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The discovery of bulk metallic glasses (BMGs) has stimulated widespread research enthusiasm because of their technological promise for practical applications and scientific importance in understanding glass formation and glass phenomena. Arising from their disordered atomic structure and unique glass-to-supercooled liquid transition, BMGs represent a new class of structural and functional materials with extraordinary properties including extreme strength at low temperature and high flexibility at high temperature, along with a number of superior chemical and physical properties. This article covers the general properties of BMGs based on a review of the historical milestones in metallic glass research, and recent progress on several fundamental issues in the development of a comprehensive understanding of the strength, ductility and glass-forming ability of BMGs and, more importantly, the correlation of these parameters with atomic structure, focusing on the outstanding questions and critical issues that appear to warrant future research. Recent advances in the applications of BMGs in microelectromechanical systems (MEMS), biomedicine and nanotechnology are also reviewed.

Electrochemical supercapacitors can deliver high levels of electrical power and offer long operating lifetimes 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , but their energy storage density is too low for many important applications 2 , 3 . Pseudocapacitive transition-metal oxides such as MnO 2 could be used to make electrodes in such supercapacitors, because they are predicted to have a high capacitance for storing electrical charge while also being inexpensive and not harmful to the environment 9 , 10 . However, the poor conductivity of MnO 2 (10 –5 –10 –6  S cm –1 ) limits the charge/discharge rate for high-power applications 10 , 11 . Here, we show that hybrid structures made of nanoporous gold and nanocrystalline MnO 2 have enhanced conductivity, resulting in a specific capacitance of the constituent MnO 2 (∼1,145 F g –1 ) that is close to the theoretical value 9 . The nanoporous gold allows electron transport through the MnO 2 , and facilitates fast ion diffusion between the MnO 2 and the electrolytes while also acting as a double-layer capacitor. The high specific capacitances and charge/discharge rates offered by such hybrid structures make them promising candidates as electrodes in supercapacitors, combining high-energy storage densities with high levels of power delivery. Hybrid structures made of nanoporous gold and nanocrystalline manganese dioxide offer high specific capacitances and high charge–discharge rates, which makes them promising candidates for the electrode materials in electrochemical supercapacitors.

Sodium-ion batteries are strategically pivotal to achieving large-scale energy storage. Layered oxides, especially manganese-based oxides, are the most popular cathodes due to their high reversible capacity and use of earth-abundant elements. However, less noticed is the fact that the interface of layered cathodes always suffers from atmospheric and electrochemical corrosion, leading to severely diminished electrochemical properties. Herein, we demonstrate an environmentally stable interface via the superficial concentration of titanium, which not only overcomes the above limitations, but also presents unique surface chemical/electrochemical properties. The results show that the atomic-scale interface is composed of spinel-like titanium (III) oxides, enhancing the structural/electrochemical stability and electronic/ionic conductivity. Consequently, the interface-engineered electrode shows excellent cycling performance among all layered manganese-based cathodes, as well as high-energy density. Our findings highlight the significance of a stable interface and, moreover, open opportunities for the design of well-tailored cathode materials for sodium storage. The interface of layered cathodes for sodium ion batteries is subject to atmospheric and electrochemical corrosions. Here, the authors demonstrate an environmentally stable interface via titanium enriched surface reconstruction in a layered manganese-based oxide.

Metallic materials are key for electrochemical energy conversion and storage when they are tailored into electrodes designed for rapid reaction kinetics, high electrical conductivities, and high stability. Nanoporous metals formed by dealloying could meet all of these requirements, as the dealloyed products beckon energy researchers with their fascinating structures and outstanding performance. In this article, we discuss the characteristics of dealloyed materials related to their functions in energy devices. We then review nanoporous metal electrodes for applications in fuel cells, supercapacitors, and batteries to provide insights into selection and design criteria for meeting the diverse needs of energy conversion and storage.

Various platinum-free electrocatalysts have been explored for hydrogen evolution reaction in acidic solutions. However, in economical water-alkali electrolysers, sluggish water dissociation kinetics (Volmer step) on platinum-free electrocatalysts results in poor hydrogen-production activities. Here we report a MoNi 4 electrocatalyst supported by MoO 2 cuboids on nickel foam (MoNi 4 /MoO 2 @Ni), which is constructed by controlling the outward diffusion of nickel atoms on annealing precursor NiMoO 4 cuboids on nickel foam. Experimental and theoretical results confirm that a rapid Tafel-step-decided hydrogen evolution proceeds on MoNi 4 electrocatalyst. As a result, the MoNi 4 electrocatalyst exhibits zero onset overpotential, an overpotential of 15 mV at 10 mA cm −2 and a low Tafel slope of 30 mV per decade in 1 M potassium hydroxide electrolyte, which are comparable to the results for platinum and superior to those for state-of-the-art platinum-free electrocatalysts. Benefiting from its scalable preparation and stability, the MoNi 4 electrocatalyst is promising for practical water-alkali electrolysers. In water-alkali electrolyzers, sluggish water dissociation kinetics on platinum-free electrocatalysts result in poor hydrogen-production activities. Here the authors report a MoNi 4 electrocatalyst which reduces the kinetic energy barrier of water dissociation, leading to improved hydrogen-production performance.

A method of producing superstrong yet ductile steels using cheaper and lighter alloying elements is described, based on minimization of the lattice misfit to achieve a maximal dispersion of nanoprecipitates, leading to ultimate precipitation strengthening. Extreme precipitation makes superstrong steel Ultrastrong and yet ductile steels are important materials for the automotive and energy industries, among others. A key subgroup is the maraging steels, martensitic steels that have been aged by extended heat treatment. They acquire their strength from semi-coherent intermetallic precipitates. In this paper, maraging steels are described in which the expensive cobalt and titanium alloying elements are entirely replaced with lightweight and inexpensive aluminium. The resulting precipitates were produced in the steel at high density and with minimal lattice mismatch strain, leading to an impressive combination of very high strength (up to 2.2 gigapascals) and good ductility (about 8.2 per cent). The materials are characterized using a suite of high-resolution techniques, including atom probe tomography, HAADF STEM and synchrotron XRD. Next-generation high-performance structural materials are required for lightweight design strategies and advanced energy applications. Maraging steels, combining a martensite matrix with nanoprecipitates, are a class of high-strength materials with the potential for matching these demands 1 , 2 , 3 . Their outstanding strength originates from semi-coherent precipitates 4 , 5 , which unavoidably exhibit a heterogeneous distribution that creates large coherency strains, which in turn may promote crack initiation under load 6 , 7 , 8 . Here we report a counterintuitive strategy for the design of ultrastrong steel alloys by high-density nanoprecipitation with minimal lattice misfit. We found that these highly dispersed, fully coherent precipitates (that is, the crystal lattice of the precipitates is almost the same as that of the surrounding matrix), showing very low lattice misfit with the matrix and high anti-phase boundary energy, strengthen alloys without sacrificing ductility. Such low lattice misfit (0.03 ± 0.04 per cent) decreases the nucleation barrier for precipitation, thus enabling and stabilizing nanoprecipitates with an extremely high number density (more than 10 24 per cubic metre) and small size (about 2.7 ± 0.2 nanometres). The minimized elastic misfit strain around the particles does not contribute much to the dislocation interaction, which is typically needed for strength increase. Instead, our strengthening mechanism exploits the chemical ordering effect that creates backstresses (the forces opposing deformation) when precipitates are cut by dislocations. We create a class of steels, strengthened by Ni(Al,Fe) precipitates, with a strength of up to 2.2 gigapascals and good ductility (about 8.2 per cent). The chemical composition of the precipitates enables a substantial reduction in cost compared to conventional maraging steels owing to the replacement of the essential but high-cost alloying elements cobalt and titanium with inexpensive and lightweight aluminium. Strengthening of this class of steel alloy is based on minimal lattice misfit to achieve maximal precipitate dispersion and high cutting stress (the stress required for dislocations to cut through coherent precipitates and thus produce plastic deformation), and we envisage that this lattice misfit design concept may be applied to many other metallic alloys.

The mechanical properties of crystalline materials can be quantitatively described by crystal defects of solute atoms, dislocations, twins, and grain boundaries with the models of solid solution strengthening, Taylor strain hardening and Hall–Petch grain boundary strengthening. However, for metallic glasses, a well-defined structure feature which dominates the mechanical properties of the disordered materials is still missing. Here, we report that nanoscale spatial heterogeneity is the inherent structural feature of metallic glasses. It has an intrinsic correlation with the strength and deformation behavior. The strength and Young’s modulus of metallic glasses can be defined by the function of the square root reciprocal of the characteristic length of the spatial heterogeneity. Moreover, the stretching exponent of time-dependent strain relaxation can be quantitatively described by the characteristic length. Our study provides compelling evidence that the spatial heterogeneity is a feasible structural indicator for portraying mechanical properties of metallic glasses. Directly relating the mechanical properties of metallic glasses to their atomic structure remains a challenge. Here, the authors use high resolution microscopy to show many mechanical properties of metallic glasses depend on a single structural parameter, the characteristic length of spatial heterogeneity.

Background It is well established that airway remodeling and inflammation are characteristics for chronic obstructive pulmonary disease (COPD). Moreover, cigarette smoke extract (CSE) promots inflammation, apoptosis and oxidative stress in COPD. And, there is evidence suggested that alantolactone (ALT), a sesquiterpene lactone isolated from Inula helenium , plays an adverse role in inflammation, apoptosis and oxidative stress. However, few studies have investigated the function and mechanism of ALT treatment on the COPD pathological process. Methods The levels of IL-1 β, TNF-α, IL-6 and IFN-γ were examined by ELISA. Cells’ apoptosis and caspase-3 activity were detected by Cell Death Detection PLUS enzyme-linked immunosorbent assay and caspase-Glo 3/7 Assay, respectively. The content of malondialdehyde (MDA) and superoxide dismutase (SOD) were determined by using MDA and SOD assay kits. Reactive oxygen species (ROS) generation was measured by DCFH-DA assay. Protein expression was assayed by Western blot. Results In the present study, we aimed to observe the protective effects of ALT against inflammation, apoptosis and oxidative stress in human bronchial epithelial Beas-2B and NHBE cells. Our results showed that different doses of CSE exposure induced Beas-2B and NHBE cell inflammatory cytokines IL-1 β, TNF-α, IL-6 and IFN-γ expression, cell apoptosis, caspase-3 activity and mediated oxidative stress markers MDA, ROS and SOD levels, while ALT treatment counteracted the effects of CSE. Further studies suggested that ALT attenuated NF-κB pathway activation. ALT also activated the Nrf2/HO-1 signal pathway through promoting Nrf2 nuclear aggregation and downstream HO-1 protein expression. HO-1 inhibitor tin protoporphyrin IX (SnPP IX) reversed the effects of ALT on Beas-2B and NHBE cell inflammation, apoptosis and oxidative stress. Conclusions The above results collectively suggested that ALT suppressed CSE-induced inflammation, apoptosis and oxidative stress by modulating the NF-ĸB and Nrf2/ HO-1 axis.

Developing low-cost electrocatalysts to replace precious Ir-based materials is key for oxygen evolution reaction (OER). Here, we report atomically dispersed nickel coordinated with nitrogen and sulfur species in porous carbon nanosheets as an electrocatalyst exhibiting excellent activity and durability for OER with a low overpotential of 1.51 V at 10 mA cm −2 and a small Tafel slope of 45 mV dec −1 in alkaline media. Such electrocatalyst represents the best among all reported transition metal- and/or heteroatom-doped carbon electrocatalysts and is even superior to benchmark Ir/C. Theoretical and experimental results demonstrate that the well-dispersed molecular S|NiN x species act as active sites for catalyzing OER. The atomic structure of S|NiN x centers in the carbon matrix is clearly disclosed by aberration-corrected scanning transmission electron microscopy and synchrotron radiation X-ray absorption spectroscopy together with computational simulations. An integrated photoanode of nanocarbon on a Fe 2 O 3 nanosheet array enables highly active solar-driven oxygen production. Water oxidation is considered the bottleneck reaction for light-driven water splitting due to the sluggish kinetics and poor stability. Here, authors show metal- and heteroatom-doped carbons as effective catalysts for both electrochemical and photoelectrochemical water splitting.

Since their discovery in 1960 1 , metallic glasses based on a wide range of elements have been developed 2 . However, the theoretical prediction of glass-forming compositions is challenging and the discovery of alloys with specific properties has so far largely been the result of trial and error 3 – 8 . Bulk metallic glasses can exhibit strength and elasticity surpassing those of conventional structural alloys 9 – 11 , but the mechanical properties of these glasses are critically dependent on the glass transition temperature. At temperatures approaching the glass transition, bulk metallic glasses undergo plastic flow, resulting in a substantial decrease in quasi-static strength. Bulk metallic glasses with glass transition temperatures greater than 1,000 kelvin have been developed, but the supercooled liquid region (between the glass transition and the crystallization temperature) is narrow, resulting in very little thermoplastic formability, which limits their practical applicability. Here we report the design of iridium/nickel/tantalum metallic glasses (and others also containing boron) with a glass transition temperature of up to 1,162 kelvin and a supercooled liquid region of 136 kelvin that is wider than that of most existing metallic glasses 12 . Our Ir–Ni–Ta–(B) glasses exhibit high strength at high temperatures compared to existing alloys: 3.7 gigapascals at 1,000 kelvin 9 , 13 . Their glass-forming ability is characterized by a critical casting thickness of three millimetres, suggesting that small-scale components for applications at high temperatures or in harsh environments can readily be obtained by thermoplastic forming 14 . To identify alloys of interest, we used a simplified combinatorial approach 6 – 8 harnessing a previously reported correlation between glass-forming ability and electrical resistivity 15 – 17 . This method is non-destructive, allowing subsequent testing of a range of physical properties on the same library of samples. The practicality of our design and discovery approach, exemplified by the identification of high-strength, high-temperature bulk metallic glasses, bodes well for enabling the discovery of other glassy alloys with exciting properties. Bulk metallic glasses made from alloys of iridium, nickel, tantalum and boron are developed by combinatorial methods, with higher strength at high temperature than those previously produced.