentially be used in rock grouting to achieve long gel times and hence greater penetration, while also maintaining sufficiently rapid gelation to minimise issues related to fingering and erosion of the fresh grout

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Section: Discussionsupporting

confidence: 54%

Use of bacterial ureolysis for improved gelation of silica sol in rock grouting

MacLachlan¹,

Mountassir²,

Lunn³

2013

Géotechnique Letters

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“…[26][27][28]29,30 y In this respect, it would also be extremely interesting to investigate the evolution of different local structures by TEM and time-resolved small angle X-ray scattering (SAXS). 32 abruptly increases at t/t gel = 5 in concomitance with a significant volume shrinkage, in contrast to what is observed in ionogels. One should also note that for all gels (with and without ionic liquids) the intensity of the 490 cm À1 mode has already reached its maximum value at t gel , and does not evolve further.z From the breadth of the methyl formate intensity profiles, it can also be inferred that not only the reaction rate, but also the release of reaction products strongly depend on the relative ionic liquid content.…”

Section: In Situ Reaction Monitoringmentioning

confidence: 59%

An investigation of the sol–gel process in ionic liquid–silica gels by time resolved Raman and 1H NMR spectroscopy

Martinelli

Nordstierna

2012

Phys. Chem. Chem. Phys.

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We report, by employing time resolved Raman and nuclear magnetic resonance (NMR) spectroscopy, on the gelation process in ionogels. These are prepared from a non-aqueous sol-gel reaction in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C(1)C(6)ImTFSI). Raman and NMR spectroscopies are complementarily used to decipher the chemical reactions that occur during synthesis and to clarify the state of the ionic liquid up to, and well beyond, gelation. We find that the ionic liquid concentration affects both the reaction rate and the gelation time (t(gel)). In addition, NMR and Raman data reveal inherently different roles of the cation and the anion in the gelation process. While the oscillating behavior of the TFSI Raman signature at ~740 cm(-1) is mainly an effect of solvation and chemical composition, the evolution of the relative chemical shifts (Δδ) of different hydrogen atoms on the imidazolium correlates with gelation, as does the width of the chemical shift of -OH containing groups (δ(OH)). We also observe that in the confined state the TFSI anion preferably adopts the cisoid conformation and experiences a stronger ion-ion interaction.

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“…Levasil silica sol studied (the samples were not heated above 110 C for practical reasons). Zackrisson et al 16,17 found for unfunctionalized colloidal silica that if the ionic strength is low, an initial reversible aggregation or cluster formation occurs, until a certain electrolyte concentration is reached, where irreversible aggregation follows. The effect of increasing the salt concentration is therefore expected to be more effective when the ionic strength is low, explaining the steeper slope in that region.…”

Section: Samplementioning

confidence: 99%