Observation of a nanophase segregation in LiCl aqueous solutions from Transient Grating Experiments

TL;DR

This study uses transient grating experiments to detect nanophase segregation in supercooled LiCl aqueous solutions, revealing temperature-independent clusters whose number increases with salt concentration.

Contribution

It provides direct experimental evidence of nanophase segregation in LiCl solutions and characterizes the properties of the clusters involved.

Findings

Nanometer-sized clusters identified in LiCl solutions.

Cluster formation occurs below 190 K.

Cluster quantity increases with salt concentration R.

Abstract

Transient Grating experiments performed on supercooled LiCl, RH2O solutions with R>6 reveal the existence of a strong, short time, extra signal which superposes to the normal signal observed for the R=6 solution and other glass forming systems. This extra signal shows up below 190 K, its shape and the associated timescale depend only on temperature, while its intensity increases with R. We show that the origin of this signal is a phase separation between clusters with a low solute concentration and the remaining, more concentrated, solution. Our analysis demonstrates that these clusters have a nanometer size and a composition which are rather temperature independent, while increasing R simply increases the number of these clusters.