Search

Critical size of droplet on metal fiber is an important parameter during the dehumidifying process, as it determines the drainage performance of metal foam heat exchangers. In the present study, the droplet shedding characteristics on metal fibers with various fiber diameters, surface wettability and inclined angles were investigated experimentally. The results show that, the critical size of droplet on metal fibers is increased by 69%-213% as the receding contact angle reduces from 132.8° to 17.2°, and it is increased by 93%-292% as the fiber diameter increases from 0.3 mm to 2.0 mm. As the inclined angle of metal fiber increases from 0° to 90°, the critical droplet size is decreased by 78%-86%. Based on the equilibrium of gravity and capillary force, a predictive correlation for the critical droplet size on metal fibers with different wettability and inclined angles was developed, and it agrees with 90% of the experimental data within a deviation of ±15%.

The magnetron sputtering has been used to prepare metal foam wicks for heat pipes by coating the surface of copper foam with zinc oxide (ZnO) nanoparticles. The main properties, including microscop...

This paper is a numerical study about the catalyst morphology CuO/ZnO/Al2O3 effects on the hydrogen production from methanol steam reforming, for proton exchange membrane fuel cells (PMEFC). The study is focused on the influences of the metal foam insert, catalyst layer segmentation, and metal foam as catalyst support on the reactor performance: hydrogen yield and methanol conversion. According to the carried simulations, it is found that these configurations improve the reformer performances compared to the continuous catalyst layer configuration. The insertion of metal foam increases the efficiency of up to 75.41% at 525 K. Also, at this reaction temperature, the segmentation of the catalyst layer in similar parts increases the reformer efficiency by 2.11%, 4.23%, 6.77%, and 8.6% for 2, 4, 8, and 16 identical parts, respectively. As well as, the metal foam as catalyst support is more efficient compared to the other configurations, the efficiency is equal to 64% at T = 495 k.

We investigate the nonlinear bending behavior of nanoporous metal foam plates within the framework of isogeometric analysis (IGA) and higher-order plate theory. The nonlocal strain gradient theory (NSGT) taking into account the length scale and nonlocal parameters has been adopted to establish a scale dependent model of metal foam nanoscale plates. Von Karman nonlinear strains are then used to take up the geometric nonlinearity. Different pore dispersions, namely uniform, symmetric and asymmetric, are confirmed. By using the principle of virtual work, nonlinear governing equations are derived and then solved by using an isogeometric analysis and iterative Newton-Raphson method. Influences of the length scale parameter, porosity distributions, nonlocal parameter and nanoporous coefficient on the nonlinear deflection of the plate are numerically experimented in detail. Some findings would play an important role for designing metal foam structures.

Cooling technology exploiting the endothermic reaction of fuel has been developed to prevent structural deformation in engines due to air friction and overheating during supersonic flight. Endothermic fuels are liquid hydrocarbon fuels that can absorb heat through endothermic reactions. The initial heat sink capacity of conventional pellet type catalysts for the endothermic reaction cannot be maintained, leading to more rapid deactivation due to coke formation. To maintain the heat sink performance of decomposition catalysts, HZSM-5 catalyst washcoated on metal foam(HZSM-5/metal foam) was used herein. The reactions were carried out in a batch reactor at 673 K at a pressure of 50 bar using methylcyclohexane (MCH) and n-dodecane as reactants. The total MCH conversion achieved with the pellets and HZSM-5/metal foam was same at 93 %. In the case of n-dodecane, the total conversion achieved with the HZSM-5/metal foam (91 %) was superior to that achieved with the pellets (69 %).

Poor thermal conductivity of phase change materials (PCMs) is the principal barrier to their widespread application. As such, numerous single or hybrid techniques have been proposed to lower the thermal resistance of PCMs. In the present paper, a hybrid approach, including the dispersing of nano-sized particles and embedding in a porous medium, was employed to augment the rate of heat transfer and melting process of the resulting nano-enhanced PCM (NePCM). Aluminum foam was used as the solid matrix, and phase-change heat transfer of a NePCM comprising n-octadecane as the phase change substance and nano-sized particles of mesoporous silica (MPSiO2) was studied. Previous experimental studies have shown that, although n-octadecane behaves as a Newtonian fluid, the mentioned NePCM behavior deviates from that of Newtonian fluids. Hence, the thermal and hydrodynamic behaviors of the non-Newtonian suspension of the NePCM in porous media were investigated numerically. Governing equations, including mass and momentum conservation for the liquid NePCM and energy equations for both solid and liquid phases, were solved using the Galerkin finite element method. The deformed mesh technique was employed to address the movement of the melting front. The finite element code was validated against several experimental and numerical works and was sufficiently accurate. Results showed that owing to the alteration of the rheological and thermophysical characteristics of the NePCM, increasing concentration of nanoparticles reduced the average Nusselt number and the normalized melt volume fraction (NMVF). It was also found that porosity played an important role in the phase-change rate. Although the steady-state condition was achieved faster in the case of lowest porosity, the maximum NMVF was achieved in the case of the highest porosity after Fourier number = 0.02.

Adsorption cooling and desalination (ACD) system powered by renewable energy has been considered as a promising solution to solve interconnected global problems such as freshwater scarcity, high-cost air conditioning, CO2 emission, and global warming. In this work, a new nanoporous silica was synthesized through a self-assembly process using a combination of ionic and non-ionic surfactants. The silica has shown unique pore structures, including high surface area and large pore volume, as well as ideal pore size distribution. The new silica was deposited (coated) over the ligaments of aluminum foam for use as a sorption bed. An uncoated aluminum foam packed with conventional silica RD (regular density) particles serves as a baseline sorption bed. The freshwater production rate and cooling power produced using the two sorbents were compared. Silica RD outperforms the new silica for cooling while the new silica is far better for desalination application. Insights for such results are provided.

The model equation method (MEM) is a new method to measure the porosity of porous materials. This paper demonstrates the application value of the MEM in the preparation of titanium foams from an experimental point of view. The results showed that the porosities calculated by the MEM were in the range of 0.533–0.701 with the spacer contents between 0.55 and -0.75. The measured values were highly consistent with those of the mass volume method, which indicates that the MEM was feasible to measure porosity. The correlation equation between porosity and spacer content has a very high prediction accuracy by a linear fitting. The elastic modulus and yield strength of titanium foams were 4.8–29 GPa and 10.2–101.1 MPa, respectively. The relative elastic modulus and relative yield strength were directly proportional to the n-th power of relative density through a nonlinear fitting. The mathematical correlations between relative mechanical properties and spacer content were established. This study not only proves that the new method of porosity measurement has an important application value, but also realizes the source control of mechanical properties of titanium foams.

The thermal performance of the latent heat thermal energy storage unit (LHTESU) can be effectively promoted by metal foam. In the present work, a new structure of metal foam with a two-dimensional porosity gradient (MFTDPG) is proposed to further accelerate the melting process inside the rectangular cavity. The MFTDPG is obtained by placing the metal foam with small porosity near the left wall and the bottom wall. With consideration of natural convection, the melting behavior under different parameters is numerically analyzed, including the direction of the porosity gradient, the temperature of the left wall, and the aspect ratio of the rectangular cavity. The results show that the structure of metal foam with vertical porosity gradient (MFVPG) and horizontal porosity gradient (MFHPG) can reduce the total melting time by 7.65% and 3.37% respectively. The MFTDPG can shorten the total melting time by 12.07% compared with the structure with uniform porosity. Furthermore, the MFTDPG can achieve the shortest melting time and the maximum thermal energy storage rate (TESR) with different wall temperatures and aspect ratios. For example, when the aspect ratio is 2.5, the total melting time of MFTDPG is reduced by 24.35%, and TESR is increased by 25.88%.

Thermal energy storage (TES) has been playing a crucial role in addressing the issue of solving the intermittent and random problems in solar energy utilization. The objective of this study is to squarely address and clarify the contribution of metal fin and foam to enhancing the phase change heat transfer by experiments. A novel hybrid fin-foam tube is proposed and its thermal performance is evaluated by experimentally comparing with other three competing structures including bare, fin, and metal foam tubes. A well-designed test rig is built and the energy storage features for the designed four TES tubes are analyzed by the complete melting time, melting front evolution, temperature variation and uniformity, and the temperature response rate. Results show that the fin-foam hybrid structure outperforms the other competing ones, demonstrating a reduction of 83.35% in complete melting time (compared with the bare tube). The transient temperature response is maximized by 529.1%. As for the single structure, both fins and metal foam can improve conductivity of phase change materials. The metal foam does a good favor to improve the uniformity of the temperature field inside the TES tube, but the fins weakened the uniformity. If the design target is temperature uniformity, adding metal foams other than fins can fulfil the task.

Open-cell aluminum foams with spherical cells have great potential application due to their reliable structural and functional performance. However, a problem of poor cell connectivity always arises during fabrication. Three precursor designs were explored to optimize the cell structure. The results showed that the lack of the treatment of the space holders caused poor cell connectivity and a lower porosity, which could be resolved by introducing alcohol as a binder or hot-pressing space holders in precursor designs. Nevertheless, a poor fluid of the granules in the former had a negative effect on porosity improvement, whereas the latter created a precursor with strong bonding between the granules with good flow characteristics and led to a significant improvement in cell connectivity and porosity. This work could provide an approach to designing precursor structures in order to tailor the structure of the final open-cell aluminum foam.

Simultaneous charging and discharging (SCD) of the latent thermal energy storage (LTES) can improve the flexibility of solar thermal systems and ensure the continuity of energy supply. Experiments and numerical simulation are conducted in this study to reveal the SCD thermal behavior of LTES device using flat micro-heat pipe array–metal foam composite structure. The effects of heat transfer fluid (HTF) temperature, volumetric flow, initial phase change material (PCM) state, and metal foam are analyzed. Results show that PCM absorbs heat from hot HTF or releases heat to cold HTF at the beginning depending on the PCM and HTF temperatures. The SCD eventually reaches an approximate steady state, cold HTF exchanges heat directly with hot HTF, power and PCM temperature remain unchanged. Low cold HTF temperature quickly reaches steady state and low final PCM temperature but has no influence on steady state power. PCM initial state and metal foam porosity do not affect the steady state power and final PCM temperature. However, they affect the time to reach steady state. Metal foam pore density has no obvious effect on SCD. SCD has more stable discharging performance than single discharging, especially when the cold HTF temperature is high.

In this study, the vibration and flutter characteristics of the graphene platelets reinforced functionally graded porous cylindrical panels subjected to the supersonic flow are investigated for the first time. The considered panels are constructed of the nanocomposites that made of matrix of open-cell metal foams with graded pore distributions and are reinforced uniformly by the graphene platelets. The typical mechanical properties of porous matrix are determined using open-cell metal foam model, which provides a typical mechanical feature to determine the relationship between coefficients of density and porosity. The effective elasticity modulus of the nanocomposite is determined based on a modified Halpin-Tsai micromechanics model, and the rule of mixture is used to calculate the Poisson's ratio and mass density. A high order shear deformable computational framework is developed with inclusion of the trapezoidal shape factor to eliminate the errors introduced by the curvature of the panels. The standard Lagrange processing in conjunction with the Navier-solution technique, with the help of the first-order piston theory, is applied to derive the equations of motion related to the vibration and flutter characteristics of the cylindrical panel with simple-supported boundary condition. Comparisons of the natural frequencies with the previous works are performed to validate the proposed model. Parameter studies are carried out, and the results in the form of graphs or tables reveal the effects of pore, graphene platelets on the supersonic flutter characteristics of the nanocomposite cylindrical panels subjected to the aerodynamic flow.

In this paper, the Taguchi optimization methodology was utilized for optimizing the production parameters of aluminum foam sandwich panels (AFSP) with different skin layers under low-velocity impact loading. The core material of AFSP was A356 aluminum foam reinforced with SiC particles produced by the CaCO3 foaming agent with 20, 30, and 40 mm thicknesses. The skin layers of plates were made of glass/epoxy with the quasi-isotropic and cross-ply layout as well as the pure aluminum layer. The drop weight impact device was used for the impact test. Three types of impactors (spherical, parabolic, and cone) were used. The evaluated impact parameters are the skin layer layout, impactor shape and core thickness of AFSP. Also, the measured response factors were the specific absorbed energy (SAE), maximum displacement (MD), and maximum impact force (MIF). The Taguchi method was used to check the effect of the production parameters on the response factors by creating the orthogonal array (OA). The results indicated that the best combination of production parameters can be determined by the application of the Taguchi method. These results can provide the optimal impact responses (the largest SAE, the smallest MD, and the smallest value of MIF). For the best SAE and MIF, A1–B1–C1 (pure aluminum/conical/20 mm core) was also investigated. Meanwhile, the optimized combination of levels for all the three production factors was examined to provide the lowest MD (A3–B2–C1, cross-ply/parabolic/20 mm core).

Metal foams are typically subjected to quasi-static or dynamic shear-compression combined loading in applications such as energy absorbers and structure protectors. The yield behavior of a metal foam under dynamic and quasi-static shear-compression combined loadings is investigated in this study. First, quasi-static and dynamic compression-shear combined tests at different loading angles are conducted using a universal testing machine and a rotatable Hopkinson bar system, respectively. Shear deformation reduces the plateau stress as the loading angle increases. Subsequently, the yield modes of the metal foam under combined loadings are investigated. Only one yield band occurs under a combined loading with large loading angles (mode I), whereas several yield bands occur under a combined loading with small loading angles (mode II). Finally, the yield surface plot of metal foam indicates significant enhancement in terms of normal stress and shear stress under dynamic loading. Quasi-static and dynamic phenomenological yield criteria for a shear-normal stress space are established to provide a brief and precise prediction of the behavior of metal foam under quasi-static and dynamic combined loadings.

Aluminum foams have recently received special attention due to their peculiar mechanical properties. For example, their energy absorption capacity in crash events and low density are very desirable...

In the present study, the microstructural characteristics, compressive strength, and corrosion behavior of aluminum-cenosphere composite foam (CF) developed by spray forming route (processed with 5 Psi (3.45 × 104 N/m2) and 10 Psi (6.90 × 104 N/m2) hydrogen pressure) has been undertaken. The microstructure of the spray-formed coupon consists of hollow cenosphere particles distributed uniformly in aluminum matrix. Compressive yield strength (YS) of the aluminum-cenosphere foam (CF) is different from commercially pure aluminum (cp-Al). It is found that the YS of the foam processed with 5 Psi is 83.62 MPa and for the foam processed at 10 Psi is 113.32 MPa as compared to 104.42 MPa for cp-Al. A detailed study of corrosion behavior through electrochemical measurements indicates that CF exhibits a reduced corrosion rate from 0.092 (for cp-Al) to 0.056 mm/year and 0.080 mm/year for the samples processed with 10 and 5 Psi, respectively. Through a detailed analysis of Nyquist and Bode plots derived from EIS measurements, it is concluded that mostly localized corrosion occurs in all the samples. The post-corrosion microstructural study confirms that interface of aluminum and cenosphere is the potential area for initiation of corrosion.

The outstanding mechanical properties and lightness of aluminum foam make it attractive as buffering and energy absorption material for spacecraft landing in deep space exploration. In this paper, cell-based model of open-cell aluminum foam has been established by Voronoi tessellation method. Through quantitative comparisons of energy absorption performance between different simulation models, it can be found that the improvement of base material properties can lead to significant enhancement of energy absorption ability, and there is an approximate linear relationship between relative density and relative energy absorption at low speeds. Characteristic deformation mode has been discussed under different compression speeds. The isotropic buffering characteristic of aluminum foam materials has been verified by the simulation of a footpad filled with aluminum foam impacting on a sloping ground.

PurposeThe purpose of this paper is to provide a summarization and review of the present author's main investigations on failure modes of reticular metal foams under different loadings in engineering applications.Design/methodology/approachWith the octahedral structure model proposed by the present authors themselves, the fundamentally mechanical relations have been systematically studied for reticular metal foams with open cells in their previous works. On this basis, such model theory is continually used to investigate the failure mode of this kind of porous materials under compression, bending, torsion and shearing, which are common loading forms in engineering applications.FindingsThe pore-strut of metal foams under different compressive loadings will fail in the tensile breaking mode when it is brittle. While it is ductile, it will tend to the shearing failure mode when the shearing strength is half or nearly half of the tensile strength for the corresponding dense material and to the tensile breaking mode when the shearing strength is higher than half of the tensile strength to a certain value. The failure modes of such porous materials under bending, torsional and shearing loads are also similarly related to their material species.Originality/valueThis paper presents a distinctive method to conveniently analyze and estimate the failure mode of metal foams under different loadings in engineering applications.

The present numerical investigation examines the performance improvement of thermoelectric generators (TEGs) by using phase change materials (PCM) and porous medium. Due to the high latent heat of PCMs, both sides of the TEG were filled with paraffin RT35 (on the cold-side) and paraffin RT69 (on the hot-side). The PCM in the cold-side of the TEG was used as a heat-sink whereas the PCM in hot-side of the TEG was used to reduce the output voltage fluctuations. Since the system was periodically subjected to heat flux from an external heat source, the paraffin in the hot-side of the TEG was also used to generate a continuous thermal heat when the heat source was cut-off. To increase the thermal conductivity of the phase change material, this investigation studied the effect of using the copper porous medium with different porosities (0.80, 0.90, and 0.95) and three different pores per inches (PPI) as 10, 20, and 40. The results show that the use of porous on the cold-side of the TEG produces more electrical energy and output voltage compared to (i) having porous medium on the hot-side and (ii) using PCM without porous medium on both sides of the thermoelectric generator. Furthermore, the results indicated that the TEG performance enhanced by increasing PPI and reducing porosity. As a result, by increasing the PPI from 10 to 40 (at 0.80 porosity) and by reducing porosity from 0.95 to 0.80 (at PPI 20), the electricity generated increases by 13.57 and 5.36%, respectively.

Purpose This study aims to generate different three-dimensional (3D) foam models using computer tomography (CT) scan and solid continuum techniques. The generated foam models were used to study deformation mechanism and the elastic-plastic behaviour with the existing experimental foam behaviour. Design/methodology/approach CT scan model was generated by combing 2D images of foam in MIMICS software. Afterwards, it was imported in ABAQUS/CAE software. However, solid continuum model was generated in ABAQUS/CAE software by using crushable foam properties. Then, the generated foam models were sets boundary conditions for a compression test. Findings CT scans capture the actual morphology of foam sample which may directly an image based finite element foam model. The sectional views of both the models were used to observe deformation mechanism on compression. The real compressive behaviour of foam was visualised in CT-Scan foam model. It was observed that CT-scan model was the more accurate modelling method than crushable foam model. Originality/value The internal structure of foam is very complex and difficult to analyse. Therefore, CT-scanning may be the accurate method for capturing the macro-level detailing of foam structure. A CT-scan foam model can be used for multiple times for mechanical analysis using a simulation software, which may reduce the manufacturing and the experimental cost and time.

Metal foam, as a potential alternative to conventional flow fields in proton-exchange membrane fuel cells (PEMFCs), has been adequately proven to possess high gas uniformity and water storage abili...

The purpose of present investigation is to study propagation of flexural wave in porous metal foam beams resting on Winkler–Pasternak foundation based upon refined higher-order shear deformable bea...

Future electronic packaging technology requires semiconductor chips having a larger size and higher power for advanced applications, e.g., new energy conversion systems, electric vehicles, and data center servers, yet traditional thermal interface materials (TIMs) with a high thermal conductivity are generally stiff materials with weak joints, which cause the accumulated thermal stress to concentrate at the chip corners, leading to cracking and popcorn problems. To address such a critical challenge, herein for the first time we report a low-cost and high-performance porous copper (Cu)-indium (In) laminar structure as TIM, which can provide a superior thermal conductivity (50 W m-1 K-1) comparable to indium, yet the Young's modulus (1.0 GPa) is an order of magnitude lower than indium, which is a state-of-the-art value. Additionally, the In-based intermetallic compound (IMC) joints enable more robust mechanical interconnection above the melting point of pure indium, providing better high-temperature performance. The discontinuous IMCs spread the global interfacial thermal stress into numerous isolated local areas, ensuring a reliable joint to resist thermal-mechanical fatigue. In the silicon-TIM-copper package testing vehicles with a large die size (1 × 1 square inch), this structure shows excellent thermal management ability and superior reliability, compared with classical indium and classic commercial silver pastes.

Metal foam material, which serves as an alternative replacement of the conventional flow distributor of proton exchange membrane (PEM) fuel cell, has been attracting much attention over last few decades. In this work, three-dimensional modeling work for PEM fuel cell containing metal foam as cathode flow distributor has been carried out. The fuel cell performance and operating characteristics of metal foam flow field and conventional parallel flow channel have been compared and discussed. The cell performance has been reasonably validated based on the corresponding experimental tests conducted in this study. The superior performance of PEM fuel cell with metal foam as cathode flow field benefits a lot from the uniform gas flow. The porous metal foam material provides more pathways for the water delivery at the interface of metal foam flow field and gas diffusion layer (GDL), accelerating water removal capability of cathode. Because of the significant oxygen transfer loss in diffusion limited parallel channel, the operation of PEM fuel cell with parallel channel is found to be more sensitive to cathode humidification and oxygen supply at inlet. Due to the more uniform and effective electron transport though the porous electrode, it is possible to use thinner GDL in metal foam PEM fuel cell. It is expected that this study could give a good baseline of operating behavior of PEM fuel cell with metal foam flow distributor.

The present article experimentally explored heat transfer through a horizontal metal foam tube with a constant wall heat flux during the subcooled flow boiling of water, Al2O3/H2O, and CuO/H2O nanofluids. To investigate the effect of using metallic foam on the subcooled flow boiling heat transfer, the results have been compared with a simple tube. Besides, The impacts of significant parameters, including subcooled inlet temperature (25–60 °C), mass flux (150–310 kg m−2 s−1), wall heat flux (100–230 kW m−2), particle type (CuO and Al2O3), and nanofluids concentration (0.5% wt., 1% wt.) were investigated on the transfer of boiling heat while measuring pressure loss and rate of heat transfer. The results show that the use of metal foam increases the heat transfer rate by 3.5–5.8 times compared to the simple tube. Comparing the subcooled flow boiling heat transfer of water and nanofluids in both metal foam and simple tubes, it was found that water has superiority over the nanofluids. Besides, the value of the thermal performance index defined as a ratio of the heat transfer enhancement to the pressure loss degradation is more than one for water and the nanofluids.

Porous materials can be used for accidental explosion prevention and suppression in process industries. In this study, an experimental study was conducted to study the effect of an aluminum foam pl...

This research proposes an innovative configuration for modifying the thermal management system of the photovoltaic (PV) panel, integrated with a phase-change material (PCM) with an attached exterior metal-foam layer to the rear part of the PCM container. The configuration enables faster heat dissipation from the system leading to longer thermal-management duration for the PV panel during the energy storage (PCM charging) mode. Also, it supports faster energy recovery (PCM discharging) rate by decreasing the amount of heat trapped in the melted part of the PCM during the solidification mode. The effects of the foam-layer inclusion, PCM thickness, and PV tilt angle are numerically simulated and revealed. A mathematical model that accounts for natural convection effects of the melted PCM and non-Darcy effects of the metal foam, is formulated and validated via previous experiments. The results show that inclusion of an exterior foam layer could increase the PCM melting time, and the corresponding PV thermal-management duration, by up to 32% and 55% respectively, depending on the PCM thickness and PV tilt angle. The results also show that reducing the tilt angle from 90° to 30° increases the melting time by about 18%. Thus, a superior PCM-based thermal management is achieved. Moreover, utilizing PCM of thickness in the range of 20–30 mm lengthens the melting time by up to 54%, enhancing the potential for improved thermal management of PV panels.

AlCa75 with equal Ca content was used to replace pure Ca for the preparation of AlSi12 foam in a stable pore structure after foaming for 20 min. The stability mechanism was studied based on the comparison between the macroscopic pore structure evolution and the second phase composition of AlCa75 and pure Ca aluminum foam. It was found that the porosity and average pore size of the AlSi12 foam with AlCa75 were stable without any abnormal large pores, and the foaming stage was prominent. The stability of AlSi12 foam with pure Ca is inferior. After 20 min of foaming, the foam bursts in the center. Combined with the microscopic characteristic analysis, it could see that the second phase produced by AlCa75 is mainly Al2Si2Ca, which can be uniformly dispersed in the matrix. The addition of pure Ca reduces the amount of the second phase and the main phase Al4Ca is easy to agglomerate. The stability mechanism shows that the Al2Si2Ca second phase, formed by AlCa75, demonstrates a better stabilizing effect in different foaming stages. Due to the premature agglomeration caused by Al4Ca and the low content of the second phase, the AlSi12 foam with pure Ca is challenging to long-term stability.

A new method for the manufacturing of pre-determined open porosity Al foams is presented in this work. Starting from a 3D foam model designed with CAD and printed with fused deposition modeling (FDM), a porous structure of poly lactic acid (PLA) has been replicated. The choice of this material has been driven by the properties in terms of recyclability and low cost. The truncated octahedron for the porosity shape has been selected due to benefit and properties ascribable to its morphology. After creating the 3D PLA model, it has been filled with liquid plaster. After its solidification, PLA is removed in oven at 600 °C so that a negative-shaped plaster mold is obtained. Successively liquid Al at 750 °C is poured in the mold inside the oven. After Al solidification, plaster can be easily removed in ultrasonic bath thus obtaining Al foam with the same morphology of the starting PLA model. This process shows great flexibility allowing to manufacture different kind of elementary cell types. Tailoring of the selected properties of the manufactured foams, e.g. the morphology, the density or the surface/volume ratio may be obtained. With this technique many other metals and alloys can be manufactured too. The potential of this production technique can be successfully employed in many application fields of metal foam. Light-weight 3D lattice structures are widely employed for multifunctional applications such as loading bearing, negative and zero thermal-expansion structures, vibration attenuation, impact and blast proof structures.

In this study, a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material (TNT) against several configurations of the composite structure. Several numerical models were carried out to study the effect of varying the thickness of the walls and the effect of adding an air layer or aluminum foam layer inside two layers of concrete in mitigating the effect of blast waves on the structure walls. The results showed that increasing the thickness of walls has a good effect on mitigating the effect of blast waves. When a layer of air was added, the effect of blast waves was exaggerated, while when a layer of aluminum foam was added the blast wave effects were mitigated with a reasonable percentage.

In-situ catalytic biomass pyrolysis for syngas production is a competitive technology for the recovery of energy in biomass. However, in conventional in-situ catalytic pyrolysis process, the mode of catalyst introduction makes it difficult to separate the catalyst from the char after pyrolysis, resulting in difficulty in catalyst recycling. We considered that the use of monolithic catalyst which has larger size than the biomass feedstock might solve the problem of the separation difficulty between the catalyst and char. In order to verify the feasibility of this strategy, NiO/γ-Al2O3 was respectively supported on ceramic honeycomb, metal foam, and metal wire mesh to produce three monolithic catalysts with different outer surface areas. Their catalytic performance for cattle manure pyrolysis was tested and the result revealed that compared with the granular NiO/γ-Al2O3, using monolithic catalysts with ceramic honeycomb, metal foam, and metal wire mesh carrier respectively increased the gas production by 37%, 33%, and 11%. The use of monolithic catalyst in in-situ catalytic biomass pyrolysis, not only simplified the separation process of catalyst and char, but also enhanced the catalysis performance.

It is well-known that flow field design is of primary importance to optimization of proton exchange membrane (PEM) fuel cell. Traditional channel-rib flow fields, e.g. parallel or serpentine channels, always lead to non-uniform distributions of reactant gas, liquid, current density and so on between the channel and rib regions. Metal foam materials with high porosity (>90%) have been proposed as alternative flow fields for PEM fuel cells. In this study, influences of metal foam flow field on the transport phenomena coupled with the electrochemical reactions in PEM fuel cell are investigated using a three-dimensional (3D) multi-phase non-isothermal model. Specifically, the full morphology of metal foam flow field is taken into account in the 3D simulation after validated against experimental permeability data. The full morphology inclusion enables capture of the detailed gas flow from the flow field into the gas diffusion layer (GDL) and the current collection at the metal foam/GDL interface. In addition, compared with the conventional channel-rib flow fields, the metal foam design greatly increases fuel cell performance in the high current density regime. In addition, the oxygen and current density distributions in PEM fuel cell with the metal foam flow field are more uniform than those in the conventional one. Though the current collection area at the GDL surface is much smaller in the metal foam flow field, the relevant Ohmic loss won't increase significantly due to the improved physical contact by the fine pore structure of metal foam over the GDL.

Some important properties of the metal foams that make them attractive materials for various purposes are their excellent stiffness to weight ratio (light-weight structure), ability to take up strain by crushing at controlled pressure (energy and impact absorption), order of magnitude higher damping capacity as compared to the solids (mechanical damping), higher natural flexural vibration frequencies (vibration control), reasonable sound absorbing capacity accompanied by durability and fire resistance (acoustic absorption), and, high area of contact accompanied by high thermal conductivity (heat exchanger). Often foam is joined or connected to cover sheets of the same metal and the whole part together is called a foam sandwich. Among all the metal foams aluminium metal foam has found the widest and diverse application. This article covers important recent literature on laser processing viz. laser forming, laser welding, laser cutting and laser additive manufacturing of metal foams. Prior to this, a link is established between foam/foam sandwich and laser processing techniques stating the limitations of other relatively more conventional processing techniques. Future research direction regarding different laser processing techniques using metal foams has also been outlined.

Aluminium alloy foams are manufactured by various methods, which include foaming of molten aluminum alloy by gas injection and powder metallurgical processing. Non-conventional methods such as direct energy deposition, syntactic method of metal foam fabrication have also been developed for the manufacturing of aluminium alloy foams. Aluminium alloy foams are cellular structure which consists of solid metal such as aluminium, steels and iron with micro pores filled with gases such as hydrogen, carbon di oxide, nitrogen, argon etc. In this research work in order to fabricate aluminum alloy 6063 foam, first aluminium alloy 6063 was melted by using stir casting method as it is economical and simple, 2 wt% titanium hydride was added and mixed into the molten aluminium alloy 6063 at temperature 800 ˚C and then the melt was allowed to cool down to room temperature in order to obtain aluminium alloy 6063 foam. The percent porosity and density of the fabricated aluminium alloy foam is determined with the help of Archimedes principle.

The deformation behavior and crashworthiness of functionally-graded foam-filled tubes (FGFTs) under drop-weight impact loading were investigated. Closed cell aluminum, A356 alloy and zinc foams fabricated by the liquid state processing were used as axial grading fillers for the manufacture of single-layer and multilayer structures with different configurations. The results indicate that the deformation of multilayer foam filled tubes initiates from the low-strength components, and then propagates in the high-strength components through the gradual increment of stress. The use of more A356 alloy and aluminum foam layers provides greater specific energy absorption (SEA) for the graded structures, whereas the high-strength zinc foam has no positive effect on the crash performance. The progressive collapse of graded structures consisting of the aluminum and A356 alloy foams occurs in a symmetric mode under quasi-static and drop-weight impact conditions. However, the zinc foam causes a combination of symmetric and extension modes as well as greater localized deformation under dynamic loading and greater local rupture in quasi-static loading condition. The Al−A356 foam-filled tubes with a combination of the highest SEA (10 J/g) and the lowest initial peak stress (σmax of 10.2 MPa) are considered as the best lightweight crashworthy structures.

The purpose of innovative engineering inventions in our modern world is not necessarily to solve a new problem, but to implement and optimize an existing solution in a more energy-efficient and cost-effective manner. This can be achieved by increasing the load-bearing capacity or reducing the weight. Using these two methods simultaneously we can produce so-called syntactic metal foams. The mechanical properties of syntactic foams are highly dependent on the filler materials’ volume. Therefore, in the course of our research, we produce gradient syntactic metal foams (GSMFs) with gradient filler volume within one metal foam. Mechanical analysis as compressive tests and microstructural analysis were performed to determine the properties of the differently filled syntactic metal foams.

On account of the low heat dissipation problem of common cooling systems, an experimental system with enhanced structures was set to improve the heat transfer of heat sink cooled by semiconductor and TiO2-water nano-fluids. The influences of structures (smooth surface, metal foam with PPI=30, cylindrical bulge (height: H=2 mm, staggered arrangement), cylindrical groove (depth: D′=2 mm, staggered arrangement)), nanoparticle mass fractions (ω=0.0–0.5 wt%), input power of the semiconductor (P=2 W, 4 W, 6 W), and Reynolds numbers (Re=414−1,119) on the flow and heat transfer properties of TiO2-water nanofluids were studied. The compositive thermal and hydraulic properties of the enhanced technologies were analyzed by thermal efficiency. Results indicated that the combination of semiconductor and metal foam shows the most excellent performance compared with other combinations and it can be enhanced by 48.1% at best. Nanofluids with ω=0.4 wt% display the best cooling capacity instead of the highest concentration. The cooling effect shows an increasing trend with the input power of the semiconductor.

Latent heat thermal energy storage (LHTES) is crucial in the application of renewable energy and waste heat recovery. A novel LHTES device with a flat micro-heat pipe array (FMHPA)–metal foam composite structure is designed in this study to obtain excellent heat transfer performance. An evaluation standard called integrated power is proposed to assess and compare the structural advantages of the LHTES device with others. Performances of FMHPA, temperature distribution, effort of inlet temperature and velocity of heat transfer fluid (HTF) are also studied in the experiments. A three-dimensional numerical model is developed to investigate the effort of porosity and pore density of metal foam on the charging process. Results show that the FMHPA–copper foam composite structure improves the performance of the LHTES device. This structure exhibits stronger heat transfer performance than that of other devices. The increasing inlet temperature of HTF has a better promotion effect on power than raising HTF velocity. High porosity is conducive to natural convection but detrimental to heat conduction. High pore density is disadvantageous to natural convection and does not affect heat conduction.

In this study, the effectiveness of three different types of Mg-based blowing agents on the structure and properties of aluminum alloy foam was compared. AlMg15Cu10 alloy foams were produced by the powder metallurgy route using pure Mg, Al50Mg50 and Al60Mg40 powders as blowing agents. Al50Mg50 and Al60Mg40 powders were synthesized by ball milling and melt milling, and were characterized by particle size analysis, XRD and SEM. Foams were characterized by using X-ray tomography, SEM and XRD. Mechanical properties were obtained through quasi-static compression tests. It was observed that the foams produced by Mg possess spherical cells whereas more polyhedral cells were obtained in the foams produced by Al50Mg50 and Al60Mg40. The finest cells were produced by Al60Mg40 powder. Variation in the cell size is attributed to the different hydrogen contents of these blowing agents. All foams resulted in a good porous structure and possess high compressive strength compared with conventional foams.

Hybrid structure between porous core and solid shell can combine lightweight open-cell structure of porous materials with good strength of solid shell. Laser welding is considered as an effective process to join porous metal with solid metallic shell. In this study, the evolution behavior of laser welding by a continuous wave (CW) disk laser welding between open-cell aluminum alloy (cast AC2A alloy) and aluminum sheet (wrought AA6063 alloy) was investigated. X-ray transmission system and a high-speed camera were performed during laser welding to investigate the dynamic keyhole, porosity formation, plasma plume, and spatter formation. Laser keyhole became unstable during entering and passing the vacancies of porous aluminum, which consequently resulted in bubble formation in the molten pool.

Heat exchangers embedded with metal foam are drawing increasing attention in the thermal application field, due to the performance of low density, large ratio of surface area to volume as well as high thermal conductivity. In these applications, compact heat exchanger, solar thermal facilities and thermal energy storage are the three core components. This paper focuses on the lasted advances in thermal applications, presenting a review of theoretical and experimental progress over metal foam in thermal application. The empirical and theoretical models for pressure drop, heat transfer coefficient and performance evaluation criteria of compact heat exchangers with metal foam are reviewed and discussed, especially different optimized configurations. There is a trade-off between heat transfer enhancement and increase of pressure drop. Some exploratory work performed by present authors are also introduced. The manufacturing, heat transfer and flow characteristics of tube bundle wrapped with metal foam are taken into account for optimization of heat exchanger. It is confirmed that the conversion mechanism of heat transfer is carried out that heat conduction is the dominative term at high dimension permeability. The correlations of heat transfer rate and pressure drop for staggered and single row tube bundle wrapped with metal foam are concluded, respectively. The effects of different bonding methods are revealed for point-contact in metal foam and base tube. The powder-sintering method can provide a stable and minimum-thickness bonding layer. Various types of solar thermal facilities utilized metal foam to improve the energy conversion efficiency from solar radiant energy to thermal energy are also reviewed and discussed, including solar collector for intermediate-low temperature utilization and solar receiver for high temperature utilization. The Last but not least, existing and future metal foam thermal application stations are overviewed.

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.

In this study, a novel way to improve performance of the air-cooled open cathode polymer electrolyte membrane fuel cell is introduced. We suggest using a metal foam in the cathode side of the planar unit fuel cell for the solution to conventional problems of the open cathode fuel cell such as excessive water evaporation from the membrane and poor transportation of air. We conduct experiment and the maximum power density of the fuel cell with metal foam increases by 25.1% compared with the conventional fuel cell without metal foam. The open cathode fuel cell with metal foam has smaller ohmic losses and concentration losses. In addition, we prove that the open cathode fuel cell with metal foam prevents excessive water evaporation and membrane drying out phenomena with numerical approach. Finally, we apply the metal foam to the air-cooled open cathode fuel cell stack as well as the planar unit cell.

Axial splitting and curling behaviour of circular sandwich metal tubes with metal foam core is investigated analytically and experimentally. The sandwich tubes split axially and the strips curl outward by prefabricated cracks at the distal end of the specimens. Axial compression experiments of circular sandwich metal tubes are carried out and deformation modes are found. A theoretical model is developed to predict the axial splitting and curling behaviour of the circular sandwich metal tubes including effects of the tearing of the cracks, plastic bending, curling, foam compression and friction. It is shown that the analytical predictions capture the experimental results reasonably. Effects of the tube thickness, foam strength, foam thickness, the number of the prefabricated cracks, and the semi-angle of the die are of vital important in energy absorption devices by the axial splitting and curling of circular sandwich tubes.

Lightweight foams with high damping capabilities are of great interest to designers. Such foams allow undesirable vibration to be passively attenuated. Metal foams with porosity values over 50% possess such characteristics, but it seems necessary to have accurate quantitative data on damping capacity of metal foams. Many researchers exclusively investigated the dynamic properties of aluminum and magnesium foams, although zinc alloys have higher damping capacity in a compact form. The purpose of this study is to evaluate the damping capacity and Young modulus of synthetic zinc foam. Here, zinc foams are produced by ALPORAS method and experimental modal analysis is employed to identify mentioned properties. Test setup and identification method based on the forced vibration and bending-vibration modes are discussed. The extracted damping’s ratios were in the range of 0.038–0.062 higher than reported values for other synthetic foams. The identified Young modulus of zinc foam with the density 1230 kg/m 3 is 1.43 GPa which is close to that of aluminum foam with the same density.

Closed-cell A356 aluminum foams have been produced by the addition of calcium carbonate (CaCO3) powder as a foaming agent to the molten aluminum without any stabilizer particles. The foaming process is performed by the addition of 2.5–3.5 wt% CaCO3 and has relative density ranges of 0.12–0.44 and cell sizes of 1.5–3.1 mm with uniform cell structures. The foaming stabilizing mechanism and effect of foaming conditions such as the amount of foaming agent, casting holding and mixing time at the furnace on the foamed samples were investigated. The stabilizing mechanism is because of the foaming gas (CO2)/melt reaction during the foaming procedure and producing some solid particles such as CaO, Al2O3 and MgO. The optimum foamed aluminum with uniform cell size distribution was obtained at 4-min mixing time and 10-min holding time with 3 wt% CaCO3 foaming agent. The porosity of aluminum foam increased as the holding time increased from 60 to 86%. Also, the average cell size increased from 1.5 to 3.1 mm when the amount of CaCO3 increased from 2.5 wt% to 3.5 wt%, respectively.

Przedmiotem badań jest trójwarstwowe pasmo płytowe poddane czteropunktowemu zginaniu. Opracowano analityczny model tego pasma, korzystając z klasycznej teorii linii łamanej nazywanej teorią Zig-Zag. W paśmie tym wyróżniono trzy przedziały: dwa brzegowe, w których występuje zginanie i ścinanie oraz jeden środkowy, w którym występuje czyste zginanie. Wyznaczono całkowite ugięcie maksymalne pasma płytowego oraz maksymalne ugięcie odcinka środkowego. Przeprowadzono obliczenia numeryczne metodą elementów skończonych (MES) dla takiego samego modelu pasma, jak wyżej wspomniany model analityczny. Próbę doświadczalną przeprowadzono na stanowisku badawczym w Instytucie Pojazdów Szynowych. Porównano wyniki badań analitycznych, numerycznych i doświadczalnych. Analizowane płyty warstwowe mogą być stosowane, m. in. jako części podłogi lub poszycia pojazdu szynowego.

In this study, aluminum foam made of Etial 160 (AlSi8Cu3Fe) was produced using vacuum die casting method and the process of artificial aging was implemented. The mechanical properties and microstructure of the fabricated foam were investigated. Results of the present study indicate that the artificial aging process has a significant effect on mechanical behavior of aluminum foam. The microstructure, surface morphology, hardness and composition of the Al alloy foam were investigated using scanning electron microscopy (SEM), the Vickers hardness test and X-ray diffraction method. The SEM–EDS and the Vickers hardness measurements show that the best temperature for precipitation hardening is 170 °C for 30 min.

A small plate heat exchanger filled with copper foam which can be applied for small scale electronic cooling is presented. The heat transfer coefficient and pressure drop of water flow inside a plate heat exchanger filled with copper foam (PHECF) are experimentally studied. The effect of copper foam pore density and water velocity on the optimum thermal performance is also presented. The experiment is performed with a Reynolds number ranging from 1200 to 2000 and copper foam pore density ranging from 30 to 50 pores per inch (PPI). The results show that the heat transfer coefficient and pressure drop increased when the water velocity and pore density increased. The heat transfer coefficient is enhanced by 20.23%, 29.37%, and 40.28% for PHECF with a pore density of 30 PPI, 40 PPI, and 50 PPI as compared to a plate heat exchanger. The total pressure drop of water flow inside PHECF is dominated by inertial drag pressure drop. Thermal performance of PHECF with 50 PPI is highest with the average thermal performance factor of 1.21. The Nusselt number and friction factor correlation of water flow inside plate heat exchanger filled with copper foam are also proposed for practical applications.