Comparative study of viscosity, diffusion coefficient, thermal conductivity and Gibbs free energy for binary liquid mixtures at varying temperatures

Phase transition of supercooled water confined in cooperative two-state domain

The question of 'what is the structure of water?' has been regarded as one of the major scientific conundrums in condensed-matter physics due to the complex phase behavior and condensed structure of supercooled water. Great effort has been made so far using both theoretical analysis based on various mathematical models and computer simulations such as molecular dynamics and first-principle. However, these theoretical and simulation studies often do not have strong evidences of condensed-matter physics to support. In this study, a cooperative domain model is formulated to describe the dynamic phase transition of supercooled water between supercooled water and amorphous ice, both of which are composed of low- and high-density liquid water. Free volume theory is initially employed to identify the working principle of dynamic phase transition and its connection to glass transition in the supercooled water. Then a cooperative two-state model is developed to characterize the dynamic anomalies of supercooled water, including density, viscosity and self-diffusion coefficient. Finally, the proposed model is verified using the experimental results reported in literature.

Selective separation and recovery of lithium, nickel, MnO2, and Co2O3 from LiNi0.5Mn0.3Co0.2O2 in spent battery

The recovery of valuable metals from the LiNi_0·5Mn_0·3Co_0·2O₂ in spent batteries deserves more attention. We report a series of feasible procedures to selectively recover the four metals (Li, Ni, Mn, and Co) using a combination of hydrometallurgical and pyrometallurgyical processes. Firstly, oxalic acid is used to dissolve Li and precipitate the other three metals in oxalate forms. It is found that under the optimal condition, about 98% of the Li is dissolved, and on average 93% of the other three metals are transformed to precipitated oxalates. The oxalates are then transformed to NiO·Mn₂O₃·Co₃O₄ by being calcinated at 723 K under atmospheric environment. The selective recovery of NiO·Mn₂O₃·Co₃O₄ can be achieved by using H₂SO₄ under three different conditions. The first step is to use H₂SO₄ to selectively dissolve CoO from the Co₃O₄. Then the combination of H₂SO₄ and ultrasound is adopted to dissolve NiO, during which the ultrasound destroys the surficial oxide film on the NiO. Afterwards, the Mn₂O₃ is transformed to MnO₂ and Mn²⁺ in heated H₂SO₄. The Co, Ni and Mn ions are dissolved in a sequence, which facilitates their separation and recovery. As the main components of the final residual solids, Co₂O₃ and MnO₂ present in distinctly different sizes and shapes, which are beneficial for their separation and direct usage.