Materials Today最新文献

Tailoring microstructures represents a daunting goal in materials science. Here, an innovative proposition is to utilize grain boundary (GB) complexions (a.k.a. interfacial phases) to manipulate microstructural evolution, which is challenging to control via only temperature and doping. Herein, we use ZnO as a model system to tailor microstructures using applied electric fields as a new “knob” to control GB structures locally via field-driven defects polarization. Specifically, continuously graded microstructures are created under applied electric fields. By employing aberration-corrected scanning transmission electron microscopy (AC STEM) in conjunction with density functional theory (DFT) and ab initio molecular dynamics (AIMD), we discover cation-deficient, oxygen-rich GBs near the anode with enhanced GB diffusivities. In addition, the field-driven redistribution of cation vacancies is deduced from a defect chemistry model, and subsequently verified by spatially resolved photoluminescence spectroscopy. This bulk defects polarization leads to preferential formation of cation-deficient (oxidized) GBs near the anode to gradually promote grain growth towards the anode. This mechanism can be utilized to create continuously graded microstructures without abnormal grain growth typically observed in prior studies. This study exemplifies a case of tailoring microstructural evolution via altering GB complexions locally with applied electric fields, and it enriches fundamental GB science.

Metallic meshes (MMs) are promising for replacement of traditional brittle metal oxide conductors to serve as flexible transparent devices for applications such as environment, energy, display, and human–machine-environment interface. The diversities of MMs in materials, fabrication mechanisms, geometrics and performances extend their applications, however the systematization of this field is rarely concerned. Here, this article summarizes fabrication strategies of MMs in terms of using hard or soft templates, which produce regular-patterned meshes or random-patterned meshes, emphasizing large scale production technology free of templates would lead the development of MMs. Secondly, mechanisms and strategies are highlighted in terms of enhancement of MMs in optoelectronic properties, thermal, chemical, and mechanical stability that are crucial for adapting different application scenarios. Accordingly, the representative applications of MMs in filters, shielding materials, nanogenerators, supercapacitors, solar cells, light-emitting devices, electroluminescent devices, smart windows, thermal management equipment, sensors, and touch panels are introduced, reflecting their respective advantages in diverse applications. Finally, promising solutions to balance the optoelectronic properties and the stability and durability of MMs are proposed to adapt to complex and extreme applications. It is convinced that this review can provide a comprehensive understanding to guide and promote the future development of flexible optoelectronic devices.

Graphene, with its outstanding electrical properties, has appealed to the attention of researchers all over the world for biosensing applications. So far, much of the research has been conducted on the field-effect modulations of carriers in the basal plane of graphene after adsorbing charged biomolecules. However, another essential aspect--the graphene edge--has been largely ignored due to the difficulties in both manufacture and characterization. Here, we propose a facile intercalation and pressure sintering approach that enables the fabrication and exposure of only graphene edges. The quantum capacitance of the exposed edges is proportional to the local density of state (DOS) and can be harvested for biochemical sensing. Notably, due to fringe electric field enhancement and biomolecular convergence at the one-dimensional graphene edges, we are able to detect four representative amino acids at 0.01 fg/mL concentrations within several minutes. These achievements in innovative quantum capacitance measurements of graphene edges, combined with simple and robust device fabrication by eliminating complex micro-nano processing, offer a new avenue for the next generation of biochemical sensors with ever-demanding sensitivities.

With the advances in space technology, weight reduction of components has been a paramount, yet challenging task. Additive manufacturing with high-performance polymers can realize lightweight and complex geometries that can also be manufactured on board. Yet polymers are electromagnetically inefficient for applications requiring electrical conductivity, such as guiding microwave signals. This work presents high-efficiency and lightweight additively-manufactured microwave components enabled by MXene coating. The waveguiding functionality was observed from 8 to 33 GHz, covering low earth orbit (LEO) frequencies, with a power-handling capability of up to 10 dB and a transmission coefficient of 93 %. After a single dip-coating cycle, the polymer waveguide performed only 2 % below an eight times heavier metallic equivalent. Frequency/polarization filtering was enabled by implementing special geometries, and a range of microwave functionalities, including resonance, was demonstrated. The MXene-coated components can replace 3D-printed and bulk metals, greatly decreasing weight and cost in space, and also in various terrestrial applications.

In response to the ever-increasing global population and the growing demand for energy and food, human activities have exerted a substantial impact on the global nitrogen cycles. In this context, the electrocatalytic upgrading of nitrogenous wastes into high-value chemicals under ambient conditions, ideally powered by renewable electricity, emerges as a promising approach to concurrently manage nitrogen-containing wastes and facilitate sustainable production of valuable chemicals. This review presents the electrochemical “waste-to-valuables” concept by discussing its practicality in terms of waste removal efficiency, valuable production efficiency, downstream recovery of valuables, potential applications, and economic feasibility. Specifically, the electrocatalytic upgrading of nitrogenous wastes, i.e., nitric oxide and nitrate as representative air and aqueous pollutants, respectively, into high-value-added chemicals, i.e., ammonia via nitric oxide/nitrate reduction and urea/amide/amine via nitrogen-integrated carbon dioxide reduction is focused. Targeting nitrogenous waste exhausts/streams with low/high concentrations, reactor design and catalyst design principles are reviewed with representative examples. Finally, the major challenges and opportunities associated with the practical applications of the “waste-to-valuables” concept are discussed.

Films with nanoengineered surfaces have found extensive utilization in versatile applications, such as freshwater harvesting, water purification, steam generation and thermal energy management. Herein, we develop a liquid metal (LM) nanoporous film on a copper substrate via a simple and scalable bubble-induced self-assembly method. The LM nanoporous film not only provides abundant nucleation sites of bubbles due to nanoscale pores, but also generates CuGa₂ intermetallic compound (IMC) as a thermal interface layer with low interfacial resistance due to in situ alloying with the copper substrate. When the film is used in ethanol-based boiling system, it shows a 172% enhanced heat transfer coefficient compared to the pristine copper. In addition, the metallic wetting force between the LM nanoporous film and CuGa₂ IMC results in a durable nanoporous film. When the LM nanoporous film is utilized for the phase-change thermal energy management of a high-power-density light emitting diode, it leads to a distinct decrease in temperature by 20.7 ℃ relative to the pristine copper. This work provides a strategy to combine nanoengineered surfaces with interface engineering to enhance phase-change heat transfer, which can result in efficient energy transport in various energy-related applications.

Narrowband emitters offer significant advantages in the fabrication of next-generation deep-blue organic light-emitting diodes (OLEDs) due to their wide color gamut, high stability, and high efficiency. It is a pressing challenge to increase the light outcoupling efficiency to further boost device performance, even though 100% internal quantum efficiency is already achievable through rational molecular design. Here, we strategically propose a novel asymmetric structure design strategy aimed at simultaneously optimizing the horizontal emitting dipole orientation and aggregation state properties of the deep-blue multi-resonance (MR) emitters. This proof-of-concept emitter A-BN is capable of displaying ultrapure deep-blue emission with a peak of ∼461 nm, a small full-width-at-half-maximum of ∼25 nm, a CIEy coordinate of ∼0.08, a high horizontal dipole ratio of ∼90 %, and a near-unity photoluminescence quantum yield of ∼98 % in the practical mass-production concentration range (1–3 wt%). The corresponding non-sensitized device achieves a maximum external quantum efficiency of 41.5% without any external light extraction techniques, representing state-of-the-art performance for deep-blue OLEDs. These findings will help drive the development of highly efficient and stable narrowband deep-blue emitters and lead to a revolution in OLED technology.

Metalenses have outstanding light-modulating performances, and studies have been conducted on them to not only replace conventional bulky and heavy refractive lenses but also to expand on them. However, their operating wavelengths have rarely covered the ultraviolet (UV) regime since UV-transparent materials are scarce and nanopatterning techniques have a small patterning area, high cost, and low throughput. These limitations are overcome in this study, and centimeter-scale and highly efficient UV metalenses are successfully mass-produced. The UV metalens is designed to operate at a wavelength of 325 nm, with a numerical aperture of 0.2. Argon fluoride photolithography is used to fabricate an 8-inch master stamp in which 300 metalenses are patterned in an array with a high resolution. The fabricated master stamp can be duplicated repeatedly using wafer-scale nanoimprint lithography. To improve efficiency, we developed a zirconium dioxide–polymer hybrid material that is scalable, easily manufacturable, UV-transparent, and high-index material. The experimental results confirm that the mass-produced metalenses operate as ideal imaging systems, exhibiting an average measured efficiency of 45.1 %.

Developing mechanical materials with high stiffness, strength, and toughness has been a longstanding pursuit. Conventional engineering materials often experience a trade-off relationship between these properties, motivating researchers to explore composite structures to overcome these limitations. This study introduces a novel approach to composite design by employing aperiodic monotiles, shapes that cover surfaces without any translational symmetry. Using a combined computational and experimental approach, we study the fracture behavior of composites crafted with these monotiles and compare their performance against conventional honeycomb and square patterns. Remarkably, our aperiodic monotile-based composites exhibited superior Young's modulus, strength, and toughness in comparison to other designs under tensile loading conditions. In addition, the aperiodic monotile structures showed consistent mechanical performance with varying crack locations and directions, which implies reliable fracture resistance under complex loadings. This study suggests that leveraging the inherent disorder of aperiodic structures can usher in a new generation of robust and resilient materials.

Lithium iron phosphate (LiFePO₄) has emerged as one of the most popular cathodes due to its excellent properties of low cost, high safety and stability. However, owing to the limited lifespan caused by degradation, the widespread use of LiFePO₄ batteries would generate a large number of spent batteries, the improper disposal of which causes environmental pollution and waste of resources. Therefore, the recycling of these batteries is important for environmental protection, resource conservation and economic efficiency. This review summarises LiFePO₄ cathode materials from their development and degradation mechanisms, illustrating the reasons and necessity of their recycling. In addition, battery recycling technologies are systematically discussed from laboratory scale to industrial production in terms of efficiency, economic benefits and environmental impact. Finally, we identify the challenges of LiFePO₄ cathode recycling and offer some perspectives on these challenges. These endeavors demonstrate that the degradation of large-scale batteries drives the formation of recycling demand. Therefore, it is necessary to accurately assess the degradation mechanism which is a precondition of cathode recycling. Besides, the cathode recycling mechanism should be paid much attention, simplifying the recycling process. Moreover, it is essential to illustrate the impact of impurities and defects generated during the cycling. As such, this review provides valuable insights in innovating and boosting LiFePO₄ cathode recycling technologies on an industrial scale.