Open-cell Foams Research Articles

Is monolithic configuration superior to random packing in a fixed bed reactor for CLC like processes?

In light of the geometric deficiencies and diffusion constraints of conventional packed-bed reactors, the potential application of monolithic configurations in fixed-bed reactors was explored using the structure-resolved CFD approach. This work delves into how geometric features of fixed beds influence flow patterns and related transport phenomena. To assess the performance of mass transfer and heterogeneous reactions in different configurations, we conducted simulations of fixed-bed chemical looping combustion (CLC) processes, in which a simplified model of non-catalytic gas-solid reactions is implemented to reduce the computational costs. Our findings highlight the importance of face contact between reaction tube and the monolithic structure, which effectively eliminates the inherent wall effects of random packing and enhances the radial heat conduction. More uniform geometry in the monolithic configuration naturally suppresses violent interstitial channeling flow in the random packing. Notably, the honeycomb configuration demonstrates an exceptionally low pressure drop, about two orders of magnitude smaller than that of the Raschig ring packing, and the designable monolithic configurations offers the potential to further reduce the pressure drop with enlarged voidage. Open-cell foams exhibit excellent convective and radial heat transport properties, promote homogeneous flow fields, and demonstrate superior performance in conjugate transport and heterogeneous reactions.

Interfacial investigation of Al/Ni in new generation of composite (Metal-3D lattice metal): Annealing time effect

In the present research, an advanced Al composite reinforced with open-cell nickel foam (OCNiF) was produced using pre-compressed and Spark Plasma Sintering (SPS). For this purpose, open-cell nickel foam with 10 PPI was placed in a mold then the open-cell nickel foam was filled with pure Al powder and pre-compressed. The initial tablet was sintered at 420 °C under the load of 40 MPa. Afterward, the parts were annealed at 470 °C for two, four, and 8 h. Microstructural investigations was carried out by Field Emission Scanning Electron Microscope (FE-SEM) and X-ray diffraction (XRD). The results showed a complementary process for sintered particles, which became more complete with increasing time of annealing stemming from diffusion. Evaluations showed that the Al3Ni phase began to nucleate after 4 h of annealing at the Al/OCNiF interface. The mentioned phase stabilized and reached to 3 % by weight through annealing After 8 h. Annealing increased the hardness of the substrate by more complete sintering. The hardness of Al3Ni and Al3Ni2 phases increased to 503 and 647 Vickers, respectively. The polarization test showed that the corrosion resistance first increased and then decreased during annealing compared to the SPS sample. Ni affected the development of the protective layer to prevent the pitting corrosion. However, as the annealing time increased, the corrosion current decreased, which was due to the absence of Ni in the protective layer and the formation of corrosion microcells due to the formation and growth of Al3Ni and Al3Ni2 phases.

4D local investigation of mechanical behavior of open-cell foams by enhanced morphological analysis and microstructure-adapted digital volume correlation for tribology applications

In ex-poro-hydrodynamic (XPHD) lubrication, fluid impregnated, open-cell elastomer foams constitute a composite material aiming to improve the load carrying and damping capacity of lubricated systems and to provide more environmentally sustainable solutions. The performance of XPHD-based devices depends on the interactions between solid and fluid phases, occurring and evolving simultaneously during dynamic compression of an imbibed foam. Even at normal regimes, the foam microstructure undergoes large deformations and is prone to strain concentrations which modify its local porosity and influence the mechanical behavior of the composite. In this context, this work focuses on the development of a systematic and accurate characterization technique for describing the main morphological changes happening under uniaxial compression of a high porosity dry open-cell polyurethane foam, by in-situ X-ray microtomography (μCT) testing. A combination of 3D image analysis and digital volume correlation (DVC) is considered to identify and trace the spatial and temporal location of key microstructural features at every loaded state. In this way, the detailed transformations of cells and pores obtained by this method are presented here to give further insight into the deformation mechanisms involved. Then, the advantages and the limits of the overall methodology in analyzing high porosity open-cell foams are regarded in terms of feature segmentation and measurement precision. Both a classic and a microstructure-adapted DVC are compared at their respective scales, and finally their sensibility to emphasize local strain heterogeneities is discussed.

Investigation of the compressive properties of three-dimensional Voronoi reticula

With the rise of additive manufacturing technologies, artificial production of stochastic cellular materials is becoming increasingly more feasible and convenient, exposing the need of accurate models able to predict their mechanical properties. However, the construction of generalized predictive models for stochastic structures is non-trivial: on the one hand, this is due to the several potential base materials, and on the other it is because of the difficulty in implementing geometrically accurate numerical models. In light of these considerations, the present work presents a systematic analysis of one the most known – and commonly used – stochastic cellular structure, the Voronoi three-dimensional lattices; the aim is providing simple empirical relations between the main properties of a generic base material and the compressive properties of the related additively manufactured stochastic Voronoi reticulum as a function of its geometry. The investigation provides novel insights on the mechanical properties of Voronoi reticula, highlighting superior efficiency with respect to their natural counterpart, the open-cell foams, and exposing unsuitability of classical equations for accurate prediction of their mechanical properties.

Generative design approach to combine architected Voronoi foams with porous collagen scaffolds to create a tunable composite biomaterial

Regenerative biomaterials for musculoskeletal defects must address multi-scale mechanical challenges. Repairing craniomaxillofacial bone defects, which are often large and irregularly shaped, requires close conformal contact between implant and defect margins to aid healing. While mineralized collagen scaffolds can promote mesenchymal stem cell osteogenic differentiation in vitro and bone formation in vivo, their mechanical performance is insufficient for surgical translation. We report a generative design approach to create scaffold-mesh composites by embedding a macro-scale polymeric Voronoi mesh into the mineralized collagen scaffold. The mechanics of architected foam reinforced composites are defined by a rigorous predictive moduli equation. We show biphasic composites localize strain during loading. Further, planar and 3D mesh-scaffold composites can be rapidly shaped to aid conformal fitting. Voronoi-based composites overcome traditional porosity-mechanics relationship limits while enabling rapid shaping of regenerative implants to conformally fit complex defects unique for individual patients. Statement of SignificanceBiomaterial strategies for (craniomaxillofacial) bone regeneration are often limited by the size and complex geometry of the defects. Voronoi structures are open-cell foams with tunable mechanical properties which have primarily been used computationally. We describe generative design strategies to create Voronoi foams via 3D-printing then embed them into an osteogenic mineralized collagen scaffold to form a multi-scale composite biomaterial. Voronoi structures have predictable and tailorable moduli, permit stain localization to defined regions of the composite, and permit conformal fitting to effect margins to aid surgical practicality and improve host-biomaterial interactions. Multi-scale composites based on Voronoi foams represent an adaptable design approach to address significant challenges to large-scale bone repair.

Sol-gel synthesis and characterization of foamed Ni3Pt alloys

This study focuses on the preparation of Ni3Pt nanoporous alloy foams through the annealing of a colloid composed of Ni(NO3)2, H2PtCl6, and starch under an argon gas atmosphere. Field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were employed to analyze the chemical composition, structure, and crystallographic properties of the obtained products. The product exhibits a three-dimensional foam structure comprising open pores with an average pore size of 300 nm. Additionally, it possesses structural supports with a thickness of approximately 140 nm within the open-pore configuration. XRD analysis confirms that the obtained product exhibits a face-centered cubic phase, indicating that it is a Ni3Pt alloy. This result is further supported by reductions insurface atomic ratio and Pt binding energy observed in the XPS analysis. The resulting open-cell Ni3Pt alloy foam exhibits a homogeneous and well-defined three-dimensional structure, offering a high specific surface area. These characteristics reveal the excellent potential of the Ni3Pt alloy foam for application in battery and electrode materials.

Investigation on mechanical properties of nickel open cell metal foam after heat treatment

This investigation aims to assess the mechanical behavior and energy absorption properties of the open-cell nickel foams. The metal foams produced by electroforming of nickel on PU foams, also a heat treatment has applied to evaporate the PU foam, then a uniaxial compression test was applied to measure maximum compressive strength, energy absorption density, efficiency, and normalized stresses. The results indicate that compared with typical open-cell nickel foams and polymer precursors when the electroforming time is 12 h and a heat treatment has applied, the aforementioned properties of the metal foams had a significant improvement. Improvement of properties will change by increasing the time of electroforming. The heat treatment improved the energy absorption density of open-cell nickel foams for 3.7 times. For the best sample which is a metal foam with 12 h of electroforming with heat treatment the first maximum compressive strength, energy absorption density, and energy absorption efficiency reach 1.84 (MPa), 3.29 (mJ/mm3), and 73%, respectively.

Selective Nitridation of Ceramic Open Cell Foams for Efficient Photothermal Heating

AbstractThis study presents the synthesis of ceramic open cell foams as a new platform for photothermal energy conversion based on the inert structural ceramic alumina and the plasmonic transition metal nitride TiN. TiO2 precursor grains inside the mixed ceramic matrix are converted to TiN via the molten salt synthesis route. Photothermal measurements using an 850 nm LED as a light source show that the ceramic foams with only ≈5% TiN in the alumina matrix showed a 34% increased efficiency in converting light to heat compared to flat ceramic discs of the same composition. The TiN content in the flat discs does not affect the heat conversion efficiency, indicating that the available surface area and the material's ability to trap and direct light to the plasmonic nanostructures are the most important parameters for its photothermal activity. These results show the feasibility of synthesizing mixed ceramics based on inert materials like alumina and transition metal nitrides. Applications in solar heating, water evaporation, and related use cases of photothermal energy conversion can be realized with improved performance over 2D materials. Particularly processes that are based on continuous flow like solar thermal heating or photothermal catalysis will benefit from this new material platform.

A STUDY ON SOUND-ABSORPTION ABILITY OF CLOSED-CELL ALUMINIUM FOAMS

Metallic foams have gained popularity in industrial applications and research due to their unique mechanical properties combined with light weight, vibroacoustic damping and high-temperature resistance. Generally, closed-cell foams have poor sound absorption properties due to their closed cellular structure when compared to open-cell foams. This paper investigates a new composite closed-cell foam for its acoustic properties. The new closed-cell aluminium fly-ash foam was made with liquid processing, using calcium carbonate (CaCO3) as the blowing agent. The effects of the fly-ash content on the cell morphology and mechanical properties were analyzed. Acoustic studies were conducted on the prepared closed-cell foam using the impedance tube method. Samples were prepared in different ways to determine the effects of the changing parameters. The results of quasi-static compression and microstructural analyses of two different combinations of the foam revealed small pore sizes with varying relative densities and compressive strengths. It is evident from the acoustic studies that the foams are capable of improved sound absorption of medium and high frequencies.

Permeability of 3D Printed Open-Cell Foam Produced Using Selective Laser Sintering

3D printing technology has gained popularity among researchers since it can produce complex geometries, such as open-cell foam. The open-cell foam shows potential in a range of applications such as energy absorption, thermal management, filtering, and acoustic damping. However, the feasibility of the applications depends on the material used to construct the 3D printed open-cell foam and its physical properties e.g, pore size and porosity. Therefore, understanding the physical properties is crucial in classifying this new generation of open-cell foams. This study aims to determine the permeability of 3D printed foams using the Forchheimer equation and compared the results with a fractional estimation method to reduce the duration of future experiments. The fractional results were validated through computational fluid dynamics (CFD) simulations. The result shows that the proposed estimation method can be used to determine the permeability of 3D printed foam with a height of 60 mm or larger, and up to six times larger than 5 PPI (pores per inch). However, it is recommended to conduct simulations of large pore size foam using a 3D model to accurately describe the local velocities in the free stream region.

Karakteristik komposit sandwich dengan inti (core) open cell foam bambu berlubang

The sandwich composite employed in this study is made of bamboo open-cell foam with plywood skin. The fibre volume percentage in the bamboo foam core was 15%, and PVAc glue was used. The open-cell foam core has a square-shaped hollow in the centre with spacings of 30mm, 40mm, and 60mm. The goal of this study is to describe sandwich composites made using hollow bamboo open-cell foam cores. Density testing (ASTM C271), flatwise compression testing (ASTM C365-05), flexural testing (ASTM C393), and water absorption testing (ASTM C272) were among the tests performed. Sandwich composites with core-opened cell foam with holes had lower average density, specific flatwise compressive strength, and specific bending strength than sandwich composites without holes, according to the study's findings. The average density of the sandwich composite with core-opened cell foam with holes dropped by 6-13% as compared to the sandwich composite without holes. The average-specific flatwise compressive strength of the sandwich composite with a hollow core decreased by 2-20%. The sandwich composite's average specific bending strength was reduced by 40-50% when the core-opened cell foam with holes was used. The percentage of water absorption in the sandwich composite is the inverse. With this feature, it is believed that hollow bamboo open-cell foam would become more widely used.

A scalable versatile methodology to construct micro/nano open-cell polypropylene foam with high oil adsorption capacity and speed

A scalable versatile methodology to construct micro/nano open-cell polypropylene foam with high oil adsorption capacity and speed

Development of an air cooling system with low material budget for high-energy physics applications

This work presents the cooling system of a future particle detector at the Large Hadron Collider (LHC): the Inner Tracking System 3 (ITS3) of the ALICE experiment. Efficient cooling is crucial for maximizing the particle measurement quality in the LHC. The system introduces open-cell carbon foams as heat exchangers that combine heat conduction and convection for the first time in a high-level engineering application. The system is designed to have an unprecedentedly low material budget, which is a requirement for particle detectors aiming at precise tracking at low particle momenta. This novel approach leads to a 80% reduction of the material budget compared to the previous version (ITS2), resulting in enhanced measurement accuracy. The study employs an experimental wind tunnel setup and numerical simulation, showing excellent agreement with mean deviations under 0.5 K that are attributed to sensor installation uncertainties. The results confirm the system adherence to the temperature requirements. Compared to the baseline design, it is shown that enhancements based on numerical simulations produce potential reductions of up to 50% in the maximum temperature variation of the detector layers.

Nuclear shielding characteristics of newly developed composite metal foams: Role of CeO2 addition and foam type

In present study, new composite materials which were produced by filling open-cell aluminum foams of different thickness and pore size with various additives were surveyed with respect to photon and fast neutron shielding effectiveness. The metal foam samples were prepared in two different series (A: 30 mm thick with a pore size of 2 pores/cm and B: 10 mm thick with a pore size of 16 pores/cm) according to thickness and pore sizes, and the foams were filled with different mixtures which include Epoxy(60)-B2O3(20)-CaO(20-x)-CeO2(x); (x; 0, 5, 10, 15 and 20 wt%) chemical compositions. Gamma, X-ray and neutron measurements of the produced samples were performed using Ultra-Ge detector, linear accelerator (LINAC) and BF3 neutron detector, respectively. The gamma-transmission measurements were achieved for 30.9, 59.54, 75, 81, 276, 303, 356, 384, and 662 keV photon energies using radioactive sources of 241Am, 137Cs, 133Ba. Linear Attenuation Coefficients (LAC) of the samples were figured out with the data acquired from the measurements and MAC, HVL, Zeff and Ne values were found by way of these values. The MAC, Zeff and Ne values of the samples increased with the rising in the percentage of CeO2 added to the mixture. The energy absorption (EABF) buildup factors of the composite metal foam samples were also determined for the energy range of 0.015–15 MeV at 1–40 mfp penetration depths. It was found that the A5 and B5 samples with 20% CeO2 additive had the least EABF values. Lastly, the shielding capability of the fabricated samples against fast neutrons was specified by executing equivalent dose measurements (EAD) and calculated macroscopic cross section (∑R) values. It was established that the A2 sample had the highest absorption dose rate of 49%. The largest of the theoretically calculated ∑R values belongs to the B5 sample with 20% CeO2 additive. Generally, it was concluded that the samples in the B series, which are thinner and have more pores, have better radiation attenuation capabilities.

Numerical and experimental study of open-cell foams for the characterization of heat exchangers

A multiscale model of open-cell foams is developed for the characterization of heat exchangers. The model is applicable to a wide range of materials, cell sizes, and porosities. The microscopic geometry is based on a periodic model that is defined by the porosity and the specific surface area of the foam considered. The representative geometrical scales of the model are validated with microscope images and computed tomography scans. The outputs of the microscopic model are the coefficients of the pressure loss curve, the thermal conductivity, and the Nusselt number. These values are used as inputs of the macroscopic model that determines the thermal performance of a macroscopic system. The results given by the models are compared with experimental data obtained from the literature, and from an experimental setup built at CERN. It is concluded that the multiscale model provides accurate results in all open-cell foams considered.

High-strength, 3D interconnected alumina ceramic foams with high porosity comparable to aerogels

A creative and simple way to overcome the general problem of open-cell ceramic foams with low intensity has been proposed here. By using boehmite as a raw material for particle-stabilized foams without adding any sacrificial phase, as-prepared open alumina foams have remarkable strength and comparable porosity levels to aerogels. That is attributed to the defect-free pore struts and the windows at the distal ends of the pore struts formed by the volumetric self-shrinking of the raw material. The alumina foams have an excellent synergy between porosity and strength, with a compressive strength of 1.54-10.01 MPa at a high porosity of 92.3-96.7%, around 10 times higher than those obtained by other methods at equal porosity. This typical 3D interconnected pore structure makes ceramic foams potentially useful for applications in filtration, catalysis, etc.

Experimental investigation and 2D mathematical modelling of copper foams packed with Rh-Al2O3 catalysts for the intensification of methane steam reforming

Efficient heat transfer is a crucial factor in the design of compact methane steam reformers for delocalized hydrogen production. The use of copper packed foams was proposed few years ago by our group to strongly intensify heat transfer in these systems, allowing the design of small-scale units with minimal radial temperature gradients. In this study, a new experimental campaign was performed to demonstrate the concept potential under industrially relevant heat fluxes and to establish an experimental foundation for validating a 2D mathematical model of the process. Copper open-cell foams were packed with a Rh/Al2O3 egg-shell catalyst and loaded into a 29.5 mm diameter tubular reactor, which was heated using a lab-scale oven. By leveraging the combined benefits of enhanced heat transfer, granted by the copper foam, and the high activity of the Rh-based eggshell catalyst, experiments were successfully performed at gas hourly space velocities (GHSV) ranging from 10 to 30 Nm3/h/kgcat, with heat duties of up to 9 MW/m3. These experiments lead to a methane conversion close to thermodynamic equilibrium while maintaining limited radial gradients within the system (maximum 20 °C across the mid-radius). A predictive pseudo-heterogeneous 2D reactor model was developed and validated against experimental data. The model accurately captured the observed trends in temperature profiles and outlet concentrations, and can be utilized for optimized design, paving the way for the development of efficient small-scale hydrogen production units.

Experimental investigation of the heat transport and pressure drop in open-cell polyurethane foams

Foam-like materials have a large specific surface area and complex structure that promotes flow turbulence, which makes them useful for heat transfer. In the literature, heat transfer in metal foams (MF) with high thermal conductivity is mainly considered. In the present paper, an experimental study of the hydraulic and heat transfer characteristics of a rectangular channel filled with polyurethane foam (PUF) inserts with a thermal conductivity of 0.2 W⋅m−1⋅K−1 in the air flow was carried out. The open-cell PUF samples had 20 and 80 pores per inch (PPI), 0.97 and 0.98 porosity, 269 µm and 60 µm fiber diameter, respectively. The Reynolds number, based on the fiber diameter ranged from 0.04 to 50. From the results of hydraulic tests, friction coefficients were determined based on the fiber diameter and permeability. The Forchheimer coefficient was 0.198 and 0.318 for 20 and 80 PPI samples, respectively. The permeability was 1.889 10−7 ⋅m2 and 7.535 10−9 ⋅m2 for 20 and 80 PPI samples, respectively. The Nusselt number for both tested PUF samples was correlated with the Reynolds number based on the fiber diameter in a power law with the Reynolds number exponent and constant equal to 0.61 and 0.037 respectively. The intensity of heat transfer in the PUF samples was 7–12 times lower than that in MF. However, a significant heat transfer enhancement is still possible compared to the empty channel up to 7 times. The heat transfer performance of PUF was higher compared to the empty channel, but the thermal performance factor was lower than one. Nevertheless, in practical situations where the mass or cost of the heat exchanger is preferable, PUF can be considered as a heat transfer intensifier.

Synergetic effect of reduced graphene oxide and reticulated open-cell aluminum hybrid composite foam for high-performance electromagnetic wave absorption

In the present work, open-cell aluminum-reduced graphene oxide composite (Al-rGO) foam with varying concentrations of reduced graphene oxide (rGO) was fabricated through the template method and foam's electrical, mechanical, and electromagnetic shielding behavior was studied. The reticulated Al-rGO foam allows the electromagnetic wave (EMW) to go inside the structure and resulting in multiple scattering which enhances the wave absorption capacity of the material. Adding rGO into open-cell aluminium foam (OCAF) enhances its shielding properties, particularly the absorption component. The Al-rGO3 foam shows a total EMI shielding of ∼62 dB at 8.4 GHz frequency and out of which 61.34 dB (> 99% of total shielding) is the absorption component. The Al-rGO foam also exhibited maximum compressive strength of 2.96 MPa and EMI shielding of ∼62 dB at 1.5 wt% rGO, even though the electrical conductivity reduces with rGO content. This may be due to a greater degree of multiple scattering of EMW inside the cellular structure and different energy losses at rGO-Al interfaces. This work shows a new way to use the lightweight metallic structure for high EMW absorption applications with good mechanical stability in the defense and aerospace sectors.

Design and evaluation of compressive properties of 3D-printed PLA stochastic open-cell foam

The deformation characteristics and mechanical behaviour of 3D-printed stochastic open-cell foam structures were experimentally studied under a quasi-static compression test. PLA foam specimens with irregular cell geometry, variable strut sections and prescribed relative density are constructed numerically using the Voronoi diagrams and prepared with fused deposition modelling. The design procedure allows controlling the strut topology easily, which makes the geometrical model suitable for studying the effect of local morphological characteristics on the mechanical performance of open-cell foam material. The effect of different morphological characteristics on the compressive mechanical behaviour of the fabricated PLA foam was examined in detail. Compression experiments prove that the mechanical properties are significantly dependent on the relative density and strut section shape. The main mechanical properties of the 3D-printed PLA foams for different cross-sectional shapes of struts were obtained via the energy-efficient method and expressed with the two common formulas existing in the literature.