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Journal ArticleDOI: 10.1021/ACSAMI.0C16869

Using X-Ray Scattering to Elucidate the Microstructural Instability of 3D Bicontinuous Nanoporous Metal Scaffolds for Use in an Aperiodic 3D Tricontinuous Conductor-Insulator-Conductor Nanocapacitor.

04 Mar 2021-ACS Applied Materials & Interfaces (American Chemical Society (ACS))-Vol. 13, Iss: 10, pp 11721-11731
Abstract: The development of three-dimensional aperiodic energy storage devices is in part impeded by the lack of appropriate aperiodic templates that can withstand the thermal conditions required to deposit energy storage materials within their void space. Herein, the feasibility of an aperiodic three-dimensional architecture for energy storage is demonstrated for the first time by constructing a tricontinuous conductor-insulator-conductor (CIC) nanocapacitor on an aperiodic nanoporous gold scaffold. To accomplish this, the scaffold was characterized using in situ small-angle X-ray scattering (SAXS) during exposure to a thermal environment, revealing that its microstructure eventually stabilizes after undergoing a phase of rapid coarsening, indicating a departure from the 1/4 time-dependent power-law coarsening behavior usually observed at the early stage of the coarsening process. Using this stability regime, we created the CIC by intentionally precoarsening and stabilizing the scaffold before depositing two dissimilar metal oxide films in its void space by atomic layer deposition. Current-voltage characteristics and electrochemical impedance spectroscopy measurements revealed that the un-optimized 3D CIC outperformed its 2D counterpart by ∼4× in terms of capacitance. This proof-of-concept device will pave the way to the development of aperiodic three-dimensional energy storage systems with enhanced energy and power densities.

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Topics: Nanoporous (50%)

5 results found

Journal ArticleDOI: 10.1021/ACSENERGYLETT.1C00324
12 Apr 2021-ACS energy letters
Abstract: While nanostructured alloy-type anodes are considered potential high-capacity alternatives to intercalation-type graphite anodes, large volume changes inherent to alloy-type anode cycling result in...

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Topics: Anode (53%), Nanoporous (53%), Battery (electricity) (50%)

3 Citations

Journal ArticleDOI: 10.1021/ACSAMI.1C12491
Shawn Maguire1, Connor Bilchak1, John S. Corsi1, Samuel S. Welborn1  +5 moreInstitutions (1)
Abstract: Most research on polymer composites has focused on adding discrete inorganic nanofillers to a polymer matrix to impart properties not found in polymers alone. However, properties such as ion conductivity and mechanical reinforcement would be greatly improved if the composite exhibited an interconnected network of inorganic and polymer phases. Here, we fabricate bicontinuous polymer-infiltrated scaffold metal (PrISM) composites by infiltrating polymer into nanoporous gold (NPG) films. Polystyrene (PS) and poly(2-vinylpyridine) (P2VP) films are infiltrated into the ∼43 nm diameter NPG pores via capillary forces during thermal annealing above the polymer glass transition temperature (Tg). The infiltration process is characterized in situ using spectroscopic ellipsometry. PS and P2VP, which have different affinities for the metal scaffold, exhibit slower segmental dynamics compared to their bulk counterparts when confined within the nanopores, as measured through Tg. The more attractive P2VP shows a 20 °C increase in Tg relative to its bulk, while PS only shows a 6 °C increase at a comparable molecular weight. The infiltrated polymer, in turn, stabilizes the gold nanopores against temporal coarsening. The broad tunability of these polymer/metal hybrids represents a unique template for designing functional network composite structures with applications ranging from flexible electronics to fuel cell membranes.

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Topics: Polymer (55%), Nanoporous (54%), Nanocomposite (54%) ... show more

Journal ArticleDOI: 10.1039/D1TA04822H
Samuel S. Welborn1, John S. Corsi1, Lin Wang1, Asaph Lee1  +2 moreInstitutions (1)
Abstract: Nanoporous gold (NP-Au) is used in various energy applications. However, little attention has been paid to the nature of surface films which can grow via side reactions during the formation of NP-Au by selective leaching. These films could significantly impact both the kinetics of NP-Au formation by selective leaching, and the performance of this NP-Au in specific energy applications. While it has been reported that complete removal of Ag from a Au–Ag parent alloy by selective leaching is kinetically more sluggish in HClO4 than in HNO3, and that the resulting structure size of NP-Au is smaller when formed in HClO4 compared to HNO3, these findings were not attributed to the growth of surface film via side reactions during selective leaching. In this work, small-angle and wide-angle X-ray scattering (SAXS and WAXS) are used in real time during NP-Au formation by selective electrolytic leaching of Ag from a Au–Ag parent alloy in 1 M HClO4 and 1 M HNO3 to demonstrate that the sluggish dealloying behavior in HClO4 results from the growth of a surface film during dealloying. In HClO4, Ag+ ions released from the Au–Ag working electrode spontaneously react with Cl− ions released from ClO4− reduction at the counter electrode to form an insoluble AgCl passive film on NP-Au. The AgCl hinders Ag dissolution and surface diffusion of Au atoms, slowing down the reaction kinetics and the rate of ligament growth. Our findings shed light on dealloying reaction mechanisms and will contribute to better control of the morphology and surface chemical state of nanoporous metals for energy applications.

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Topics: Selective leaching (55%), Nanoporous (54%), Leaching (metallurgy) (53%) ... show more

Journal ArticleDOI: 10.1016/J.SCRIPTAMAT.2021.114215
01 Jan 2022-Scripta Materialia
Abstract: Dealloyed nanoporous gold spontaneously coarsens when exposed to moderate temperatures (thermal coarsening), or to non-inert gases or liquids at room temperature (chemical coarsening). Although considerable research has been done on post-dealloying thermal coarsening, little attention has been paid to post-dealloying chemical coarsening, occurring not during, but after dealloying. Here, we use small- and wide-angle X-ray scattering (SAXS/WAXS) techniques to study the post-dealloying chemical coarsening behavior of dealloyed nanoporous gold samples aged in nitric acid over the course of 6 days at room temperature. A quantitative relationship between the ligament size and coarsening time is derived. Typically, our SAXS data reveals that the ligament size in nanoporous gold chemically coarsens according to a ∼1/4 time-dependent power law, which is characteristic of a surface diffusion-dominated process. The derived relationship between the ligament size and coarsening time will guide the design of nanoporous gold with desired structure size to optimize its (electro)chemical properties.

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Topics: Nanoporous (57%)

Journal ArticleDOI: 10.1016/J.SCRIPTAMAT.2021.113901
15 Jul 2021-Scripta Materialia
Abstract: Dealloyed nanoporous gold (NP-Au) is commonly created with hazardous chemicals including strong oxidizing acids. This work presents a green alternative to the common methods for making NP-Au. In this work, we create NP-Au by free corrosion dealloying of a Au-Cu parent alloy at room temperature in a near-neutral pH aqueous solution of ethylenediaminetetraacetic acid (EDTA), a non-toxic chelating ligand. The oxygen reduction reaction (ORR), catalyzed by activated carbon cloth (ACC), is employed to drive selective oxidation of Cu into Cu2+ ions, and EDTA is used to sequester the Cu2+ ions, preventing passivating copper oxide (CuOx)-forming reactions. We call this methodology chelation-mediated dealloying. Using small-angle x-ray scattering (SAXS), x-ray diffraction (XRD), and scanning electron microscopy (SEM), we observe that the NP-Au produced under mild conditions is similar to that produced by free corrosion dealloying in nitric acid (HNO3), a highly hazardous and strong oxidizing acid.

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Topics: Oxidizing acid (56%), Nitric acid (54%), Nanoporous (54%) ... show more

70 results found

Open accessJournal ArticleDOI: 10.1038/NMAT3601
Veronica Augustyn1, Jeremy Come2, Jeremy Come3, Michael A. Lowe4  +8 moreInstitutions (4)
01 Jun 2013-Nature Materials
Abstract: Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions, as observed with RuO2·xH2O in an acidic electrolyte. However, we recently demonstrated that a pseudocapacitive mechanism occurs when lithium ions are inserted into mesoporous and nanocrystal films of orthorhombic Nb2O5 (T-Nb2O5; refs 1, 2). Here, we quantify the kinetics of charge storage in T-Nb2O5: currents that vary inversely with time, charge-storage capacity that is mostly independent of rate, and redox peaks that exhibit small voltage offsets even at high rates. We also define the structural characteristics necessary for this process, termed intercalation pseudocapacitance, which are a crystalline network that offers two-dimensional transport pathways and little structural change on intercalation. The principal benefit realized from intercalation pseudocapacitance is that high levels of charge storage are achieved within short periods of time because there are no limitations from solid-state diffusion. Thick electrodes (up to 40 μm thick) prepared with T-Nb2O5 offer the promise of exploiting intercalation pseudocapacitance to obtain high-rate charge-storage devices.

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2,746 Citations

Journal ArticleDOI: 10.1016/0001-6160(61)90182-1
John W. Cahn1Institutions (1)
01 Sep 1961-Acta Metallurgica
Abstract: The stability of a solid solution to all infinitesimal composition fluctuations is considered, taking surface tension and elastic energy into account. It is found that for infinite isotropic solids, free from imperfections the spinodal marks the limit of metastability to such fluctuations only if there is no change in molar volume with composition. Otherwise the elastic energy due to a fluctuation stabilizes the solution and alters the criterion for the limit of metastability. For an unstable solution the kinetics of decomposition are discussed and the expected mean particle size or wavelength of the most rapidly growing fluctuation is derived.

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Topics: Spinodal (63%), Spinodal decomposition (58%), Metastability (57%) ... show more

2,574 Citations

Open accessJournal ArticleDOI: 10.1038/NATURE13970
04 Dec 2014-Nature
Abstract: Safe and powerful energy storage devices are becoming increasingly important. Charging times of seconds to minutes, with power densities exceeding those of batteries, can in principle be provided by electrochemical capacitors--in particular, pseudocapacitors. Recent research has focused mainly on improving the gravimetric performance of the electrodes of such systems, but for portable electronics and vehicles volume is at a premium. The best volumetric capacitances of carbon-based electrodes are around 300 farads per cubic centimetre; hydrated ruthenium oxide can reach capacitances of 1,000 to 1,500 farads per cubic centimetre with great cyclability, but only in thin films. Recently, electrodes made of two-dimensional titanium carbide (Ti3C2, a member of the 'MXene' family), produced by etching aluminium from titanium aluminium carbide (Ti3AlC2, a 'MAX' phase) in concentrated hydrofluoric acid, have been shown to have volumetric capacitances of over 300 farads per cubic centimetre. Here we report a method of producing this material using a solution of lithium fluoride and hydrochloric acid. The resulting hydrophilic material swells in volume when hydrated, and can be shaped like clay and dried into a highly conductive solid or rolled into films tens of micrometres thick. Additive-free films of this titanium carbide 'clay' have volumetric capacitances of up to 900 farads per cubic centimetre, with excellent cyclability and rate performances. This capacitance is almost twice that of our previous report, and our synthetic method also offers a much faster route to film production as well as the avoidance of handling hazardous concentrated hydrofluoric acid.

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Topics: Cubic centimetre (59%), Aluminium carbide (54%), Titanium carbide (54%) ... show more

2,466 Citations

Open accessJournal ArticleDOI: 10.1038/35068529
Jonah Erlebacher1, Jonah Erlebacher2, Michael J. Aziz1, Alain Karma3  +2 moreInstitutions (3)
22 Mar 2001-Nature
Abstract: Dealloying is a common corrosion process during which an alloy is 'parted' by the selective dissolution of the most electrochemically active of its elements. This process results in the formation of a nanoporous sponge composed almost entirely of the more noble alloy constituents. Although considerable attention has been devoted to the morphological aspects of the dealloying process, its underlying physical mechanism has remained unclear. Here we propose a continuum model that is fully consistent with experiments and theoretical simulations of alloy dissolution, and demonstrate that nanoporosity in metals is due to an intrinsic dynamical pattern formation process. That is, pores form because the more noble atoms are chemically driven to aggregate into two-dimensional clusters by a phase separation process (spinodal decomposition) at the solid-electrolyte interface, and the surface area continuously increases owing to etching. Together, these processes evolve porosity with a characteristic length scale predicted by our continuum model. We expect that chemically tailored nanoporous gold made by dealloying Ag-Au should be suitable for sensor applications, particularly in a biomaterials context.

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Topics: Nanoporous (51%)

2,188 Citations

Journal ArticleDOI: 10.1063/1.1940727
Abstract: Atomic layer deposition(ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions,reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research.

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Topics: Atomic layer deposition (55%)

2,036 Citations