École Supérieure d'Ingénieurs en Génie Électrique

B20-type structure was predominantly formed as the main phase in FeGe1-xSix alloys (x = 0.01–0.07) via conventional alloying and annealing processes without high-pressure and high-temperature synthesis. The obtained phases were characterised by X-ray diffraction measurements, scanning electron microscopy, and scanning transmission electron microscopy, which infer that the B20 phase has high crystallinity and dilute Si content. A single phase B20-type structure was formed by annealing the FeGe0.97Si0.03 alloy ingot at 873 K for 10 days. The substitution effects on magnetic properties were also investigated, which showed that the Curie temperature of the B20 phases decreased just slightly with the increasing solute Si content. The facile synthesis method is expected to be applicable to further research on the physical properties of B20-type alloys, including the latest subject of magnetic skyrmions.

Influenza viruses exhibit high mutation rates and extensive genetic diversity, which hinder effective vaccine development and facilitate immune evasion (Taubenberger and Morens, 2006; Barr et al., 2010). These mutations arise from the error-prone viral RNA-dependent RNA polymerase, generating highly heterogeneous viral populations within individual hosts that conform to the quasi-species model of a cloud of related genomes evolving under selection (Domingo et al., 2012). Accurate characterization of this intra-host diversity is crucial for understanding viral evolution and improving vaccine design, yet conventional RNA sequencing often fails to detect low-frequency variants because of technical errors during sample preparation and sequencing. Here, we implement a single unique molecular identifier strategy that reduces sequencing artifacts and achieves an error rate of ~10⁻⁵, enabling single-particle-level quantification of quasi-species diversity. Mutation frequencies greatly exceeding background error confirm their biological origin, while information-theoretic metrics such as Shannon entropy and Jensen-Shannon divergence reveal non-random mutation distributions under selective constraints. This framework supports detailed studies of intra-host viral evolution and may inform artificial intelligence-driven prediction of mutational trajectories and more effective influenza vaccine strategies.

Serious defects in metal piping systems used in factories, power stations, and similar facilities can cause serious accidents. Regular inspections for metal pipework are therefore important. However, all conventional non-destructive inspection (NDI) methods are often time-consuming and inconvenient. To address this issue, we propose a simpler and more innovative inspection technique based on electromagnetic waves.

Examples of graphite nodularity by ISO method, I n N sg (nunber of particles)

Alkaline water electrolysis is a promising method, though the degradation of electrodes under intermittent operation and high overpotential are necessary to be resolved.1) High durability and high activity of electrodes are not often concomitant. Self-repairing catalysts are usefl to achieve both of these characteristics. Hybrid cobalt hydroxide nanosheets (denoted as Co-ns) have been used as self-repairing catalysts. Co-ns is a nanosheet comprising cobalt hydroxide sheet modified with a tripodal ligand (tris(hydroxymethyl)aminomethane) (Fig.1). Brucite-type cobalt hydroxides exhibit high electrocatalytic activity to oxygen evolution reaction (OER) and tripodal ligand contributes to repairing ability.2) Co-ns is electrochemically deposited on a substrate during electrolysis. The electrochemical deposition rates depend on the overpotential of OER,3) though other factors affecting deposition rate are not yet clear. In this study, the deposition rate of Co-ns was measured using Ni and SUS304 substrates, and the effect of Fe species was investigated.Electrochemical measurements were performed using a PFA three-electrode cell. Ni or SUS304 plate, etched with boiling or 50 °C hydrochloric acid, respectively, was used as a working electrode. A reversible hydrogen electrode (RHE) and Ni coils were used as the reference and counter electrodes, respectively. Co-ns or CoFe-ns was dispersed in 1 M KOH electrolyte at various concentrations, and the catalyst layer was formed by constant current electrolysis (30 min × 8 times) at 800 mA cm–2. Catalytic performance was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).When Co-ns or CoFe-ns are dispersed in the electrolyte, the catalysts are deposited on the electrode to form a catalyst layer. In this process, Co-ns is transformed to CoOOH by oxidation of surface ligand and Co2+. The deposited amount of Co in the catalyst (m Co) was calculated from the cathodic charge in CV at 0.8–1.5 V vs. RHE (Q c) which is linearly correlated with m Co.2 ) The variation of m Co with the duration of electrolysis is shown in Fig.2 for each substrate. Assuming that the electrochemical deposition rate (v) is proportional to the frequency of the collision of catalyst particles with the surface of electrode, the deposition rate constant k' can be obtained by v=Δm Co/Δt=k'C Co, where Δm Co, Δt, and C Co represent the changes in m Co, duration of electrolysis, and the concentration of catalysts in the electrolyte.Plots of k’ as a function of the average potential during electrolysis, correlations with three different slopes were observed on Ni/Co-ns, SUS304/Co-ns, Ni/CoFe-ns (Fig.3). In the plots of SUS304/Co-ns, k’ at the first 30 min was out of the linear relationship of other plots, and it was similar to k’ of Ni/Co-ns, which implied two mechanisms of the deposition of Co-ns on SUS304. One is the deposition of catalysts on the substrate (catalyst–substrate reaction) at the first 30 min, and the other is the deposition of catalysts on the CoOOH layer (catalyst–catalyst reaction) after 30 min. m Co for Ni and SUS304 up to 30 minutes of electrolysis was similar to each other (Fig.2), whereas there was a significant difference in m Co after 30 min. It is considered that the substrate-catalyst reaction rate was at the same degree, and the catalyst-catalyst reaction rate is much faster on SUS304.To clarify the reason for different catalyst–catalyst reaction rates, the effect of Fe incorporated in the CoOOH layer was investigated. It is considered that the deposited CoOOH incorporate Fe3+ leached from the substrate and accelerated the catalyst-catalyst reaction (Fe/Co=0.078). When CoFe-ns (Fe/Co=0.18) was used as a catalyst, faster deposition rate and lower average potential during electrolysis were observed compared to Ni/Co-ns. Therefore, Fe species accelerated catalyst–catalyst reactions and also improves activity. The plots of SUS304/Co-ns are in between those of Ni/CoFe-ns and Ni/Co-ns. This suggests that Fe3+ leached from the electrodes are incorporated in CoOOH when Co-ns formed a thin layer on SUS304 in the early stage of electrolysis, resulting in a structure like CoFe-ns. As the catalyst layer becomes thicker with the progress of electrolysis, the incorporation of Fe3+ should be slower. Thus, the deposition rate becomes similar to that of Co-ns/Ni at the later stage of electrolysis.In conclusion, the electrochemical deposition of self-repairing catalyst proceeds in two stages, considered as substrate-catalyst and catalyst-catalyst reactions, and catalyst-catalyst reaction is accelerated by containing Fe3+ in catalyst layer. We also found that the activity is increased when Fe is contained in the catalyst layer. References 1) R. D. L. Smith et al., Science, 340, 6128 (2013).2)Y. Kuroda et al., Chem. Eur. J., 23 , 5023 (2017).3) R. Nakajima et al., ChemSusChem, 16, e202300384 (2023). Figure 1

The development of high-performance membranes for alkaline water electrolysis (AWE) is crucial for scaling up green hydrogen production. Conventional porous diaphragms used in AWE must balance ionic conductivity and gas crossover suppression, where increased porosity enhances conductivity but compromises gas separation efficiency. This study introduces an innovative membrane with selective gas permeability, enabling efficient operation under industrial conditions with enhanced durability.The proposed membrane exhibits anisotropic gas permeability, meaning it preferentially suppresses gas crossover in one direction more than the other [1]. This effect is achieved by a unique asymmetric structure, where one side of the membrane is smoother and denser, acting as an effective gas barrier, while the other side remains more porous to maintain high ionic conductivity. Notably, the membrane's ionic resistance (0.2 Ω cm²) is comparable to that of the commercial Zirfon Perl UTP500 diaphragm, while simultaneously demonstrating superior gas crossover mitigation.To assess performance, the membrane was tested in a 4-cell alkaline water electrolyzer stack under various operating conditions. Gas purity measurements confirmed that the membrane orientation significantly influences gas separation efficiency. In orientation-2 (smooth side facing the anode), H₂ permeation to the anode side was significantly reduced, as shown in Figure 1(a), while maintaining hydrogen purity above 99.6 vol% even at low current densities. Conversely, in orientation-1 (smooth side facing the cathode), H₂ purity approached nearly 100 vol% due to the substantial suppression of oxygen crossover, as illustrated in Figure 1(b). Furthermore, the flux density of permeated H₂ remained largely unaffected by current density in both orientations, as shown in Figure 1(c), indicating that hydrogen crossover was primarily governed by diffusion rather than electrochemical driving forces. In contrast, the flux density of permeated O₂ increased significantly with current density in orientation-2, as depicted in Figure 1(d), suggesting a strong correlation with electro-osmotic drag effects. These results highlight the membrane’s ability to extend the operational range of alkaline electrolyzers while reducing the risk of explosive gas mixtures.The durability of the membrane was evaluated over 900 hours of continuous operation at 1.0 A cm⁻² in 7 M KOH at 60 °C, demonstrating stable performance without significant degradation. Furthermore, pre-treatment studies revealed that soaking the membrane in pure water for one day significantly improved its ionic conductivity, making it compatible with commercial electrolyzer systems.This research demonstrates that integrating a selective gas permeability membrane into alkaline water electrolyzers can enhance efficiency, improve hydrogen purity, and extend operational flexibility, particularly under fluctuating renewable energy conditions. These findings contribute to the advancement of low-cost, durable, and scalable electrolysis technologies, supporting the widespread adoption of green hydrogen in a future hydrogen economy. Acknowledgments: This research was partially supported by JPNP 20003 project that was commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

In recent years, the importance of sustainable energy has rapidly escalated due to increasingly severe environmental concerns and the exhaustion of fossil fuels. Among these, renewable energy sources such as hydrogen, solar, and wind energy have garnered growing attention and research interest as crucial pathways to achieving zero carbon emissions. Hydrogen, being the most plentiful element in the universe, boasts rich resources and widespread sources. Hydrogen gas is also one of the highest energy density fuels and, upon combustion, produces only water, making it clean and non-polluting1. Among the methods for hydrogen production, water electrolysis stands out as the most efficient and cleanest approach, representing a promising direction for breakthroughs in energy technology. In the water electrolysis reaction, oxygen evolution reaction (OER) occurs at the anode while hydrogen evolution reaction (HER) occurs at the cathode. However, due to their involvement in multi-electron transfer processes, both reactions exhibit sluggish kinetics, requiring substantial overpotentials to drive them forward. This necessity has prompted the development of efficient electrocatalysts to expedite the reactions. Catalysts based on Ru and Ir are considered benchmark catalysts for water electrolysis due to their excellent OER activity and long-term stability2. Among the available options, Ru-based catalysts stand out due to their greater resource availability and lower cost, while also exhibiting superior catalytic activity compared to Ir-based catalysts. Nonetheless, the poor stability and corrosion resistance hinder the development of this type of material.Recent studies have indicated that introducing transition metal elements into conventional Ru-based oxide catalysts can alter the catalyst's electronic structure and bonding situations to some extent, potentially enhancing the catalytic activity and long-term stability of Ru-based water electrolysis catalysts3. According to previous studies, the RuO2-Co3O4 heterointerface in acidic electrolytes significantly enhances the catalytic stability of the OER catalyst. The electronic interaction at the interface alters the electron cloud density around Ru, lowering the reaction activation energy barrier and improving the reaction kinetics. Additionally, the interface coupling between the two nanoscale crystalline phases provides more favorable microstructural features, such as hollow structures and oxygen vacancies, which further enhance catalytic performance4. In this study, we synthesized a series of RuCoOx catalysts using a simple glucose-blowing method at different temperatures and heating times (heating for 5 hours at 350 °C, heating for 5 hours at 500 °C, heating for 7 hours at 350 °C, and heating for 7 hours at 500 °C), and focused on investigating the catalytic performance of these catalysts for OER (Figure 1a.) and HER (Figure 1b.) in an acidic environment (0.1 mol·L-1 HClO4 solution). Linear sweep voltammetry (LSV) results demonstrated the relationship between the catalytic performance of the RuCoOx series catalysts and the heating temperature and duration during synthesis. The electrocatalytic performance of the RuCoOx series catalysts generally exhibited a negative correlation with the calcination time. Among them, the sample heated at 350 °C for 5 hours achieved overpotentials of 263 mV for OER and 46 mV for HER at a current density of 10 mA·cm-2, and demonstrate the best long-term stability. Additionally, we analyzed the changes in the electronic structure of the catalysts during the water electrolysis reaction using in situ or operando X-ray absorption spectroscopy (XAS) to track active structures for understanding catalytic mechanisms (Figure 1c.).Figure 1. (a) LSV curves of OER for RuCoOx; (b) LSV curves of HER for RuCoOx. (c) Operando O K-edge test results for RuCoOx@350 ℃, 5 h. Acknowledgment This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

In recent years, various electronic devices, including micromachine technology (MEMS), have been developed by nanotechnology. Since electrodeposition in an aqueous solution does not require a vacuum environment, various microfabrication and epitaxial control using electrodeposition have been investigated. Therefore, it is important to precisely and rapidly control the nanoscale interface structure during the electrodeposition process, and it is essential to elucidate the reaction process in the small region.Various methods have been studied for in-situ observation. The scanning probe microscope have given a way for atomic-scale observation, which can be applied to electrochemical nucleation and growth processes in an aqueous solution. However, the conventional scanning probe microscopes (scanning tunneling microscope: STM, atomic force microscope: AFM) require a few minutes to measure a surface, making it difficult to catch up the dynamic nucleation.A high-speed scanning probe microscope has the potential to overcome both the temporal and spatial problems. Magnussen et al. invented the video-rate STM and observed electrochemical interfacial phenomena such as metal nucleation, adatom diffusion, and molecular adsorption [1]. On the other hand, High-speed AFM (HS-AFM) was studied for biological samples [2]. Therefore, it is applicable to the imaging of soft surfaces and weakly adsorbed specimens.Taking advantage of the features of HS-AFM, we have observed Cu [3] and Zn deposition and dissolution (Fig. 1) as well as electrolytic nanobubble evolution [4]. In may talk, I would like to present dynamic behaviors of electrochemical nucleation and growth.

Magnetic gears, which can transmit power without mechanical contact, offer lower vibration and acoustic noise compared with conventional mechanical gears. A flux-modulated-type magnetic gear stands out due to its high efficiency and torque density because all the permanent magnets consistently contribute to power transmission. This paper discusses the torque-to-weight ratio improvement and permanent magnet usage reduction of large-scale flux-modulated-type magnetic gears, aiming to construct highly reliable, lightweight, and resource-saving offshore wind power generation systems with magnetic gears. First, to demonstrate the effect of the Halbach array on the torque, an air gap flux density waveform in a prototype magnetic gear with Halbach array magnets is directly measured and compared with that using conventional parallel array magnets. Next, by applying the ideas of the Halbach array and multi-polarization into large-scale magnetic gears, improvements in the torque-to-weight ratio and reductions in permanent magnet usage are demonstrated using the finite element method (FEM).

To quantitatively predict the microstructure using a cellular automaton (CA) model, problems such as the calculation accuracy of the interface curvature and occurrence of mass-balance errors must be overcome. In this study, we focus on mass-balance errors, develop a unique CA model that considers the solid–liquid interface movement associated with solidification and melting, and investigate the effects of mass-balance errors on microstructural evolution. Mass-balance errors occur in CA models based on a two-domain approach that separately defines the solute concentration distribution in solid and liquid phases. We identified the causes of mass-balance errors and quantitatively estimated them, and then conducted a simulation of the microstructural evolution of Al-4.5mass%Cu alloy during isothermal undercooling and continuous cooling with and without mass-balance error corrections. During isothermal undercooling, if the mass-balance error is not corrected, the solute concentration increases during the coarsening of the dendrite arms, and the increase is greater with increasing undercooling, which causes the solid–liquid interface to melt despite the isothermal process. During continuous cooling, if the mass-balance error is not corrected, the solute concentration decreases during arm coarsening in the middle of solidification. Under the simulation conditions, the absolute percentage error of the solute concentration relative to the initial composition exhibited maximum values of 1.31% and 14.9% during isothermal undercooling and continuous cooling, respectively. Under both conditions, the values are almost zero if the mass-balance error is corrected. Therefore, mass-balance errors can be appropriately corrected in the proposed CA model based on a two-domain approach.