Arrested state of clay-water suspensions: Gel or glass?

Abstract

The aging of a charged colloidal system has been studied by small-angle x-ray scattering, in the exchanged momentum range Q=0.03-5 nm(-1) , and by dynamic light scattering, at different clay concentrations (C(w)=0.6-2.8%) . The static structure factor S(Q) has been determined as a function of both aging time and concentration. This is the direct experimental evidence of the existence and evolution with aging time of two different arrested states in a single system simply obtained only by changing its volume fraction: an inhomogeneous state is reached at low concentrations, while a homogeneous one is found at high concentrations.

Shear-induced fragmentation of laponite suspensions

“…The sol-gel transition in Laponite has been investigated mostly using light scattering [27,28,29,30,31]. The ageing properties of Laponite have triggered lots of effort and debate about the exact nature of these nonergodic states, in particular, about whether the material is actually a "gel" or a (Wigner) "glass" [30,32,33,34,35,36,37,38]. Moreover, due to their out-of-equilibrium nature, Laponite suspensions were used to test possible violations of the fluctuationdissipation theorem (FDT) [39,40].…”

Aging of rotational diffusion in colloidal gels and glasses

“…Figure 2(b) is similar to what was reported in previous works for the colloidal glass of Laponite [9]: the slow relaxation times associated with translational and rotational degrees of freedom grow exponentially with waiting time and remain parallel to each other. In the low concentration samples that were previously identified as gels [15,23,24], the slow relaxation time grows faster than exponentially for both VV and VH correlations as shown in Fig. 2(d).…”

“…Similar to the translational degrees of freedom that was reported previously [14,15,24], the aging dynamics of rotation in colloidal gels and glasses is different. One can observe two distinct routes of evolution for the rotational dynamics, providing us with another criterion [15,23,27] to distinguish colloidal gels (low concentrations) and glasses (high concentrations).…”

“…This behavior is observed at moderately low volume fractions φ ≈ 0.001-0.015 [14,15]. The aging dynamics of translational diffusion and structure factor in both ergodic and nonergodic regimes have been studied extensively over the past decade [14,15,23,24], revealing a dramatic slowing down of the translational motion. Interestingly, the intermediate scattering function measurements of Laponite suspensions have revealed that low and high concentration samples evolve in a distinctly different manner [14,15,23].…”

“…The aging dynamics of translational diffusion and structure factor in both ergodic and nonergodic regimes have been studied extensively over the past decade [14,15,23,24], revealing a dramatic slowing down of the translational motion. Interestingly, the intermediate scattering function measurements of Laponite suspensions have revealed that low and high concentration samples evolve in a distinctly different manner [14,15,23]. Based on different aging behaviors of the translational diffusion as well as the structure factor, the nonequilibrium states of Laponite suspensions in pure water have been identified to be a colloidal gel at low concentrations C < 1.5 wt% and a colloidal glass at higher concentrations C > 1.5 wt% [15,23,24].…”