Fumitaka Hayashi

Functional powder materials, including emerging photocatalysts and porous materials, can be incorporated into high‐surface‐area fiber sheets for industrial applications such as hydrogen production and water treatment. Although this can be achieved using electrostatic layer‐by‐layer assembly, time‐consuming repeated dip–rinse cycles have hindered commercial‐scale production. In this study, a high‐throughput integration strategy based on electrostatic assembly is developed to avoid such repetitive cycling. This approach requires a single dip‐dry step, enabling an impressive throughput of >1,000 m ² per day using a commercial‐scale impregnation coater, wherein the powder particles are electrostatically pre‐complexed with silica or alumina nanoparticles. These nanoparticles ultimately form the backbone of the porous binder, ensuring the adhesion and activity of the functional thin films. Although demonstrated using powdered titanium dioxide and activated carbon, this strategy establishes a broadly applicable framework for designing and integrating surface‐charged functional powder materials.

Microstructural control of multicomponent oxides, particularly control of particle uniformity and crystallinity, is essential for achieving functionality; however, clear synthesis guidelines remain scarce. For complex materials, such as Li3.5Ge0.5V0.5O4 (LGVO), crystal growth optimization has been pursued through empirical trial-and-error approaches. In this study, we systematically investigated the flux-assisted crystal growth of LGVO using a rational approach integrating experimental investigations with statistical process optimization, to quantitatively understand the LGVO growth behavior. First, experimental investigations of the LGVO crystal growth mechanism revealed the dual role played by the Li3BO3 flux: physically creating a homogeneous reaction field and chemically suppressing secondary phases. Mechanistic insights from these investigations were used to define representative flux‐assisted conditions within the identified process window, under which LGVO crystals exhibited high uniformity and crystallinity, as indicated by a low particle‐size coefficient of variation (CV) and narrow FWHM across multiple diffraction peaks. Next, based on the mechanistic insights, we employed Gaussian process regression and Bayesian optimization to navigate the trade-off between uniformity and crystallinity. This approach successfully corroborated and refined the mechanistically derived process window (solute concentration: 85–90 mol%, temperature: 750–900 °C) for synthesizing high-quality LGVO crystals. These results demonstrate that statistical modeling can effectively complement mechanistic understanding in complex flux-assisted crystal growth systems.

This study explores magnesium titanate (MgTiO₃; MTO) as a durable ceramic adsorbent for per- and polyfluoroalkyl substance (PFAS) remediation under extreme acidic conditions. MTO exhibits outstanding acid resistance, retaining its crystal structure even at pH 1.0 with negligible Mg and Ti leaching. At pH 4.5, adsorption isotherms reach saturation, yielding maximum capacities of 8.92 mg g⁻¹ for perfluorooctane sulfonate (PFOS) and 6.42 mg g⁻¹ for perfluorooctanoic acid (PFOA). Adsorption kinetics show rapid uptake, followed by a slower diffusion-controlled regime, with apparent equilibration times of ∼120 min for PFOS and ∼300 min for PFOA. Time-resolved kinetic analyses, including square-root-of-time, pseudo-second-order, and double-exponential models, reveal a characteristic two-stage adsorption process dominated by diffusion resistance. Two-site Langmuir isotherms further support this behaviour by distinguishing high-affinity and non-specific adsorption domains. Spectroscopic analyses elucidate distinct adsorption mechanisms: PFOS adsorbs predominantly via an outer-sphere electrostatic pathway constrained by surface crowding, whereas PFOA undergoes a transition from site-specific inner-sphere coordination at Mg/Ti sites to slower outer-sphere accumulation. These findings demonstrate that PFOS and PFOA exhibit fundamentally different adsorption mechanisms on the same ceramic surface, governed by headgroup chemistry and surface coordination. By integrating exceptional acid durability with mechanistic insight, this work provides a foundation for the rational design of PFAS adsorbents for aggressive industrial wastewater treatment.

We introduced multiple metal cations to substitute Nb in hexaniobate single crystals. The high-entropy effect led to much more efficient exfoliation compared to that of the pristine hexaniobate without requiring strong acids or bases.

Using a chloride-based flux, single-phase layered perovskite Gd _{2−4 x} Y _x Sm _x Tb _x Ho _x Ti ₂ O ₅ S ₂ ( x = 0.10–0.33) single crystals were grown, representing the first successful synthesis of high-entropy ceramics in the perovskite-type oxysulfide system.