Integrated study of experiment and first‐principles computation for the characterization of a corium type ZrO8 complex in a Zr‐doped fluorite UO2

We, for the first time, observe ZrO₈ complex in Zr‐doped UO₂, which is a corium structure, using experimental characterization integrated with first‐principle computational validation. Atomic level structure of U_1?yZr_yO₂ pellets (y = 0.01, 0.03, 0.05, and 0.1) is identified using Raman spectroscopy measurement and X‐ray diffraction pattern analysis. The lattice constants shrink with increasing Zr doping levels, which consistently represents in the positive shift of T_2g Raman vibration peak around 445 cm^?1. More interestingly, conventionally unknown new Raman peak appears around 598 cm^?1, which has not been observed in neither a pure ZrO₂ nor UO₂ doped with tetravalent elements other than Zr. We unveil that the new peak originates from ZrO₈‐type complex formed on the fluorite UO₂. Our study provides precise understanding on the formation mechanisms and material properties of the corium in the hypervalent oxide.     

Stability boundary analysis of magnetohydrodynamic circulator for the intermediate heat transfer system of prototype gen IV sodium fast reactor

One of the most important parts in the development of generation IV nuclear reactors is safety. In the research on generation IV sodium‐cooled fast reactors, magnetohydrodynamic (MHD) circulators have received attention for the stable transport of coolants. In this study, the stability of an MHD circulator was evaluated using a mathematical approach to obtain the critical value of the developed pressure. The critical developed pressure equation is a function of the flow rate and dimensionless parameters, which were derived from the theoretical model of the MHD circulator with a dimensionless scaled velocity, flow rate, and pressure. The stability conditions expressed using the critical value of the developed pressure and dimensionless parameters were investigated according to the changes in the main design variables of the MHD circulator. The relationships between the dimensionless parameters, stability, and main design variables constituting the stability boundary of the MHD circulator were analysed. The stability of the MHD circulator is considered safe when the stability criterion ε is lower than 1. The geometrical variables such as the duct thickness or width of the flow gap and electrical variables such as the frequency were the main parameters affecting the flow stability in the MHD circulator.     

Development of new energy management strategy for a household fuel cell/battery hybrid system

This work aims to construct an efficient and robust fuel cell/battery hybrid operating system for a household application. The ability to dispatch the power demands, sustain the state of charge (SOC) of battery, optimize the power consumption, and more importantly, ensure the durability as well as extend the lifetime of a fuel cell system is the basic requirements of the hybrid operating system. New power management strategy based on fuzzy logical combined state machine control is developed, and its effectiveness is compared with various strategies such as dynamic programming (DP), state machine control, and fuzzy logical control with simulation. Experimental results are also presented, except for DP because of difficulties in achieving real‐time implementation and much faster response to load variation. The given current from the energy management system (EMS) as a reference of the fuel cell output current is determined by filtering out various harmful signals. The new power management strategy is applied to a 1‐kW stationary fuel cell/battery hybrid system. Results show that the fuel cell hybrid system can run much smoothly with prolonged lifetime.     

Computational screening of anode materials for potassium‐ion batteries

Potassium ion batteries (PIBs) are promising alternatives to Li‐ion batteries due to the abundance of potassium. However, the development of PIBs is in its early stages, and only a few anode materials have been reported. Herein, we explored anode materials for PIBs using high‐throughput computational screening. The alloying and conversion reactions of prospective anode materials were investigated using the Materials Project database. Grand potential diagrams were obtained to examine the reaction potential and theoretical capacity of the anode materials. Calculation results indicated that P, As, Si, and Sb anodes exhibited high theoretical capacities. In addition, the screening results revealed that phosphides generally exhibit a lower reaction potential compared with those of sulfides and oxides. A total of 18 binary compounds that exhibited a high theoretical capacity and a low reaction potential (greater than 450 mAh/g and 0.7 V) were identified as promising anode materials for PIBs. In particular, ZnP₂, CuP₂, SiP, NiP₃, CoP₃, V₃S₄, Nb₃S₅, Bi₂O₃, and Ga₂O₃ exhibited high theoretical capacities.     

Amelioration in physicochemical properties and single cell performance of sulfonated poly(ether ether ketone) block copolymer composite membrane using sulfonated carbon nanotubes for intermediate humidity fuel cells

A composite membrane composed of a sulfonated diblock copolymer (SDBC) based on poly(ether ether ketone) blocks copolymerized with partially fluorinated poly(arylene ether sulfone) and sulfonated carbon nanotubes (SCNTs) was fabricated by simple solution casting. Addition of the SCNT filler enhanced the water absorption and proton conductivity of membranes because of the increased per‐cluster volume of sulfonic acid groups, at the same time reinforced the membranes' thermal and mechanical properties. The SDBC/SCNT‐1.5 membrane exhibited the most improved physicochemical properties among all materials. It obtained a proton conductivity of 10.1 mS/cm at 120°C under 20% relative humidity (RH) which was 2.6 times more improved than the pristine membrane (3.9 mS/cm). Moreover, the single cell performance of the SDBC/SCNT‐1.5 membrane at 60°C and 60% RH at ambient pressure exhibited a peak power density of 171 mW/cm² at a load current density of 378 mA/cm², while the pristine membrane exhibited 119 mW/cm² at a load current density of 294 mA/cm². Overall, the composite membrane exhibited very promising characteristics to be used as polymer electrolyte membrane in fuel cells operated at intermediate RH.