Open Cellular Material Research Articles

Study on heat transfer in two-layer porous media with heat generation in porous media

A mathematical model involving the mechanism of heat transfer in two-layer porous materials with the heat generation between two porous materials was studied. Open-cellular material with porosity (ϕ) ranging from 0.70 to 0.8 and a porous thickness of 0.02 m was used. The porosity of the first layer was kept at 0.70 but the second layer was varied in the range of 0.73 to 0.79. The heat generation (q̇gen) was a heat flux of 100 to 10,000 W/m2. The air velocity (uf) of 0.4 m/s flowed through the porous material in the x-direction. The governing equation used in the calculation was a two-phase (gas or fluid and solid) energy conservative equation. The heat radiative equation in porous materials was determined by the P1 approximation method. In the model, the temperature profiles (the gas (Tf) and the solid (Ts) phases) and the local energy balance (LEB) of both phases were reported. From the studies, the profile trend of the gas (Tf) and the solid (Ts) temperatures depended on the heat generation (q̇gen). However, the inverse results were obtained by the effect of the porosity of the porous material (ϕ). In the local energy balance (LEB) of the gas phase (or fluid), the main effective terms were the convection (CVF) and the interaction (INT) with almost no thermal conduction (CDF). The interaction (INT) and the heat radiation (RAS) in the solid phase gave a significant effect and there was insignificant conduction (CDS). This was described by both the gas (fluid or air) and solid phases becoming low thermal conduction for the heat transfer mechanism in the case of heat generation between the two-layer porous media. In both phases at the same position, the total energy balance becomes zero according to thermodynamic law.

Uniaxial Compression Behavior of Open Cellular Materials with Spinodal Morphologies Fabricated by Additive Manufacturing

Uniaxial Compression Behavior of Open Cellular Materials with Spinodal Morphologies Fabricated by Additive Manufacturing

Virtually Wall-Less Tubular Sponges as Compartmentalized Reaction Containers.

Sponges are open cellular materials with numerous interesting features. However, the potential of compartmentalized sponges has not been explored although many new properties and applications could be envisioned. We found that compartmentalized fibrous ultraporous polymer sponges with superhydrophobic surfaces could be designed as virtually wall-less reaction containers. With this, for example, the efficient removal of CO2 from water and the controlled mineralization of calcium carbonate are possible. The high porosity (>99%) and superhydrophobicity make these sponges ideal candidates to hold alkanolamine solution for absorbing CO2 and exchange gas through the walls of the sponges. The tubular sponge exhibits a much higher evaporation rate than a glass tube with the same diameter due to the much larger contact area between water and air. Therefore, the spongy reaction container also possesses a much faster adsorption rate, smaller equilibration time and higher efficiency for CO2 adsorption than the glass tube container. In addition, these tubular sponges are also utilized to precipitate calcium carbonate by ammonium carbonate decomposition, which can control the deposition rates and products by tailoring the porosity and surface chemistry in the future. These new sponges provide an ideal basis for numerous new applications, for example, as breathable pipe lines for gas-liquid exchange, slag slurry carbonization, humidifier, and blood enricher.

Elastic modulus of tetrakaidecahedron open-cell cellular materials

In order to investigate the influence of the microstructure of open cellular materials on its properties, numerical simulations were performed to the open-cell tetrakaidecahedron model with a circle-strut transitional–junction. By means of the finite elements method, the influence of microstructure and relative density on elastic modulus is obtained. Results show that circle-strut radius and transitional–junction curvature radius are the primary factors of the relative density increment; influence of the non-linearity of relative density on relative elastic modulus is similar to that of the circle-strut radius on relative elastic modulus, both are obviously greater than that of the transitional–junction curvature radius on relative elastic modulus. For low-density cellular materials, the solid materials added at the intersecting part of the circle-struts brings same influence on elastic modulus for the model, but for high-density cellular materials, the solid materials added at the intersecting part of the circle-struts has greater influence on elastic modulus.

Surface modification of monolithic PolyHIPE Polymers for anionic functionality and their ion exchange behavior

ABSTRACTMonolithic PolyHIPE Polymer (PHP), being a highly porous, low density, open cellular material was produced by polymerization of a high internal phase emulsion (HIPE) in which the polymerizable continuous phase consisted of monomers, styrene (STY), and divinyl benzene (DVB). The inner dispersed phase (90 vol %) was an aqueous solution containing 0.4 wt % potassium persulphate as initiator. The resulting porous structure had 12% crosslinking density. Surface chemistry of the monoliths was modified by chloromethylation and amination to impart anionic functionality. Surface modified monoliths had ion exchange capacity of 3.01 meq/g, and had the ability to uptake water about 10 times of its mass. It was used Cr (VI) ion removal from aqueous solution. The experimental results investigated for both the Langmuir and the Dubinin–Radushkevich adsorption models. The maximum Cr (VI) adsorptions are 126.6 mg Cr (VI)/g and 129.3 mg Cr (VI)/g, respectively. The mean free energy E of adsorption is 11.18 kJ/mol according to the Dubinin–Radushkevich adsorption model, indicating that the adsorption occurs through a chemical ion‐exchange process and it is not diffusion limited. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42286.

A lightweight X-type metallic lattice in single-phase forced convection

The superior capability of bearing thermal and mechanical loads to other types of open cellular materials has led to advances in developing new periodic cellular materials. We introduce a lightweight X-type lattice fabricated via the metal sheet folding and present its thermo-fluidic characteristics in single-phase forced convection. For fixed porosity, thermal conductivity and Reynolds number, the X-type lattice provides overall heat removal capacity up to two times higher than reference periodic cellular materials. The unique morphology of the X-type lattice results in a large scale spiral primary flow, which interacts with several secondary flows. These fluid flow behaviors and the induced complex flow mixing substantially enhance heat transfer on both the substrate and ligaments. However, the X-type lattice causes roughly three times higher pressure drop than reference periodic cellular materials for a given Reynolds number. Overall, superior heat transfer is achieved by the X-type lattice for a fixed pumping power.

Sulfonation of crosslinked styrene/divinyl benzene copolymer beads formed from porous foam and ion adsorption of copper by them: column adsorption modeling

The porous foam is made by the polymerisation of a high internal phase emulsion and it is a highly porous, low density, open cellular material. Surface properties of the foam were chemically modified via a sulfonation process. Sulfonation added ‒SO3(‒)H(+) groups to the polymer matrix. The ion adsorption behavior of copper ions on sulfonated polymer beads, depending on inlet concentration (10-60 mg/L), pH of inlet solution (2.00-5.20) and flow velocity (1.7-11.4 m/h) was studied. It was shown that the amount of copper adsorbed was not affected with increasing concentration of feed solutions and flow velocity. Also the process was highly pH dependent. The maximum removal was 117.96 mg Cu/g dry adsorbent at flow velocity 11.4 m/h. Column experimental tests were conducted to provide data for theoretical modeling and to verify the system performance of the process. A theoretical column model adopted in this work was found to describe well the ion adsorption breakthrough characteristics.

Micromechanical approach for the behaviour of open cell foams

The objective of this paper is the prediction of the macroscopic behaviour of open-cell foams in elasticity and viscoelasticity as function of their microstructure by using a micromechanical approach. Open cellular materials are characterised by remarkable mechanical properties with light weight. Such materials are largely used in various applications mainly in energy absorption. Polyurethane foam is used as an application once its microstructure is majorly described by an open-cell foam. Finite Element computations are performed on a unit cell subjected to periodic boundary conditions. Then, a micromechanical model based on Cosserat homogenisation framework is performed to predict the macroscopic elasticity. The linear viscoelastic behaviour is deduced from elastic results by taking advantage of correspondence principle. Finally, the results are confronted to various models developed in literature.

Microstructures and Properties for a Superalloy Powder Mixture Process by Electron Beam Melting

The microstructures and residual hardnesses for solid components of 2-phase TiAl (Ti-48Al-2Nb-2Cr in a / o ) and Inconel 625 (Ni-19Cr-9Mo-4Nb in w / o ) fabricated by electron beam melting (EBM) were compared with a 10:1 blend of TiAl: alloy 625 pre-alloyed powders producing a complex alloy having the composition 48Ti-24Al-9Ni-8Nb-4.5Cr-4Ni (in w / o ). The blended alloy hardness (HV) reached 7.5 GPa in contrast to 1.4 GPa for the Alloy 625 and 4.0 for the 2-phase TiAl alloy. Reticulated mesh samples and stochastic foam samples prepared from the blended alloy by EBM exhibited a relative stiffness versus relative density plotted on a log-log basis consistent with other reference alloys fitted to a straight line with a slope n = 2 for ideal open cellular materials.

Open-Cellular Co-Base and Ni-Base Superalloys Fabricated by Electron Beam Melting.

Reticulated mesh samples of Co-29Cr-6Mo alloy and Ni-21Cr-9Mo-4Nb alloy (625) and stochastic foam samples of Co-29Cr-6Mo alloy fabricated by electron beam melting were characterized by optical metallography, and the dynamic stiffness (Young’s modulus) was measured by resonant frequency analysis. The relative stiffness (E/Es) versus relative density (ρ/ρs) plotted on a log-log basis resulted in a fitted straight line with a slope n ≅ 2, consistent with that for ideal open cellular materials.

Characterization of open-cell cellular material structures with pore fillers

Due to their mechanical properties, cellular material structures are often used in automotive, aerospace, ship and railway industries, as elements for deformational energy absorption. New advanced cellular material structures have been evaluated and characterised in the scope of this study in order to determine their energy absorption capability through the deformation process. Parametric computational simulations in the framework of the finite element method have been used for this purpose. Newly developed computational models of regular open-cell cellular material structures considering viscous pore fillers have been developed and their response under impact conditions was analysed using the explicit code LS-DYNA. The results of the performed study show that introduction of viscous fillers indeed increases the energy absorption capability of open-cellular material structures. Additionally, it was determined that the size of the cellular material (number of cells) dramatically influences the cellular structure response and that the filler influence is stronger in cellular structures with higher relative density.

Polyhipe foam materials as filtration media

A novel method of preparing low-density microporous polymeric foam materials has been utilised to produce media which are effective in crossflow microfiltration applications. Polyhipe polymer (PHP) is produced by the polymerisation of a high-internal-phase emulsion (HIPE), resulting in a homogeneous, highly porous, low-density, open cellular material. Crossflow filtration modules made from PHP have been tested using a computer-controlled filtration unit to investigate the effects of membrane skin porosity and surface modification on their filtration performance.