The high cost and complexity of fabrication limit the large-scale application of flexible inorganic thermoelectric materials. Currently, Bi2Te3-based materials are the only commercially viable option, but the inclusion of Te significantly increases production costs. This study presents a simple and cost-effective method for fabricating flexible Ag2Se films, employing a combination of solvothermal synthesis, screen printing, and spark plasma sintering. The incorporation of a small amount of Te improves film density and facilitates Te diffusion doping, leading to Ag2Se films with a high power factor of 25.7 μW cm-1 K-2 and a figure of merit (ZT) of 1.06 at 303 K. These films exhibit excellent flexibility, retaining 96% of their performance after 1000 bending cycles at a 5 mm bending radius. Additionally, we design a flexible thermoelectric device featuring a triangular p-n junction structure based on these films. This device achieves a normalized power density of 4.8 μW cm-2 K-2 at a temperature difference of 20 K and a maximum cooling of 29.8 K with an input current of 92.4 mA. These findings highlight the potential of this fabrication method for developing thermoelectric materials and devices for energy harvesting and cooling applications.

This study reports a one-step electrodeposition of ternary mesoporous gold-silver-copper (mAuAgCu) alloy films by using diblock copolymers as pore-directing agents. Additionally, it examines the effects of alloy composition on the electrocatalytic performance of mAuAgCu thin films. Using advanced characterization techniques, such as scanning transmission electron microscopy and X-ray photoelectron spectroscopy, the interplay between alloy composition, surface structure, and catalytic performance is revealed. The optimized mAu(0.60)Ag(0.20)Cu(0.20) alloy (prepared from the precursor solution with an Au:Ag:Cu ratio of 60:20:20) demonstrates the highest catalytic activity for glucose sensing. This is because the introduction of Cu facilitates a uniform distribution of defects in this mesoporous ternary alloy through controlled reduction, leading to a higher electrochemically active surface area (ECSA) and more active sites for electrochemical reactions. This research provides valuable insights into designing trimetallic alloys, demonstrating how the surface structure and alloy composition can control the catalytic performance for electrochemical applications.

Additive manufacturing (AM) features repeated thermal cycles due to the track- and layer-wise fabrication process. However, the unique thermal cycling often encourages the precipitation of detrimental phases, such as the isothermal omega phase in metastable beta titanium alloys, which cause severe embrittlement. This study aims to address omega phase embrittlement in Ti-13.5Mo (wt%) metastable beta titanium alloy fabricated by laser powder bed fusion (L-PBF) through Sn additions. It is shown that 5.0 wt% Sn microparticles can be reliably in-situ alloyed with Ti-13.5Mo by L-PBF to effectively inhibit the formation of the commensurate isothermal omega phase in the binary Ti-13.5Mo alloy. Detailed microstructural characterizations and simulations of the precipitation kinetics reveal that both Ti-13.5Mo with and without Sn exhibit densely populated omega phase throughout the microstructures. However, the Sn addition retards development of the final commensurate form of isothermal omega phase, thereby mitigating its embrittling effects. As a result, Ti-13.5Mo+5Sn fabricated by L-PBF exbibits a good balance of strength and ductility which outperforms those of similar alloys produced by conventional manufacturing routines. Since the Ti-Mo binary system forms the basis of important multicomponent titanium alloys, the finding in this work is expected to be applicable beyond the binary alloy considered here and provides a framework for the design of beta titanium alloys for AM that are resistant to omega phase embrittlement.

Vanadium (V) is a promising paleoredox tracer in ancient marine sediments due its range of possible oxidation states (+3 to +5) and its unique redox-sensitivity. However, the interactions between V and the sulfide minerals common under ancient depositional conditions remain poorly studied. Iron monosulfide (FeS) is the first sulfide phase to form in anoxic-sulfidic waters and sediments, and an important precursor for sedimentary pyrite. Here we investigate the adsorption of dissolved V-V by freshly precipitated FeS under conditions relevant to marine waters. We report near complete removal of aqueous V (94-98%; similar to 2 x 10(-5) M) by FeS (1 g L-1) in anoxic seawater within 24 h. Synchrotron-based X-ray absorption spectroscopy (XAS) at the V and Fe K-edges shows that aqueous V-V was rapidly (<60 s) reduced to solid-phase V-III during reductive sorption by FeS. Iron K-edge and X-ray diffraction data show that the products of the subsequent oxidation of V-III-bearing FeS were elemental sulfur and lepidocrocite. Solid-phase V was oxidized within 24 h from +2.97 to +4.0, with no loss of V to solution. EXAFS analysis suggests, based on the predominance of V center dot center dot center dot Fe backscatters at similar to 3.0 angstrom, that octahedral V-IV may have been incorporated in the structure of lepidocrocite during its formation. These results provide valuable insight into the relationship of V and FeS in marine environments, including the adsorption mechanism and V speciation relevant to the fate of V during early diagenesis in marine sediments.

Heat treatment serves as a viable strategy to effectively mitigate the intense corrosion of biodegradable WE43 alloys. However, limited comprehension of the passivation mechanisms underlying heat treatment and the dilemma to quantitatively examine the evolution of hydrogen gas in vivo introduce uncertainties in designing heat treatments for developing clinically applicable WE43. This work aims to advance this knowledge by applying cutting-edge atom probe tomography to provide atomic-scale insights into the passivation roles of rare earth (RE)-rich β1 (Mg3(Y, Nd)) and β' (Mg12NdY) nanophases induced by T6 heat treatment at 250 °C, and employing machine learning-based image analysis techniques to quantitatively unveil WE43's in vivo gas evolution during a 12-week implantation. It was found that nanosized β1 and β' phases can effectively improve WE43's corrosion resistance by inducing an accelerated passivation effect on the surface and confining the distribution of hydrogen ions in the matrix. Female rats presented slightly higher corrosion rates than male rats in weeks 1 and 4 but lower hydrogen gas volumes in vivo, while male rats possessed a superior ability to metabolise hydrogen gas in vivo. Notably, latent gas evolution against the corrosion rates was found which peaked at week 4 and subsided at week 12 despite the gradually decreased corrosion rates from week 1 to 12. This study offers insights for engineering heat treatments to develop clinically applicable WE43 with acceptable corrosion rates and in vivo gas generation at various implantation stages. STATEMENT OF SIGNIFICANCE: The study aimed to reveal the role of β1 and β' nanophases on the good corrosion resistance of WE43. The influence of these nanophases on WE43's corrosion performance has not been totally understood. Similarly, the understanding of hydrogen gas evolution as it relates to the magnesium implant's corrosion rate lacks clarity. Atom probe tomography (APT) indicates β1 and β' nanophases trap hydrogen, removing H2 from the lattice and disabling its catalytic role in Mg oxidation. Machine learning-aided analyses of computed tomography (CT) scan images indicate latent gas evolution, contradicting the monotonic in vivo H2 evolution that is widely accepted.

Demand for energy-efficient transportation has led to increased use of lightweight aluminium alloys due to their exceptional strength-to-weight. Meanwhile, aluminium-based metal matrix composites (MMCs) are being developed to enhance wear resistance and strength. However, traditional ceramic reinforcements often have poor bonding with the matrix, compromising performance. Here, we demonstrate the use of a novel ex-situ AlN reinforcement powder to enhance sintering and interfacial bonding for powder metallurgy preparation of Al/AlN MMCs. We compared two series of Al/AlN MMCs featuring 10 vol.% ex-situ AlN reinforcement, one prepared using commercial AlN powder, and the other using our novel AlN reinforcement prepared by low temperature direct nitridation of Al powder. Metallic Al contained in the synthesized reinforcement significantly improved interfacial adhesion between matrix and reinforcement and enhanced densification during sintering. This resulted in a substantial improvement in tensile mechanical properties, with an 11.5% increase in ultimate tensile strength and almost five-fold improvement in ductility compared to composites prepared using the conventional ceramic AlN reinforcement. This study provides a strategy for powder metallurgy production of advanced Al/AlN MMCs with superior physical and mechanical properties.

Coarse columnar grains and heterogeneously distributed phases commonly form in metallic alloys produced by three-dimensional (3D) printing and are often considered undesirable because they can impart nonuniform and inferior mechanical properties. We demonstrate a design strategy to unlock consistent and enhanced properties directly from 3D printing. Using Ti−5Al−5Mo−5V−3Cr as a model alloy, we show that adding molybdenum (Mo) nanoparticles promotes grain refinement during solidification and suppresses the formation of phase heterogeneities during solid-state thermal cycling. The microstructural change because of the bifunctional additive results in uniform mechanical properties and simultaneous enhancement of both strength and ductility. We demonstrate how this alloy can be modified by a single component to address unfavorable microstructures, providing a pathway to achieve desirable mechanical characteristics directly from 3D printing.

Alkali metal batteries have high energy densities required to power future devices; however, uneven metal deposition is a critical barrier to achieving long lifespans. We have developed an elegant noncryogenic transmission electron microscopy method which has facilitated the first observations of epitaxial deposition in alkali metal batteries. Using this method, we have confirmed epitaxial interactions between (002) sodium crystallite planes and (01-11) planes in zinc current collectors. Such epitaxial interactions decrease nucleation energy barriers and promote even metal growth. This study offers fresh inspiration for the development of electron microscopy techniques tailored to electron-sensitive battery materials and sets a new agenda for the development of battery technologies.

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The thermal cycling of additive manufacturing can act as an in-situ intrinsic heat treatment (IHT), thereby producing spatially dependent microstructures and mechanical properties. This work demonstrates how to minimise the IHT effect to achieve uniform and enhanced tensile ductility of Ti−5Al−5Mo−5V−3Cr produced by laser powder bed fusion (L-PBF). It is found that the thermal cycling, in conjunction with substrate heating, can trigger the formation of isothermal ω and/or α phases in the β matrix, which leads to non-uniform and inferior tensile ductility. Ceasing substrate heating and/or increasing interlayer deposition time from 15 to 30 s enable substantial ductility improvement but fail to eliminate the ductility variation. Through designing a gradient interlayer deposition time (30 s – 45 s – 30 s), the tensile ductility increases 4–5 fold to ∼19% without any notable variation. The design strategy may help to tailor the microstructures and mechanical properties of other alloys which suffer from the same issue.

Triply periodic minimal surface (TPMS) titanium lattice structures produced by laser powder bed fusion (L-PBF) are promising for the future of bone tissue implant applications. However, growing concerns surrounding the cytotoxicity of Ti6Al4V and the high cost and poor wear performance of novel beta titanium alloys limits their practical applications. Titanium matrix composites (TMCs) have an improved strength to stiffness ratio and wear resistance making them ideal for biomedical applications. In this work, a TiB reinforced TMC was produced in situ in L-PBF using 2 vol% boron nitride (BN) nanopowder addition with an 80% porous gyroid TPMS geometry. The lattices exhibited strength to stiffness ratio up to 2.5% with a modulus of 2.5 GPa and yield strength of 62.3 MPa, ideal for cancellous bone applications. TMC strengthening is facilitated by the high aspect ratio TiB reinforcement with best properties achieved after post process heat treatment, which increased the TiB aspect ratio and resulted in a quasi-continuous network microstructure with fine alpha Ti grains. Significant attention was given to optimisation of the L-PBF parameters to achieve a high solid density > 99.5% and bulk porosity > 77% close to the designed 80%. Direct contact cytotoxicity tests showed TMCs have promise as biomaterials, particularly after heat treatment which reacted residual surface BN.

The use of selective laser melting(SLM)to produce titanium matrix composites(TMCs)with high strength while retaining sufficient tensile ductility suitable for structural applications is emerging as an attractive opportunity in the field of advanced manufacturing.However,the presence of coarse ceramic reinforcements as well as difficulties in optimizing the SLM process is a barrier to the application of TMCs.In this study,we demonstrated the production of TMCs reinforced with in situ high aspect ratio TiB nanowhiskers by selective laser melting using nanosized BN powder additions.Pure Ti with 2.5 vol.％nanosized BN powder showed promise for producing high performance TMCs with retained ductility.BN acted to produce TiB nanowhiskers with diameter＜50 nm.Further,by controlling post process furnace annealing TiB retained a low diameter but exhibited a high aspect ratio,up to 400.In addition to TiB re-finement,nanosized BN addition promoted grain refinement during SLM,both acting as a solute to induce nucleation events and,as TiB is formed,providing nucleation sites leading to an ultrafine grain structure in as printed samples and after annealing.The produced TMCs exhibit high tensile yield strength,up to 1392 MPa,while retaining tensile ductility up to 10％.This study has shown how nanoscale design in powder bed fusion additive manufacturing techniques can be used to produce high performance TMCs through a combination of refined grain structure and high aspect ratio TiB leading to TMCs with signifi-cant improvement in strength,isotropic properties and retained tensile ductility.

Titanium and its alloys have been employed in the biomedical industry as implants and show promise for more broad applications because of their excellent mechanical properties and low density. However, high cost, poor wear properties, low hardness and associated side effects caused by leaching of alloy elements in some titanium alloys has been the bottleneck to their wide application. TiB reinforcement has shown promise as both a surface coating for Ti implants and also as a composite reinforcement phase. In this study, a low-cost TiB-reinforced alpha titanium matrix composite (TMC) is developed. The composite microstructure includes ultrahigh aspect ratio TiB nanowhiskers with a length up to 23 μm and aspect ratio of 400 and a low average Ti grain size. TiB nanowhiskers are formed in situ by the reaction between Ti and BN nanopowder. The TMC exhibited hardness of above 10.4 GPa, elastic modulus above 165 GPa and hardness to Young's modulus ratio of 0.062 representing 304%, 170% and 180% increases in hardness, modulus and hardness to modulus ratio, respectively, when compared to commercially pure titanium. The TiB nanowhisker-reinforced TMC has good biocompatibility and shows excellent mechanical properties for biomedical implant applications.

With the increase in demand for high speed and efficient transport, there is a growing call for lightweight materials with high specific properties. Titanium matrix composites (TMCs) are one material of growing interest, whose properties make them a competitive replacement for many superalloys used in the aerospace industry. However, high cost, poor ductility, and the lack of a reliable manufacturing process have limited their application. In this study, we demonstrate the fabrication of high-performance titanium matrix composites reinforced with a network of high aspect ratio TiB nanowhiskers to overcome these challenges. A unique combination of fine BN nanopowder and a low-cost sintering method was employed. Ultralong, 40–50 μm TiB nanowhiskers with an aspect ratio of 500 have been produced from the in situ reaction between Ti and BN during slow heating/cooling, with temperatures at and below 1100 °C. As-sintered composites reached a hardness of 8.52 GPa, a reduced Young's modulus of 152 GPa, and a yield strength of 1236.5 MPa, a 250% increase when compared to pure titanium as measured by nanoindentation. The improved mechanical properties were attributed to the ultrahigh aspect ratio of TiB, the low titanium grain size, and the near continuous network of TiB reinforcement. Slow heating/cooling allows for control of TiB formation to achieve the maximum aspect ratio as well as complete conversion of BN to TiB. In addition, the TiB network in the grain boundary acted to restrict Ti grain growth during manufacturing and improve the overall TMC properties. The proposed manufacturing method has great potential for the low-cost production of high performance TMCs.