Terahertz Driven Ultrafast Energy Dissipation in Aqueous Ionic Solutions

Solvation of ions changes the physical, chemical and thermodynamic properties of water. The microscopic origin of this process is believed to be the ion-induced perturbation in the structure and dynamics of the hydrogen (H)-bonding network of water. Here, we provide microscopic insight on the local structural deformation of the H-bonding network of water by ions, via investigating the dissipation of external energy in salt solutions by a novel time-resolved terahertz (THz)-Raman spectroscopy. We resonantly drive the low-frequency rotational dynamics of water molecules by intense THz pulses and probe the Raman response of their intermolecular translational motions. We find that the intermolecular rotational-to-translational energy transfer is enhanced by highly-charged cations and it is drastically reduced by highly-charged anions, scaling with the ion surface charge density and concentration. Our molecular dynamics simulations further reveal that the water-water H-bond strength between the first and the second solvation shells of cations (anions) increases (decreases), signifying the opposite effects of cations and anions on the local structure of water. The impact of ion polarity on the ultrafast energy dissipation in water, resembles the effect of ions on stabilization and denaturation of proteins.

Quantum kinetic energy and isotope fractionation in aqueous ionic solutions

Decomposition of the quantum kinetic energy and isotope fractionation ratios uncovers the local solvation structures in aqueous ionic solutions.

Investigation of Quenchants Based on Sodium Aqueous Ionic Solutions

The mechanical properties of steel components are influenced by the microstructure, which is determined by the heat treatment cycle. In the quenching of the steel: water, oil, aqueous polymer solutions and aqueous salt solutions (brine) can be used as quenchants, which exhibit different characteristic cooling mechanisms. For example, when water is used as the cooling media, a stable vapor film is formed around the hot component resulting in nonuniformity of surface heat transfer during the cooling process, which is often responsible for distortion, and cracking. Using salt based on sodium (Na) as an additive forming a solution with distilled water was able to reduce or eliminate the vapor film, enhance the cooling rate and keep the heat flux in high values during the most part of the drop of the temperature that is better for a more homogeneous cooling. This work investigated the cooling performance of different salt solutions and quenching bath parameters (temperature and agitation). These analyses were made using cooling curves and heat flux to quantify the behavior and hardening power capacity of these salt solutions.

Dynamic heterogeneity in aqueous ionic solutions

It is well known that supercooled liquids have heterogeneous dynamics, but it is still unclear whether dynamic heterogeneity also exists in aqueous ionic solutions at room or even higher temperatures.