Drop of Pressure Behavior of Open-Cell Aluminum Foams at High Pressure Flow

Open-cell aluminum foams were produced by the replication technique in three different pore sizes, ranging from 0.71 to 4.75 mm. The manufactured specimens were physically characterized, determining their porosity, relative density, pores per inch and interconnection windows density. A new experimental design is proposed in order to assess the drop of pressure behavior resulting from the injection of gasoline additive at increasing high pressure intervals, ranging from 200 to 25,000 psi, reproducing the tests at room temperature and 200 °C. The regime governing the flow through the investigated samples was determined as a function of flowrate and the foams physical properties. The structural capacity of open-cell Al foams to conduct highly pressurized flow was evaluated by means of compression tests. It was found that at room temperature, the drop of pressure behavior is strongly associated to physical parameters, whilst at 200 °C, dimensional and geometrical properties are negligible. In addition, in this investigation, it is presumed that the studied foams have the structural capacity to conduct fluids at critical conditions of pressure and temperature.

Modeling of three-phase continuously operating open-cell foam catalyst packings: sugar hydrogenation to sugar alcohols

An advanced comprehensive and transient multiphase model for a trickle bed reactor with solid foam packings was developed. A new simulation model for isothermal three-phase (gas–liquid–solid) catalytic tubular reactor models was presented where axial, radial and catalyst layer effects were included. The gas, liquid and solid phase mass balances included most of the individual terms for solid foam packing (e.g. kinetics, liquid-solid and intraparticle mass transfer effects). Hydrogenation of arabinose and galactose mixture on a ruthenium catalyst supported by carbon-coated aluminum foams was applied as a fundamentally and industrially relevant case study. Parameter estimations allowed to obtain reliable and significant parameters. To test the model performance, a sensitivity analysis was performed and the effect of the kinetic parameters and the operation conditions on the arabinose and galactose conversions was studied in detail. The model described here is applicable for other three-phase continuous catalytic reactors with solid foam packings.

Zn–Al Layered Double Hydroxides Synthesized on Aluminum Foams for Fluoride Removal from Water

Fluoride excess in water represents an environmental issue and a risk for human health since it can cause several diseases, such as fluorosis, osteoporosis, and damage of the nervous system. Layered double hydroxides (LDHs) can be exploited to remove this contaminant from water by taking advantage of their high ion-exchange capability. LDHs are generally mixed with polluted water in the form of powders, which then cause the problem of uneasy separation of the contaminated LDH sludge from the purified liquid. In this work, Zn–Al LDH films were directly grown in situ on aluminum foams that acted both as the reactant and substrate. This method enabled the removal of fluoride ions by simple immersion, with ensuing withdrawal of the foam from the de-contaminated water. Different LDH synthesis methods and aluminum foam types were investigated to improve the adsorption process. The contact time, initial fluoride concentration, adsorbent dosage, and pH were studied as the parameters that affect the fluoride adsorption capacity and efficiency. The highest absorption efficiency of approximately 70% was obtained by using two separate growth methods after four hours, and it effectively reduced the fluoride concentration from 3 mg/L to 1.1 mg/L, which is below the threshold value set by WHO for drinking water.

A NONLINEAR STRAIN-DEPENDENT VARIABLE-ORDER FRACTIONAL MODEL WITH APPLICATIONS TO ALUMINUM FOAMS

In this paper, a power-law strain-dependent variable order is first incorporated into the fractional constitutive model and employed to describe mechanical behaviors of aluminum foams under quasi-static compression and tension. Comparative results illustrate that power-law strain-dependent variable order is capable of better describing stress–strain responses compared with the traditional linear one. The evolution of fractional order along with the porosities or relative densities can be well qualitatively interpreted by its physical meaning. Furthermore, the model is also extended to characterize the impact behaviors under large constant strain rates. It is observed that fractional model with sinusoidal variable order agrees well with the experimental data of aluminum foams with impact and non-impact surfaces.

Al-Based Foams as Permanent Cores in Al Castings: Effect of Surface Skin Thickness and Composition on Infiltration and Core-Shell Bonding

An emerging and still poorly explored application of aluminum foams is their potential use as permanent cores (inserts) in the casting of aluminum alloys. In this context, Al-based foams can introduce a weight reduction, the obtainment of cavities, a strength increase, the ability to absorb impact energy and vibration, acoustic insulation ability, the possibility to simplify the technological processes (no removal/recycling of traditional sand cores), and finally, they can be fully recyclable. Cymat-type Al foams with thin outer skin were used as permanent cores in Al-alloy gravity casting in the present research. Al-foams were characterized in terms of porosity, density, cell wall and skin thickness, surface chemical composition and morphology, and compression resistance. Cast objects with foam inserts were characterized by means of optical microscopy. The preservation of up to 50% of the initial porosity was observed for foam inserts with higher density. Metallurgical bonding between the foam core and the cast metal was observed in some regions.

Sustainable Production of Powder Metallurgy Aluminum Foams Sintered by Concentrated Solar Energy

Porous aluminum foams were successfully fabricated following the space-holder powder metallurgy method with a solar sintering stage. Al foams with porosities of 50, 60, and 70 vol.% were sintered in a low-cost Fresnel lens. Green parts were prepared using aluminum powder as the main metallic material and saccharose as a soluble space-holder. The dissolution stage was designed for each foam and required longer periods of time, between 8 and 32 h, as the design porosity increased. Brown parts were fully sintered by concentrated solar energy at a lower temperature (500 °C) and for shorter times (12–20 min) than those required by conventional sintering techniques (640 °C, ~9 h). The evaluation of density and the characterization of pore size and distribution in the sintered foams was carried out. All obtained foams were stable and presented a homogeneously distributed porosity, very close to the design porosity, with differences lower than 2.1 vol.%, and with approximately half being characterized as open porosity. Moreover, the solar sintered foams presented a high quality, and similar or even greater mechanical properties (such as compressive strength and impact energy absorption) than those achieved by conventional techniques. Foams with 50 vol.% of porosity exhibited the best mechanical behavior, in terms of impact-energy absorption (24.42 MJ/m3) and compressive strength (27.4 MPa).