Science and Technology of Advanced Materials最新文献

This study investigates the pressure-dependent structural response of ammonium phosphomolybdate hydrate (APMH) under four distinct pressure-transmitting media (PTMs): distilled water, methanol, ethanol, and silicone oil. Synchrotron X-ray diffraction combined with Rietveld refinement confirmed that APMH maintains the archetypal Keggin-type framework while incorporating approximately ten crystallographic water molecules per unit cell, distributed over two distinct coordination sites (OW1 and OW2). High-pressure diffraction experiments revealed pronounced PTM-dependent compressional behaviors. In water, APMH undergoes an abrupt 2.6% volume collapse near 2 GPa followed by framework stiffening, while silicone oil induces significant densification above ~4 GPa. By contrast, methanol and ethanol promote smooth, elastic contraction without discontinuities. Bulk moduli derived from equation-of-state fitting span a wide range, from ~28 GPa under low-pressure silicone oil to 321 GPa at high pressures, highlighting the critical role of PTM chemistry and penetrability. Microstrain analysis further identified anisotropic deformation, with the (222) planes particularly sensitive to stress accumulation under both water and silicone oil. These results demonstrate that APMH compressibility is not an intrinsic constant, but a variable property governed by external medium.

Co₂FeSi is considered a half-metallic ferromagnet and a Weyl semimetal, however, its predicted properties have been shown to be heavily influenced by how the on-site Coulomb interaction is incorporated, which remains controversial. In this study, we measure the anomalous Nernst conductivity (α _xy ) and anisotropic magnetoresistance (AMR) effect of a Co₂FeSi thin film from low temperature to room temperature, and compare the results with those of first-principles calculations using different values for on-site Coulomb interaction at the Co site (U _Co). Our measurements reveal that α _xy is less than 0.1 A m^-1 K^-1 at room temperature and decreases slightly with the temperature. The observed values of α _xy are more than one order of magnitude smaller than the predictions unless a small but finite U _Co is incorporated. The AMR effect exhibits a notable sign change from negative to positive with increasing temperature, which is inconsistent with the predicted band structure calculated using a large U _Co value. By combining these experimental observations with first-principles calculations, we estimate that the appropriate U _Co value is approximately 1-2 eV. Our findings provide valuable insight into the correlation effect in Co₂FeSi, emphasizing the critical role of the on-site Coulomb interaction in accurately describing the transport properties of Co-based Heusler alloys.

Topological magnets such as magnetic Weyl and nodal-line semimetals possess topologically non-trivial band structures in magnetically ordered states. In this class of materials, the Berry curvature in momentum space can be significantly enhanced, resulting in thermoelectric responses that exceed empirical scaling laws based on magnetization. Such large transverse thermoelectric effects enable flexible thin-film-based lateral device structures, leading to novel energy-harvesting technologies and sensors beneficial for Internet of Things (IoT) sensors and wearable devices. In this review, we outline recent progress in the study of the large transverse thermoelectric effects in topological magnets.

The humid and highly dynamic milieu of the oral cavity and gastrointestinal tract poses formidable challenges to the precise localization and functionality of drugs and materials. Consequently, materials endowed with intrinsic wet adhesion properties hold great promise for the treatment of oral and gastrointestinal disorders. To a certain extent, the evolution of biomaterials has propelled progress in clinical diagnostics and therapeutic modalities. Wet-adhesive hydrogels, which can adapt to the moist and variable conditions of the digestive tract, display a spectrum of favorable biological attributes, such as antibacterial, anti-inflammatory, antioxidant, and hemostatic effects. These properties render them invaluable in the precision treatment of oral and gastrointestinal diseases. In this review, we scrutinize the adhesion mechanisms of wet-adhesive hydrogels and explore how their biological functions enable them to function efficiently within the gastrointestinal environment.

The blood-brain barrier (BBB) is the protective interface that isolates the central nervous system from circulating blood, which restricts approximately 98% of small molecule drugs and nearly all large molecules from entering the brain. Current methods to bypass the BBB, such as laser-guided interstitial thermal therapy and magnetic resonance guided focused ultrasound, are fraught with risks like impairing BBB integrity and brain damage, and are not suitable for long-term treatment. Nanocarriers have emerged as promising tools due to their ability to enhance drug delivery across the BBB while minimizing systemic toxicity. These nanocarriers leverage mechanisms including receptor-mediated, carrier-mediated, cell mediated and extra-stimuli mediated transport to improve BBB traverse and brain targeting. The review evaluates these strategies separately, discussing their potential and limitations for clinical application, and highlights recent advancements in integrating and optimizing nanocarriers utilizing synergistic strategies for the treatment and diagnosis of neurological disorders, including tumors, Alzheimer's disease, Parkinson's disease, and brain infections.

We investigated a vacuum thin-film process using laser ablation to fabricate heterostructures of halide perovskite CsPbBr₃ for light-emitting diode (LED) applications. A CsPbBr₃ single crystal synthesized via inverse temperature crystallization was used as the target material for pulsed laser deposition. CsPbBr₃ films were deposited at 150°C, 200°C and 250°C. Structural and optical analysis has revealed that the optimum temperature is 200°C, which display the highest crystallinity and photoluminescence emission efficiency. Time-resolved microwave photoconductivity characterization revealed that the CsPbBr₃ film exhibited a high effective mobility of 2.47 cm²/Vs and long photocarrier lifetime of 16.5 μs. The lifetime is comparable to that of bulk CsPbBr₃ single crystals. This indicates that the polycrystalline CsPbBr₃ film had a low density of defect structures that promote nonradiative recombination. Furthermore, we applied this process to fabricate a LED device using halide perovskite heterostructures. This resulted in a strong green electroluminescence emission. The laser ablation process using ultraviolet and infrared light is suitable for forming heterostructures with an electron transportation layer of oxide Mg_0.3Zn_0.7O film and a hole transportation layer of an organic α-NPD film. The film synthesis process is likely to be effective for evaluating heterointerfaces of various materials displaying remarkable crystallinity without exposure to air.

[This retracts the article DOI: 10.1080/14686996.2024.2320083.].

The planar and lateral HCl-gas etching behavior of (001) β-Ga₂O₃ under oxygen supply were investigated at partial pressures of P ⁰(O₂) = 0-2.5 kPa and 645-1038°C, while maintaining a constant HCl supply partial pressure of P ⁰(HCl) at 63 Pa. At 747°C, the planar etch rate (PER) exhibited a slight decrease with increasing P ⁰(O₂). Notably, at P ⁰(O₂) = 1.25 kPa, the PER increased with temperature, demonstrating a plateau between 747 and 848°C, whereas the thermodynamically calculated etching driving force did not. Even minimal O₂ supply effectively suppressed root mean square (RMS) roughness to <1 nm at 747°C. At P ⁰(O₂) = 1.25 kPa, RMS roughness remained at  <2 nm at up to 847°C, but sharply increased to  >7 nm above 947°C, indicating that lower temperatures realize smoother surfaces. Lateral etch rate (LER) analysis, employing a spoke-wheel pattern mask at 747°C revealed significant anisotropy, demonstrating a kidney-like polar plot pattern, with minimum values in the <100 > direction and maximum values in the  <010> direction. Although P ⁰(O₂) had a limited effect on anisotropy, temperature increase significantly enhanced the LER, particularly along the ± 20°-rotated directions from  <100> . Above 947°C, etched sidewalls exhibited a multi-faceted morphology owing to the formation of {310} and {3̅10} facets depending on the spoke direction, whereas the sidewalls were relatively smooth below 848°C. These findings underscore the potential of controlled HCl-gas etching for the plasma-free processing of β-Ga₂O₃, enabling the fabrication of high-performance devices.

We performed resonance shear measurements (RSM) using the low-temperature surface force apparatus (LT-SFA) to investigate how rubber composition influences the viscoelasticity of the rubber-ice interface. RSM data showed quite different behaviours depending on the styrene contents (5, 23 and 45 wt%) of poly(styrene-co-butadiene) rubbers. A mechanical model for RSM was applied to obtain the interface's viscous (b _s) and elastic (k _s) parameters across a temperature range of ca. -20°C to 0°C. All rubber-ice interfaces at a temperature of ca. -18° to -10°C showed a significant decrease in viscosity of 1 to 2 orders of magnitude in the maximum compared to the silica-ice interface, presenting properties of the ice premelted layer. This was attributed to the dominant viscoelastic contributions of the rubber with decreasing styrene content, and therefore to the decreasing glass transition temperature (T _g = -74, -55, and -31℃). The decrease in the viscosity was enhanced more for lower T _g rubbers. Between -10°C and -5°C, the rubber-ice viscosities converged at a value lower than silica-ice, which was indicative that the interfacial viscoelasticity in this regime was determined by increased contributions from the premelted layer of ice which was probably modulated by polymer-ice interactions. Finally, above -5°C all samples showed a rapid decay in viscosity and elasticity, suggesting that the premelted layer of ice is the main contributor. This study successfully demonstrated that rubber composition could have a profound impact on the viscoelasticity of the rubber-ice interface.

[This retracts the article DOI: 10.1080/14686996.2024.2341611.].