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Preprints, Working Papers, ... (Preprint) Year : 2023

Aluminosilicate colloidal gels : from the early age to the crystallization of zeolite

Abstract

Aluminosilicate hydrogels are often considered as precursors for the crystallisation of zeolites carried out under hydrothermal conditions. The preparation of mechanically homogeneous aluminosilicate gels allows the study of these materials in another way, especially by bulk rheology, and through the observation of the aging dynamics until the precipitation of crystalline zeolites. The first part of this study deals with the establishment of ternary diagrams, in order to identify the suitable chemical formulation for the preparation of a homogeneous gel. Recently, we have shown that these gels can be considered as fractal weak colloidal gels, exhibiting both glassy and gel-like characteristics according to the probed length and time scales [Keshavarz et al., PNAS, 2021, 118 (15), e2022339118]. By monitoring the evolution in the viscoelastic modulus during the gelation reaction, combined with measurements of the frequency dependence of the mature gels and by yielding the gel under large deformation, we first propose an empirical law considering the partial order of reaction on each chemical elements, to predict the gelation time according to the chemical formulation. Secondly, the scaling behavior of the elastic properties of this colloidal gel shows that a strong link behavior, [Shih et.al., PRA, 1990, 4 (42), 4772], is initially observed and then moves towards a weak link regime, especially by modifying the sodium concentration. The long term aging results in a shrinkage of the gel, concomitant to the coming out of interstitial liquid at the surface due to syneresis mechanism. Zeolites precipitate through crystallisation by a particle attachment mechanism, when thermodynamic equilibrium is reached. The stoichiometry of the precipitated zeolites is not only consistent with the remaining species concentration in the supernatant but surprisingly, it is also very close to the partial order of reaction of the chemical elements involved in the determination of the critical gel point. This indicates a strong correlation between the morphology and the texture of the amorphous gel network at early age and those of the final solid precipitated crystals.
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Origin : Files produced by the author(s)
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Dates and versions

hal-04245615 , version 1 (17-10-2023)

Identifiers

  • HAL Id : hal-04245615 , version 1

Cite

Donatien Gomes Rodrigues, Bavand Keshavarz, Nicolas Courtois, Jan Ilavskid, Gareth H. Mckinley, et al.. Aluminosilicate colloidal gels : from the early age to the crystallization of zeolite. 2023. ⟨hal-04245615⟩
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