Nanoporous metallic foams with high surface area and novel functional behavior are positioned to stimulate new multifunctional and metamaterial applications. However, there are fundamental challenges in achieving uniform nanopores and tailorable morphology. Emerging templating methods offer a wide range of applicable metallic species while enhancing control of pore morphology, uniformity, and interconnectivity. Here, a critical review of nanoporous metal fabrication is presented, with focus on templating methods utilizing nanoporous polymeric templates. Metals are introduced into percolative nanochannels of sacrificial templates by deposition, and subsequent removal of templates yields ordered nanoporous metals. We introduce approaches for preparing nanoporous templates, including utilizing block copolymer self-assembly that yields periodic gyroid networks. While metallization of templates by electrodeposition has been demonstrated, electroless deposition permits uniform deposition by many metallic species and infiltration of narrow pores. Examples of nanoporous metals with uniform pore sizes below 50 nm fabricated by templating methods are examined.

Lithium–sulphur (Li–S) batteries are one of the most promising candidates for the next generation of energy storage systems to alleviate the energy crisis. However, Li–S batteries’ commercialization faces the challenges of low active materials utilization, poor cycling life, and low energy density. Recently, tremendous progress has been achieved in improving the electrode performances and tap density by using the nanostructured metal compounds in Li–S batteries. In this review, we not only present the latest various nanostructured metal compounds applications in Li–S batteries, including metal oxides, metal sulphides, metal carbides, metal nitrides, and metal organic frameworks, but also we focus on the interaction mechanisms between these polar metal compounds with polysulphides. The issues and bottlenecks of these metal compounds are concluded and the corresponding available solutions to address these issues are proposed. This systematic discussion and proposed strategies can offer avenues to the practical application of Li–S batteries in the near future.

Natural gas consumption has grown from 5.0 trillion cubic feet (TCF) in 1949 to 27.0 TCF in 2014 and is expected to be ∼31.6 TCF in 2040. This large demand requires an effective technology to purify natural gas. Nitrogen is a significant impurity in natural gas and has to be removed since it decreases the natural gas energy content. The benchmark technology to remove nitrogen from natural gas is cryogenic distillation, which is costly and energy intensive. Membrane technology could play a key role in making this separation less energy intensive and therefore economically feasible. Molecular sieve membranes are ideal candidates to remove natural gas impurities because of their exceptional size-exclusion properties, high thermal and chemical resistance. In this review, the state of the art of molecular sieve membranes for N2/CH4 separation, separation mechanisms involved, and future directions of these emerging membranes for natural gas purification are critically discussed.

The successful applications of graphene nanomaterials in nanobiotechnology and medicine as well as their effective translation into real clinical utility hinge significantly on a thorough understanding of their nanotoxicological profile. Of all aspects of biocompatibility, the hemocompatibility of graphene nanomaterials with different blood constituents in the circulatory system is one of the most important elements that needs to be well elucidated. Once administered into biological systems, graphene nanomaterials may inevitably come into contact with the surrounding plasma proteins and blood cells. Crucially, the interactions between these hematological entities and graphene nanomaterials will influence the overall efficacy of their biomedical applications. As such, a comprehensive understanding of the hemotoxicity of graphene nanomaterials is critically important. This review presents an up-to-date elucidation of the hemotoxicity of graphene nanomaterials through their interactions with blood proteins and cells, as well as offers some perspectives on the current challenges, opportunities, and future development of this important field.

Mesoscale heterogeneous material systems are efficient and adaptive to real world environments, owing to the non-uniform stress fields that result from the convolution of component geometries, loading conditions, and environmental changes. With the advent of multi-material additive manufacturing, the production of heterogeneous material systems with a pre-defined mesoscale material distribution becomes feasible. This unlocks the design freedom at a characteristic length scale between the macroscale geometry and microstructures, but also calls for a new design framework to optimize the mesoscale material distribution in multi-material additive manufacturing. Here, we propose and demonstrate such a design framework by incorporating digital image correlation-based deformation mapping with 3D finite element modeling-based computational optimization. The constitutive behavior of each constituent material or their mixtures is calibrated by matching the local deformation data. The optimal mesoscale material distribution can then be determined using global optimization algorithms and validated experimentally.

Microstructure and phase evolution in magnetron sputtered nanocrystalline tungsten and tungsten alloy thin films are explored through in situ TEM annealing experiments at temperatures up to 1000 °C. Grain growth in unalloyed nanocrystalline tungsten transpires through a discontinuous process at temperatures up to 550 °C, which is coupled to an allotropic phase transformation of metastable β-tungsten with the A-15 cubic structure to stable body centered cubic (BCC) α-tungsten. Complete transformation to the BCC α-phase is accompanied by the convergence to a unimodal nanocrystalline structure at 650 °C, signaling a transition to continuous grain growth. Alloy films synthesized with compositions of W–20 at.% Ti and W–15 at.% Cr exhibit only the BCC α-phase in the as-deposited state, which indicate the addition of solute stabilizes the films against the formation of metastable β-tungsten. Thermal stability of the alloy films is significantly improved over their unalloyed counterpart up to 1000 °C, and grain coarsening occurs solely through a continuous growth process. The contrasting thermal stability between W–Ti and W–Cr is attributed to different grain boundary segregation states, thus demonstrating the critical role of grain boundary chemistry in the design of solute-stabilized nanocrystalline alloys.

Two α-alumina + YSZ samples were prepared by sintering for 3 h one at 1500 °C and the other at 1700 °C. The samples were then converted to Na-β″-alumina + YSZ by vapor phase conversion. Characterization techniques such as X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy in addition to dimensional geometrical changes reveal the evolution of slight anisotropy in these samples during conversion. This results in an electrical conductivity anisotropy factor of about 5.5 and 1.8 for samples sintered at 1500 °C and 1700 °C, respectively. In all samples, the higher ionic conductivity was measured across the sample thickness as opposed to parallel to the disc faces. The ionic conductivity measurements show the conductivity of about 0.15 S/cm and 0.07 S/cm at 300 °C for samples sintered at 1500 °C and 1700 °C, respectively. The larger anisotropy in samples sintered at 1500 °C is explained by the higher aspect ratio of grains in this sample and by different Na concentrations.