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Articoli di riviste sul tema "3D foam electrodes"
1
Siwek, K. I., S. Eugénio, I. Aldama, J. M. Rojo, J. M. Amarilla, A. P. C. Ribeiro, T. M. Silva e M. F. Montemor. "Tailored 3D Foams Decorated with Nanostructured Manganese Oxide for Asymmetric Electrochemical Capacitors". Journal of The Electrochemical Society 169, n. 2 (1 febbraio 2022): 020511. http://dx.doi.org/10.1149/1945-7111/ac4d66.
Testo completoAbstract (sommario):
Tailored 3D (Ni and NiCo) metallic foam architectures were produced by electrodeposition and decorated via electrochemical routes with manganese oxide (MnOx) to serve as positive electrodes for supercapacitors. For comparative purposes, an electrode made of commercial Ni foam was also prepared. The foam-based electrodes were paired with a carbon cloth electrode and used to assemble asymmetric electrochemical cells. The electrochemical response of these cells was studied by applying different electrochemical techniques. In addition, two different protocols (cycling and floating) were applied to assess cells durability and fade. Despite the significant differences in the decorated foams morphology and structure their electrochemical responses revealed similar trends. The electrodes made of tailored foams showed higher specific capacitance, better capacitance retention at high current load and enhanced cycling stability compared to the electrodes made of commercial foam. The asymmetric cells made with the tailored foams revealed higher (maximum) specific energy (11–14 Wh kg−1) and specific power (1.3–1.4 × 104 W kg−1) compared to cells assembled with commercial foams (8.4 Wh kg−1 and 6.3 × 103 W kg−1). The durability tests evidenced that corrosion of the NiCo electrodeposited foams and electrochemical dissolution of MnOx are possible causes of cells degradation.
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Vainoris, Modestas, Henrikas Cesiulis e Natalia Tsyntsaru. "Metal Foam Electrode as a Cathode for Copper Electrowinning". Coatings 10, n. 9 (25 agosto 2020): 822. http://dx.doi.org/10.3390/coatings10090822.
Testo completoAbstract (sommario):
The geometry of porous materials is complex, and the determination of the true surface area is important because it affects current density, how certain reactions will progress, their rates, etc. In this work, we have investigated the dependence of the electrochemical deposition of copper coatings on the geometry of the copper substrate (flat plates or 3D foams). Chronoamperometric measurements show that copper deposition occurs 3 times faster on copper foams than on a flat electrode with the same geometric area in the same potential range, making metal foams great electrodes for electrowinning. Using electrochemical impedance spectroscopy (EIS), the mechanism of copper deposition was determined at various concentrations and potentials, and the capacities of the double electric layer (DL) for both types of electrodes were calculated. The DL capacity on the foam electrodes is up to 14 times higher than that on the plates. From EIS data, it was determined that the charge transfer resistance on the Cu foam electrode is 1.5–1.7 times lower than that on the Cu plate electrode. Therefore, metal foam electrodes are great candidates to be used for processes that are controlled by activation polarization or by the adsorption of intermediate compounds (heterogeneous catalysis) and processes occurring on the entire surface of the electrode.
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Oehm, Jonas, Marc Kamlah e Volker Knoblauch. "Ultra-Thick Cathodes for High-Energy Lithium-Ion Batteries Based on Aluminium Foams—Microstructural Evolution during Densification and Its Impact on the Electrochemical Properties". Batteries 9, n. 6 (31 maggio 2023): 303. http://dx.doi.org/10.3390/batteries9060303.
Testo completoAbstract (sommario):
Using three-dimensional (3D) metal foams as current collectors is considered to be a promising approach to improve the areal specific capacity and meet the demand for increased energy density of lithium-ion batteries. Electrodes with an open-porous metal foam as current collector exhibit a 3D connected electronic network within the active mass, shortening the electron transport pathways and lowering the electrodes’ intrinsic electronic resistance. In this study, NMC622 cathodes using an aluminium foam as current collector with a measured areal capacity of up to 7.6 mAh cm−2 were investigated. To this end, the infiltrated foams were densified to various thicknesses between 200 µm and 400 µm corresponding to an electrode porosity between 65% and 30%. The microstructural analysis reveals (i) the elimination of shrinking cavities and a decrease in the porosity of the infiltrated active mass, (ii) an improved contact of active mass to the current collector structure and (iii) a pronounced clogging of the surface pores. The electrochemical properties such as capacity and rate capability are correlated to the electrode’s microstructure, demonstrating that densification is necessary to improve active material utilization and volumetric capacity. However, strong densification impairs the rate capability caused by increased pore resistance and hindered electrolyte accessibility.
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Ansari, Sajid Ali, Hicham Mahfoz Kotb e Mohamad M. Ahmad. "Wrinkle-Shaped Nickel Sulfide Grown on Three-Dimensional Nickel Foam: A Binder-Free Electrode Designed for High-Performance Electrochemical Supercapacitor Applications". Crystals 12, n. 6 (25 maggio 2022): 757. http://dx.doi.org/10.3390/cryst12060757.
Testo completoAbstract (sommario):
Recently, three-dimensional nickel foam (3D-Nf) has been increasingly studied; however, further modifications in nanoscale surface modification are necessary for particular applications. In this work, three-dimensional hierarchically porous nanogranular NiS (NiS-3D-Nf) and wrinkle-shaped NiS (w-NiS-3D-Nf) structures were fabricated directly on nickel foam by a simple one-step solvothermal process using two different solvents. Several characterization techniques, including X-ray diffraction pattern, X-ray photoelectron spectroscopy, and scanning electron microscopy, were used to characterize the samples’ properties. To prove their applicability, supercapacitor electrodes were tested directly in a three-electrode assembly cell. The resulting w-NiS-3D-Nf electrodes exhibited greater capacitive activity than the NiS-3D-Nf electrodes. The optimized w-NiS-3D-Nf electrodes delivered an excellent specific capacitance of 770 Fg−1, at a current density of 1 Ag−1, compared with the NiS-3D-Nf electrodes (162.0 Fg−1 @ 1 Ag−1), with a cyclic stability of over 92.67% capacitance retention after 2200 cycles. The resultant unique structure with integrated hierarchical three-dimensional configuration can not only enhance abundant accessible surface areas but also produce strong adhesion to the 3D-Nf, facilitating the fast transportation of ions and electrons for the electrochemical reaction via the conductive 3D-Nf. This set of results suggests that the modification of 3D-Nf surfaces with a suitable solvent has highly significant effects on morphology, and ultimately, electrochemical performance. Additionally, the current preparation approach is simple and worthwhile, and thus offers great potential for supercapacitor applications.
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Ferriday, Thomas B., Suhas Nuggehalli Sampathkumar, Peter Hugh Middleton, Jan Van Herle e Mohan Lal Kolhe. "How Acid Washing Nickel Foam Substrates Improves the Efficiency of the Alkaline Hydrogen Evolution Reaction". Energies 16, n. 5 (21 febbraio 2023): 2083. http://dx.doi.org/10.3390/en16052083.
Testo completoAbstract (sommario):
Nickel foam substrates are frequently utilised as porous 3D substrates for renewable energy applications. The preparation of these substrates usually includes an acid-washing step, but the degree to which this step affects the final electrochemical performance after spray-coating a catalyst ink is unreported. Herein, we report the effects of acid washing through physicochemical and electrochemical characterisation. The electrochemical performance was determined through repeated measurements of catalyst-coated nickel foam substrates both with and without the initial step of acid washing. It was found that acid washing increased the current density by 17.9% for the acid-treated MoS2-coated nickel foam electrode. This increment was affiliated with an electrochemically active surface area that increased by 11.2%, and a Tafel analysis indicated that the acid-treated MoS2-coated electrodes facilitated the initial water dissociation step of the hydrogen evolution reaction with greater ease. Similar effects were also discovered for acid-treated PtIr(1:3)/C-coated nickel foam substrates. The stability was also improved; the degradation rate was reduced by 18.9% for the acid-treated MoS2-coated electrodes. This demonstrates the utility of acid washing nickel foam electrodes.
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Arinova, Anar, e Arailym Nurpeissova. "Electrophoretic Deposition of Polyethylene Oxide-Based Gel-Polymer Electrolyte for 3D Lithium-Ion Batteries". ECS Meeting Abstracts MA2023-02, n. 23 (22 dicembre 2023): 3280. http://dx.doi.org/10.1149/ma2023-02233280mtgabs.
Testo completoAbstract (sommario):
Despite the advances made in lithium-ion batteries (LIBs) over the last few decades, improved energy and power density is still required for portable devices, transit, and stationary applications [1-3]. Along with developing new materials, optimizing the shape of the battery electrodes is critical for improving the battery performance since the structure of these electrodes has a large impact on ion movement and reaction kinetics. The appeal of 3D structured batteries comes from certain operating features that are not available with conventional 2D geometries. One important feature is the ability to increase areal capacity (mAh cm−2) within a given footprint area of the electrode .Up to today, various methods were employed to coat the foam-type 3D electrodes with polymer or solid-state electrolytes: spin coating, layer-by-layer, and drop coating. Nonetheless, only a number of full-cell operation cases were disclosed, which led to the conclusion that, despite many attempts, drawbacks still exist in solving the homogeneous coating problem of polymer electrolytes. In this work, we report on the simple and facile coating process of polymer electrolyte on the intricate 3D structured NiO@Ni foam anode with the electrophoretic technique. To the best of our knowledge, it was not yet reported in the literature. The conformally coated polymer layer is proven to be very thin and homogeneous without any defects. The NiO@Ni foam/PEO configuration without the use of a commercial separator displayed stable cyclability up to 100 cycles with capacity retention of 88% and coulombic efficiency of 99%. The results are very promising for solving the problem of integrating polymer electrolytes onto any 3D structured anodes. In summary, a facile and simple electrophoretic technique was employed to conformally coat PEO gel-polymer electrolyte onto foam-type NiO/Ni anode for LIBs for the first time. Two electrodes of NiO/Ni foam as a working electrode and Pt metal as a counter electrode were used for the EPD process. Where the PEO solution acted as an electrolyte and, in the end, formed on the NiO/Ni foam surface. Through investigating various layers of PEO, it was concluded that the method allowed obtaining homogeneous thin films of around 2.66 μm for optimal 10 layers, which were free of cracks and defects. The electrochemical performance of the gel-polymer electrolyte PEO with commercially available liquid electrolyte 1M LiPF6 electrolyte solution in EC/EMC/DC was comparable to the traditional separator when used without it in a half-cell with lithium. The cycling stability results displayed an outstanding performance for the PEO electrolyte, delivering a capacity of 406 mAh g-1 at a 0.1 C rate after the 100th cycle. The stability of the formed PEO on the surface of the anode was demonstrated by FTIR analysis after 100 cycles. The stated simple approach allowed a cell operation at room temperature without a commercial separator, which is an excellent result for further developing high-energy-density full 3D batteries.
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Kim, Kookhan, Ji-Yong Eom, Jongmin Kim e Yang Soo Kim. "3D Lithium-Metal Anode for High-Energy Lithium-Metal Batteries". ECS Meeting Abstracts MA2024-02, n. 7 (22 novembre 2024): 947. https://doi.org/10.1149/ma2024-027947mtgabs.
Testo completoAbstract (sommario):
Lithium metal is often regarded as the ultimate anode for lithium-ion batteries (LIBs) due to its superior specific capacity (3,860 mAh g-1) and density (0.534 g cm-3). However, the real-world application of Li-metal electrodes is presently hindered by unregulated Li-plating and stripping, leading to unwanted dendritic growth and significant volume change during cycles. To overcome these challenges, we suggest a three-dimensional (3D) Li-metal anode, which incorporates 3D Ni foam as a current collector through a molten Li impregnation process. Our theoretical simulations and experimental results show that this 3D Li-metal electrode establishes an extensive contact area between the active Li metal and the current collector. This is advantageous in enhancing the reversibility by lowering the overpotential for Li-plating and stripping and suppressing the dendritic growth of Li during charge/discharge cycles. Moreover, the 3D Ni foam framework effectively mitigates dimensional change of the Li-metal electrode. For practical applications, we evaluate the viability of the 3D Li-metal electrode in a full-cell in comparison to a traditional 2D Li-metal electrode. We anticipate that our findings will contribute to the development of advanced Li-metal batteries.
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Sliozberg, Kirill, Yauhen Aniskevich, Ugur Kayran, Justus Masa e Wolfgang Schuhmann. "CoFe–OH Double Hydroxide Films Electrodeposited on Ni-Foam as Electrocatalyst for the Oxygen Evolution Reaction". Zeitschrift für Physikalische Chemie 234, n. 5 (26 maggio 2020): 995–1019. http://dx.doi.org/10.1515/zpch-2019-1466.
Testo completoAbstract (sommario):
AbstractCobalt-iron double hydroxide (CoFe–OH) films were electrochemically deposited on 3D Ni foam electrodes for the oxygen evolution reaction (OER). The dependence of the OER activity on film composition and thickness was evaluated, which revealed an optimal Fe:Co ratio of about 1:2.33. The composition of the catalyst film was observed to vary with film thickness. The electrodeposition parameters were carefully controlled to yield microstructured Ni-foam decorated with CoFe–OH films of controlled thickness and composition. The most active electrode exhibited an overpotential as low as 360 mV OER at an industrial scale current density of 400 mA cm−2 that remained stable for at least 320 h. This work contributes towards the fabrication of practical electrodes with the focus on the development of stable electrodes for electrocatalytic oxygen evolution at high current densities.
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Nawaz, Bushra, Ghulam Ali, Muhammad Obaid Ullah, Sarish Rehman e Fazal Abbas. "Investigation of the Electrochemical Properties of Ni0.5Zn0.5Fe2O4 as Binder-Based and Binder-Free Electrodes of Supercapacitors". Energies 14, n. 11 (4 giugno 2021): 3297. http://dx.doi.org/10.3390/en14113297.
Testo completoAbstract (sommario):
In this work, Ni0.5Zn0.5Fe2O4 is synthesized as binder-based (NZF) and binder-free electrodes (NZF@NF). The binder-free electrode is directly synthesized on nickel foam via facile hydrothermal techniques. The crystalline phase of both of these electrodes is examined through X-ray diffraction. Their morphology is investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (TEM), which revealed the well-defined nanostructure with the shape like thin hexagonal platelets. The chemical composition is verified by energy dispersive spectroscopy (EDS). Their electrochemical properties are analyzed by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The NZF@NF electrode has outperformed the binder-based NZF electrode in terms of electrochemical performance owing to the 3D interconnected structure of the nickel foam. The NZF@NF electrode has delivered a high specific capacity of 504 F g−1 at the current density of 1 A g−1, while its counterpart has delivered a specific capacity of 151 F g−1 at the same current density.
10
Cheng, Guanhua, Qingguo Bai, Conghui Si, Wanfeng Yang, Chaoqun Dong, Hao Wang, Yulai Gao e Zhonghua Zhang. "Nickel oxide nanopetal-decorated 3D nickel network with enhanced pseudocapacitive properties". RSC Advances 5, n. 20 (2015): 15042–51. http://dx.doi.org/10.1039/c4ra15556d.
Testo completoTesi sul tema "3D foam electrodes"
1
Adjez, Yanis. "Stimulation of Electrocatalytic Reduction of Nitrate by Immobilized Ionic Liquids". Electronic Thesis or Diss., Sorbonne université, 2024. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2024SORUS337.pdf.
Testo completoAbstract (sommario):
La pollution de l'eau par les nitrates représente un défi environnemental majeur et constitue l'une des dix violations les plus courantes de la qualité de l'eau dans le monde. Ce défi offre une opportunité pour l'économie circulaire, car l'électrolyse des nitrates a été proposée comme une méthode durable pour la valorisation des effluents contaminés par les nitrates grâce à la production décentralisée et simultanée d'ammoniac (un produit chimique de base). En particulier, la réduction électrochimique des nitrates (REN) est une stratégie prometteuse et durable pour résoudre le problème critique de la pollution des sources d'eau par les nitrates. Plusieurs matériaux abondants sur Terre, tels que le cuivre et l'étain, ont été proposés comme matériaux électrocatalytiques adaptés pour la REN. Jusqu'à présent, la plupart des études électrochimiques fondamentales ont été menées dans des conditions potentiostatiques. En revanche, cette étude présente une évaluation de la REN dans des conditions galvanostatiques pour atteindre des conditions opérationnelles plus représentatives pour des systèmes ingénierisés de plus grande envergure. Cependant, cela provoque l'apparition de la réaction concomitante de dégagement de l'hydrogène (HER), qui se produit à un potentiel thermodynamique similaire à celui de la REN. Ainsi, l'efficacité faradique de la REN diminue considérablement dans des conditions galvanostatiques réalistes en raison de la concurrence avec la HER. Ce projet aborde ce défi fondamental en électrocatalyse et propose une nouvelle stratégie basée sur l'immobilisation de molécules ioniques à base d'imidazolium sur la surface de la cathode pour inhiber sélectivement la HER et améliorer la REN. Notamment, cette recherche explore une gamme de matériaux de cathodiques hybrides, y compris des électrodes à base de carbone et de métal sous forme de plaques 2D et de mousses 3D, reconnues pour leur potentiel dans les applications réelles de la REN. Le succès de l'immobilisation de la couche organique ionique sur les cathodes a été confirmé par différentes techniques de caractérisation physico-chimiques et par une évaluation subséquente de l'activité et de la sélectivité électrocatalytiques, démontrant une sélectivité et une efficacité faradique améliorées pour la production d'ammoniac sur les cathodes hybrides, deux fois supérieures à celles du matériau d'électrode nu pour la REN dans les mêmes conditions expérimentalesNitrate pollution in water represents a significant environmental challenge and is one of the top ten most common water quality violations worldwide. This challenge offers an opportunity for the circular economy as nitrate electrolysis has been suggested as a sustainable method for valorization of nitrate-contaminated effluents by simultaneous decentralized ammonia production (a commodity chemical). In particular, the electrochemical reduction of nitrate (ERN) is a promising and sustainable strategy for addressing the critical issue of nitrate pollution in water sources. Several earth abundant materials such as copper and tin have been suggested as suitable electrocatalytic materials for ERN. Mostly fundamental electrochemical studies under potentiostatic conditions are reported so far. In contrast, this study presents ERN evaluation under galvanostatic conditions for achieving more representative operational conditions for larger engineered systems. However, this provokes the appearance of the concomitant hydrogen evolution reaction (HER), which takes place at a similar thermodynamic potential than ERN. Thus, faradaic efficiency for ERN significantly diminishes under realistic galvanostatic conditions due to the competition with HER. This project addresses this fundamental challenge in electrocatalysis and proposes a novel strategy based on the immobilization of imidazolium-based ionic molecules on the surface of the cathode to selectively inhibit HER and enhance ERN. Notably, this research explores a range of hybrid cathode materials, including 2D plate and 3D foam carbon- and metal-based electrodes, which are recognized for their potential in real world applications for ERN. The success of the ionic organic layer immobilization onto the cathodes was confirmed through different physicochemical characterization techniques and subsequent electrocatalytic activity and selectivity evaluation, which demonstrated an enhanced selectivity and faradaic efficiency for ammonia production on hybrid cathodes twice as much as the bare electrode material for ERN under the same experimental conditions
Capitoli di libri sul tema "3D foam electrodes"
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Jena, Debdeep. "Electrons in the Quantum World". In Quantum Physics of Semiconductor Materials and Devices, 83–122. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780198856849.003.0005.
Testo completoAbstract (sommario):
Abstract This chapter discusses the following questions: • How does application of quantum mechanics and statistics to free electrons help reveal their wavefunctions ?, momentum, energy, density of states, energy density, and quantum mechanical cur- rents? • How do the above physical properties of electrons depend on the number of dimensions the electron is allowed to move in? Specif- ically, what are the similarities and differences of the properties for electrons moving in 1D, 2D, and 3D? • How did quantum mechanics and quantum statistics of free elec- trons resolve the discrepancies of the classical Drude model of the behavior of electrons in solids, and what phenomena could still not be explained? • A few exactly solved situations when electrons are not free, but form bound states, in which case there is no motion of electrons.
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Schweitzer, George K., e Lester L. Pesterfield. "The V–Cr–Mn Group". In The Aqueous Chemistry of the Elements. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780195393354.003.0016.
Testo completoAbstract (sommario):
The three elements to be treated in this chapter (V, Cr, Mn) are the third, fourth, and fifth members of the first transition series. The first two members (Sc, Ti) have been treated in previous chapters (Chapters 12 and 13). The ten elements of this first transition series (Sc through Zn) are characterized by electron activity in the 3d–4s levels. All elements in the 3d transition series are metals, and many of their compounds tend to be colored as a result of unpaired electrons. Most of the elements have a strong tendency to form complex ions due to participation of the d electrons in bonding. Since both the 4s and the 3d electrons are active, most of the elements show a considerable variety of oxidation states (Sc and Zn being exceptions). For the first five (Sc through Mn), the maximum oxidation number is the total number of electrons in the 4s and 3d levels. Complexing is often so strong that the most stable oxidation state for simple compounds may differ from that for complex compounds. a. E–pH diagram. The E–pH diagram in Figure 14.1 shows V in oxidation states of 0, II, III, IV, and V. This diagram, which involves vanadium at 10−3.0 M is somewhat oversimplified in that there are some isopolyanions present in the 4–6 pH regions. The prevalence of isopolyanions increases as the V concentration increases. This is illustrated in Figure 14.2 which has V at 10−1.0 M. Further, the cations V+2, V+3, VO+2, and VO2+ are probably aquated to satisfy a coordination number of six, and the V(OH)3 may actually be hydrated V2O3. Note that the soluble solution chemistries of V(IV) and V(V) are dominated by the VO+2 and VO2+ complex ions. Three of these cations (III, IV, V) are subject to hydrolysis, the processes setting in around pH values of just under 3, 3, and 2. The E–pH diagram indicates that elemental V is very active, but a thin coat of oxide protects it from all except strong action.
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Krishnan, Kannan M. "Transmission and Analytical Electron Microscopy". In Principles of Materials Characterization and Metrology, 552–692. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198830252.003.0009.
Testo completoAbstract (sommario):
Transmission electron microscopy provides information on all aspects of the microstructure — structural, atomic, chemical, electronic, magnetic, etc. — at the highest spatial resolution in physical and biological materials, with applications ranging from fundamental studies to process metrology in the semiconductor industry. Developments in correcting electron-optical aberrations have improved TEM resolution to sub-Å levels. Coherent Bragg scattering (diffraction), incoherent Rutherford scattering (atomic mass), and interference (phase) are some contrast mechanisms in TEM. For phase contrast, optimum imaging is observed at the Scherzer defocus. Magnetic domains are imaged in Fresnel, Foucault, or differential phase contrast (DPC) modes. Off-axis electron holography measures phase shifts of the electron wave, and is affected by magnetic and electrostatic fields of the specimen. In scanning-transmission (STEM) mode, a focused electron beam is scanned across the specimen to sequentially form an image; a high-angle annular dark field detector gives Z-contrast images with elemental specificity and atomic resolution. Series of (S)TEM images, recorded every one or two degrees about a tilt axis, over as large a tilt-range as possible, are back-projected to reconstruct a 3D tomographic image. Inelastically scattered electrons, collected in the forward direction, form the energy-loss spectrum (EELS), and reveal the unoccupied local density of states, partitioned by site symmetry, nature of the chemical species, and the angular momentum of the final state. Energy-lost electrons are imaged by recording them, pixel-by-pixel, as a sequence of spectra (spectrum imaging), or by choosing electrons that have lost a specific energy (energy-filtered TEM). De-excitation processes (characteristic X-ray emission) are detected by energy dispersive methods, providing compositional microanalysis, including chemical maps. Overall, specimen preparation methods, even with many recent developments, including focused ion beam milling, truly limit applications of TEM.
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Schweitzer, George K., e Lester L. Pesterfield. "The Fe–Co–Ni Group". In The Aqueous Chemistry of the Elements. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780195393354.003.0017.
Testo completoAbstract (sommario):
The three elements to be treated in this chapter (Fe, Co, Ni) are the sixth, seventh, and eighth members of the first transition series. The first five members (Sc, Ti, V, Cr, Mn) have been treated in previous chapters (Chapters 12, 13, and 14). The ten elements of this first transition series (Sc through Zn) are characterized by electron activity in the 4s–3d levels. All elements in the 3d transition series are metals, and many of their compounds tend to be colored as a result of unpaired electrons. Most of the elements have a strong tendency to form complex ions due to participation of the d electrons in bonding. Unlike the previous three elements (V, Cr, Mn), these three do not show a variety of oxidation states. The higher oxidation states are almost absent in compounds, Fe showing principally the II and III, Co the II and III, and Ni only the II. The III states are less stable than the II states unless they are stabilized by complex formation. The resemblance of these three elements is notable, they being more like each other than they are to the elements below them. a. E–pH diagram. The E–pH diagram in Figure 15.1 shows Fe in oxidation states of 0, II, and III. This diagram, which involves iron at 10−1.0 M is oversimplified in several ways. The Fe(II) and Fe(III) cations are more properly designated as Fe(HOH)6+2 and Fe(HOH)6+3, reflecting the coordination number of 6. The region just to the left of the Fe+2/Fe(OH)2 line involves Fe(OH)+, and the region just to the left of the Fe+3/FeO(OH) line involves numerous hydroxo complexes such as Fe(HOH)5OH+2 and Fe(HOH)4(OH)2+. At very high pH values, there is a tendency for Fe(OH)2 to be converted to HFeO2−, and at very high E values, the powerful oxidant, red-purple FeO4−2 can be produced. When these latter five species are introduced, Figure 15.2 results. This, too, is probably simplified since it is known that other species are present, such as Fe2(OH)4+4 and Fe3(OH)4+5. The species FeO4−2 can only be prepared in a very strong base.
Atti di convegni sul tema "3D foam electrodes"
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Dai, Rui, Beomjin Kwon e Qiong Nian. "A Novel Packing Hollow Dodecahedron Model to Study the Mechanical and Thermal Properties of Stocastic Metallic Foams". In ASME 2021 16th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/msec2021-60520.
Testo completoAbstract (sommario):
Abstract Stochastic foam with hierarchy order pore structure possesses distinguished physical properties such as high strength to weight ratio, super lightweight, and extremely large specific area. These exceptional properties make stochastic foam as a competitive material for versatile applications e.g., heat exchangers, battery electrodes, automotive components, magnetic shielding, catalyst devices and etc. Recently, the more advanced hollow cellular (shellular) architectures with well-developed structure connections are studied and expected to surpass the solid micro/nanolattices. However, in terms of theoretical predicting and studying of the cellular foam architecture, currently no systematic model can be utilized to accurately capture both of its mechanical and thermal properties especially with hollow struts due to complexity induced by its stochastic and highly reticulate nature. Herein, for the first time, a novel packing three-dimensional (3D) hollow dodecahedron (HPD) model is proposed to simulate the cellular architecture. An electrochemical deposition process is utilized to manufacture the metallic foam with hollow struts. Mechanical and thermal testing of the as-manufactured foams are carried out to compare with the HPD model. HPD model is proved to accurately capture both the topology and the physical properties of stochastic foam at the similar relative density. Particularly, the proposed model makes it possible to readily access and track the physical behavior of stochastic foam architecture. Accordingly, this work will also offer inspiration for designing an efficient foam for specific applications.
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Chytanya Chinnam, Krishna, Seyed Sepehr Moeini, Simonetta Tuti e Giulia Lanzara. "Annealed Pyrolytic Graphitic Carbon Electrodes for Piezoelectric Acoustic Nanoweb". In ASME 2023 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/smasis2023-111178.
Testo completoAbstract (sommario):
Abstract The primary challenge in realizing an ultimate lightweight and flexible acoustic sensing device is the electrode material. To obtain the best device performance expensive gold electrodes have been used in the literature due to the relatively higher electrical conductivity. In this paper we implement an annealed pyrolytic graphitic carbon on carbon fibers to form a low-cost highly performing porous electrode for acoustic applications. The electrode is prepared by using a 400-micron thick PMMA membrane electrospun on a unidirectional carbon fiber textile. The electrode is then used to form an acoustic sensor via a hybrid 3D printing-electrospinning-pyrolysis approach which allowed to deliver an overall flexible acoustic device. Preliminary results show a low noise level functional material with reasonably high electromechanical output to a wide range of acoustic frequencies. The higher sensitivity of the material with respect to the devices formed with continuous electrodes, is to be attributed to the porosity of the electrode material which enhances the vibrating air particles to interact with the interacting membrane directly and homogenously.
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Berhan, L., C. W. Wang e A. M. Sastry. "Damage Initiation in Bonded Particulate Networks: 3D Simulations". In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/ad-25304.
Testo completoAbstract (sommario):
Abstract Several promising Li-ion technologies incorporate micro- and nanoarchitectured carbon networks, typically in the form of whisker/particle blends bonded with thermoplastic binders, in the electrodes. Degradation of these battery electrode materials is currently a persistent problem, with damage presenting as blistering and/or delamination. We are investigating bonding in micro- and nanostructured materials in order to predict onset of this degradation of these stochastic materials. Here, we describe a general methodology in modeling the small junctures in these porous network materials. We have found previously that the joint properties are the controlling feature in a significant class of materials, and suggest that 3D simulations on the bonds may be used in 2D simulations of overall network behavior.
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Gunda, Naga Siva Kumar, e Sushanta K. Mitra. "Quantification of Microstructural and Transport Properties of Solid Oxide Fuel Cells From Three-Dimensional Physically Realistic Network Structures". In ASME 2011 9th International Conference on Fuel Cell Science, Engineering and Technology collocated with ASME 2011 5th International Conference on Energy Sustainability. ASMEDC, 2011. http://dx.doi.org/10.1115/fuelcell2011-54929.
Testo completoAbstract (sommario):
The present work investigated a new method of calculating effective transport properties of solid oxide fuel cell (SOFC) electrodes from three-dimensional (3D) physically realistic network structures. These physically realistic network structures are topological equivalent representations of reconstructed microstructures in the form of spheres (nodes or bodies) and cylinders (segments or throats). Maximal ball algorithm is used to extract these physically realistic network structures from the series of two-dimensional (2D) cross-sectional images of SOFC electrodes. Dual-beam focused ion beam - scanning electron microscopy (FIB-SEM) is performed on SOFC electrodes to acquire series of 2D cross-sectional images. Finite element method is implemented to compute the effective transport properties from the network structures. As an example, we applied this method to calculate the effective gas diffusivity of lanthanum strontium manganite (LSM) of SOFC. The results obtained from physically realistic network structures are compared with reconstructed 3D microstructures.
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Fan, Jinsheng, Brittany Newell, Jose Garcia, Richard M. Voyles e Robert A. Nawrocki. "Contact-Poling Enhanced, Fully 3D Printed PVdF Pressure Sensors: Towards 3D Printed Functional Materials". In ASME 2021 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/smasis2021-67832.
Testo completoAbstract (sommario):
Abstract This work presents a new process to print piezoelectric polymer-based sensors through additive manufacturing via three-dimensional (3D) printing technology. 3D printing has become an efficient method to fabricate devices with complex geometric structures and embedded functionalities. The motivation of this research was to explore a path towards fully 3D printed multifunctional thin and flexible sensing devices. The 3D printed methods used were Fused Deposition Modelling and Direct Ink Writing. A fully 3D printed sensor consisting of a (2.54 cm × 2.54 cm) poly(vinylidene fluoride) (PVdF) film with thickness in the range of ∼250 μm to 350 μm was sandwiched between two fast-drying silver paint printed electrodes with thickness ranging from ∼10 μm to 50 μm. The arithmetic average roughness, Ra, of typical printed PVdF profiles with and without printed silver electrodes was ∼12.9 μm and ∼7.3 μm, respectively. Silver electrodes were printed to facilitate contact poling and to collect charges generated due to piezoelectricity. The average piezoelectric activity of printed unpoled films was 7.13 pC/N. The polarization in the printed PVdF films was realized by conventional contact poling at elevated temperatures (100, 110, 120 and 130 °C, respectively) with step increased electric fields, which were varied from 0.4 MV/m to 14 MV/m at 1 MV/m increments. To perform contact poling, PVdF films were immersed in mineral oil and a controlled voltage was applied to electrodes on one side while electrodes on the opposite side were grounded. The extrusion process during 3D printing and the subsequent contact poling process enabled the phase transition from the thermally stable α-phase to the piezoelectric active β-phase and the rearranging of the dipole alignments. The efficiency of poling was evaluated through measurement of the average value of the charge generated by six poled PVdF films in response to mechanical input increasing from 0.29 N to 1.91 N with ∼0.27 N increments. The highest average piezoelectric activity obtained was 59.2 pC/N, and a single device of 96.44 pC/N, at step increased poling voltages up to 3.5 kV under a fixed temperature 120 °C. The results demonstrate that by increasing the poling voltages and time, a higher piezoelectric activity (about 8 times compared to unpoled films) was achieved, indicating improvement of the β-phase content. This study provides a new method for continuous and direct printing of piezoelectric devices from PVdF polymeric filament. This technology opens a new path towards fully 3D printed free-form structured functional materials for sensing applications.
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Histed, Rebecca, Justin Ngo, Omar A. Hussain, Chantel Lapins, Kam K. Leang, Yiliang Liao e Matteo Aureli. "Ionic Polymer Metal Composite Sensors With Engineered Interfaces (eIPMCs): Compression Sensing Modeling and Experiments". In ASME 2020 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/dscc2020-3289.
Testo completoAbstract (sommario):
Abstract In this paper, we examine the development of tailored 3D-structured (engineered) polymer-metal interfaces to create enhanced ionic polymer-metal composite (eIPMC) sensors towards soft, self-powered, high sensitivity strain sensor applications. First, a physics-based chemoelectromechanical model is developed to predict the sensor behavior of eIPMCs by incorporating structure microfeature effects in the mechanical response of the material. The model incorporates electrode surface properties, such as microscale feature thickness, size and spacing, to help define the mechanical response and transport characteristics of the polymer-electrode interface. Second, two novel approaches are described to create functional samples of eIPMC sensors using fused deposition manufacturing and inkjet printing technologies. Sample eIPMC sensors are fabricated for experimental characterization. Finally, experimental results are provided to show superior performance in the sensing capabilities compared to traditional sensors fabricated from sheet-form material. The results also validate important predictive aspects of the proposed minimal model.
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Goncharova, Olga V. "Quasi-Zero-Dimensional Media Formed by Thin-Film Technique: Microstructure, Subpicosecond Optical Nonlinearities, Applications". In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/up.1996.tue.40.
Testo completoAbstract (sommario):
Three-dimensional (3D) confinement of excitons or electrons motion in nanometer-sized microcrystallites (nanocrystals — NCs) is an important phenomenon in physics, and is expected to bring a significant improvement to ultrafast functional devices. In the past ten years, several types of quasi-zero-dimensional (QZD) media such as dielectric matrices containing dispersed semiconductor- as well as metal NCs have been realized by using various techniques. Recently, we have succeeded in the preparation of thin-film QZD media. A reliable process has also been developed for the fabrication of thin-film Fabry-Perot interferometers (TFIs) with intermediate layers in form of QZD media.
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Edgerton, Alex, Joseph Najem e Donald Leo. "A Hydrogel-Based Droplet Interface Lipid Bilayer Network". In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7580.
Testo completoAbstract (sommario):
In this work, we present a process for the fabrication of meso-scale hydrogel-based lipid bilayer arrays. The hydrogels support lipid monolayers at an oil-water interface, and when brought together, form stable bilayers. The substrates are formed using 3D printed molds and include built-in, customizable circuits patterned with silver paint. The system can be adapted to varying network sizes and circuit designs, and new arrays are fabricated quickly and inexpensively using common laboratory techniques. An enclosed 3×3 array with 3 mm spacing between neighboring hydrogels and electrodes to individually examine each bilayer has been created using this method. An alternative test setup was also developed to better observe the formation of bilayers in a small array. Using this setup, two bilayers were formed simultaneously, demonstrating the feasibility of this type of system and providing valuable information for expanding and improving the enclosed network. Many of the design concepts presented here can be adapted for use at smaller scales using microfabrication techniques.
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Yafia, Mohamed, e Homayoun Najjaran. "The Effect of Changing the Gap Height on Droplet Deformation During Transport in Digital Microfluidics Systems". In ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icnmm2014-21296.
Testo completoAbstract (sommario):
The objective of this paper is to characterize the droplet deformation during transport and to show how the droplet morphology changes at different gap heights in digital microfluidics systems. The aspect ratio defined as the ratio between the gap height to the electrode side length will be varied within the range of high to extremely low. In this way, we will demonstrate that the droplet morphology significantly changes during transport when the aspect ratio is changed. Analogous to the channel dimensions, the gap height and the electrode side length are the two most important geometrical variables affecting droplet motion in digital microfluidic systems. In this study, the droplet deformation was found to be minimal at higher aspect ratios. Contrarily, the droplet will exhibit severe necking and elongation at very low aspect ratios. The deformation and necking patterns were found to be similar to the necking pattern that happens during splitting. However, the droplet exhibits this necking when it is only driven by one activated electrode during the transport process. On the other hand, the droplet is pulled by driving forces from two opposite directions in the conventional splitting process. Extended simulations are performed to investigate the effect of changing the aspect ratio and the actuation voltage used. The simulations were performed by FLOW-3D software which uses the volume of fluid (VOF) technique. The results confirm the effect of changing the gap height on the droplet behavior during motion. The extreme deformation and necking happens only at very low aspect ratios. In this case, the transport process starts by moving a small portion of the droplet toward the activated electrode. When this small portion advances toward the activated electrode the rest of the droplet is not greatly affected or pulled toward the same direction. It can be noticed that the remaining portion of the droplet is not moving at the initial stages of motion and the droplet start to be squeezed gradually through a neck instead of moving in a bulk form. Further observations demonstrated droplet elongation and delayed response of the back portion of the droplet compared to the motion of the leading edge. Analyzing the motion by analytical models can be inaccurate as they assume that the droplet retains its circular shape. Therefore, CFD simulations can demonstrate the droplet behavior better than the analytical models where the droplet exhibits severe deformation and deviation from the circular shape.
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Ishino, Yojiro, Naoki Hayashi, Yuta Ishiko, Ahmad Zaid Nazari, Kimihiro Nagase, Kazuma Kakimoto e Yu Saiki. "Schlieren 3D-CT Reconstruction of Instantaneous Density Distributions of Spark-Ignited Flame Kernels of Fuel-Rich Propane-Air Premixture". In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-7423.
Testo completoAbstract (sommario):
For 3D observation of high speed flames, non-scanning 3D-CT technique using a multi-directional quantitative schlieren system with flash light source, is proposed for instantaneous density distribution of unsteady premixed flames. This “Schlieren 3D-CT” is based on (i) simultaneous acquisition of flash-light schlieren images taken from numerous directions, and (ii) 3D-CT reconstruction of the images by an appropriate CT algorithm. In this technique, for simultaneous schlieren photography, the custom-made 20-directional schlieren camera has been constructed and used. This camera consists of 20 optical systems of single-directional quantitative schlieren system. Each system is composed of two convex achromatic lenses of 50 mm in diameter and 300 mm in focal length, a light source unit, a schlieren stop of a vertical knife edge and a digital camera. The light unit has a flash (9 micro-sec duration) light source of a uniform luminance rectangular area of 1 mm × 1 mm. Both of the uniformity of the luminosity and the definite shape are essential for a quantitative schlieren observation. Sensitivity of the digital cameras are calibrated with a stepped neutral density filter. Target flames are located at the center of the camera. The image set of 20 directional schlieren images are processed as follows. First the schlieren picture brightness is shifted by no-flame-schlieren picture brightness in order to obtain the real schlieren brightness images. Second, brightness of these images is scaled by Gladstone-Dale constant of air. Finally, the scaled brightness is horizontally integrated to form “density thickness images”, which can be used for CT reconstruction of density distribution. The density thickness images are used for CT reconstruction by MLEM (maximum likelihood-expectation maximization) CT-algorithm to obtain the 3D reconstruction of instantaneous density distribution. In this investigation, the “density thickness” projection images of 400(H) × 500(V) pixel (32.0 mm × 40.0 mm) are used for 3D-CT reconstruction to produce 3D data of 400(x) × 400(y) × 500(z) pixel (32.0 mm × 32.0 mm × 40.0 mm). The voxel size is 0.08 mm each direction. In this investigation, the target flame is spark-ignited flame kernels. The flame kernels are made by spark ignition for a fuel-rich propane-air premixed gas. First, laminar flow is selected as the premixed gas flow to establish the spherically expanding laminar flame. The CT reconstruction result show the spherical shape of flame kernel with a pair of deep wrinkles. The wrinkle is considered to be caused by spark electrodes. Next turbulent flows behind turbulence promoting grid is selected. The corrugated shape flame kernel is obtained. The schlieren 3D-CT measurements are made for the complicated kernels. CT results expresses the instantaneous 3D turbulent flame kernel shapes.