Dichotomic aging behaviour in a colloidal glass

Angelini, Roberta; Zulian, Laura; Fluerasu, Andrei; Madsen, Anders; Ruocco, G.; Ruzicka, Barbara

doi:10.1039/c3sm52173g

Cited by 70 publications

(78 citation statements)

References 27 publications

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“…While a stretched behaviour with bo1 has been reported for spontaneously aged samples at all waiting times, a surprising behaviour is found for the rejuvenated samples upon varying the rejuvenation time, t R . Samples rejuvenated before a certain critical time t c show a stretched behaviour (bo1) while samples rejuvenated after t c exhibit a compressed behaviour (b41) in agreement with a recent study 31 . This is shown in the inset of Fig.…”

Section: Dilution Experimentssupporting

confidence: 91%

Glass–glass transition during aging of a colloidal clay

et al. 2014

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Colloidal suspensions are characterized by a variety of microscopic interactions, which generate unconventional phase diagrams encompassing fluid, gel and glassy states and offer the possibility to study new phase and/or state transitions. Among these, glass-glass transitions are rare to be found, especially at ambient conditions. Here, through a combination of dilution experiments, X-ray photon correlation spectroscopy, small angle X-ray scattering, rheological measurements and Monte Carlo simulations, we provide evidence of a spontaneous glass-glass transition in a colloidal clay. Two different glassy states are distinguished with evolving waiting time: a first one, dominated by long-range screened Coulombic repulsion (Wigner glass) and a second one, stabilized by orientational attractions (Disconnected House of Cards glass), occurring after a much longer time. These findings may have implications for heterogeneously charged systems out-of-equilibrium and for applications where a fine control of the local order and/or long term stability of the amorphous materials are required.

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Section: Dilution Experimentssupporting

confidence: 91%

Glass–glass transition during aging of a colloidal clay

et al. 2014

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“…While a stretched shape would suggest a distribution of Brownian diffusors, with a heterogeneous distribution of relaxation times, the transition to a compressed shape, accompanied by n ≈ 1 is a signature of an arrested system. Similar stretched-compressed dynamical crossovers have been also reported in a few different out-of-equilibrium materials such as nanoparticles in a glass-former matrix [35], metallic glasses [36], and, very recently, in Laponite suspensions by Angelini et al [37]. In the last, the authors observed γ ≈ 0.75 in an aged Laponite suspension (C w = 3.0%), while rejuvenation by means of mechanical perturbation seems to induce a more compressed shape (γ = 1.5 at low q, decaying to 1.25 as q increases).…”

Section: B Intrinsic Dynamics Probed By Gi-xpcssupporting

confidence: 80%

Controlling the dynamics of a bidimensional gel above and below its percolation transition

et al. 2014

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The morphology and the microscopic internal dynamics of a bidimensional gel formed by spontaneous aggregation of gold nanoparticles confined at the water surface are investigated by a suite of techniques, including grazing-incidence x-ray photon correlation spectroscopy (GI-XPCS). The range of concentrations studied spans across the percolation transition for the formation of the gel. The dynamical features observed by GI-XPCS are interpreted in view of the results of microscopic imaging; an intrinsic link between the mechanical modulus and internal dynamics is demonstrated for all the concentrations. Our work presents an example of a transition from a stretched to a compressed correlation function actively controlled by quasistatically varying the relevant thermodynamic variable. Moreover, by applying a model proposed some time ago by Duri and Cipelletti [Europhys. Lett. 76, 972 (2006)] we are able to build a master curve for the shape parameter, whose scaling factor allows us to quantify a "long-time displacement length." This characteristic length is shown to converge, as the concentration is increased, to the "short-time localization length" determined by pseudo-Debye-Waller analysis of the initial contrast. Finally, the intrinsic dynamics of the system is then compared with that induced by means of a delicate mechanical perturbation applied to the interface.

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“…In this scenario, the stretched exponential behaviour observed in NS4 might be related to its stress-free nature, as discussed in topological approaches to the glassy network 25,26 . A similar compressed/stressed and stretched/ stress-free scenario has been recently proposed for a colloidal suspension of Laponite under an external shear field 43 . Finally, it is worth noticing that the very same absence of visible physical aging at the microscopic scale has been also detected after long annealing in metallic glasses 20,21 .…”

Section: Resultsmentioning

confidence: 56%

Revealing the fast atomic motion of network glasses

Baldi²,

et al. 2014

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Still very little is known on the relaxation dynamics of glasses at the microscopic level due to the lack of experiments and theories. It is commonly believed that glasses are in a dynamical arrested state, with relaxation times too large to be observed on human time scales. Here we provide the experimental evidence that glasses display fast atomic rearrangements within a few minutes, even in the deep glassy state. Following the evolution of the structural relaxation in a sodium silicate glass, we find that this fast dynamics is accompanied by the absence of any detectable aging, suggesting a decoupling of the relaxation time and the viscosity in the glass. The relaxation time is strongly affected by the network structure with a marked increase at the mesoscopic scale associated with the ion-conducting pathways. Our results modify the conception of the glassy state and asks for a new microscopic theory.

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Dichotomic aging behaviour in a colloidal glass

Cited by 70 publications

References 27 publications

Glass–glass transition during aging of a colloidal clay

Glass–glass transition during aging of a colloidal clay

Controlling the dynamics of a bidimensional gel above and below its percolation transition

Revealing the fast atomic motion of network glasses

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