Electrochemical cell recharging by solvent separation and transfer processes.

Electrochemical conversion and storage of unutilized renewable energy will contribute to decarbonization. Here, we create the concept of a liquid electrochemical cell that discharges between the anodic and cathodic sides by reverse reactions of the same redox couple in different solvation states, which are created by differences in the mixture ratios of two solvents called the main solvent (MS) and the transferred solvent (TS). The cell can be charged by a transfer of the TS between the discharged anolyte and catholyte. As an example, we demonstrate a cell utilizing a ferro-/ferricyanide redox couple. Stable discharging and charging via the proposed method is achieved by utilizing water (MS) and acetone (TS). Additionally, dominating factors in the design of a high-performance system are discussed, focusing on the electron acceptability of the MS and the TS. The cell voltages are successfully tuned, and a cell voltage of 0.63 V is achieved by the combination of dimethyl sulfoxide (MS) and water (TS). Moreover, the cell can be customized by various electrochemical reaction systems, which can allow multiple options for the charging processes. This concept provides new approaches for the utilization of diverse energy sources as an input for the charging of electrochemical cells.

Accuracy of equilibrium magnetization mapping in sliced two-dimensional spoiled gradient-recalled echo pulse sequence with variable flip angle.

PURPOSE: To evaluate the accuracy of an equilibrium magnetization (M0 ) map obtained using a two-dimensional (2D) spoiled gradient-recalled echo (SPGR) pulse sequence with variable flip angle (VFA). MATERIALS AND METHODS: Single-slice 2D SPGR images of 4% agar gel phantoms with different gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) concentrations (0-1 mM) were obtained with a VFA (2-30°). The 2D SPGR-VFA data were acquired with different repetition times (TRs; 7.8-117.2 ms), Gaussian and sinc RF pulses, and different field strengths (4.7, 7, and 9.4 Tesla). M0 and T1 maps were calculated from the 2D SPGR-VFA data. M0 and T1 values were compared with those calculated from free-relaxed 2D gradient-recalled echo (GRE) images and inversion recovery-prepared 2D SPGR images. The M0 and T1 slice profiles were also investigated. RESULTS: Consistent M0 values were obtained, regardless of the different Gd concentrations, TRs, and pulse sequences. The M0 slice profiles calculated from the sliced SPGR-VFA data quantitatively reproduced those calculated from the free-relaxed sliced GRE. In contrast, the T1 values calculated from the 2D SPGR-VFA data were underestimated at a high Gd concentration, short TR, and Gaussian RF pulse. CONCLUSION: M0 values calculated from 2D SPGR-VFA images are highly quantitative.

Water content distribution in a polymer electrolyte membrane for advanced fuel cell system with liquid water supply.

To better understand the operation of a new fuel cell design, we used magnetic resonance imaging (MRI) to measure the water content distribution in a polymer electrolyte membrane under fuel cell operation with and without a supply of liquid water. The supply of liquid water to the membrane improved the cell performance by increasing the water content in the membrane and thus reducing the electrical resistance of the membrane. The study also showed that MRI is a promising method to investigate the distribution of water in the membrane of a fuel cell under operating conditions.

Velocity measurement of clay intrusion through a sudden contraction step using a tagging pulse sequence.

Magnetic resonance imaging (MRI) with a spatial tagging sequence was used to measure the velocity distribution of clay that was forced past a sudden contraction. A spatial tagging sequence provided magnetic resonance images of clay that allowed measurement of the velocity distribution in the clay, which can provide profound insights on the deformation process of clay during the intrusion process. The experiments were conducted using a specially-designed vessel that could operate at up to 30 MPa. The vessel offers a rectangle test section with a sudden contraction step that had a ratio of contraction of 2:1. The vessel was installed into a commercial magnetic resonance imaging equipment and then the fluid motion of clay flowing into the narrow contracted channel was quantitatively investigated to examine behaviors of flowing clay as non-Newtonian fluid. MRI results are compared with those obtained by computational fluid dynamics (CFD) calculation. Velocity distributions obtained from each tag displacement did not well agree with those predicted by CFD results near the contraction step where the fluid accelerated rapidly. However, a post-processing on calculation results, in which virtual tag displacement is calculated, gave better agreement with experiment and enabled us to compare MRI results with CFD results.