Institut Jean Lamour

The precise modulation of phosphorus species and physicochemical properties in metal-free carbon materials holds significant potential for enhancing their electrocatalytic performance in the hydrogen evolution reaction (HER). In this study, we precisely tune the phosphorus species during the pyrolysis of phytic acid (PA). Pluronic® F127 acts as a protective agent, preventing the close proximity of phosphorus groups in PA molecules during pyrolysis. This interaction inhibits the formation of polyphosphoric groups during carbonization and leads instead to isolated P functionalities embedded in carbon basal planes. Comprehensive characterization, including cross-polarization magic angle spinning solid-state 31 P-NMR, XPS, and DFT simulations identified the phosphorus species and elucidated their structural and electronic properties. The precise tuning of phosphorous functional groups enabled by Pluronic® F127 in metal-free carbon materials boosting the phosphorous based state-of-the-art HER catalytic performance. These findings underscore the underexplored potential of surfactants beyond morphological templating, offering a powerful strategy for tailoring surface chemistry and advancing the design of next-generation metal-free electrocatalysts. • Pluronic® F127 prevents phosphorus aggregation, enabling isolated P sites. • Surfactants modulate phosphorus species, enhancing HER electrocatalysis. • P-doped carbon catalyst achieves -0.19 V vs. RHE, rivaling metal-based HER. • Study paves the way for metal-free catalysts in sustainable hydrogen production.

We report the nuclear magnetic resonance dispersion (NMRD) profile of superparamagnetic iron oxide nanoparticles (SPIONs) and compare the values obtained from its analysis with those from standard methods. Recorded at 1H Larmor frequencies from 10 kHz to 600 MHz (0.23 mT to 14.1 T, static magnetic field), this profile covers water 1H dynamics across a broad timescale encompassing all medically relevant magnetic field strengths in magnetic resonance imaging (MRI). This extensive coverage enables the extraction of accurate physicochemical parameters of the nanoparticles that dictate their efficiency (relaxivity). To support this approach, other conventional characterization methods, including TEM, DLS/zeta potential, and VSM, were employed and compared with the NMRD findings. To ensure robustness, the NMRD profiles were recorded at both 25°C and 37°C. Analysis of NMRD profiles, in conjunction with the appropriate theoretical model, successfully characterized SPIONs, yielding coherent parameters that compare favorably with those from conventional characterization methods.

Acoustic Holograms In their Research Article (10.1002/sstr.202500354), Yifan Zhu, Hui Zhang, Badreddine Assouar, and co-workers report the concept of acoustic phase holographic imaging by metasurfaces that reveals the intrinsic coupling mechanism between amplitude and phase. They describe the governing equations for their dynamic coupling relationship, enabling phase holographic imaging acoustic communication with anti-attenuation and anti-interference properties. They furthermore experimentally demonstrate this new concept of phase holographic imaging.

Interlayer Dzyaloshinskii-Moriya interaction (IL-DMI) in synthetic magnetic structures has attracted extensive interest for greatly facilitating deterministic spin-orbit torque (SOT)-driven information writing and topologically non-trivial 3D magnetic Hopfion forming. However, its distinct role in synthetic ferrimagnets (SFi) remains unexplored, where the conjunction of asymmetric magnetic moments and antisymmetric nature of IL-DMI leads to more diverse spin configurations and applications. Here, we reveal the unidirectional and chiral nature of IL-DMI in SFi, further unlocking application directions of IL-DMI in neuromorphic computing. Particularly, the IL-DMI-induced effective field increases approximately twentyfold while interacting with two asymmetric antiparallel-aligned moments, greatly facilitating future IL-DMI detection. Unlike previous digital-like switching, we find that the interplay of IL-DMI, SOT, and thermal effect gives rise to an analog-like switching behavior. Leveraging this, we develop an SOT-based non-probabilistic leaky-integrate-fire neuron device utilizing the micromagnetic analog-like switching model. Compared to probabilistic neurons, this provides a hardware support Spiking neural network, interlayer Dzyaloshinskii-Moriya interaction, spin-orbit torque, synthetic ferrimagnetsfor ultralow power, high-sparsity, and high-accuracy spiking neural networks.

This study investigates the dynamics of radio-frequency (RF) sheaths in magnetized plasmas, relevant to Ion Cyclotron Resonance Heating (ICRH) systems in fusion devices. Using a 1D3V Particle-In-Cell (PIC) model, we analyzed the rectification of the sheath potential and its dependence on the RF frequency and the magnetic field inclination with respect to the wall. Simulations reveal that grazing magnetic field angles significantly enhance the time-averaged sheath potential, sometimes exceeding the applied RF voltage due to increased electron transit times and residual charge buildup. These effects are most pronounced for RF frequencies between 1 and 5 times the ion cyclotron frequency. Additionally, we uncover a mechanism responsible for the enhancement of electron heating at grazing incidences, where electrons interact more frequently with the expanding sheaths and experience strong electric fields, leading to the formation of energetic electron bursts. This acceleration is linked to the observed increase in rectified potential and may have critical implications for material sputtering and impurity generation on ICRF antenna surfaces.

• An “all-in-one” biomass-based direct reduction shaft furnace is feasible. • CO is produced in situ by the Boudouard reaction; the CO-CO 2 gas is recycled. • Charcoal is devolatilized at the top of the reactor but is gasified at the bottom. • CO 2 emissions are 8 times lower than those of the usual steelmaking route. • Life cycle assessment also revealed lower other environmental impacts. The iron- and steelmaking industry contributes significantly to greenhouse gas emissions because steel is produced in large quantities, and fossil coal is used as the energy source and reducing agent for this production. Substituting biogenic carbon from biomass for fossil coal could drastically reduce the contribution of the iron- and steelmaking industry to global warming. Based on biomass, we propose a novel, breakthrough ironmaking process (BIORED), in which charcoal lumps and iron ore pellets are loaded at the top of a shaft reactor. CO, the reducing agent that converts iron oxide ore to metallic iron, is produced in situ by charcoal gasification. The exhaust gas mixture (CO–CO 2 ) is recycled for CO reuse and energy savings. The feasibility of such a process was investigated following a modeling approach that involves laboratory experiments. The results show that charcoal is devolatilized at the top and gasified at the bottom, whereas iron ore is reduced along the shaft, reaching a satisfactory metallization degree at the bottom. A specific experimental protocol was designed for the validation of the model, and the experimental results agreed with the computed results. The environmental performance of the BIORED-based steelmaking route was compared with that of the conventional route via life cycle assessment. The new route emits up to 8 times less CO 2 and has lower impacts on most of the other environmental categories.

Ternary and quaternary alloys based on Bi2Te3 remain to date the most efficient materials for thermoelectric cooling around room temperature. Among the various strategies developed over the last decades to further enhance their performance, nanostructuration induced by melt-spinning has proven to be effective, yielding higher values of the dimensionless thermoelectric figure of merit, attributed primarily to a significant decrease in the lattice thermal conductivity {{{kappa }}}_{{{L}}}. Here, we present measurements of the total thermal conductivity {kappa } of two polycrystalline samples of the alloy Bi0.4Sb1.6Te3 prepared by conventional powder metallurgy and melt-spinning at low temperatures and under high magnetic fields of up to 14 T that challenge this view. By directly accessing {{{kappa }}}_{{{L}}} without relying on the Wiedemann-Franz law, we show that both samples exhibit a similar {{{kappa }}}_{{{L}}}({{T}}) dependence below ∼70 K. The difference with the {{{kappa }}}_{{{L}}}({{T}}) dependences predicted by this simple law is tied to anomalously low Lorenz number {{L}}, the values and temperature dependence of which are shaped by inelastic scattering processes that relax charge and energy flows in an inequivalent manner. Not captured by conventional transport models, the finite-temperature, downward deviations of {{L}}({{T}}) are successfully reproduced by a theoretical model that includes inelastic electron-electron and electron-optical phonon scattering. These findings show that the melt-spinning-induced nanostructuration has a weaker influence on {{{kappa }}}_{{{L}}} than previously thought, and pave the way to a better understanding of the deviations from the Wiedemann-Franz law reported in a growing number of complex thermoelectric materials.

Fundamentally understanding lattice dynamics and thermal transport behavior in liquid-like, partially occupied compounds remains a long-standing challenge in condensed matter physics. Here, the microscopic mechanisms are investigated underlying the ultralow thermal conductivity in ordered/liquid-like Cu3BiS3 by combining experimental methods with first-principles calculations. The ordered structure and liquid-like are first experimentally synthesized and characterized, partially Cu-atom occupied Cu3BiS3 structure with increasing temperature. Selfconsistent phonon calculations are then combined, including bubble-diagram corrections, with the Wigner transport equation, considering both phonon propagation and diffuson contributions, to evaluate the anharmonic lattice dynamics and thermal conductivity in phase-change Cu3BiS3. The theoretical model predicts an ultralow thermal conductivity of 0.34 Wm-1K-1 at 400 K, dominated by diffuson contributions, which accurately reproduces and explains the experimental data. Importantly, the machine-learning-based molecular dynamics (MD) simulations not only reproduced the partially Cu-atom occupied Cu3BiS3 structure with the space group Pnma but also successfully replicated the thermal conductivity obtained from experiments and Wigner transport calculations. This observation highlights the negligible impact of ionic mobility arising from partially occupied Cu sites on the thermal conductivity in diffuson-dominated thermal transport compounds. This work sheds light on the minimal impact of ionic mobility on ultralow thermal conductivity in phase-change materials. It demonstrates that the Wigner transport equationaccurately describes thermal transport behavior in partially occupied phases with diffuson-dominant thermaltransport.