Al Foam Research Articles

Effectiveness of a PCM-based heat sink with partially filled metal foam for thermal management of electronics

Electronics often experience overheating, which occurs when insufficient or improper cooling causes temperatures to rise quickly, potentially leading to component failure. Recently, a passive technique utilizing phase change material (PCM)-based heat sinks is suitable for modern electronic cooling. However, due to its low thermal conductivity, Aluminum (Al) foam as a thermal conductivity enhancer (TCE) is used. In this study, a partial filling approach is employed, involving a heat sink designed to cool a protruding electronic component (EC) attached to a metal fin. The enthalpy-porosity method and the thermal equilibrium model are applied. Results show that the efficiency of the heat sink is improved by increasing the filling ratio of the Al foam, thereby reducing the EC temperature by 15.85 °C, shortness the melting time by more than 1000 s, and the overall effective conductivity enhanced by 25 times compared to the case without Al foam. In addition, the optimal partial filling ratio is determined to be 2/3, due to the considerable savings of 33.33 % in material cost and overall heat sink weight. The findings suggest that partial filling is a strategy that can be employed to achieve a more comprehensive performance in thermal management using PCM-based heat sinks.

The wettability of pure liquid aluminum on oxide substrates

AbstractOxide particles are considered to be one of the reasons for the stability of cellular porous Al foam. Thus, the contact angle (ө) of molten pure aluminum on oxide substrates, including Al2O3, CaO·2Al2O3 (CA2), CaO·6Al2O3 (CA6), mullite (3Al2O3·2SiO2), and SiO2 was measured in a vacuum heating microscope at a temperature of 950°C to determine the value of wettability of molten aluminum on various oxides. Thereafter, the measured contact angles followed the tendency as mullite (155°) > CA6 (152°) > MgAl2O4 (151°) > Al2O3 (149°) > SiO2 (124°) > CA2 (100°). Furthermore, the cross‐sectional area between molten aluminum and substrates was thoroughly analyzed, and the reaction products, such as the Al2O3 layer at the interface, have been detected. Thermo‐Calc, with the combination of available databases, was used to perform thermodynamic simulations and to discuss and predict possible reactions under the current experimental conditions.

Li-Ion Batteries with a Binder-Free Cathode of Carbon Nanotubes-LiFePO4-Al Foam

With the increasing demand for Li resources worldwide, the easy recycling of Li-ion batteries materials becomes essential. We report a binder-free cathode consisting of carbon nanotubes (CNTs) and LiFePO4 (LFP) nanoparticles embedded in a 3D Al network. The electrode stability depends on the CNT ratio, where 3% CNT-wrapping LFPs provide a stable structure free of detachment from Al foam, as observed on Al foil. The binder-free cathode sheet exhibited excellent performance for high-rate discharge and long-term cycle life. Materials on the cathode can be easily detached with ultrasonic treatment when immersed in organic solvent, which is advantageous for a green and high-efficiency strategy of recycling all valuable materials compared to the binder-used electrode.

Investigation on the Structural and Mechanical Properties of Al Foam Manufactured by Spark Plasma Sintering and Compression Molding Methods

Investigation on the Structural and Mechanical Properties of Al Foam Manufactured by Spark Plasma Sintering and Compression Molding Methods

Preparation of cylindrical Chitosan/β-Cyclodextrin/MIL-68(Al) foam column for solid-phase extraction of sulfonamides in water, urine, and milk

This study describes the preparation of a cylindrical polymer foam column termed Chitosan/β-Cyclodextrin/MIL-68(Al) (CS/β-CD/MIL-68(Al)). An ice template-freeze drying technique was employed to prepare the CS/β-CD/MIL-68(Al) foam column by embedding MIL-68(Al) in a polymer matrix comprising cross-linked chitosan (CS) and β-cyclodextrin (β-CD). The cylindrical CS/β-CD/MIL-68(Al) foam was subsequently inserted into a syringe to develop a solid phase extraction (SPE) device. Without the requirement for an external force, the sample solution passed easily through the SPE column thanks to the porous structure of the CS/β-CD/MIL-68(Al) foam column. Moreover, the CS/β-CD/MIL-68(Al) foam column was thought to be a superior absorbent for SPE since it included the adsorptive benefits of CS, β-CD, and MIL-68(Al). The SPE was utilized in conjunction with high-performance liquid chromatography to analyze six sulfonamides found in milk, urine, and water. With matrix effects ranging from 80.49 % to 104.9 % with RSD values of 0.4–14.0 %, the method showed high recoveries ranging from 80.6 to 107.4 % for water samples, 93.4–105.2 % for urine, and 87.4–100.9 % for milk. It also demonstrated good linearity in the range of 10–258 ng·mL-1 with the limits of detection ranging from 1.88 to 2.58 ng·mL-1. The cylindrical CS/β-CD/MIL-68(Al) foam column prepared in this work offered several advantages, including its simple fabrication, excellent water stability, absence of pollutants, biodegradability, and reusability. It is particularly well-suited for SPE. Furthermore, the developed SPE method, employing CS/β-CD/MIL-68(Al) foam column, is straightforward and precise, and its benefits, including affordability, ease of preparation, lack of specialized equipment, and solvent economy, underline its broad applicability for the pretreatment of aqueous samples.

Pressure propagation mechanism of open-cell aluminium foam within a pipe under hypervelocity impact

Low-density open-cell aluminium (Al) foam exhibits a different deformation mode under hypervelocity impacts compared to being subjected to medium-low speed and quasi-static compression. In this case, material flows between cells in the form of metal jets and propagates forward. This paper establishes the open-cell Al foam model based on Voronoi tessellation. Using numerical methods, one-dimensional hypervelocity constant velocity impact experiments of 1–6 km/s inside a closed pipe are conducted on Al foam with different internal structure parameters (average cell diameter: 2–3.5 mm; ligament width: 0.251–1 mm). Propagation mechanism of pressure waves in foams and the key factors affecting the propagation velocity are investigated. Three zones are divided according to the condition of jet distribution along the impact direction: unaffected zone, jet influence zone, and particle accumulation zone. The variation of the length of different zones with impact velocity is discussed: higher velocities result in longer jet influence zones but shorter particle accumulation zones. Meanwhile, length of zones is closely related to the width of Al foam ligament and cell pore diameter: the larger the diameter of cell pores and the smaller the width of ligaments, the longer the length of the jet influence zone. Time dependence is exhibited in the length of jet influence zone for the large cell pore diameter specimens(≥0.03 cm). Particle pressures are extracted using the one-dimensional averaging method, which propagates forward significantly lower than in dense materials. Dominant factors affecting the pressure wave propagation of open-cell Al foam, i.e., the internal unloading space, are obtained by combining two-dimensional hypervelocity impact simulation experiments with different boundary conditions. A strong correlation between metal jet distribution and particle pressure propagation is observed.

Analysis of the Meso‐Mechanical Deformation Behavior of Al Foams and Ni/Al Hybrid Foams Using Time‐Lapse Micro‐Computed Tomography Measurements and 3D Optical Flow

Metal foams are an interesting class of bio‐inspired materials for lightweight construction and energy absorption. Commonly, aluminum (Al) foams are used. However, the mechanical properties have been improved by coating pure Al foams with a nanocrystalline nickel (Ni) coating resulting in Ni/Al hybrid foams. Herein, the meso‐mechanical deformation mechanisms in Al foams and the changes in the mechanisms in Ni/Al hybrid foams are studied using time‐lapse micro‐computed tomography measurements in comparison between numerical modeling using voxel finite element models and evaluation of displacement fields using 3D optical flow. This gives never‐seen insights into the highly localized 3D deformation mechanisms within the entire volume of the foams and not only on the surfaces as given by conventional digital image correlation methods. Displacements calculated by the 3D optical flow algorithm demonstrate its possibility to reveal a significant concentration of plastic deformation, particularly evident when deformation occurs within a distinct, slightly inclined band in the central region. Common numerical simulations using standard plasticity models do not accurately capture this localized deformation, underscoring the need to integrate damage and softening models into the simulation.

High temperature and mesostructure effect on aluminum foam compression responses

Closed-cell Al foam is widely utilized in high-temperature environments due to its high strength-to-weight ratio and considerable energy absorption capability. However, the mechanical properties depend on temperature and mesostructure. In this paper, the compressive responses of Al foams at temperatures ranging from 25 ℃ to 600 ℃ are investigated by experimental tests and two types of high-fidelity finite element simulations, including the X-ray computed tomography (CT) reconstructed model and Voronoi model. A deep learning approach is employed to remove tiny pores of CT slices, simplifying geometry features and improving the computational efficiency of the CT reconstructed model. A novel improved Voronoi model with high accuracy is proposed, considering the nonuniform distribution of cell wall thickness in actual closed-cell Al foams. A temperature-depend macro constitutive model is established and validated through the experimental and numerical results. This work reveals the influence mechanism of temperature and mesostructure on the mechanical responses of Al foams, and exhibits significant potential for the application of Al foams in high temperature environment.

Al and A356 Alloy Foam Castings Modified with Low Concentrations of Nano-Sized Particles: Structural Study and Compressive Strength Tests

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.

Effect of Calcium Addition on the Aluminum Alloy A201 Foam

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.

Preparation and Compression Behavior of High Porosity, Microporous Open-Cell Al Foam Using Supergravity Infiltration Method.

By employing a method that combines a NaCl compacting template and supergravity infiltration, open-cell aluminum (Al) foam with varying porosities was prepared. The Al foam fabricated has a pore size of 400 µm and porosity ranging from 0.72 to 0.88. The experimental results indicate that, with an increase in compaction pressure during the NaCl compacting process, the porosity of the foam Al increases and the struts become finer. As the gravity coefficient increases, the density and integrity of the foam Al also increase. Due to the effectiveness of supergravity in overcoming the infiltration resistance between the NaCl preform and molten Al, the supergravity infiltration method holds promise as a practical new technique for fabricating high-porosity open-cell Al foam.

Strengthening mechanism of porous aluminum foam by micro-arc discharge

Even with their wide usage, porous metal foams (PMFs) are limited by their poor mechanical strength owing to their inherent porous structures. This study employed a combination of vacuum sintering and microarc oxidation (MAO) to enhance the mechanical properties and corrosion resistance of Al foam while maintaining its low density. Tribological tests and microstructural analysis demonstrated the stable friction coefficients and excellent wear resistance of the MAO-treated PMFs. Further, the microarc discharge strengthening mechanism was explained, and a physical model was proposed. Finally, this approach produced wear-resistant porous Al foams, offering a promising solution to overcome the limitations of PMFs.

Experimental investigation of the melting performance of a low porosity metal foam/PCM composite heat sink in various configurations

Thermal management is crucial in achieving optimum performance of electronics, reliability, and life. To provide a higher heat dissipation rate over the electronics, metal foam/phase change material (PCM) composites with relatively low porosity have been experimented with in previous efforts. This study aimed to test the thermal performance of metal foam/PCM composite heat sink configurations under a constant heat load. Regular open-cell Al and Al6082-based metallic foams with relatively low-porosity values of 25% to 78%, and pore sizes of 8, 10, and 12 mm were manufactured by the casting method using spherical NaCl space holders. The n-eicosane and the Rubitherm RT-42 were used as PCM. The thermal performance of heat sink configurations was presented through transient temperature history, the solid-liquid interface progress, the safe operating time, and thermal resistance. The results showed that the relatively low-porosity foam configurations with various pore sizes have considerable potential for electronics cooling. The safe operating time of the Al foam/n-eicosane composite heat sink with a porosity of 72% and pore size of 8 mm was obtained as high as 1328 s (22.13 min) with about 380% improvement compared to the heat sink without foam. Al foam and n-eicosane perform better than Al6082 and RT-42, respectively. It is noted that lower thermal resistance and higher safe operating times are achieved for heat sink configurations with higher porosity and smaller pore sizes.

Electrogeneration of H2O2 through carbon-based ink on Al foam for electro-Fenton treatment of micropollutants in water

In the present work, the catalytic efficiency of inks based on different carbon materials, namely activated carbon (AC), carbon graphite (CG), and carbon black (CB) was investigated for the oxygen reduction reaction (ORR). Additionally, we explored the feasibility of using this ink as a coating for an Aluminum foam (Alfoam) cathode in an electrochemical cell. The goal was to utilize this setup to produce hydrogen peroxide (H2O2) in the electro-Fenton (EF) process, targeting for treating water contaminated with contaminants of emerging concern (CECs).Among the materials investigated, all of them exhibited the ability to facilitate the ORR. However, AC proved to be the most suitable material due to its optimal balance between physical and electrocatalytic properties, thus enabling the formation of H2O2. When the different inks were applied to the surface of aluminum foam, it was observed that only the ink based on carbon black CB achieved a homogeneous distribution with the same ink quantity. As a result, it was observed that the Alfoam/CB electrode exhibited the highest H2O2 generation capacity, producing 45.6 mg L-1, followed by electro-generation of 5.1 mg L-1 using Alfoam/AC and 11 mg L-1 using Alfoam/CG. Furthermore, the application of Alfoam/CB in EF processes allowed for the almost complete degradation of 15 emerging contaminants of concern (CECs) present in secondary effluent. The innovative outcome of this study positions the developed technology as a promising and effective alternative for the treatment of water contaminated with CECs, demonstrating significant potential for industrial-scale application.

Effect of tooltip profile and tilt angle on Al8090-TiH2/Al2O3 foam and its mechanical characterization

Metal foams are used for industrial purposes because of their lightweight structure, high specific modulus of elasticity, and excellent energy-absorbing capacity. Various techniques have been used for the development of metal foam. In the present study, Al8090 foam is fabricated by the uniform mixing of TiH2/Al2O3 particles with the help of the stirring action of the tool probe. The groove cutting method is used to prepare the Al metal matrix and friction stir processing is performed over the grooves for even dispersion of the blowing powder to produce the precursor of the localized aluminium (Al) foam. Special purpose inclined fixtures with different angles are fabricated to produce tilt on the three-axis vertical machining centre. Three different tip profiles, namely plane cylindrical, threaded cylindrical and square are selected for processing along with the fixture plate angle set at three levels of 1°, 1.5° and 2.5°. Tool rotational and traversing speed rate is kept constant and its influence has been assessed on the foam's porosity, hardness and compressive strength. Scanning electron microscopy and energy-dispersive X-ray spectroscopy tests have also been performed to analyse the foam's morphology and found that the square tip pin with 1.5° fixture plate angle has the best mechanical properties.

Preparation of a Multifunctional and Multipurpose Chitosan/Cyclodextrin/MIL-68(Al) Foam Column and Examining Its Adsorption Properties for Anionic and Cationic Dyes and Sulfonamides.

A multifunctional cylindrical hybrid foam column, referred to as the chitosan/cyclodextrin/MIL-68(Al) (CS/CD/MIL-68(Al)) foam column, was prepared for the first time. The prepared foam column could be used for the adsorption/removal of hydrophilic and hydrophobic contaminants by different forms. Here, it was placed in hydrophilic dye solutions to investigate the adsorption behavior of methylene blue and trypan blue. The adsorption process followed the pseudo-second-order kinetic model with R2 ranging from 0.9983 to 0.9998 for methylene blue and from 0.9993 to 1.0000 for trypan blue, and the adsorption process was consistent with the Langmuir isothermal model with R2 greater than 0.96. The RL values for methylene blue and trypan blue were 0.8871 and 0.5366, respectively, which were present between 0 and 1, indicating that the adsorption behaviors of the two dyes onto the CS/CD/MIL-68(Al) foam column were favorable. The maximum adsorption capacities (Qm) of methylene blue and trypan blue were 60.61 and 454.55 mg/g at 298 K, respectively. Also, the CS/CD/MIL-68(Al) foam column was spun into a syringe and used to adsorb trace hydrophobic sulfonamides from water in the form of filtration. The porous structure impeded the need for any external force and equipment, allowing the water sample to pass through the foam column smoothly. The conditions of the CS/CD/MIL-68(Al) foam column were optimized. The adsorption was carried out under the condition of pH = 4, the amount of the adsorbent was two foam columns, and no salt was added. It was found that the removal rate of the CS/CD/MIL-68(Al) foam column for six sulfonamides was 100%, and it could be reused at least five times. Therefore, this CS/CD/MIL-68(Al) foam column had a simple preparation method, offered a flexible and diverse form of use, was nonpolluting, biodegradable, and reusable, and could have a wider application in the field of environmental pollutant removal and adsorption.

Blast mitigation analysis of novel designed sandwich structures using novel approaches

Sandwich panels have excellent explosion and impact resistance capabilities. Thus, by combining square and circular honeycombs in various ways, innovative blast-proof steel sandwich panels were developed in this numerical study. A series of dynamic explicit analyses were performed at 1 to 3 kg of TNT blasts for a constant stand-off distance (SoD) of 100 mm to identify an efficiently designed sandwich panel. Further work was carried out to achieve successive improvements in the efficiently designed steel sandwich panel’s blast mitigation performance by applying different patterns of Al foam filling and fiber metal laminate (FML) facing. The ability to absorb energy, core crushing, and face deflection under blast loadings were utilized to examine the novel designed sandwich panels’ blast resistance. The Johnson-Cook (J-C) model and Hashin’s and Puck-Schurmann’s criteria were applied to accurately determine the damage behavior of steel and composite parts of the structures, respectively. The obtained results showed that the combination of square and circular honeycomb cores in a sandwich construction significantly increased blast resistance for both layered and unlayered honeycomb cases compared to the standard square honeycomb core employed in the sandwich structure (S-SS). A further enhancement in blast resistance was seen when the bottom honeycomb core of layered honeycomb was filled with foam. The further employment of the FML top face highly advanced the blast performance of the novel designed sandwich panel, and it can be applied to various parts of armor vehicles to save soldiers’ lives from air-blasts.

Analyses of impact energy-absorbing performance of open- and closed-cell Al foams using modified split Hopkinson pressure bar

Al foams have been developed to meet increasing demands for effective reduction of impacts in military, automotive, civil-engineering, and aerospace applications. However, evaluating their energy-absorbing performance is very difficult, as most of the impacted energy is quickly dissipated as interior pores are rapidly closed. In this study, a split Hopkinson pressure bar (SHPB) was modified by utilizing the incident wave alone, using a deceleration-measuring module placed between the striker and incident bars to reliably evaluate the energy-absorbing performance of open- and closed-cell Al foams with different densities and porosities. The impact momentum (Ibar), which was regarded as the overall energy of the incident wave produced by the impact of the striker bar, and the maximum impact acceleration (amax), which indicated the largest change of impact velocity, were used as main evaluation parameters. The ratio of the reduced amount of amax in comparison with the amax of the none-specimen case, i.e., amax reduction ratio, was lowest in the open-cell low-density specimens and increased as the specimen thickness or density increased, i.e., in the order of the open-cell high-density, closed-cell low-density, and closed-cell high-density specimens. Thus, the thicker higher-density foam specimens worked more effectively for the better energy-absorbing performance. The present modified SHPB is outstanding for the energy-buffering concepts and mechanism-focused interpretations of the amax and Ibar data, since the quantitative energy-absorption analyses have hardly been conducted because of the energetic and mechanical complexities. It also provides an excellent idea to improve or develop various Al foams having high amax reduction ratios.

Research Progress on Mechanical Behavior of Closed-Cell Al Foams Influenced by Different TiH2 and SiC Additions and Correlation Porosity-Mechanical Properties

Closed-cell aluminium foams with different compositions have been manufactured starting from powders and also characterized from a morphological point of view and by means of compressive tests in order to determine mechanical properties. Circularity, equivalent diameter, and average porosity area of such foams have been calculated from the analysis of cross-sections as well specific energy absorption in compression tests. Samples with a higher amount of blowing agent (TiH2) have the highest energy absorption while samples with a higher amount of stabilizing agent (SiC) exhibit good foam properties overall (best compromise between morphology and energy absorption). The analysis of morphological properties, such as area, circularity, and equivalent diameter, can provide a better understanding of the foam’s structure and porosity––parameters which can be manipulated to enhance the foam’s properties for specific applications, both structural and functional.

English

Recently, there has been a high interest in using lightweight aluminum foams for automotive, railway and aerospace operations. Because of its high ductility and deformability, Aluminum foam is generally used for energy absorption for crashworthiness applications. To keep safe and avoid occupant injuries, it is necessary to absorb the kinetic energy generated during impact. Thus, to absorb high kinetic energy, the crash box material needs a special material microstructure, which is light in weight and can absorb further energy than the being one like CaCo3, CBC, or SiC. B4C etc. In particular, the analysis of energy absorption of aluminum foam in automotive for energy absorption applications is limited. The main objective of this exploration is to analyze and optimize the porosity size and voids percentage on impact energy absorption of aluminum foam using a numerical approach. For this purpose, first, fifteen CAD Al foam samples were developed by using Digimat multi-scale material modeling software. Second, cubic elements with circular bubble shape at 5, 10 and 15 void percentage and at 1.5 mm, 2 mm,2.5 mm, 3 mm and 3.5 mm bubble sizes were modeled. Finally, the numerical analysis of impact energy by using ANSYS workbench19.2 Explicit dynamics by applying initial low velocity was performed. The parameters were compared to each other to optimize the proper percentage composition and cell size for the best energy absorption applications. The effects of bubble shape, foaming agent and percentage composition on energy immersion were discussed. In this study, the analysis was fulfilled by determining and comparing the energy absorptions of all the models and, finally, comparing them with existing foaming agents.