Al Foam Research Articles

Modelling the conditions for natural convection onset in open-cell porous Al/paraffin composite phase change materials: Effects of temperature, paraffin type and metallic structure geometry

Composite Phase Change Materials (PCMs) can be made combining a PCM, i.e., a material that is able store/release heat by its melting/solidification, and a low-amount of well distributed high-melting and high-thermal conductivity phase with the aim of improving the overall conductivity of the material and keeping its high heat storage capability. The composite made by a paraffin and a porous structure of aluminium (Al) has been considered as the representative of this material class. The design of these materials should not only take into account the melting temperature (Tm) and the volume fraction of the paraffin, but also the geometrical distribution and coarseness of the Al phase, which relate to the effective thermal conductivity of the composite as well as the occurrence of natural convection once the PCM is in the molten state. In the present paper, the inverse Body Centred Cubic (BCC) structure has been confirmed to be the most suitable to model high porosity Al foams. For their BCC modelled structure, an analytical equation is proposed for the evaluation of the overall thermal conductivity of the composite PCMs. Also, new best fit equations for predicting permeability of BBC structure are proposed. Analytical description is also given for the Rayleigh-Darcy number obtained as a product of material-dependent term (related to Tm and volume fraction of PCM) and the geometry dependent term (related to volume fraction of PCM, permeability as well as to material coarseness alternatively given in terms of pores per inch, pore size or unit cell length). The model has been validated by means of literature available experimental data. The proposed simplified model can further be adjusted to correlate the onset of natural convection through the local temperature gradient for the composite PCMs.

Study of thermal behavior of Aluminium foams in batteries of electric vehicles

The temperature of batteries in electric vehicles increases with time due to internal chemical reactions. This temperature rise is undesirable because it promotes corrosion and affects the battery life and thus a coolant can be used to prevent the temperature rise. The use of lightweight material and thermal management properties have a huge impact when designing a battery, especially, when using Aluminium foams it gives an exceptional advantage ranging from lightness, ductility to excellent absorption and conductivity making it a great deal for the future-oriented development of electric vehicles and market acceptance. The current research work tries to prove that Al foam can be used as a coolant in batteries of electric vehicles because of its porosity and density. The battery and Al foam are modelled in SOLIDWORKS and simulations are conducted in CFD and transient thermal to observe the heat transfer, flow characteristics and cooling effect on foam surface. The pores in Al foam are placed in three different patterns and two sizes (3mm and 5 mm) while modelling and hence six distinct models of Al foam are taken into study. The results from the simulations are compared and the Al foam that reduces maximum temperature at the outlet is chosen as the best coolant.

Polypyrrole Modification of High Sulfur-Loaded Three-Dimensional Aluminum Foam Cathode in Lithium–Sulfur Batteries for High-Rate Capability

A low-resistance polypyrrole (PPy) film that can achieve high rates (rates of >1C) while suppressing polysulfide dissolution is developed in this study. To achieve high-rate characteristic in a sulfur cathode with high sulfur loading, a three-dimensional (3D) aluminum foam current collector is used and the Li+ concentration of the PPy film is enhanced by a glyme–Li equimolar complex as the polymerization electrolyte. A PPy–sulfur/ketjenblack (S/KB) 3D aluminum foam laminated cell with a sulfur loading of 5 mg cm−2 is prepared. Consequently, a high discharge capacity of 794 mAh g−1-sulfur at 3.0C is achieved using 1 M lithium bis-(trifluoromethylsulfonyl)imide (LiTFSI) with dimethoxyethane (DME) and 1,3-dioxolane (DOL), (DME/DOL = 1/1 vol.) as the electrolyte and Li foil as the anode. In the cycling test, PPy-S/KB 3D Al foam cathode achieved a significant improvement in discharge capacity retention compared to bare S/KB 3D Al foam cathode without PPy coating. Moreover, almost no polysulfide dissolution is confirmed from the ultraviolet–visible spectrum of the electrolyte after the cycle evaluation. Here, we prepare a 3D structure S/KB cathode that can support high rates while suppressing sulfur dissolution by PPy coating, and reveal its potential for lithium–sulfur battery application.

Design and Fabrication of Highly Porous Replicated Aluminum Foam Using Double-Granular Space Holder.

Porous materials are widely employed in a wide variety of industrial applications due to their advanced functional performance. Porous aluminum is among the most attractive metallic materials. It can be produced using repeatable methods involving a replicated Al foam that also provides porosity control. In this work, a highly porous replicated Al foam was fabricated. First, the model of multifunctional packing density was used and corrected to select the appropriate space holders. Then, Al foam was produced using a double-granular sodium chloride space holder. The obtained results showed a maximum porosity of 65% that was achieved using a mix of coarse, irregular granules with spherical granules of intermediate size.

Comparison between finite element and experimental evidences of innovative W lattice materials for sacrificial limiter applications

Power exhaust is a key mission for the realization of fusion electricity. Engineering challenges may arise from the extreme heat fluxes developed during plasma transients, above the limit offered by existing materials. These can reduce the lifetime of plasma-facing components (PFCs), imposing extraordinary maintenance, reactor safety issues and ultimately delayed return to normal operation. Concerning the EU DEMO reactor, discrete sacrificial limiters are being investigated as the last safety resource of the reactor’s wall in case of unmitigated events. Within this context, micro-engineered tungsten (W) lattices are proposed to cope with unmitigated plasma disruptions. Unlike bulk W, lattices can be tailored to meet the operational requirements of the limiter, compromise between steady-state and off-design performances while avoiding overloading of the heat sink and delay the need for extraordinary maintenance. By calibrating an equivalent solid model originally developed and validated for open-cell aluminum (Al) foams, tailored lattices have been modelled and samples fabricated through additive manufacturing for characterization and testing, currently ongoing.In the present work, the thermal response of lattice samples during thermal shock high heat flux (HHF) tests performed at the linear facility QSPA Kh-50 facility is simulated using ANSYS and compared with available results. Enthalpy changes of W were imposed to simulate phase change. Good agreement with experiments and SDC-IC reference up to melting point was observed. Ultimately, a thermal quench of an unmitigated DEMO disruption was simulated involving an original MAPDL routine that removes mesh elements at the melting or vaporization point.

Predicting thermal and mechanical performance of stochastic and architected foams

This study conducted pore-scale simulations to estimate the stagnant thermal conductivity and mechanical performance of stochastic metal foams and architected metal foams. The stagnant thermal conductivity of 5-, 10-, 20- and 40-ppi commercial aluminum foams were estimated to be 6.74, 6.49, 5.97, and 7.16 W/m/K, respectively. Thermal conductivity depended mainly on porosity and was not a strong function of pore size. The pore-scale models simulated thermal conductivities of 40-ppi Al foam along three orthogonal directions are 7.16, 7.92, and 7.56 W/m/K, respectively, indicating a strong isotropic nature. Compared with stochastic foams, the architected foam with a triply periodic minimal surface showed 103% higher thermal conductivity, 488% higher stiffness, and 265% more energy absorption capability. The findings reported here not only provide a fundamental understanding of the interplay between performance and architecture but also open a new avenue to create multifunctional foams.

Microstructural damage behaviour of Al foams

Microheterogeneous materials such as metal foams exhibit a strong structure-property-relationship. The macroscopic material properties depend on the pore geometry and especially on the strut geometry and the microstructure of the struts such as the grain structure. Since the grain structure in the struts differs from that of the corresponding bulk material, it is of utmost importance to perform microtensile tests on individual struts. Previous works on aluminium foams outlined strong scattering in this micromechanical properties. A possible reason for the scattering might be micro-porosity and inclusions in the struts resulting from the manufacturing of metal foams by investment casting. The present contribution deals with ex situ and In situ microtensile tests to elucidate reasons for the scattering in the micromechanical properties determined from microtensile tests on individual struts. In situ tensile tests using high resolution X-ray computed tomography were used to study the microstructural failure mechanisms in aluminium foam struts. The results were further proven by additional ex situ tensile experiments on struts, which were analysed by low resolution X-ray computed tomography prior to tensile testing to allow for more specimens and hence for better statistics. Micro-porosity and primary inclusions were found to be the main reason for differences in the micromechanical properties of individual aluminium foam struts.

Analysis of the Applicability of Effective Thermophysical Properties to Composite Phase Change Materials

Coarse form-stable phase change materials (FS-PCMs) can tailor the properties of pure PCMs. This is often attained by the presence of high-melting, high-thermal conductivity metallic phase which enhances the thermal energy storage/release. The evaluation of the thermal response of these composite materials in unsteady conditions, is not an easy task, and simplifications introduced to deal with them must be carefully considered. A set of FS-PCMs of prismatic geometry with polymeric wax as PCM and an Al foam with various pore sizes, modelled as BCC lattice has been considered in this paper. The thermal response under a set of boundary conditions with constant heat flux at the bottom surface, all other being adiabatic, was investigated both by direct simulations approach modelling the two phases and the ‘1-temperature model’, which considers the material as homogeneous and characterized by a proper set of effective properties. The ‘1-temperature model’ is able to closely reproduce the whole the local thermal history only within certain validity ranges, even if it can well reproduce the ‘average’ energy storage due to the transformation of the PCM phase.

Bending residual strength of damaged Al foam sandwiches through UT and IRT analyses

In the present work, the effect of low-speed impact on the static residual strength of aluminum foam sandwiches having GFRP skins has been evaluated. Two different configurations have been considered, which differs both for thickness and layup used for the manufacturing of GFRP skins. The detection and the quantification of the damage induced by impact have exploited the potentiality of pulsed thermography and phased array ultrasonic techniques, which gives the possibility to provide synergistic and complementary information. Mechanical strength has been evaluated through three-point bending tests carried out on undamaged and damaged specimens. Static tests allowed also evaluating the failure mode of panels and the changes induced by the presence of a low-speed impact zone.

Microstructures, Aging Behavior and Thermal Expansion of 7075 Al–Silica Particle Waste Composite Foams Produced with Recycled Aluminum Cans

7075 Al–SiO2 composite foams were prepared by direct melt foaming method. The microstructures of the composite foams showed uniformly distributed particles in the composite foams. Aging studies showed that the hardness values of as-quenched composite foams were higher than that of 7075 Al foam and all the foam samples revealed two clear aging peaks. The aging behavior of the 7075 Al foam was different in kinetic and magnitude from of the 7075 Al–SiO2 composites, where the levels of peak hardness attained in the two peaks of 7075 Al foam were higher than those of the composite foams. Also, the aging times to attain the two peaks of the 7075 Al foam were shorter than those of the composite foams. DTA analyses indicated that the precipitation sequences of the composite foams were similar to that of the 7075 Al foam. However, the precipitation peaks of the composite foams were shifted to higher temperatures and the sizes of the hardening precipitate formation peaks in the composite foams were decreased, indicating that the formation of hardening precipitate zones was suppressed by the incorporation of the SiO2 particles or increasing the content of the foaming agent. The CTE of the 7075 Al foam was higher than that of the 7075 Al–15 vol % SiO2 composite foam.

Viscoelastic and high strain rate response of anisotropic graphene-polymer nanocomposites fabricated with stereolithographic 3D printing

The viscoelastic and high strain rate response of stereolithographically 3D printed graphene - PMMA nanocomposites was investigated using dynamic mechanical analysis (DMA) and the Split-Hopkinson pressure bar. The obtained experimental data were compared with the quantitative predictions of a simple viscoelastic micromechanical model. Our results confirmed that property anisotropy of the graphene nanocomposites arose from the alignment of graphene platelets along the printing axis within the polymer matrix. If a load is applied along this axis, the nanocomposite will adopt an isostrain (Voigt) geometry, exhibiting large dynamic modulus and strength values. These properties were found to improve with increasing graphene concentrations, up to 0.05 wt%, and post-print bake temperatures, up to 120 °C. Supporting evidence from differential scanning calorimetry and DMA temperature sweep test indicates that this is due to good interfacial bonding between the graphene and polymer, which allowed for efficient load transfer, and that a post-print heat treatment can increase the degree of cure in the polymer. Similar trends were observed for complex lattices fabricated using the same method. Comparing the dynamic mechanical properties of the graphene nanocomposites against that of other lightweight engineering materials, it was found that the nanocomposites exhibited specific strengths that were higher than most Al alloys and comparable to the best literature values reported for graphene – polymer and carbon nanotube – polymer composites. The additively manufactured graphene nanocomposite lattices also showed better energy absorption capabilities than balsa wood, syntactic ceramic foams and Al foams on a per unit weight basis. These results are remarkable considering that the amount of graphene added (≤ 0.10 wt%) was an order of magnitude lower than that usually employed in other studies.

High-rate and high sulfur-loaded lithium-sulfur batteries with a polypyrrole-coated sulfur cathode on a 3D aluminum foam current collector

In this study, the high-rate performance of high sulfur-loaded cathodes have been demonstrated using a novel battery that comprises of a 3 dimensional aluminum foam (current collector), sulfur (active material), acetylene black (conductive additive), and polypyrrole (PPy) coating. Consequently, a stacked laminated cell was prepared, which comprised of two 70 × 70 mm2 PPy-sulfur/ketjen black sheets (sulfur-loading = 4.3 mg/cm2), 1 M lithium bis-(trifluoromethylsulfonyl)imide (LiTFSI) with dimethoxyethane (DME) and 1,3-dioxolane (DOL), (DME/DOL = 1/1 vol%), and three Li foils as the cathodes, electrolyte, and anodes, respectively. The 1 M LiTFSI DME/DOL electrolyte, which is suitable for high rate, is applicable because the PPy coating suppresses dissolution of polysulfide into the electrolyte. The discharge capacities were 462 mAh (1075 mAh/g sulfur) at 0.4C (267 mA) and 251 mAh (583 mAh/g-sulfur) at 3.8C (2670 mA). An enhanced conductive path was formed in the cathode by the 3D Al foam and AB, which considerably improved the high-rate performance. This demonstration is particularly significant from the viewpoint of commercializing the high-power output and high-energy–density Li-S batteries for industrial applications such as small mobile device and drone power source.

Laminated Cell Properties of Lithium Sulfur Battery Using Polypyrrole Modified High Sulfur Loading Cathode with Comparing Al Foil and 3D Foam Current Collectors

In order to solve the problem of polysulfide dissolution into the electrolyte on sulfur-based cathodes, we have proposed a novel method to coat a sulfur cathode with Li+ permselective polypyrrole (PPy) by oxidative electropolymerization. The PPy coated S/KB (PPy-S/KB) cathode demonstrated relatively high specific capacity for 300 cycles stably with coulomb efficiency more than 97% in a coin cell [PPy-S/KB(S loading = 0.5 mg cm2) // 1.0 M LiTFSI DME/DOL (1:1 vol.) // Li] [1,2]. However, to increase energy density further, it is essential to increase sulfur-loading in the cathode. As increasing of sulfur-loading, lower PPy resistance is required to respond high current density.In this study, sulfur cathodes with sulfur-loadings of 1 mg cm-2, 2.5 mg cm-2, 5 mg cm-2 with Al foil current collectors and sulfur-loadings of 5 mg cm-2, 10 mg cm-2 and 15 mg cm-2 with 3D Al foam current collectors were prepared. The S/KB composite slurry was prepared by mixing 96.5 wt. of the S/KB composite (S/KB=6/4 by wt.) and 3.5 wt. of CMC/SBR. The slurry was applied to Al foil or Al foam to have an arbitrary sulfur-loading. PPy was coated on the cathode by using lithium-glyme equimolar ratio complex (LiTFSI: triglyme (1: 1, mol) + LiTFSI: monoglyme (1: 2, mol) (1: 1, vol.)) as a polymerization bath and the same technique as in our previous report [1,2]. Stacked laminated cells consist of 20*20 mm2 S/KB cathode with/without PPy, 1M LiTFSI DME/DOL (1/1 vol.) as electrolyte and Li foil as anode were prepared (E/S was 5-35).Fig. 1 shows the relationship between the sulfur-loading and the discharge capacity density using Al foil or 3D Al foam. Although the discharge capacity density decreased when sulfur-loading was increased to 5 mg cm-2 with Al foil (E/S=7), a high discharge capacity density of 1190 mAh/g-sulfur was maintained even when S loading was increased to 15 mg cm-2 with 3D Al foam (E/S=5). In the case of Al foil current collector, the discharge capacity density decreased with an increase in the sulfur loading would be caused by decreased sulfur utilization with longer paths of Li ions. On the other hand, since 3D Al foam has a better path for Li ions and electrons than a normal coated electrode, a high sulfur utilization was maintained even with a high sulfur-loading. Fig. 2 shows a charge/discharge curve of sulfur-loading of 10 mg cm2 with PPy coating at 0.01 C. Overcharging due to polysulfide dissolution was not observed even in DME/DOL electrolyte by the PPy coating, and a high discharge capacity of 1248 mAh/g-sulfur was achieved (E/S=9), while without PPy coationg, polysulfide dissolution and less discharge capacity were observed. It was confirmed that the PPy coating suppressed the dissolution of sulfur into the electrolyte and increased the utilization of sulfur, thereby slightly increasing the discharge capacity as compared to that without PPy coating. We will report the rate characteristics and cycle characteristics of laminated cells with various sulfur-loadings, PPy film thicknesses, and conductive additives.

300Wh/Kg Class High-Energy Li-S Laminated Batteries Using High-Sulfur Loading Cathode on 3D Mesh Structured Aluminum Foam

[Introduction] In recent years, lithium-sulfur batteries can be expected as a promising candidate for next generation energy storage devices because of its high energy density. Generally, the cathode is fabricated by infiltration of sulfur into Ketjen black (KB) with aluminum foil current collector. However, it is not easy to increase the sulfur loading amounts and maintain the rate performances for electric vehicles which are required more than 3C rate, due to the lack of Li ion and electron paths. To solve this issue, we have reported the new type sulfur electrode prepared using 3D mesh structured Al foam, resulting in increased sulfur loading amounts which are 5 - 10 times or more compared to conventional sulfur cathode fabricated using 2D structured aluminum foil current collector [1], [2], [3]. In this study, we optimized the fabrication method of sulfur cathode for high sulfur loading on 3D mesh structured Al foam for a high energy density Li-S laminated battery.[Experimental] S/KB composite was obtained by mixing sulfur and KB with weight ratio of 6:4, by heating at 155 °C for 12 h under N2 atmosphere. Afterward obtained S/KB composite was dispersed by ball milling for 12h. S/KB cathode was fabricated by S/KB slurry (weight ratio of S/KB (6/4) : Binder = 96.5 : 3.5). The high sulfur loaded cathode (15.3 mg/cm2) was obtained using 3D mesh structured Al foam (1mm in thickness). To assemble the cell, the cathode was pressed (0.4 mm in thickness). 5 Ah class laminated cell (70 x 70 mm) was prepared using the S/KB cathodes (6 stacked), Li anodes (7 stacked), separators (7 stacked), and the electrolyte (LiTFSI: G1(monoglyme)/G3(triglyme): HFE(hydrofluoroether)= 1: 1: 4 (molar ratio)). Electrochemical performances were tested with voltage range between 1.0 V – 3.3 V after activation process.In addition, coin cells were prepared using above materials to evaluate the ionic conductivity by DC polarization method.[Results and Discussion] To design a high energy density cell such as laminated type cell, it is important to optimize the ratio between using amount of electrolyte and solid materials in electrode. Fig. 1 shows the relationship between the calculated E/S ratio (electrolyte amount (µℓ)/sulfur loading amounts (mg)), porosity filling rate of electrolyte (%), and the gravimetric energy density (Wh/kg). It was possible to reduce the electrolyte filling rate to 100% which is corresponding to E/S = 1.7, achieving the 340 Wh/kg theoretically. It is important to secure an ion path in whole electrode to optimize utilization of E/S ratio. In our previous report, we fabricated the S/KB cathode using 3D mesh structured Al foam regardless of the porosity, implying that it has bad ion conductivity. To improve the ion conductivity of S/KB cathode which has high sulfur loading amounts, we prepared a cathode that loaded S/KB very uniformly and retained the high porosity of the 3D mesh structured Al foam.As a result, we confirmed that the S/KB cathode/3D Al mesh which has good porosity shows improved ionic conductivity than control sample fabricated by conventional method.Fig. 2 shows the charge/discharge curve of Li-S laminated battery prepared by a new method with optimized E/S ratio of 2.3 (conventional method requires high E/S ratio of 3.6 or more). High capacity of 5.2 Ah, and energy density (301 Wh/kg and 435 Wh/ℓ, excluding laminate and tab) was achieved with high sulfur loaded laminated cell (sulfur loading amount of 15.4 mg/cm2, 1156 mAh/g-S).

Fabrication of high-porosity open-cell aluminum foam via high-temperature deformation of CaCl2 space-holders

In this study, we found that porous CaCl2 granules can be easily deformed under certain pressure and temperature conditions. Based on this finding, a new infiltration process that employs CaCl2 granules as space-holders was developed to prepare aluminum (Al) foam with high porosity. In this process, porous CaCl2 granule preforms were first subjected to hot-pressing deformation, which provided two benefits: 1) the density of the preform was increased, thereby increasing the porosity of the final prepared open-cell Al foam (over 80%) and 2) the contact surface of the neighboring CaCl2 granules was increased. After hot-pressing, the sizes of the dissolution and removal channels of CaCl2 increased. Consequently, the space-holder particles could be completely removed, which is just the most difficult bottleneck problem in the traditional infiltration process applying salt particles as space-holders in which the salt removal is not enough and the porosity is lower than 65%.

Effect of Heat Treatment on the Microstructure, Compressive Property, and Energy Absorption Response of the Al–Mg–Si Alloy Foams

Due to the various structural and functional characteristics of lightweight, energy absorption, and sound/heat insulation, etc., metallic foam materials have been increasingly developed in recent years, especially for the most widely used alloy foams. Herein, the Al–Mg–Si alloy foams with a porosity of 60% are prepared by a powder metallurgy technology in which the carbamide is used as the space holder material. The effect of solution treatment on the microstructure, compressive property, and energy absorption response of the as‐prepared Al–Mg–Si alloy foams is studied. The results show that when the solution temperature (T) is increased from 25 to 555 °C, the room temperature compressive strength of the Al–Mg–Si alloy foams increases from 11.2 to 26.7 MPa, but decreases when T is more than 555 °C. The strengthening mechanisms of solution treatment mainly lie in that the dislocation movement between the grain boundaries can be effectively blocked by the precipitated phases. As to the high‐temperature compressive property of the Al–Mg–Si alloy foams that are solution treated at 555 °C, the compressive strength is found to decrease from 28.7 to 12.3 MPa when the compression temperature is elevated up to 250 °C. Correspondingly, the energy absorption decreases from 17.02 to 9.14 MJ m−3. Compared to the pure Al foam, the high‐temperature softening effect for the Al–Mg–Si alloy foams is more remarkable, which is due to the formation of microcracks in the alloy matrix. The current research provides a cost‐effective and easy‐handle approach to enhance the compressive strength and energy absorption ability of the metallic foam materials.

New Insight into Predicting the Compression Flow Behavior of Metal Foam

A novel constitutive model for predicting the compression behaviors of closed-cell Al foam was proposed. In contrast to existing models, it gives a nonlinear stress-strain response, which is in accordance with the hardening behaviors of foam. The new constitutive relation is derived based on the mean-field approximation and isothermal reversible compression approximation of ideal gas. Except for the overestimated densification behavior, good agreement is observed between the stress-strain curves and the predictions of the model.

Role of foam anisotropy used in the phase-change composite material for the hybrid thermal management system of lithium-ion battery

Abstract Hybrid kind of thermal management systems (TMSs) is emerging as a powerful, reliable, and efficient cooling device for controlling the temperature of Li-ion cells in the battery pack of an electric vehicle. Adding metal foams to a pure PCM (which results in a composite material) is a suitable way for the enhancement of the passive part's performance. In this paper, a novel hybrid TMS that uses cooling water channels (as the active part of TMS) and a composite of paraffin PCM and Al foam surrounding each lithium 18650 cylindrical cell (as the passive part of TMS) is introduced, and the role of foam anisotropy (according to the three main axial, radial, and tangential directions in the cylindrical coordinate system) on its performance is investigated, for the first time. The results of this study show that the hybrid operating mode of TMS consists of two periods: PCM recovery and cell cooling. In the first period, most of the water's cooling capability is paid for the solidification of PCM through a progressive process from top to bottom; and hence, less cell cooling effect is achievable. The results demonstrate that only increasing the tangential conductivity has a notable positive effect on the average cell temperature and the liquid fraction. Additionally, only increasing the axial thermal conductivity has a positive effect on the controlling of the maximum temperature difference through the cell.

High energy and high power density supercapacitor with 3D Al foam-based thick graphene electrode: Fabrication and simulation

Thick electrode was promising to increase the energy density in device (battery or supercapacitor) scale, but always suffered the ion polarization upon high rate discharge. We reported the use of 3D Al foam (current collector) to host graphene (with high surface area but very low packing density) to fabricate 450 ​μm thick electrode with mass loading of 10–15 ​mg ​cm−2. The space confinement effect of Al wires on graphene at any regions offered sufficient ordered diffusion channel of liquids, alleviating the ion polarization significantly, compared to the same thick graphene sheet pasted on 2D Al foil by simulation with COMSOL software. The 100 ​F pouch supercapacitor with ionic liquids at 4 ​V exhibited low contact resistance, high specific capacitance in a wide range of current densities, and simultaneously the volumetric energy density of 18 ​Wh L−1 and the power density of 5 ​kW ​kg−1, far better than those of current commercial device.

Deformation Behavior and Crashworthiness of Functionally Graded Metallic Foam-Filled Tubes Under Drop-Weight Impact Testing

This article investigates the low-velocity impact behavior and crashworthiness of metallic foams and functionally graded foam-filled tubes (FGFTs). Closed cell Zn, Al, and A356 alloy foams fabricated by the direct foaming method are used as axial grading fillers for the manufacture of single-, double-, triple-, and quad-layer structures. The microstructural examinations are implemented by an optical microscope and a field emission scanning electron microscope. The drop-weight impact testing is performed on the metallic foams and FGFTs with a free fall velocity of 5.42 m/s and energy of 294.3 J. The influence of material, density, number, and arrangement of foam layers on the deformation behavior and specific energy absorption (SEA) is studied. The results indicate the multiple crushing response and stepwise increment of stress through distinct plateau regions in the FGFTs. The A356 foam with low density and great inherent strength provides the highest SEA, whereas high density and brittle matrix of the Zn foam deteriorate the SEA of FGFTs. The maximum SEA of 261 J/(g cm−3) is achieved in the double-layer A356-Al foam-filled tube. The best crashworthiness is fulfilled in multilayer A356-Al structures owing to a combination of high SEA and low peak crushing strength (σpeak).