Dynamics of supercooled water in highly compacted clays studied by neutron scattering

González Sánchez, Fatima; Jurányi, Fanni; Gimmi, Thomas; Van Loon, Luc; Seydel, Tilo; Unruh, Tobias (2008). Dynamics of supercooled water in highly compacted clays studied by neutron scattering. Journal of Physics: Condensed Matter, 20(41), p. 415102. Institute of Physics Publishing IOP 10.1088/0953-8984/20/41/415102

[img] Text
Gimmi_González.pdf - Published Version
Restricted to registered users only
Available under License Publisher holds Copyright.

Download (818kB) | Request a copy

The freezing behavior of water confined in compacted charged and uncharged clays (montmorillonite in Na-and Ca-forms, illite in Na-and Ca-forms, kaolinite and pyrophyllite) was investigated by neutron scattering. Firstly, the amount of frozen (immobile) water was measured as a function of temperature at the IN16 backscattering spectrometer, Institute Laue-Langevin (ILL). Water in uncharged, partly hydrophobic (kaolinite) and fully hydrophobic (pyrophyllite) clays exhibited a similar freezing and melting behavior to that of bulk water. In contrast, water in charged clays which are hydrophilic could be significantly supercooled. To observe the water dynamics in these clays, further experiments were performed using quasielastic neutron scattering. At temperatures of 250, 260 and 270 K the diffusive motion of water could still be observed, but with a strong reduction in the water mobility as compared with the values obtained above 273 K. The diffusion coefficients followed a non-Arrhenius temperature dependence well described by the Vogel-Fulcher-Tammann and the fractional power relations. The fits revealed that Na-and Ca-montmorillonite and Ca-illite have similar Vogel-Fulcher-Tammann temperatures (T-VFT, often referred to as the glass transition temperature) of similar to 120 K and similar temperatures at which the water undergoes the 'strong-fragile' transition, T-s similar to 210 K. On the other hand, Na-illite had significantly larger values of T-VFT similar to 180 K and T-s similar to 240 K. Surprisingly, Ca-illite has a similar freezing behavior of water to that of montmorillonites, even though it has a rather different structure. We attribute this to the stronger hydration of Ca ions as compared with the Na ions occurring in the illite clays.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Gimmi, Thomas

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0953-8984

Publisher:

Institute of Physics Publishing IOP

Language:

English

Submitter:

Thomas Gimmi

Date Deposited:

22 Sep 2014 14:19

Last Modified:

26 Jun 2016 01:50

Publisher DOI:

10.1088/0953-8984/20/41/415102

BORIS DOI:

10.7892/boris.47671

URI:

https://boris.unibe.ch/id/eprint/47671

Actions (login required)

Edit item Edit item
Provide Feedback