15,282 research outputs found

    Giant osmotic pressure in the forced wetting of hydrophobic nanopores

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    The forced intrusion of water in hydrophobic nanoporous pulverulent material is of interest for quick storage of energy. With nanometric pores the energy storage capacity is controlled by interfacial phenomena. With subnanometric pores, we demonstrate that a breakdown occurs with the emergence of molecular exclusion as a leading contribution. This bulk exclusion effect leads to an osmotic contribution to the pressure that can reach levels never previously sustained. We illustrate on various electrolytes and different microporous materials, that a simple osmotic pressure law accounts quantitatively for the enhancement of the intrusion and extrusion pressures governing the forced wetting and spontaneous drying of the nanopores. Using electrolyte solutions, energy storage and power capacities can be widely enhanced

    Metallic muscles and beyond:nanofoams at work

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    In this contribution for the Golden Jubilee issue commemorating the 50th anniversary of the Journal of Materials Science, we will discuss the challenges and opportunities of nanoporous metals and their composites as novel energy conversion materials. In particular, we will concentrate on electrical-to-mechanical energy conversion using nanoporous metal-polymer composite materials. A materials system that mimic the properties of human skeletal muscles upon an outside stimulus is coined an 'artificial muscle.' In contrast to piezoceramics, nanoporous metallic materials offer a unique combination of low operating voltages, relatively large strain amplitudes, high stiffness, and strength. Here we will discuss smart materials where large macroscopic strain amplitudes up to 10 % and strain-rates up to 10(-2) s(-1) can be achieved in nanoporous metal/polymer composite. These strain amplitudes and strain-rates are roughly 2 and 5 orders of magnitude larger than those achieved in common actuator materials, respectively. Continuing on the theme of energy-related applications, in the summary and outlook, we discuss two recent developments toward the integration of nanoporous metals into energy conversion and storage systems. We specifically focus on the exciting potential of nanoporous metals as anodes for high-performance water electrolyzers and in next-generation lithium-ion batteries

    Recent advances in hydrogen storage technologies based on nanoporous carbon materials

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    AbstractHydrogen is a promising energy carrier that can potentially facilitate a transition from fossil fuels to sustainable energy sources without producing harmful by-products. Prior to realizing a hydrogen economy, however, viable hydrogen storage materials must be developed. Physical adsorption in porous solids provides an opportunity for hydrogen storage under low-stringency conditions. Physically adsorbed hydrogen molecules are weakly bound to a surface and, hence, are easily released. Among the various surface candidates, porous carbons appear to provide efficient hydrogen storage, with the advantages that porous carbon is relatively low-cost to produce and is easily prepared. In this review, we summarize the preparation methods, pore characteristics, and hydrogen storage capacities of representative nanoporous carbons, including activated carbons, zeolite-templated carbon, and carbide-derived carbon. We focus particularly on a series of nanoporous carbons developed recently: metal–organic framework-derived carbons, which exhibit promising properties for use in hydrogen storage applications

    Hierarchical macro-nanoporous metals for leakage-free high-thermal conductivity shape-stabilized phase change materials

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    Impregnation of Phase Change Materials (PCMs) into a porous medium is a promising way to stabilize their shape and improve thermal conductivity which are essential for thermal energy storage and thermal management of small-size applications, such as electronic devices or batteries. However, in these composites a general understanding of how leakage is related to the characteristics of the porous material is still lacking. As a result, the energy density and the antileakage capability are often antagonistically coupled. In this work we overcome the current limitations, showing that a high energy density can be reached together with superior anti-leakage performance by using hierarchical macro-nanoporous metals for PCMs impregnation. By analyzing capillary phenomena and synthesizing a new type of material, it was demonstrated that a hierarchical trimodal macro-nanoporous metal (copper) provides superior antileakage capability (due to strong capillary forces of nanopores), high energy density (90vol% of PCM load due to macropores) and improves the charging/discharging kinetics, due to a three-fold enhancement of thermal conductivity. It was further demonstrated by CFD simulations that such a composite can be used for thermal management of a battery pack and unlike pure PCM it is capable of maintaining the maximum temperature below the safety limit. The present results pave the way for the application of hierarchical macro-nanoporous metals for high-energy density, leakage-free, and shape-stabilized PCMs with enhanced thermal conductivity. These innovative composites can significantly facilitate the thermal management of compact systems such as electronic devices or high-power batteries by improving their efficiency, durability and sustainabilit

    Lithium Storage in Nanoporous Complex Oxide 12CaO•7Al2O3 (C12A7)

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    Porous materials have generated a great deal of interest for use in energy storage technologies, as their architectures have high surface areas due to their porous nature. They are promising candidates for use in many fields such as gas storage, metal storage, gas separation, sensing and magnetism. Novel porous materials which are non-toxic, cheap and have high storage capacities are actively considered for the storage of Li ions in Li-ion batteries. In this study, we employed density functional theory simulations to examine the encapsulation of lithium in both stoichiometric and electride forms of C12A7. This study shows that in both forms of C12A7, Li atoms are thermodynamically stable when compared with isolated gas-phase atoms. Lithium encapsulation through the stoichiometric form (C12A7:O2−) turns its insulating nature metallic and introduces Li+ ions in the lattice. The resulting compound may be of interest as an electrode material for use in Li-ion batteries, as it possesses a metallic character and consists of Li+ ions. The electride form (C12A7:e−) retains its metallic character upon encapsulation, but the concentration of electrons increases in the lattice along with the formation of Li+ ions. The promising features of this material can be tested by performing intercalation experiments in order to determine its applicability in Li-ion batteries

    Intrusion and extrusion of water in hydrophobic nanopores

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    Heterogeneous systems composed of hydrophobic nanoporous materials and water are capable, depending on their characteristics, of efficiently dissipating (dampers) or storing ("molecular springs") energy. However, it is difficult to predict their properties based on macroscopic theories-classical capillarity for intrusion and classical nucleation theory (CNT) for extrusion-because of the peculiar behavior of water in extreme confinement. Here we use advanced molecular dynamics techniques to shed light on these nonclassical effects, which are often difficult to investigate directly via experiments, owing to the reduced dimensions of the pores. The string method in collective variables is used to simulate, without artifacts, the microscopic mechanism of water intrusion and extrusion in the pores, which are thermally activated, rare events. Simulations reveal three important nonclassical effects: the nucleation free-energy barriers are reduced eightfold compared with CNT, the intrusion pressure is increased due to nanoscale confinement, and the intrusion/extrusion hysteresis is practically suppressed for pores with diameters below 1.2 nm. The frequency and size dependence of hysteresis exposed by the present simulations explains several experimental results on nanoporous materials. Understanding physical phenomena peculiar to nanoconfined water paves the way for a better design of nanoporous materials for energy applications; for instance, by decreasing the size of the nanopores alone, it is possible to change their behavior from dampers to molecular springs
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