Open-cell Foams Research Articles

CO2 methanation over open cell foams prepared via chemical conversion coating

In the framework of the CO2 utilization, and of the integration of renewable energy sources into the power generation scenario, the methanation reaction plays a key role, being the core of the power-to-gas, or power-to-X, processes. Structured catalysts are widely recognized for being particularly promising in exothermic processes, as they ensure a better thermal management of the heat generated within the system. In recent years, the application of metallic structures has spread. Nevertheless, the functionalization of these structures via washcoating procedure has several disadvantages. Herein, it is highlighted the potential of ceria chemical-conversion coating (CCC) as technique for the preparation of methanation catalysts, and optimize the Ni deposition procedure on such structures. In this work, the suitability of the obtained catalysts for CO2 methanation was evaluated in several operating conditions, obtaining CO2 conversion as high as 70 % below 400 °C with the most promising sample. In a first analysis, it was demonstrated that the catalysts prepared through the CCC technique can be applied in the CO2 methanation systems. In addition, through a kinetic analysis it was highlighted that the preparation method could be a key parameter for the selectivity of the process, driving the system towards a direct CO2 methanation or to the CO-path mechanism, therefore further studies should be performed to better explore this aspect.

Preparation of Open-Cell Long-Chain Branched Polypropylene Foams for Oil Absorption.

This study aimed to prepare open-cell foams using a blend of long-chain branched polypropylene and polyolefin elastomer (LCBPP/POE) for the production of reusable oil absorbents. The supercritical CO2 foaming process was conducted using a two-step batch rapid depressurization method. This unique two-step foaming approach significantly expanded the temperature and pressure windows, resulting in more uniform cells with smaller sizes, ultimately leading to higher expansion ratios and an increased open cell content. The foaming process was optimized by adjusting parameters, such as the LCBPP/POE ratio, foaming temperature, and foaming pressure, reaching a maximum open cell content of 97.6% and a maximum expansion ratio of 48. The influence of polypropylene (PP) crystallization was investigated with the aid of scanning electron microscopy and differential scanning calorimetry. Furthermore, the hydrophobic and lipophilic characteristics of the LCBPP/POE open-cell foam were determined via contact angle measurements and oil/water separation tests. Oil absorption tests revealed that the blended LCBPP/POE foam has a higher oil absorption capacity than that of the pure LCBPP foam. The cyclic oil absorption tests demonstrated the outstanding ductility and recoverability of the LCBPP/POE open-cell foam in comparison to those of the pure LCBPP foam. Over 10 cycles, the LCBPP/POE foam maintained a substantial adsorption capacity, retaining 99.3% of its initial oil absorption capacity. With its notable features, including a high open cell content, excellent hydrophobic and lipophilic characteristics, superior oil absorption capacity, impressive cyclic oil absorption performance, and robust reusability, LCBPP/POE open-cell foams exhibit significant promise as potential oil adsorbents for use in oil spill cleanup applications.

Fabrication of bio-based biodegradable poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composite foams for highly efficient oil-water separation

The open-cell bio-based biodegradable polymer foams show good application prospect in dealing with the serious environmental issue caused by oil spill and organic solvents spills, while the cell structures and hydrophobic properties of the foams limit their performance. In this work, the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was selected to help prepare bio-based biodegradable poly(lactic acid) (PLA) foams. Based on a two-step foaming method, the crystallization ability of different samples was regulated by the “original crystals” together with PHBV in the foaming process, where skeleton structures were provided to facilitate the open-cell structures and promote their mechanical property. As illustrated, PHBV facilitated the formation of open-cell PLA foams, where the foams displayed superior oil-water separation capacity. The maximum volume expansion ratio of the foams was 80.08, the contact angle of deionized water reached to 134.5°, the adsorption capacity for oil or organic solvents was 10.8 g/g-51.8 g/g, and the adsorption capacity for CCl4 can still maintained 83.5 % of the initial value after 10 adsorption-desorption cycles. This work not only clarified the foaming mechanism of open-cell foams, but also provided a green and simple method for preparing bio-based biodegradable foams possessing excellent oil-water separation performance.

Manufacturing Method and Thermal Properties of Open-Cell Type Aluminum Foam by Replication Casting Process

Open-cell type aluminum foam possesses unique structural characteristics comprising numerous interconnected pores within. This intriguing structure facilitates the passage of fluids (gas or liquid) through the interior of the open-cell type aluminum foams, enabling easy transfer to the exterior. The objective of this study is to manufacture open-cell type aluminum foams with varying pore sizes using the replication casting process and to evaluate their thermal properties. The equipment designed for the production of open-cell type aluminum foams consists of a chamber and an inner container. The chamber is connected to a vacuum line and an Ar gas line, with the container positioned inside. The aluminum alloys utilized for the foams were A356 and ADC12, and Na2CO3 served as the space holder. As a result of manufacturing the foams, there was no significant difference of porosity with space holder size and alloy types, the porosity averaged around 62%. To investigate the thermal properties of open-cell type aluminum foams in relation to pore size and alloy types, temperature variations were measured during sample heating via the hot plate method. Consequently, it was confirmed that the thermal properties of the foams were influenced by the structural conditions and alloy types.

Thermal characteristics of metal foamed flat plate with circular and elliptical impinging jets

ABSTRACT Here, the thermal characteristics of open-cell metal foam (OCMF) integrated stainless steel (SS) foil are investigated experimentally during air jet impingement using circular and elliptical nozzles. The aspect ratio (AR) of the elliptical nozzle is varied from 2 to 4, the Reynolds number (Re) is varied within 5000 - 25,000 and the impinging distance (z/d) is varied within 3–7 during tests. Thin foil thermal imaging infrared thermography has been utilized to record the temperature, and the measured temperature data is used to estimate the performance parameters. The thermal performance is evaluated based on the local, average, and stagnation Nusselt number (Nu) for different configurations. The integration of OCMF with SS foil has been found to significantly enhance heat transfer at the stagnation point in different nozzle configurations. At a Reynolds number (Re) of 5000, the percentage increase in stagnation Nu with foam compared to when there is no foam is found to be 80%, 46%, 38%, and 24% for nozzles with AR of 1, 2, 3, and 4, respectively. The local (0 ≤ x/d ≤2) and average values of Nu for lower impinging distance (z/d ≤5) are found to be higher for the elliptical nozzles, while for z/d ˃ 5, the circular nozzle is found to exhibit better performance. The peak average Nu with nozzle AR = 4 at Re = 25000 is found to be higher than nozzle AR of 3, 2, and 1 by 6.75%, 8.72%, and 23.44%, respectively. Additionally, for the same Re, the peak average Nu of nozzles with AR = 4, AR = 3, and AR = 2 is higher than the circular nozzle by 23.44%, 15.62%, and 13.54%, respectively. New correlations based on experimental results are proposed to determine the local and average Nusselt number as a function of various operating parameters.

Parameter analysis and rapid design of porosity gradient distribution for open-cell metal foam in the latent thermal energy storage unit

The positive gradient porosity design of metal foam is used to improve the thermal performance of the vertical shell-and-tube latent thermal energy storage (LTES) unit. To optimize the gradient design, quantitative analysis is of vital importance. Therefore, the relative offset number EX is proposed in this study, which indicates the porosity difference between upper/down porosity and the mean porosity. Based on the numerical model of a shell-and-tube LTES unit filled with composite phase change material (CPCM) on the shell side, the effects of parameters, including the inlet HTF temperature and velocity, LTES dimensions, porosity, and thermal conductivity of the metal foam on the optimal gradient design are discussed. The optimal EX exhibits little relation with the inlet temperature but increases with the LTES height and thermal conductivity, while decreases with inlet velocity, porosity, and LTES outer radius. With the correlation between the optimal EX and the relative dimensionless number, the effects of these parameters on the optimal EX are integrated and quantified as experience equations so that the optimal porosity gradient of metal foam and the relative reduction melting time can be rapidly obtained under a wide variety of practical applications.

Antimicrobial foam-filter based on commercial support coated with polydopamine and silver nanoparticles for water treatment

Fresh water is a critical resource on the planet and the treatment techniques employed worldwide are often insufficient at removing contaminants, leading to their release in the environment. This work displays the development of a foam-filter based on open-cell polyurethane foams coated with polydopamine and an antimicrobial metal for water treatment processes. A simple coating method is proposed and the resulting tool is characterized. Its antimicrobial activity is assessed on pure water-based cultures of Staphylococcus aureus, Escherichia coli, Legionella pneumophila and Candida albicans in optimal growth conditions. This study also investigates the stability and reusability of the foam-filter. The results show that silver grafting via this one-step original approach (namely OCPUF@PDA/Ag) exhibits a good antimicrobial activity on the selected microorganisms, with a complete microbicidal effect against C. albicans and E. coli after 3 h of contact time (5 and 6 Log decrease, respectively), and after 24 h of contact time for S. aureus. The foam-filter shows great stability and recyclability as it can be reused at least 4 times with the same overall activity, as well as significant antifouling properties. The mechanism of action was partially investigated and shows that reactive oxygen species are generated inside the bacterial cells after contact with the foam. This study gives a starting framework for the development of a bio-inspired polydopamine material with interesting physical, antifouling and antimicrobial properties applicable in water treatment processes.

Mechanical and corrosion properties of highly porous Ta-Nb-Sn alloy for intervertebral disc in spinal applications

Abstract In this study, low Young’s modulus, highly porous Ta-Nb-Sn alloy foam was manufactured by using the space holder method. The aim of this study is development of an alloy with high wear resistance, with Young’s modulus, with good imaging (MRI, CT) properties, and with high bioactivity. Ta alloy foam can be used in spinal applications (intervertebral disc) or dental applications. The space holder method enables the manufacturing of open-cell foam with a low elastic modulus. Powder mixtures were prepared through mechanical alloying. Carbamide was used to form pores. Ta has suitable strength, ductility, corrosion resistance, and biocompatibility. Ta has high price, however, and a high melting temperature, high activity, and high density. Nb addition lowered the melting temperature, elastic modulus, and cost of using Ta. The sinterability of Ta was enhanced by Sn addition. The corrosion behaviour of Ta alloy was examined. Young’s modulus was determined by compression and ultrasonic tests. Tomography and radiography tests were also used.

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.

Experimental study about the impact of open cell aluminium foam (OCAF) insertion in salt-based phase change material (PCM) for electronics thermal management

Thermal management of electronic components is a critical task in a harsh thermal environment. Spacecraft and satellites' electronics are susceptible to highly intermittent heating and cooling thermal conditions, which imposes challenges for robust thermal management system design. Phase change materials (PCM) are a promising solution for overcoming these challenges and enhancing thermal control performance. The lower PCM thermal conductivity and PCM supercooling limit PCM utilisation in electronic thermal control systems. The present study aims to provide solutions for enhancing the heat transfer within the PCM, boosting the PCM thermal conductivity, and diminishing the PCM supercooling. The open-cell aluminium foam (OCAF) was adopted for boosting the heat transfer within the PCM. A thermal management module (TMM) integrated with a salt-based PCM/OCAF composite was developed for electronics thermal management. The TMM was tested under intermittent thermal conditions of heating and cooling. An electric heater and Peltier cooler were affixed to the TMM for the heating and cooling process, respectively. Three levels of heat fluxes were adopted: 700, 1000, and 1400 W/m2. The heating process lasted one hour; then, the TMM was cooled by the Peltier element to the initial temperature. The research novelty covers the gap in understanding how OCAF affects salt-based PCM supercooling when subjected to varying heating loads during intermittent cycles. The outcomes reported a remarkable improvement in thermal management efficiency. The PCM-based TMM reduced the highest temperature by about 20.4 %, 21.6 %, and 23 % at the three heating levels. The OCAF diminished the PCM supercooling curiously. The reduction in PCM supercooling was 43.5 % compared to the 100 % PCM case obtained at the heat flux of 1400 W/m2.

Preparation and tribological properties of different kinds of metal foam-polytetrafluoroethylene co-continuous phase composites

Co-continuous phase composites of polytetrafluoroethylene (PTFE) interpenetrated with five kinds of open-cell metal foams, Cu, Ni, Fe, CuNi and FeNi, were prepared via emulsion impregnation, vacuum impregnation and free sintering. The microstructure, mechanical performance, thermal stability and tribological behavior characteristics of these materials were investigated. The results showed that the filling efficiency of PTFE was between 76.1% and 98.7%. The developed composites generally exhibited enhanced strength and thermal stability. In particular, their wear rate under dry friction conditions was reduced by 63–95% compared with pure PTFE resin, which was ascribed to the effective transfer of friction heat and the enhanced load bearing capacity. However, their tribological performance weakened in a simulated seawater environment because of the diffusion of seawater in the materials and corrosion of the metal skeletons.

Overall elastic characterization of equivalent FE models for aluminum foams through computational homogenization approach and genetic algorithm optimization

Aluminum foams are gaining increasing interest because of their widespread set of functional attributes combined with highly specific structural properties and affordable manufacturing processes. The finite element analysis of foam materials is typically performed with complex and time-consuming 3D models. Here, a beam FE model strategy is utilized to obtain a precise and time-saving simulation instrument for open-cell aluminum foams. The beam FE modeling is based on the Kelvin cell as a fundamental unit and provides a simplified geometrical description of the intersection node between ligaments whose elastic properties need to be adjusted through a calibration procedure. The beam FE model elastic properties are measured through a homogenization procedure that evaluates the elastic constants of an equivalent material. The issue of model calibration is formulated as an optimization problem exploiting the NSGA-II genetic algorithm. This procedure allows obtaining the full elastic calibration of the beam FE model, reproducing the orthotropic elastic behavior of the aluminum foams with reduced computational efforts.

Production and Characterization of Ta-Sn Alloy Foam for Biomedical Applications

In this study, Ta-Sn alloy foam was manufactured by using space holder method for biomedical applications. The aim of the study is development of an alloy with suitable mechanical properties, with good medical imaging (digital radiography, computed tomography) properties (radiopacity), with high bioactivity. Powder metallurgy-based space holder method enables manufacturing of open-cell foam with low elastic modulus. Powder mixtures were prepared by mechanical alloying. Carbamide was used as a pore former. Ta has suitable radiopacity, strength, ductility, corrosion resistance and biocompatibility. But Ta has high price, high melting temperature, high activity, and high density. Sn addition was lowered the melting temperature, and cost of Ta. Sinterability of Ta, which is a refractory metal, was enhanced by Sn addition. Corrosion behaviour of Ta alloy was examined. Young’s modulus was determined by compression and ultrasonic tests. Increasing Sn content of the alloy increased the Young’s modulus. Increasing porosity decreased the Young’s modulus. Ta alloy has no cytotoxic potential according to neutral red test. Sn addition was lowered the polarization resistance and slightly increased the corrosion rate of Ta-Sn alloy samples.

Experimental and numerical investigations of an open-cell copper foam (OCCF)/phase change material (PCM) composite-based module for satellite avionics thermal management in a thermal vacuum chamber (TVC)

Small satellites' thermal control in the space environment is crucial. Phase change materials (PCM) are promising options for satellite thermal management in space thermal conditions. The current work provides an experimental and numerical investigation of a thermal control module (TCM) using an open-cell copper foam (OCCF)/PCM combination. The experimental tests were carried out in a thermal vacuum chamber (TVC), which simulated the vacuum space environment. The PCM thermal conductivity was boosted using OCCF and aluminium fins. The metallic parallel fins divided the heat sink into six cuboid cavities and were filled with PCM. Two samples with different pores per inch (PPI) of OCCF were adopted, one with 10 PPI and the other with 20 PPI. For the experimental work, the adopted PCM was SP 31. Two levels of heating loads were applied to the TCM: 10 W and 7 W. The numerical model was verified using the experimental work findings. The experimental work concluded that the PCM capsulation sealing is a dominant factor for successful capsule design under vacuum operation. The thermal conductivity enhancers (TCEs) remarkably improved the thermal management performance of the PCM. The case with PCM reported a reduction in the maximum temperature by about 43.67 % and 41.4 % at 7 W and 10 W, respectively, relative to the case without PCM. The PCM/fins combination could improve the PCM performance and mitigate the maximum temperature from 41.7 °C to 39.6 °C with a reduction percentage of 5 %. The OCCF reported better thermal performance than the metallic fins. The OCCF with 10 PPI decreased the PCM maximum temperature by 10.3 %. The OCCF with 20 PPI reported a reduction in the PCM maximum temperature by 13.8 % at 10 W heating power.

Electrical energy harvesting by connected form stable phase change material composites

Over the years, thermoelectric energy harvesting has been becoming a topic of intensive research and thermoelectric power generator has been utilized in various energy harvesting applications. However, a thermoelectric device is required to harvest energy, which has relatively low efficiency and high cost. To overcome such a common problem, the objective of this study is to generate electrical energy without using thermoelectric devices. To this end, an advanced energy harvester composed of two different phase change material composites was explored. It was hypothesized that based on the well-known Seebeck effect, stable electrical energy output would be feasible without a thermoelectric device, by directly connecting two types of phase change materials with different electrical conductivities and different phase transition temperatures. In this study, polydimethylsiloxane open-cell foam embedded with single walled carbon nanotubes was prepared and utilized as a supporting material to fabricate form stable phase change material composites. Two types of polydimethylsiloxane open-cell foams were prepared by embedding single walled carbon nanotubes, which had a weight fraction of 0.33 % and 0.1 %, respectively, leading to different electrical conductivities. The different electrical conductivities of the supporting foams are vital to cause electron motion. Two types of phase change materials with different phase change temperatures were selected as working materials by filling them into the polydimethylsiloxane open-cell foams. Based on the test results, it is found that direct connection of 1-tetradecanol and polyethylene glycol composites can produce stable electrical voltage and current under different thermal energy inputs: through the change of external temperature from 25 °C to 80 °C, through the light-on/-off process, and through heat flow treatment. The maximum output voltage was up to 1.18 mV with a 50 % energy harvesting efficiency and the harvesting time was maintained for 50 min. To confirm the temperature profiles of the phase change material composites, numerical simulation was conducted and the thermal properties during the phase transition process were estimated, with good agreement. This research would create a new concept of thermoelectric energy harvesting for further development in practical applications.

Gold Nanoparticle‐Coated Bioceramics for Plasmonically Enhanced Molecule Detection via Surface‐Enhanced Raman Scattering

Herein, feasibility of plasmonically enhanced molecule detection via surface‐enhanced Raman scattering for ceramics that are commonly used as bone or tooth replacement materials is evaluated. Open cell foams of Bioglass 45S5, the commercial hydroxyapatite‐based product Bio‐Oss, and bioinert zirconia‐toughened‐alumina (ZTA) are coated with Au nanoparticles via colloidal deposition to introduce plasmonic effects. Depending on the pore size, gold‐functionalized plasmonic porous Bioglass shows effective Raman enhancement factor (eEF) up to , while depositing gold nanoparticles on Bio‐Oss and porous ZTA resulted in eEF of and respectively. The performance of the plasmonic porous bioceramics under simulated biological conditions is examined in situ in the biological medium fetal bovine serum (FBS) and during extended incubation in mineralizing simulated body fluid (SBF). Most notably, the plasmonic porous Bioglass still delivered an eEF around after 28 days of incubation in SBF, indicating promising stability in simulated biological conditions without significant difference in SBF bioactivity before and after Au deposition. Accordingly, the plasmonically enhanced porous bioceramics offer the possibility for real‐time and sensitive molecule detection at SBF and FBS conditions and can be further developed for sensing of specific biomarkers, for example, in the context of osseointegration of bone replacement materials.

Tensile strength and damage of open-cell ceramic foams under cylindrical splitting test

Tensile strength and damage of open-cell ceramic foams under cylindrical splitting test

Об одном из подходов к прогнозированию и повышению шумопоглощения в кабинах транспортно-технологических машин

Noise is one of the main harmful production factors in the mining industry. The results of a hygienic assessment of working conditions indicate that exceeding the maximum permissible noise levels in 50 % of cases is recorded at the workplaces of drivers of the transport and technological machines. One of the efficient measures to reduce medium- and high-frequency noise in the cabins of transport and technological machines is the use of noise-absorbing upholsteries mounted on their metal panels. The article presents a computational and experimental procedure based on determining the reverberation coefficient of sound absorption of flat-sheet pressed samples of materials manufactured using the production technology of serial molded upholsteries. The material samples contained a base layer of open-cell polyurethane foam, a reinforcing layer of fiberglass, a thermally activated adhesive layer, a front layer of needle-punched fabric, and a back layer of non-woven fabric. The values were determined related to the sound absorption coefficient of flat-sheet pressed samples of materials manufactured using representative technology. The measurements were carried out with different sizes of air gaps relative to the reflective surface. As an example, the results of calculating the equivalent sound absorption area of the roof lining of a truck cab are considered. The obtained values of the equivalent sound absorption area for the original design option are below the target values for this part by up to 31 %. The original version was modified by changing the thickness of the molding of the blank and its location relative to the metal panel of the cabin without changing the material and design. As follows from the calculation results, the values of the equivalent sound absorption area of the roof lining in the modified version ensure that the target requirements are met.

Numerical instantiation of complex open-cell metal foam microstructure and evaluation of its thermal performance on the melting of composite phase change material

Numerical instantiation of complex open-cell metal foam microstructure and evaluation of its thermal performance on the melting of composite phase change material

Wake characteristics of wall-mounted solid and foam-covered circular cylinders

The wake characteristics of wall-mounted finite submerged solid and foam-covered circular cylinders (height/diameter = 0.9) are explored using large-eddy simulation for a Reynolds number (based on the cylinder diameter) of 13 000, and the simulation results are validated using particle image velocimetry. The foam-covered cylinder consists of an inner cylinder wrapped with a highly porous open-cell foam and capped by circular plates at the top and bottom. Two recirculation regions are identified for both cylinders, based on time-averaged data, one downstream and another above the top surface of the cylinder. The presence of the foam induces changes in the characteristics of both recirculation regions. The foam covering also interrupts the formation of large periodic structures, the evidence of which can be seen in the temporal distribution and discrete Fourier analysis of the force coefficients and velocity fluctuations. The temporal lateral oscillations, represented by the coefficient of sway, are observed for the solid cylinder but are suppressed in the case of the foam-covered cylinder. Two dominating frequencies are consistently present for the solid cylinder, but no such frequencies can be identified for the foam-covered cylinder. Finally, spectral proper orthogonal decomposition modes are presented in order to further substantiate the findings.