Science and Technology of Advanced Materials最新文献

Open systems on the surfaces of soft materials induce dissipative structures such as evaporative self-organization. Based on the viscous fingering phenomena, we demonstrate a meniscus splitting phenomena by evaporating an aqueous solution of versatile polyvinyl alcohol (PVA) solution from a Hele-Shaw cell. To understand it as a universal phenomenon independent of the polymer species, the distinct evolutionary pathways to pattern formation were evaluated, focusing on the interface deformation and directional deposition of the polymer. The PVA solution, which showed a steep concentration-dependent viscosity gradient under a local moderate humidity gradient, was capable of bridging the cell gap for vertical membrane formation. The interfacial shape transformation from one downward concave to multiple upward convex shapes is controllable not only by tuning the physical properties of the polymer but also by conditioning the water evaporating atmosphere. We envision that demonstrations with different cell aperture designs will expand the realization of this phenomenon using other synthetic polymers or chemical species. Such an open system design with humidity tuning is a strategy for exposure to non-equilibrium phenomena using various soft materials, particles, fibers, and networks.

Micro-particles with an internal helical liquid crystalline (LC) molecular order serve as efficient and highly compact circularly polarized luminescence (CPL) emitters. However, the coupling between CPL emission and the interior LC molecular order remains poorly understood at the single particle level. Here, we synthesized microspheres from an LC monomer RM23 together with a fluorescent dye and a chiral additive (R/S-BPy) and investigated their CPL properties. Polarized optical microscopy and angle-dependent CPL observations at a single-particle level revealed randomly distributed one-handed helical domains in each sphere, leading to CPL emission with an average dissymmetry factor value |g _lum| of 0.05 regardless the observation angle. The color of the CPL emission is tunable in the range of 450-700 nm by varying the fluorescent dyes doped in the spheres.

We utilized twin network analysis of polycrystalline materials through graph theory to visualize microstructures and examine the behavior of dislocation cluster generation in multicrystalline silicon grown by directional solidification. This approach allows for a rapid and statistical understanding of microstructures and their correlations by representing these features and their changes as network graphs. Our analysis revealed that dislocation clusters are formed at asymmetric Σ27a grain boundaries, which result from a specific twinning process. Gaining this knowledge is expected to assist in identifying grain boundary groups that can minimize the formation of dislocation clusters.

Influences of the stacking sequence and in-plane ordering of Zn₆Y₈ atomic clusters on the basal slip in long-period stacking-ordered (LPSO) phases in the Mg-Zn-Y systems were investigated by micropillar compression of single crystals at room temperature. The critical resolved shear stress (CRSS) values for basal slip do not depend much on the stacking sequence of the LPSO structures and the degree of the in-plane ordering of Zn₆Y₈ atomic clusters. The CRSS values increase with the decrease in the specimen size, following an inverse power-law relationship with a very large power-law exponent of about 0.88. Atomic-resolution scanning transmission electron microscopy (STEM) imaging of core structures of basal edge dislocations in the Mg-Zn-Y LPSO phase with a perfect in-plane ordering of Zn₆Y₈ atomic clusters revealed that the Burgers vector is b = (a/3)[2 $\stackrel{-}{1}$ $\stackrel{-}{1}$ 0] and the basal dislocations glide between the atomic planes which do not cut through Zn₆Y₈ atomic clusters.

YbMnSb₂, a topological semimetal with an exotic band structure, has recently been found to exhibit potential thermoelectric transport properties in its single-crystalline formality. The fabrication of polycrystals, which have the advantages of easy synthesis and doping tunability, will advance the transport studies of YbMnSb₂ but face challenges. Here, we found that the polycrystalline YbMnSb₂, synthesized using the conventional melting method, unexpectedly exhibits obvious impurities due to the competing phase YbMn₂Sb₂. To avoid the high-temperature synthesis, high-quality polycrystalline bulk YbMnSb₂, as well as three other RMnSb₂ (R = Sr, Ba, Eu), were successfully prepared by mechanical alloying followed by spark plasma sintering. Based on the high-quality polycrystalline samples, it was discovered that YbMnSb₂ reacts with oxygen during heating in the presence of small amounts of oxygen, resulting in MnSb, Yb₂O₃, and Sb. A similar oxidation phenomenon also occurs for the other RMnSb₂. This work provides a feasible method for synthesizing high-quality RMnSb₂ polycrystals, which should also be suitable for the other isostructural topological semimetals, paving the way for future studies of their transport properties.

Carbon materials with ordered frameworks and atomically dispersed metal sites, referred to as ordered carbonaceous frameworks (OCFs), have attracted considerable attention for their promising potential in fundamental research and diverse practical applications, particularly in electrocatalysis. In this work, we synthesize Fe-incorporated OCF (Fe-OCF) with a heme-like structure through structure-preserving pyrolysis of Fe-porphyrin with four ethynyl groups. Fe-OCF is characterized by its ordered microporous framework, incorporating atomically dispersed Fe(III) sites with a high content of 6.9 wt%, analogous to metal-organic frameworks. At the same time, Fe-OCF possesses the advantages of carbon materials, including chemical stability, thermal stability, and electrical conductivity. Remarkably, Fe-OCF mimics the functionality of a sensor enzyme by facilitating the redox reaction of hydrogen peroxide, which is regulated by an applied potential, thereby enabling bidirectional catalytic behavior. Fe-OCF exhibits a linear reduction current response to hydrogen peroxide, underscoring its efficient electron transfer and catalytic properties. Moreover, Fe-OCF demonstrates superior stability compared to molecular Fe-porphyrin, further emphasizing its potential application as a novel hydrogen peroxide sensor. These results emphasize the significant potential of Fe-based OCFs as advanced materials for artificial enzyme applications and next-generation hydrogen peroxide sensing technology.

Superconductors exhibit low thermal conductivity (κ) due to the suppression of electronic thermal conduction in the superconducting states with Cooper pairs. This change in κ enables superconductors to function as magneto-thermal switches (MTS). In this article, we review MTS behavior in pure-metal superconductors, phase-separated superconductors, and alloy-based superconductors. A large switching ratio can be achieved using high-purity superconducting metals. Nonvolatile MTS is observed in phase-separated superconductors, where the flux-trapping states are crucial for the nonvolatile MTS.

The p-type thermoelectric (TE) material α-MgAgSb is a promising tellurium-free bismuth telluride substitute for cooling and waste heat harvesting applications between room temperature and 573 K. Optimization of the material resulted in high values of figure of merit (zT _max = 1.3) to date, but performance optimization of TE devices also requires minimizing the electrical contact resistance between the TE material and the electrodes. Here, we investigate the metallization of MgAgSb with MgCuSb, providing microstructural and electrical analyses of the interfaces for functionalized legs obtained from a combined sintering of both materials systematically varying temperature, duration and pressure. Analysis of the obtained results reveals the formation of an interdiffusion layer of Ag₃Sb with varying thickness in all samples, but the contact resistance remains consistently below 10 μΩ cm². Microprobe measurements of the Seebeck coefficient indicate a change in carrier concentration in the TE material close to the interface, visualizing interdiffusion processes between MgAgSb and MgCuSb. We furthermore demonstrate that MgCuSb can successfully be applied as an electrode on pre-compacted MgAgSb samples, resulting in the first ever reported successful two-step contacting of MgAgSb. The obtained sample exhibits a strong mechanical contact without any crack at the interface, as well as a very low electrical contact resistance below 7 µΩ cm², representing less than 5% of the total leg resistance. Successful contacting of pre-compacted material is a step forward towards module fabrication as it enables better control of the TE leg length and thus device performance.

While high-voltage operation of mid-Ni layered oxide cathodes in full-cell Li-ion batteries is essential for achieving high energy density, it inevitably accelerates electrode degradation, ultimately resulting in capacity loss. However, the underlying degradation mechanisms under high-voltage conditions remain poorly understood. In this study, we reveal that anode slippage - induced by cross-talk-driven surface degradation - is the dominant factor in capacity fade during high-voltage (4.35 or 4.40 V) cycling of single-crystal mid-Ni layered oxide (SC-NCM)/graphite pouch full-cells. Electrochemical and post-mortem analyses show that, although high-voltage operation induces cathode surface degradation, including lattice oxygen loss and phase transitions, its direct impact on capacity loss is relatively minor compared to that of the anode. Instead, anode degradation is primarily caused by cross-talk effects from cathode Ni dissolution, which promote the accumulation of irreversible organic byproducts - such as LiOx and Li₂CO₃ - within the solid electrolyte interphase (SEI) layer of the graphite anode. This leads to increased resistance and reduced anode electrochemical activity, disrupting electrode balance and accelerating full-cell capacity fade. These findings highlight the critical role of anode degradation in high-voltage operation and emphasize the importance of mitigating cross-talk effects. A comprehensive understanding of cross-talk-induced anode slippage is therefore critical for the rational design of high-voltage mid-Ni full-cell systems with long-term durability.

Active matter, characterized by its ability to exhibit autonomous and dynamic behavior, has emerged as a promising platform for mimicking complex biological processes. In biological systems, electrochemical signaling plays a vital role in regulating their dynamic processes, such as muscle contraction. Drawing inspiration from these mechanisms, we demonstrate that electrochemical signaling can effectively modulate the autonomous motion of self-oscillating gels (SOGs), a model active matter system driven by the Belousov - Zhabotinsky reaction. Electrochemical stimulation generates signal transducers, HBrO₂ and Br^-, enabling the modulation of the autonomous motion of SOGs, including the termination and acceleration of volumetric oscillations. Our findings reveal that the response of SOGs to electrochemical signals is influenced by their geometry, orientation, and the duration of applied potential. These results establish electrochemical signaling as a powerful approach for controlling the behavior of active matter, bridging the gap between synthetic systems and biological mechanisms. By advancing the understanding of active matter dynamics, this work paves the way for applications in soft robotics, adaptive materials, and bioinspired actuators.