RESUMO
The type of self-assembled structure has a significant impact on the ionic conductivity of block copolymer or liquid crystalline (LC) ion conductors. In this study, we focus on the effect of self-assembled structures on the ionic conductivity of a non-block copolymer, LC ion conductor, which is a mixture of an azobenzene monomer (NbAzo), pentaerythritol tetre(3-mercapropionate) (PETMP), and a lithium salt, lithium bis(trifluoromethane)sulfonimide (LiTFSI). The self-assembled structures and ionic conductivities of ion conductors having different doping ratios of lithium salt to monomer were examined. With the increase in the doping ratio, the self-assembled structure transforms from lamellae (LAM) to double gyroid (GYR). The effect of self-assembled structure on ionic conductivity was analyzed; it was found that the conductivity of the GYR structure was about 3.6 times that of the LAM one, indicating that obtaining the GYR structure is more effective in improving ionic conductivity.
RESUMO
The microscopic structures of ThF4-LiF and ThF4-LiF-BeF2 molten salts have been systematically investigated by in situ high-temperature X-ray absorption fine-structure (XAFS) spectroscopy combined with molecular-dynamics (MD) simulations. The results reveal that the local structure of thorium ions was much more disordered in the molten state of the ThF4-LiF-BeF2 salt than that in ThF4-LiF, implying that the Th and F ions were exchanged more frequently in the presence of Be ions. The structures of medium-range-ordered coordination shells (such as Th-F2nd and Th-Th) have been emphasized by experimental and theoretical XAFS analysis, and they play a significant role in transport properties. Using MD simulations, the bonding properties in the molten ThF4-LiF and ThF4-LiF-BeF2 mixtures were evaluated, confirming the above conclusion. This research is, to the best of our knowledge, the first systematic study on the ThF4-LiF-BeF2 molten salt via quantitative in situ XAFS analysis and MD simulations.