Search

Due to their nanoscale features, nanometric multilayers can have a large variation in properties for varying bilayer heights. While the hardening at small feature sizes and the consequent softening at even smaller feature sizes have been observed for decades, the underlying mechanisms are still under debate. In this study, molecular dynamics uniaxial compression simulations are employed to study the mechanical properties of Al/Ni multilayers for bilayer heights h from 100 nm down to 5 nm. The effect of the microstructure on Young's modulus and the yield strength was investigated. Furthermore, the mechanical properties of equiatomic and equivolumetric multilayers were compared. A comparison with experimental results from the literature showed good agreement. Both the hardening at intermediate bilayer heights as well as the softening at very small bilayer heights were observed. The results are discussed in the context of possible hardening and softening mechanisms. While the Hall–Petch effect with a h − 1 / 2 scaling is not contradicted, it is shown that, although the underlying mechanisms are different, both the hardening as well as the softening are based on a general size effect with a scaling of ln (h) / h. [ABSTRACT FROM AUTHOR]

Ferroelectric (Al, Sc)N thin films have the potential for use in low-power memory applications. This study demonstrates the thickness scalability of ferroelectricity down to an approximately 20 nm-thick (Al0.8Sc0.2)N film sandwiched between microfabricable TiN electrodes. The impact of the deposition gas atmosphere during the sputtering process and the top electrode materials on the crystal structures and ferroelectric properties was investigated for 20–30 nm-thick (Al0.8Sc0.2)N thin films deposited on Si substrates covered with a TiN layer by radio frequency magnetron sputtering. The deposition atmosphere did not strongly affect the crystal structures of the 30 nm-thick (Al0.8Sc0.2)N films but significantly affected their ferroelectric properties. The leakage current density decreased for films deposited under pure N2 gas compared to the films deposited under a gas mixture of 0.67Ar + 0.33N2. The ferroelectric properties of 20 nm-thick (Al0.8Sc0.2)N films were changed by the top electrode materials; both the switching electric field and its maximum applicable electric field increased for the TiN top electrodes compared with the Pt top electrodes, improving the saturation characteristics of the remnant polarization (Pr) against the applied electric field. Consequently, the 20 nm-thick (Al0.8Sc0.2)N film sandwiched between the microfabricable TiN top and bottom electrodes showed ferroelectricity without noticeable degradation with decreasing film thickness; the film maintained large Pr values of over 100 μC/cm2 in the temperature range from room temperature to 150 °C. The present data open the door to scalable ferroelectric random-access memories using almost thickness-degradation-free thin (Al, Sc)N films with microfabricable TiN electrodes. [ABSTRACT FROM AUTHOR]

Water sublimators play a critical role in efficiently managing the high thermal load of spacecraft in a vacuum environment, ensuring their proper functioning. This article focuses on a novel cold plate water sublimator driven by a porous sublimation tube structure, which is still in the theoretical research stage. Numerical methods are employed to study the evaporation, freezing, and sublimation processes, with validation against experimental data. The average absolute error of the four operating conditions is 1.33 K, and the ice layer thickness error is 8.33 %. Additionally, a method to calculate the effective thermal conductivity of porous aluminum foam is proposed, with a model error of 9 %. The sublimator's heat transfer characteristics are significantly influenced by the porosity of the aluminum foam and sublimation tubes. The impacts on temperature behavior, ice thickness, feed water pressure, and stress are carefully examined. Results reveal aluminum foam porosity of 0.7 and sublimation tube porosity of 0.3. Moreover, the study explores how different heat loads affect the sublimator's operation mode. Heat loads above 2 W/cm2 cause evaporation and dryness within the sublimation tube, while excessively small heat loads lead to ice formation and increased stress on the aluminum foam structure. These findings provide valuable insights for water sublimator design. [ABSTRACT FROM AUTHOR]

Due to the high energy absorption capability and excellent bending strength of the sandwich panels, they are mostly preferred as protective structures against explosive blast attacks. The evaluation of their blast-mitigation characteristics through experiments is highly dangerous, costly, time-consuming, and polluting for the environment. Therefore, in this presented work, a series of numerical analyses were performed to evaluate the blast mitigation of the outstanding sandwich panels with honeycomb, corrugated, auxetic, and foam cores. The masses of sandwich panels were kept constant, and their areal densities were maintained constant throughout the study to effectively compare their performance under identical air blast loading conditions. To apply the air blast loads to the designed sandwiches, 1–3kg of spherical-shaped trinitrotoluene charges were used for a 100mm stand-off distance. The sandwiches are made of high-strength AL-6XN steel and crushable aluminum foam. The rate-dependent Johnson–Cook constitutive model of plasticity and the crushable foam model with volumetric hardening were used for the evaluation of sandwich panels’ plastic deformations. The findings of the work depicted that the honeycomb core is more efficient than the other core structures of the same masses because the sandwich panels with honeycomb core provide smaller back skin deflections, globalized core crushing, and higher core energy absorption than the other sandwich panels for extreme conditions of air blast loading. [ABSTRACT FROM AUTHOR]

Highlights The hybrid sandwich structures possessing composite faces and an aluminum foam (ALF) core exhibit lightweight and superior impact resistance. However, limited studies pay attention to the mechanical behavior of hybrid sandwich beams with various ALF densities. The present article has focused on the influence of foam densities on the quasi‐static and low‐velocity impact (LVI) behaviors of hybrid sandwich beams with aramid‐fiber‐reinforced polymer (AFRP) faces and ALF core. The failure mode, loading response, and energy absorption of sandwich beams have been obtained experimentally and the failure map with a wide range of dimensional configurations has been established theoretically. Increasing core density significantly enhances the load‐carrying capacity of the sandwich beam, and the enhanced effect becomes more obvious for a thicker core. The medium‐density ALFs provide the maximum specific energy absorption, while the high‐density ALFs offer the highest energy absorption for hybrid sandwich beams. The applicability of core densities in hybrid sandwich structures is provided. Normal strain distribution under quasi‐static loading is analyzed using DIC. AFRP face microbuckling provides higher impact resistance than core failure. The applicability of core density in hybrid sandwich structures is given. [ABSTRACT FROM AUTHOR]

In this work, a double tubular structure consisting of auxetic tubular structures and aluminum foam was proposed. The mechanical properties of the aluminum foam-filled auxetic tubular structures and aluminum foam-filled conventional tubes under uniaxial compression were compared numerically and experimentally. Compared with conventional aluminum foam-filled tubular structures (FFT), aluminum foam-filled auxetic double tubular structures (FFADT) have stable compression deformation and superior energy absorption because of stronger interaction between the aluminum foam and the auxetic tube. Although the FFADT exhibits lower bearing capacity but overcomes the shortcomings of larger peak force and larger load fluctuation that usually occurs in conventional tubes. [ABSTRACT FROM AUTHOR]

Open-cell type aluminum foams with various structural conditions and alloy compositions were manufactured using the replication casting process. The porosity of the foams ranged from 55% to 62%, with pore sizes of 0.7~1.0 mm, 1.0~2.0 mm, and 2.8~3.4 mm. The alloys employed included commercial A356 and A383, as well as Al-6Mg-(0, 2, 4, 6)Si alloys. Compression tests were conducted under various conditions of the foams, and the results were comparatively analyzed based on the detailed structural conditions and alloy compositions. It was observed that for the same alloy composition and equivalent porosity, a reduction in pore size led to an increased number of cell walls, enhancing energy dispersion and resulting in higher compressive yield strength and energy absorption. Under the same pore size, a decrease in porosity increased the relative density and cell wall thickness, leading to improved compressive yield strength and energy absorption. Furthermore, compressive evaluation based on alloy composition revealed the influence of the inherent mechanical properties of the material on the mechanical properties of open-cell type aluminum foams. Specifically, it was confirmed that alloys with higher ductility exhibited elastic behavior of the internal cells under external stress, significantly influencing the energy absorption of foams. [ABSTRACT FROM AUTHOR]

Open‐cell aluminum foams are gaining importance for the design of lightweight structures and as electrodes in lithium‐ion batteries. AlSi7Mg0.3 foams are produced by a modified investment casting process. By tuning the mold temperature, a change from the usual nearly monocrystalline dendritic to a polycrystalline globular grain structure is achieved. Tension and compression tests on single struts and foam specimens, respectively, are combined with digital image correlation, scanning electron microscopy, and phase contrast‐enhanced microcomputed tomography in a synchrotron facility to correlate the mechanical properties and the failure mechanisms with the microstructure. The "globular" foams exhibit a lower strength and a less pronounced subsequent stress drop than the "dendritic" foams and the deformation mechanism changes from shear band‐dominated failure to a layer‐by‐layer collapse, because of the lower strength and higher ductility of the "globular" struts. The "dendritic" struts have a more homogeneous microstructure, while the "globular" struts often contain silicon agglomerates in their central region. Accordingly, the latter struts exhibit a higher degree of scatter for the fracture strain. Thus, the arrangement of the silicon particles and the eutectic determines the mechanical properties on the strut level and thereby the failure behavior on the foam level. [ABSTRACT FROM AUTHOR]

Gradient aluminum foam as a filling material for CFRP thin-walled square tubes is a new energy-absorbing structure. In this paper, an axial quasi-static compression experiment and numerical simulation were carried out on CFRP thin-walled square tubes filled with gradient aluminum foam, the crushing process and failure modes of hollow and filled tubes under typical lay-up angles were analyzed, and the effects of lay-up mode, CFRP wall thickness and gradient aluminum foam filling on the crashworthiness of filled structures were investigated. The results showed that gradient aluminum foam can significantly improve the crashworthiness of CFRP thin-walled square tubes, and the crashworthiness of structures filled with positive gradient aluminum foam is better than that filled with negative gradient and single-density aluminum foam. In this paper, it is proved that the CFRP thin-walled square tube filled with gradient aluminum foam is an energy-absorbing structure with excellent crashworthiness, providing certain reference for the design of CFRP thin-walled structures filled with gradient aluminum foam. [ABSTRACT FROM AUTHOR]

The influence of metal foam thickness on the convection and conduction heat transfer is studied by measuring the local heat transfer of a smooth flat plate, attached and detached metal foamed flat plate under multiple jet impingement conditions. 27 jets of 3 mm diameter are introduced from a jet plate. These jets impinge on a thin stainless steel foil that serves as a targeted plate. The pitch of the jets is 4d in both the spanwise and streamwise directions. The spent fluid is exiting in all directions. The influence of metal foam thickness is investigated for an open-cell aluminum foam with 4, 8, and 12 mm thickness. The porosity of aluminum metal foam is 0.92. The pore density (pores per inch) is 20 PPI. The local heat transfer is measured using infrared thermography and a thin metal foil technique. A smooth flat plate impinged by multiple jets serves as a reference case. The evaluation of the convection and conduction heat transfer offered by the metal foamed flat plate is obtained with the help of the detached foam configuration. The jet diameter-based Reynolds number ranges from 2500 to 15000. The range of the jet to plate spacing covered is 3d to 6d. Depending on the metal foam thickness, the metal foamed flat plate offers additional hydraulic resistance to the jet flow and conduction effect. The additional hydraulic resistance attenuates the convective heat transfer and is represented by attenuation factor (α). For metal foam having 4, 8, and 12 mm thickness, the attenuation factor is around 1.11, 0.99, and 0.64, respectively. The conduction effect offered by metal foam is responsible for the enhancement of the heat transfer. The conduction effect is represented as an enhancement factor (E). For metal foam having 4, 8, and 12 mm thickness, the enhancement factor is around 1.51, 1.58, and 2.32, respectively. The conduction effect presented in the metal foamed flat plate dominates over the attenuation in the convective heat transfer. The overall enhancement offered by 4, 8, and 12 mm metal foamed flat plate is around 1.67, 1.56, and 1.48, respectively. [ABSTRACT FROM AUTHOR]

The energy-absorbing capacity and friction phenomena of different closed-cell aluminium foam-filled Al tube types are investigated through experimental compression tests. Concerning the kind of investigation, free, radial-constrained and friction tests occurred. The radial-constrained compression test results confirm that the process requires significantly more compression energy than without the constrain. Pushing away different pre-compressed foams inside the aluminium tube, the static and kinematic frictional resistances can be determined and the energy required to move them can be calculated. Knowing the value of the energy required for the frictional resistance, we can obtain how much of the energy surplus in radially inhibited compression is caused by the friction phenomena. The main goal present study is to reveal the magnitude of friction between the foam and the wall of the tube during the radially constrained test. The investigation used 0.4 and 0.7 g/cm3 density closed-cell aluminium foam whilst a compressive test was applied where the force–displacement data were recorded to calculate the absorbed energy due to friction. Considering the results of the test, it can be stated that 18% of the invested energy was used to overcome friction in the case of lighter foam and almost 23% with 0.7 g/cm3 foam during the radial-constrained test. [ABSTRACT FROM AUTHOR]

This research introduces a novel approach to establishing a connection between the aluminum foam mesostructure features and mechanical properties. The proposed framework utilizes deep learning techniques to predict mechanical properties and enables a reverse structural design process for aluminum foam. Two-dimensional mesostructural images of aluminum foam are acquired using surface scanning and image recognition methods. Based on experiments and simulations, the compressive stress–strain response of aluminum foam is selected to establish the basic mechanical properties dataset. A two-dimensional convolutional neural network is utilized to predict aluminum foam mechanical properties, and a conditional generative adversarial network is used for reverse structural design. A two-way high-precision mapping relationship of aluminum foam is established, which links the mesostructure features with mechanical properties. The research results show that the established deep learning framework performs well in both forward prediction and reverse structural design. The error percentage of the forward mechanical properties prediction is within 3%, while the error percentage of the mechanical properties of the structure generated by the inverse structural design model is within 4%. The framework enables efficient and accurate mechanical property prediction and reverse design of aluminum foam structures. The deep learning framework has high engineering application potential and expansibility, extending the deep learning application scope in the porous materials field. [ABSTRACT FROM AUTHOR]

Aluminum foams have emerged as a remarkable engineering material, exhibiting exceptional structural performance and many excellent properties. This has led to a rise in their application in various fields. The investigation and development of aluminum foam have led to the discovery of multiple applications in numerous industries, including the aerospace, automotive, petrochemical, and building materials industries. Foam made of aluminum, one of the most well-known examples of metallic foams, is a significant technological advancement in the foams industry. This article aims to comprehensively analyze the manufacturing techniques that employ blowing agents, such as alumina, titanium hydride, and sodium chloride. This article explores the unique properties and diverse applications of aluminum foams. In addition, the current status of research and development in aluminum foam is discussed. It accomplishes this by providing an overview of existing developments and identifying future opportunities in this industry. This review article is an invaluable resource for academics and industry professionals interested in aluminum foams, as it provides valuable insights into production procedures, properties, applications, and ongoing research. [ABSTRACT FROM AUTHOR]

This study analyses the heat transfer performance of metal foam heat exchangers through experimental measurements. Using counter-gravity infiltration casting, open-cell aluminium foam elements were manufactured to embed a copper tube for internal mass flow containment. Heat transfer experiments were conducted under natural and forced convection conditions, with the airflow controlled in a wind tunnel. A stream of warm water within the internal foam component served as the heat source, transferring thermal energy to the surrounding air flowing through the external foam component of the heat exchanger. The results showed a significantly enhanced heat transfer performance with aluminium foam compared to a single copper tube. Thermal resistance models were developed to elucidate the heat transfer mechanisms, highlighting the effectiveness of air-cooled metal foam heat exchangers. These findings underscore the potential of metal foam heat exchangers as cost-effective alternatives for various thermal management applications. [ABSTRACT FROM AUTHOR]

Reactive multilayers store large amounts of chemical energy, which can be released through a self-sustaining reaction. One way of triggering the self-sustaining reaction is mechanical ignition, which is a prerequisite for designing a self-healing system. For potential integration into various devices, it is important to understand how Al/Ni reactive multilayers behave under shock compression. In this study, molecular dynamics (MD) simulations are employed to investigate Al/Ni reactive multilayers under shock compression. MD simulations allow for the understanding of what is happening at the atomistic level. Furthermore, they give access to bilayer heights that are difficult to study otherwise. This allows studying the shock wave propagation from bilayer heights of 100 down to 5 nm, while at the same time observing what is happening atomistically. Shock compression is studied both, for interfaces parallel and normal to the shock wave. It is shown that when the shock wave is parallel to the Al–Ni interfaces, there is a clear relationship between bilayer height and effective elastic modulus, which is not true when the interfaces are normal to the shock wave. Furthermore, intermixing of Al and Ni, as a prerequisite for ignition, strongly depends on the bilayer height as well as the impact velocity. Behind the shock wave, a phase transformation occurs, which strongly depends on the impact velocity, with a weak dependence on the bilayer height. Furthermore, void nucleation and fracture are observed, where the voids start nucleating in the Al layers. [ABSTRACT FROM AUTHOR]

The stability and accuracy of atomic devices can be degraded by the evolution of their cell inner atmosphere. Hence, the undesired entrance or leakage of background or buffer gas, respectively, that can permeate through the cell walls, should be slowed down. In this work, we investigate helium permeation in microfabricated alkali vapor cells filled with He and whose windows are made of borosilicate glass (BSG) or aluminosilicate glass (ASG). The permeation is then derived from routine measurements of the pressure-shifted hyperfine transition frequency of an atomic clock. We first confirm that ASG reduces the He permeation rate by more than two orders of magnitude, in comparison to BSG. In addition, we demonstrate that Al 2 O 3 thin-film coatings, known to avoid alkali consumption in vapor cells, can also significantly reduce He permeation. The permeation through BSG is thereby reduced by a factor up to 130, whereas the one through ASG is decreased by a factor up to 5.0 compared to uncoated substrates. These results may contribute to the development of miniaturized atomic clocks and sensors with improved long-term stability or sensitivity. [ABSTRACT FROM AUTHOR]

The present work investigates factors which control the stress generated at the back face of end wall-mounted shock-loaded aluminum foam. When the applied shock pressure is higher than the plastic strength of the foam, the foam deforms plastically generating a compaction wave traveling below shock velocity. Wave reflection and momentum transfer at the end wall result in shock amplification. With increasing foam length, the stress at the end wall decreases, finally leading to shock mitigation. A relation between compaction wave characteristics, foam densification, and stress generated at the end wall is established. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) and their composites are gaining popularity due to their exceptional strength qualities. It is well known that adding CNTs to metal foam composites boosts compressive strength. On the other hand CNT addition is still a costly process due to high cost of the CNTs. This study presents a novel and cost-effective solution by selectively adding CNTs to the structurally weakest regions of aluminum foam materials produced via powder metallurgy, employing a newly developed focused multi-step additive method. The cell borders of aluminum foam are strengthened with multiple spherical layers of CNTs, using a transfer method by initially coating the space holders used at the foaming process. The strength increase effect of this CNT addition method was compared with the widely known aluminum foam production parameters via a 4-parameter design of experiment (DOE) study. Compressive strength values of the samples were evaluated using a constant speed compression test acc. to ISO13314. The compacting pressure, CNT concentration, sintering temperature, and sintering period were chosen as DOE parameters, and 78% of the interactions effecting on final compressive strength could be explained with the model. As a result, it was established that, compared to the other parameters, sintering duration had the highest influence on compressive strength. But besides It has also been shown that adding 0.53% CNT by weight only to the cell border regions increases overall strength by 9%. This weight-strength increase ratio is compared with similar studies in the literature and found to be providing a production cost advantage due to the lower amount of CNT addition requirement for the comparable weight relative strength increase. Focused strength increase method has potential to enable controlled failure of foam materials by selectively strengthening strength critical areas of a component. [ABSTRACT FROM AUTHOR]

An experimental investigation was carried out on high porosity metal foams subjected to array jet impingement with an objective to develop enhanced heat transfer configurations. In this study, we propose an integrated thermal management system (TMS) aimed toward leveraging the conjugate heat transfer capabilities of target plate, metal foam, and the jet plate--all made from aluminum and assembled such that a proper contact between them can be established. Steady-state heat transfer experiments were carried out for 10 and 20 pores per inch (PPI) aluminum foams of 0.93 porosity. Both metal foams were 12.7-mm thick. The normalized jet-to-jet spacing was varied from 2 to 12 times the jet diameter, while the jet diameter was fixed. The ratio of the jet plate thickness and jet diameter (nozzle aspect ratio) was 6.35, which ensured proper development of jets inside the nozzles. Experiments were conducted over a wide range of Reynolds number (based on jet diameter) varied from 100 to 5000. The obtained convective heat transfer coefficient for different configuration was evaluated in context with pressure drop. The analysis of experimental results reveal that large open area ratio jets combined with high porosity metal foams provide highly efficient and high-performance cooling for the investigated range of Reynolds numbers. [ABSTRACT FROM AUTHOR]

Aluminum foams are among the materials that have many applications in the construction of various building elements, including sandwich panels. This category of materials has unique features due to low density, the presence of small holes, sound insulation, thermal insulation, and corrosion resistance. In this paper, the Voronoi tessellation method is proposed to simulate the porous configuration of aluminum foams, which has the high capability to generate a porous structure with different densities. It is demonstrated that the Voronoi tessellation method can generate porous structures with different densities, hole sizes, and wall thicknesses stably. Moreover, the Voronoi tessellation method has a high speed and can be used to construct different sizes of aluminum foams. A comparison of the configurations obtained from the Voronoi tessellation method and experimental tests demonstrates the capability and competence of this method in generating the porous structure of the aluminum foam. In order to investigate the mechanical behavior numerically, the uniaxial tension test is applied to the aluminum nanofoams using the molecular dynamics (MD) method. The MD analysis is performed in the LAMMPS open-access software using the embedded-atom model (EAM) interatomic potential. The periodic boundary condition is imposed in all the boundaries of the atomistic model to satisfy the essential condition of the representative volume element (RVE) based on the homogenization theory. After minimization and relaxation of RVE, the uniaxial tension test is applied in an increment manner to reduce the strain rate effect. The evolution of the stress-strain curve, along with the stress contours, are presented for the aluminum nanofoam during the uniaxial tension test. Young’s modulus of nanofoam obtained by numerical analysis is compared to that of experimental data to confirm the accuracy of the computational modeling. Moreover, the results emphasize the high dependence of the mechanical behavior of aluminum nanofoams on the density and porosity.

[Display omitted] Three-dimensional interconnected nickel–cobalt layered double hydroxides (NiCo-LDHs) were prepared on nickel foam by ion exchange using a cobalt-based metal–organic framework (Co-MOF) as a template at different temperatures. The effects of the Co-MOF preparation temperature on the growth, mass, morphology, and electrochemical properties of the Co-MOF and derived NiCo-LDH samples were studied. The synthesis temperature from 30 to 50 °C gradually increased the mass of the active material and the thickness of the Co-MOF sheets grown on the nickel foam. The higher the temperature is, the larger the proportion of Co3+. β-Cobalt hydroxide (β-Co(OH) 2) sheets were generated above 60 °C. The morphology and mass loading pattern of the derived flocculent layer clusters of NiCo-LDH were inherited from metal-organic frameworks (MOFs). The areal capacitance of NiCo-LDH shows an inverted U-shaped curve trend with increasing temperature. The electrode material synthesized at 50 °C had a tremendous specific capacitance of 7631 mF·cm−2 at a current density of 2 mA·cm−2. The asymmetric supercapacitor assembled with the sample and active carbon (AC) achieved an energy density of 55.0 Wh·kg−1 at a power density of 800.0 W·kg−1, demonstrating the great potential of the NiCo-LDH material for energy storage. This work presents a new strategy for designing and fabricating advanced green supercapacitor materials with large power and energy densities. [ABSTRACT FROM AUTHOR]

Porous materials with sound absorption and load‐bearing capabilities are in demand in engineering fields like aviation and rail transportation. However, achieving both properties simultaneously is challenging due to the trade‐off between interconnected pores for sound absorption and mechanical strength. Inspired by quilling art, a novel design using spiral material formed by rolling planar materials into helical structures is proposed. Experimental results show high structural strength through self‐locking mechanisms, while double porosities from interlayer spiral slits and aligned submillimeter pores provide excellent sound absorption. These spiral sheets surpass foam aluminum in specific strength (up to 5.1 MPa) and approach aerogels in sound absorption (average coefficient of 0.93 within 0–6400 Hz). With its adaptability to various planar materials, this spiral design allows for hybrid combinations of different materials for multi‐functionality, paving the way for designing advanced, lightweight porous materials for broad applications. [ABSTRACT FROM AUTHOR]

Prebaked carbon anode is the primary consumable material in the aluminum reduction cell, and its quality directly affects the energy consumption of aluminum production. An impregnation-baking process of the anode was proposed to reduce the anode porosity, improve the quality of the anodes, and reduce additional carbon consumption. The theoretical analysis and industrial testing on the impregnation-baking process were carried out. Firstly, the coal tar pitch was immersed into the anode carbon block through the impregnation process. An anode impregnation model was developed and used for theoretical calculations to analyze the effects of pressure and temperature on the impregnation process. The accuracy of the model was verified experimentally. Secondly, the impregnated anodes were placed in an electromagnetic induction heating furnace for baking to carbonize the immersed pitch. The thermogravimetric and pyrolysis kinetics methods were used to analyze the baking process of the impregnated anodes. Finally, the impregnated-baked anodes were compared with common anodes regarding their impact on the technical and economic indicators of the aluminum electrolysis process in industrial tests. The results showed that the physicochemical properties of the impregnated-baked anodes were significantly improved, with the bulk density increase of 0.1 g/cm3, air permeability reduction of 0.54 nPm, compressive strength enhancement of 9.43 MPa, and electrical resistivity decrease of 10 uΩ·m. The anode service life was increased from 31 to 35 days, the current efficiency was increased by 0.44 %, and the operating voltage was reduced by 17 mV, which improved economic benefit significantly. • An impregnation-baking process of the anode for aluminum electrolysis was proposed. • An anode impregnation model was developed. • Baking process was optimized by thermogravimetric and pyrolysis kinetics analysis. • A significant improvement in the economic benefits of using impregnated-baked anode. [ABSTRACT FROM AUTHOR]

In earthquakes, foundations of structures may encounter damages due to faulting. To address this issue, numerous innovative mitigation methods have been introduced. Among these, an efficient solution involves constructing a trench wall filled with a material capable of not only absorbing the faulting energy but also diverting the propagation route of fault rupture. In this research, a novel material called closed-cell aluminum foam (CCAF) is introduced to be implemented within the trench wall considering its noticeable energy absorbing and flexibility. To evaluate the performance of the trench wall filled with CCAF [or Aluminum Foam Wall (AFW)] under fault rupture conditions, ABAQUS, a Finite Element Method software, is employed for numerical analyses and the obtained results are validated against centrifuge experimental data for both free field and shallow foundation's presence conditions. Based on the findings, the application of AFW resulted in a substantial reduction in the rotation degree of the shallow foundation. In one case, it experienced a significant decrease from 11.64° to a mere 0.48°. Furthermore, when compared to alternative mitigation methods such as Smart Wall Barrier (SWB) or Soil Bentonite Wall (SBW), AFW exhibited superior performance under identical conditions. In similar conditions, AFW achieved a remarkable rotation degree of 0.06°, while SWB and SBW registered rotation degrees of 0.4° and 0.2°, respectively. The obtained results indicate that AFW demonstrates a promising ability to efficiently absorb faulting energy and divert the propagation of fault rupture. [ABSTRACT FROM AUTHOR]

Additive manufacturing for open-cell aluminum foam is attracting attention because the cell morphology determined by the characteristics of the aluminum foam can be accurately controlled according to the application. However, there are few reports on the additive manufacturing of closed-cell aluminum foams. Wire arc additive manufacturing (WAAM) is a low-cost additive manufacturing method and has potential for manufacturing closed-cell aluminum foams from a wire precursor. In this study, WAAM was used to produce closed-cell aluminum foam. The precursor round bar was obtained by hot-pressing a mixture of pure aluminum powder, 3 mass% TiH2 powder, and 1 mass% Al2O3 powder. After the precursor round bar with a diameter of 15mm was inserted into an A5052 aluminum alloy tube with an outer diameter of 19mm and inner diameter of 15.5 mm, the assemblage was swaged to a precursor wire measuring ϕ1.6 © 100 mm. The WAAM equipment was based on the torch of a TIG arc welding machine that moved under numerical control. Foam formation tests were carried out with the precursor wire at a torch travel speed range from 120mm/min to 620mm/min. An additive foaming test was also carried out using a precursor wire measuring ϕ1.6 © 100mm to investigate welding of the second layer to the first layer while the second layer was foaming. The density of the aluminum foam was measured by Archimedes' method to calculate the porosity. The aluminum foam samples were cut perpendicular to the long axis, and cross-sections were observed with an optical microscope. For the single-layer aluminum foam formed with a TIG arc, the maximum porosity of 60% was obtained at a travel speed of 320mm/min. A two-layer aluminum foam with a porosity of 18% and mean pore diameter of approximately 86µm was obtained in the additive experiment. The second and first layers were bonded without forming a boundary. These results indicate that closed-cell aluminum foam was successfully produced using WAAM. However, the viscosity of the base aluminum of the precursor wire must be high to obtain a high-porosity aluminum foam with WAAM. [ABSTRACT FROM AUTHOR]

Porous materials with ultrahigh specific strength are highly desirable for aerospace, automotive and construction applications. However, because of the harsh processing of metal foams and intrinsic low strength of polymer foams, both are difficult to meet the demand for scalable development of structural foams. Herein, we present a supramolecular metallic foam (SMF) enabled by core-shell nanostructured liquid metals connected with high-density metal-ligand coordination and hydrogen bonding interactions, which maintain fluid to avoid stress concentration during foam processing at subzero temperatures. The resulted SMFs exhibit ultrahigh specific strength of 489.68 kN m kg−1 (about 5 times and 56 times higher than aluminum foams and polyurethane foams) and specific modulus of 281.23 kN m kg−1 to withstand the repeated loading of a car, overturning the previous understanding of the difficulty to achieve ultrahigh mechanical properties in traditional polymeric or organic foams. More importantly, end-of-life SMFs can be reprocessed into value-added products (e.g., fibers and films) by facile water reprocessing due to the high-density interfacial supramolecular bonding. We envisage this work will not only pave the way for porous structural materials design but also show the sustainable solution to plastic environmental risks. Porous materials with high strength are desirable for many applications. Here, the authors present a supramolecular metallic foam enabled by nanostructured liquid metals connected with high-density metal-ligand coordination to exhibit ultrahigh specific strength and recyclability. [ABSTRACT FROM AUTHOR]

The advancement of Li-metal batteries is significantly impeded by the presence of unstable solid electrolyte interphase and Li dendrites upon cycling. Herein, we present an innovative approach to address these issues through the synergetic regulation of solid electrolyte interphase mechanics and Li crystallography using yttrium fluoride/polymethyl methacrylate composite layer. Specifically, we demonstrate the in-situ generation of Y-doped lithium metal through the reaction of composite layer with Li metal, which reduces the surface energy of the (200) plane, and tunes the preferential crystallographic orientation to (200) plane from conventional (110) plane during Li plating. These changes effectively passivate Li metal, thereby significantly reducing undesired side reactions between Li and electrolytes by 4 times. Meanwhile, the composite layer with suitable modulus (~1.02 GPa) can enhance mechanical stability and maintain structural stability of SEI. Consequently, a 4.2 Ah pouch cell with high energy density of 468 Wh kg−1 and remarkable capacity stability of 0.08% decay/cycle is demonstrated under harsh condition, such as high-areal-capacity cathode (6 mAh cm−2), lean electrolyte (1.98 g Ah−1), and high current density (3 mA cm−2). Our findings highlight the potential of reactive composite layer as a promising strategy for the development of stable Li-metal batteries. The application of Li-metal batteries (LMBs) is impeded by unstable solid electrolyte interphase (SEI) and uncontrollable Li dendrites growth. Here, the authors present an YF3/PMMA composite layer to achieve high-performance LMBs via the synergetic regulation of SEI mechanics and Li crystallography. [ABSTRACT FROM AUTHOR]

Metal curved panels are commonly used in engineering structures, but they may be more susceptible to damage under impact loads compared to flat panels. Polyurea coating has been proposed as a solution to improve impact resistance. Therefore, this study investigates the impact resistance performance of curved composite panels by applying polyurea coating to aluminum‐based panels with different curvatures. First, a numerical model of polyurea‐coated aluminum composite panels was established using the finite element software LS‐DYNA, and the sensitivity of model mesh and the numerical model validity were carried out. Then, the impact resistance performance of polyurea‐coated aluminum‐based flat panels was studied from the aspects such as deformation modes and energy dissipation, and the influence of polyurea layer thickness and coating position on the impact resistance performance of polyurea‐coated aluminum composite panels was analyzed. Based on the above results, numerical models of polyurea‐coated aluminum‐based curved panels under different curvatures are further established, and the impact resistance performance of composite curved panels and the structural forms for effective protection against impact loads are comprehensively analyzed. The research results indicate that double‐sided polyurea coating is the optimal coating method for both aluminum flat panels and aluminum curved panels. After the coating thickness reaches 4 mm, there is no significant improvement in the structural impact resistance performance. The impact deformation of curved panels can be divided into four stages: dynamic buckling, plastic indentation, rebound deformation, and vibration. The concave surface has strong impact and deformation resistance, and the convex surface has strong impact resistance. The research results have important theoretical implications for the safe engineering design of protective structures using metal curved panels. [ABSTRACT FROM AUTHOR]

Auxetic honeycomb sandwich structures (AHS) composed of a single material generally exhibit comparatively lower energy absorption (EA) and platform stress, as compared to traditional non-auxetic sandwich structures (TNS). To address this limitation, the present study examines the use of aluminum foam (AF) as a filling material in the re-entrant honeycomb sandwich structure (RS). Filling the AHS with AF greatly enhances both the EA and platform stress in comparison to filling the TNS with AF, while the auxetic composite honeycomb sandwich structure effectively addresses interface delamination observed in traditional non-auxetic composite sandwich structures. Subsequently, the positive–negative Poisson's ratio coupling designs are proposed to strengthen the mechanical features of a single honeycomb sandwich structure. The analysis results show that the coupling structure optimizes the mechanical properties by leveraging the high bearing capacity of the hexagonal honeycomb and the great interaction between the re-entrant honeycomb and the filling material. In contrast with traditional non-auxetic sandwich structures, the proposed auxetic composite honeycomb sandwich structures demonstrate superior EA and platform stress performance, suggesting their immense potential for utilization in protective engineering. [ABSTRACT FROM AUTHOR]

Aluminium smelter waste (ASW) is a big contributor to landfills, and its recycling has been of great interest. This study investigates the tribological properties of aluminium matrix syntactic foams manufactured using an Al 6082 alloy and ASW. Ball-on-disc tests were conducted under both dry and lubricated conditions. Under dry sliding conditions, the coefficient of friction (COF) had an initial sharp increase, followed by a gradual decrease and finally a steady state as the sliding distance increased. The wear surfaces showed the presence of adhesive, abrasive and oxidative wear, with some presence of delamination. Syntactic foams containing small ASW particles led to a decrease in surface roughness, decrease in the average COF and decrease in specific wear. Heating large ASW particles before manufacturing the syntactic foams enhanced overall wear properties because the particles are hardened due to a compositional change. The T6 treatment of the syntactic foams enhanced the wear properties due to the hardening of the Al matrix. The average COF of the ASW syntactic foams was higher than that of the E-sphere syntactic foam, which was predominantly abrasive wear. The specific wear of the ASW syntactic foams can be higher or lower than the E-sphere syntactic foam, depending on the ASW particle size. Under lubricated sliding test conditions, the wear was reduced significantly, and the type changed from predominantly adhesive to predominantly abrasive. The porous ASW particles acted as lubricant reservoirs and provided a constant supply of lubricant, further improving the lubrication effect. [ABSTRACT FROM AUTHOR]

To study the effect of calcium on the porosity, sphericity, and microstructure of Al-Cu foams, a gradient calcium content (0.5, 1.0, 1.5, and 2.0 wt%) is added into aluminum A201 alloy (Al-Cu alloy) for the cellular aluminum foam preparation via the melt foaming method (TiH2 is used as a bubbling agent). Thereafter, the porosity of the prepared Al foams and their pore size are found to increase, and the sphericity of pores tends to approach to unit with calcium addition. This phenomenon is then explained through the modified thermophysical properties (i.e., surface tension and viscosity) of A201 alloy melts caused by the calcium addition. After the microstructure analysis, a bunch of secondary phases in the A201 + Ca alloy foams, e.g., CalAl2Si2, Al2Cu, and Al20CaTi2 as well as an eutectic phase with a great copper content Al8CaCu4 are detected by means of scanning electron microscopy/energy-dispersive X-Ray spectroscopy and X-Ray diffraction analysis. [ABSTRACT FROM AUTHOR]

High endothermic heat of SO 3 decomposition reaction ( Δ H R ∼+ 98 kJ mol −1 ) can lead to significant thermal gradients (lower temperatures) inside the catalyst particle, depending up on mass diffusion, heat conduction and intrinsic reaction kinetics in the particle. The lower catalyst effectiveness (due to thermal gradients) leads to lower decomposition conversions in Packed Bed Reactors (PBR), which has to be maximized. In this study, a multi-scale model (Double Porosity Model, DPM) is used for the estimation of non-isothermal effectiveness factor (η) of Cr-Fe 2 O 3 catalyst types; less porous pellet and porous foam types. η obtained using DPM (foam∼0.249 and pellet∼0.147) are found to be in good agreement with experimental data and also with the results of derived model (Weisz model). Further, effect of porosity and size/diameter on η are studied and obtained the optimum porosity required for maximum η. The present study is useful for estimation and optimization of non-isothermal η of catalysts. • Estimation of effectiveness factor (η) of Cr-Fe 2 O 3 catalyst for SO 3 decomposition • η of catalysts obtained using the model (DPM) are 0.249 (foam) and 0.147 (pellet) • η obtained using DPM are compared with results of Weisz model and experimental data • Significant temperature drop is found in foam type catalyst (ΔT∼12K) than pellet type • Optimum porosity required for maximum non-isothermal η (η ∼0.32) is found to be ∼0.6 [ABSTRACT FROM AUTHOR]

The article presents the results of numerical modeling and experimental studies of the dynamics of temperature fields on the aluminum sample surface after a short repetitively-pulsed energy impact on the surface, and at the synergy of high-intensity titanium ion implantation into aluminum with a simultaneous repetitively-pulsed energy impact of the beam on the surface. The data on the accumulation and spatial distribution of implanted titanium in aluminum are presented. Using the samples heated by a repetitively-pulsed ion beam to the temperatures of 300°C and 500°C with an additional heating during each pulse to a temperature approaching that of melting, a possibility of ion doping of aluminum with titanium to the depths of up to 5 and 8 μm, respectively, is shown. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to elucidate the machining properties of low-cost expanded clay-reinforced syntactic foams by using different neural network models for the first time in the literature. The main goal of this endeavor is to create a casting machining-neural network modeling flow-line for real-time foam manufacturing in the industry. Design/methodology/approach: Samples were manufactured via an industry-based die-casting technology. For the slot milling tests performed with different cutting speeds, depth of cut and lubrication conditions, a 3-axis computer numerical control (CNC) machine was used and the force data were collected through a digital dynamometer. These signals were used as input parameters in neural network modelings. Findings: Among the algorithms, the scaled-conjugated-gradient (SCG) methodology was the weakest average results, whereas the Levenberg–Marquard (LM) approach was highly successful in foreseeing the cutting forces. As for the input variables, an increase in the depth of cut entailed the cutting forces, and this circumstance was more obvious at the higher cutting speeds. Research limitations/implications: The effect of milling parameters on the cutting forces of low-cost clay-filled metallic syntactics was examined, and the correct detection of these impacts is considerably prominent in this paper. On the other side, tool life and wear analyses can be studied in future investigations. Practical implications: It was indicated that the milling forces of the clay-added AA7075 syntactic foams, depending on the cutting parameters, can be anticipated through artificial neural network modeling. Social implications: It is hoped that analyzing the influence of the cutting parameters using neural network models on the slot milling forces of metallic syntactic foams (MSFs) will be notably useful for research and development (R&D) researchers and design engineers. Originality/value: This work is the first investigation that focuses on the estimation of slot milling forces of the expanded clay-added AA7075 syntactic foams by using different artificial neural network modeling approaches. [ABSTRACT FROM AUTHOR]

This study aimed to improve the energy absorption capabilities of auxetic structures, which are used in sandwich structures in engineering. To achieve this, the study used a combination of CFRP and aluminum materials in a hybrid double arrow-head auxetic (DAHA) structure. This paper conducted experiments and simulations to analyze the mechanical properties of the hybrid DAHA structures and found that the mixture ratio of hybrid material, ply angles of CFRP laminates, and inclination angles of beams significantly influenced the energy absorption performance of the structures. Additionally, the proposed hybrid DAHA structures outperformed other control groups when the thickness ratio of CFRP was 75%. The inclination angles of beams also affected the energy absorption capacity by changing the structural void of DAHA structures. These findings offer new insights into enhancing the energy absorption capacity of hybrid auxetic structures. The proposed hybrid structures can absorb more energy by 56.4% with a lower peak crushing force comparing with the traditional metal auxetic structure. Therefore, the CFRP/Aluminum hybrid auxetic structure has a bright future in the energy absorption fields. [ABSTRACT FROM AUTHOR]

Aluminum foam sandwich (AFS) are widely used in energy absorption because of their light weight and excellent energy dissipation capabilities. In this study, energy absorption, deformation modes, and dynamic response of AFS under low-velocity impact are investigated using experimental and numerical approaches. Dynamic impact tests are performed utilizing a drop hammer impact test on AFS with different core densities, face sheet thicknesses, and impact energy. Based on the 3D Voronoi foam model, a full-scale finite element model (FEM) is developed to simulate the mechanical response of AFS under low-velocity impact, and verified by experimental results. The contributions of different AFS components to energy absorption at various impact velocities are further analyzed, along with the effects of face sheet thickness distribution. The results indicate that the performance of the face sheet and core and the impact energy have a remarkable influence on the low-velocity impact response and damage modes of the AFS. The type of structure configuration, "thin top and thick bottom," enables the AFS better play its energy absorption while ensuring the overall light weight. This study provides a reference for the design and optimization of the face sheet thickness of AFS when it is used as an energy-absorbing member and improves their design efficiency. [ABSTRACT FROM AUTHOR]

A composite structure containing a metallic skeleton and polyurea elastomer interpenetrating phase was fabricated, and its anti-penetration performance for low-velocity large mass fragments was experimentally studied. The protection capacity of three polyurea was compared based on the penetration resistance force measurement. Results show that the polyurea coating layer at the backside improves the performance of the polyurea-filled spherical cell porous aluminum (SCPA) plate due to its backside support effect and phase transition effect, which are accompanied by a large amount of energy absorption. The frontal-side-coated polyurea layer failed to shear and provided a very limited strengthening effect on the penetration resistance of the interpenetrating phase composite panel. The filling polyurea in SCPA increased the damage area and formed a compression cone for the backside coating layer, leading to a significant stress diffusion effect. The anti-penetration performance was synergistically improved by the plug block effect of the interpenetrating phase composite and the backside support effect of the PU coating layer. Compared with SCPA, the initial impact failure strength and the average resistance force of the composite plate were improved by 120–200% and 108–274%, respectively. [ABSTRACT FROM AUTHOR]

Cylindrical foam castings of Al and A356 alloy were produced using a melt foaming method with the introduction of Ca and TiH2. Foam crystallization takes place in a cooled thin-walled metal mold. Samples cut off from the foam castings are investigated by X-ray tomography, quantitative data for porosity, average pores diameter and average cells wall thickness are obtained. It is found that the porosity is mainly open. Same samples are tested in quasi-static mode and the compressive strength is determined. The influence of porosity on compressive strength is analyzed. [ABSTRACT FROM AUTHOR]

Aluminum and A356 alloy foam castings are produced using a melt-foaming method. Prior to foaming, the melt is modified with nano-sized particles (SiC, TiN, or Al2O3). The nano-sized particles are mixed with micro-sized Al particles, which are ultrasonically treated and hot-extruded. Thus, the so-called "modifying nano-composition" is obtained. The resulting compositions are introduced into the melt of the Al foam at the following mass concentrations of nanoparticles: SiC: 0.038 wt. %; TiN: 0.045 wt. %; and Al2O3: 0.046 wt. %. For the A356 foam, we use the following concentrations: SiC: 0.039 wt. %; TiN: 0.052 wt. %; and Al2O3: 0.086 wt. %. The macrostructure of the foam castings is investigated by CT scanning and 3D analysis. The pore size distributions and accumulative fraction dependencies are determined for all samples. The microstructure of the foam castings is investigated by SEM-EDS analysis. The results confirmed the presence of individual nano-sized particles, as well as clusters of particles in foam walls. The conducted compression tests show a significant increase in the plateau stress (up to 237%) of the modified aluminum foam castings compared to non-modified castings. However, a similar effect of the nano-compositions on A356 alloy foam castings is not observed. The obtained results show that the above-indicated concentrations of nanoparticles can positively influence the mechanical properties of aluminum foam castings. The novelty of the current study is two-fold: (1) such low concentrations of added nanoparticles have never been used before to alter Al foam's properties, and (2) an original method of introducing the nanoparticles into the melt is applied in the form of nano-compositions. [ABSTRACT FROM AUTHOR]

An aluminum foam sandwich (AFS) is a lightweight material that has great potential for applications in the automotive industry. In this work, the production routes of metal foams and metal foam sandwiches are reviewed. We compare the mechanical properties of AFS, such as high mass-specific bending stiffness, compressive strength and crash-absorption capacity, with other materials such as steel, aluminum alloys, or fiber composites and place them in a cost/weight comparison. Additional functional properties such as high electromagnetic damping, increased sound absorption, and improved fire resistance underline its multi-functional character. Furthermore, possible joining techniques and parts of AFS for modern car bodies, such as the battery box, are discussed. [ABSTRACT FROM AUTHOR]

Aluminum (Al) toxicity poses a significant challenge to agricultural productivity, particularly in acidic soils. The banana crop, predominantly cultivated in tropical and subtropical climates, often grapples with low pH and Al toxicity. This study seeks to explore the differential responses of two banana genotypes with varying Al tolerance (Baodao and Baxi) to Al exposure (100 and 500 µM) for 24 h. Microscopic analysis uncovered distinctive structural modifications in root cells, with Baodao displaying more severe alterations in response to Al stress. There was higher superoxide (O2−.) and hydrogen peroxide (H2O2) production and lipid peroxidation in Baodao indicating enhanced oxidative stress and membrane damage. Al accumulation in root tips was higher in Baxi than Baodao, while the roots of Baodao had a higher accumulation of callose. Nutrient content analysis revealed alterations in ion levels, highlighting the impact of Al exposure on nutrient uptake and homeostasis. In summary, Al differentially affects callose deposition, which, in turn, leads to Al uptake and nutrient homeostasis alteration in two contrasting banana genotypes. This intricate interplay is a key factor in understanding plant responses to aluminum toxicity and can inform strategies for crop improvement and soil management in aluminum-stressed environments. [ABSTRACT FROM AUTHOR]

For composite metal foam structures to be used as load‐bearing and energy‐absorbing elements, comprehensive testing should be done. Therefore, an extensive characterization of foam‐filled structures by various load types, such as axial and lateral compression, as well as three‐point bending, is carried out, aiming to differentiate the behavior of various cross‐sectional geometry foam‐filled hollow sections and the application of a tough epoxy adhesive and a ductile polysiloxane adhesive. Applying the epoxy adhesive improves the overall energy absorption by 10% during axial compression compared to the sum of the foam and empty hollow section. The application of the polysiloxane adhesive over the epoxy one increases the deflection at failure during three‐point bending by an average of 58%. The deformation and strength during axial compression and three‐point bending are hollow section dominated, while the foam core dominates the deformation and the strength during lateral compression for both produce composite foam‐filled hollow sections with epoxy and polysiloxane adhesive bonding. [ABSTRACT FROM AUTHOR]

Titanium-based physical vapor deposition (PVD) coatings, such as titanium nitride (TiN) and titanium niobium nitride (TiNbN), are common solutions for surface modifications in medical applications. Ex vivo studies of retrieved knee implants indicate the demand for increased scratch and abrasion resistance of PVD coatings in clinical applications. Based on the promising mechanical performance of titanium aluminum nitride (TiAlN) as a coating for tools, the aim of this study was to evaluate the impact of the chemical composition of titanium-based nitride coatings with aluminum (Al) and niobium (Nb). Nine titanium aluminum niobium nitride (Ti1−x−yAlxNbyN) coatings with 0.4 ≤ x < 0.7 and 0 ≤ y ≤ 0.18, as well as commercial TiN and TiNbN, were coated in an industrial scale arc PVD process, following a randomized, multifactorial response surface design. The deposition rate, the scratch resistance, and the hardness were measured following standardized protocols. The microstructure of the coating was analyzed by SEM and XRD. In addition, the surface roughness was determined by laser scanning microscopy. A quadratic regression was performed to determine the impact of the chemical composition on coating properties. Experimental results and regression analyses revealed the significant impact of the chemical composition of Ti1−x−yAlxNbyN on the coating microstructure, mechanics, and morphology. Scratch resistance for initial crack formation and cohesive failure could be increased decisively, compared to TiN. [ABSTRACT FROM AUTHOR]