ABSTRACT
Metallic foam is a popular topic due to its diverse industrial applications and unique combination of properties. Metallic foam is significantly lighter than nonfoam metal materials due to its porous structure, which incorporates a substantial amount of air or voids. This lower density makes metallic foam advantageous in applications in which weight reduction is critical. This makes it ideal for the aerospace, automotive, and construction industries; also, its versatile nature continues to make it an attractive material for various industrial applications such as impact absorbers, heat exchangers, and biomedical and marine engineering. However, the choice between metallic foam and nonfoam metal also depends on other factors like mechanical properties, cost, and specific application requirements. This review describes various fabrication methods of metallic foam that include the liquid metallurgy route which uses liquid or semiliquid metal, the powder metallurgy route uses metal in powder form, metal ion, and the metal vapor route which uses electrolytic deposition method to produce metallic foam. These methods include direct gas injection, adding blowing agents in solid or liquid metals, investment casting, the addition of a space holder in the precursor, metallic ion, vapor deposition on a polymer sponge, and many more. The morphology of metallic foam depends upon the method that is chosen for fabrication, and up to 98% porosity can be achieved by these methods. Additive manufacturing for metallic foam fabrication is an emerging field based on selective laser melting and electron beam melting principles. It has exceptional possibilities for generating complicated 3D shapes and customizing the material characteristics. The main purpose of this review article is to give significant insights into the various production procedures for metallic foams to researchers, engineers, and industry experts, assisting in the selection of acceptable methods depending on individual application needs. This review investigates the manufacturing conditions for metallic foams and finally discusses their advantages, drawbacks, and obstacles in mass production. The findings add to current efforts to expand metallic foam technology and encourage its wider application across diverse sectors, opening the path for future research and development.
ABSTRACT
The current work is an expansion of our previous numerical model in which we investigated the motion behavior of mold inclusions in the presence of interfacial tension effects. In this paper, we used computational fluid dynamic simulations to examine the influence of interfacial tension on inclusion motion behavior near to the solid-liquid interface (solidifying shell). We have used a multiphase model in which molten steel (SPFH590), sulfur, and alumina inclusions have been considered as different phases. In addition, we assume minimal to negligible velocity at the solid-liquid interface, and we restrict the numerical simulation to only include critical phenomena like heat transport and interfacial tension distribution in two-dimensional space. The two-phase simulation of molten steel mixed with sulfur and alumina was modeled on volume of fluid (VOF) method. Furthermore, the concentration of the surfactant (sulfur) in molten steel was defined using a species model. The surfactant concentration and temperature affect the Marangoni forces, and subsequently affects the interfacial tension applied on inclusion particles. It was found that the alteration in interfacial tension causes the inclusion particles to be pushed and swallowed near the solidifying boundaries. In addition, we have compared the computational results of interfacial tension, and it was found to be in good agreement with experimental correlations.
ABSTRACT
The problem of industrial wastewater containing heavy metals is always a big concern, especially Cu2+, which interprets the soil activity in farmland and leaves a negative impact on the environment by damaging the health of animals. Various methods have been proposed as countermeasures against heavy-metal contaminations, and, as a part of this, an electrospun nanofibrous adsorption method for wastewater treatment is presented as an alternative. Poly(lactic acid) (PLA) is a biopolymer with an intrinsic hydrophobic property that has been considered one of the sustainable nanofibrous adsorbents for carrying adsorbate. Due to the hydrophobic nature of PLA, it is difficult to adsorb Cu2+ contained in wastewater. In this study, the hydrophilic PLA/poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEG-PPG-PEG) nanofibrous adsorbents with different silicon dioxide (SiO2) concentrations were successfully prepared by electrospinning. A hydrophilic group of PEG-PPG-PEG was imparted in PLA by the blending method. The prepared PLA/PEG-PPG-PEG/SiO2 nanofibrous adsorbents were analyzed with their morphological, contact angle analysis, and chemical structure. The Cu2+ adsorption capacities of the different PLA/PEG-PPG-PEG/SiO2 nanofibrous adsorbents were also investigated. The adsorption results indicated that the Cu2+ removal capacity of PLA/PEG-PPG-PEG/SiO2 nanofibrous adsorbents was higher than that of pure ones. Additionally, as an affinity nanofibrous adsorbent, its adsorption capacity was maintained after multiple recycling processes (desorption and re-adsorption). It is expected to be a promising nanofibrous adsorbents that will adsorb Cu2+ for wastewater treatment.
ABSTRACT
Inclusions entrapped by the solidifying front during continuous casting adversely affect the properties of the final steel products. In this study, we investigated the effect of the interfacial tension due to surfactant concentration, particularly sulfur, on alumina inclusion motion behavior during molten steel solidification in a continuous casting mold. A two-dimensional numerical model was developed in Ansys Fluent software to simulate the inclusion motion in a continuous casting mold. Further, the impacts of different values of the alumina inclusion diameter, sulfur concentration, and melt temperature were studied to understand the inclusion motion behavior. The inclusion diameter affected the inclusion distribution throughout the domain. The alumina inclusion entrapment percentage varied in the case of sulfur mixing (using an empirical relationship for modeling). It was found that the removal percentage varied according to the sulfur concentration. The addition of sulfur at concentrations from 10 ppm to 70 ppm resulted in a 4% increase in the removal of alumina inclusions (trapped in the solidifying shell), except for the 100-ppm case. Smaller-sized inclusion particles had a 25% higher chance of entrapment at the top level of the mold. Under the effect of a higher surface tension gradient between inclusions and the melt, the predicted findings show that inclusions were vulnerable to engulfment by the solidification front.
ABSTRACT
Fog is a resource with great potential to capture fresh water from the atmosphere, regardless of the geographical and hydrological conditions. Micro-sized fog collection requires materials with hydrophilic/phobic patterns. In this study, we prepared hydrophilic poly(lactic acid) (PLA)/poly(ethylene glycol)-poly(propyl glycol)-poly(ethylene glycol) (PEG-PPG-PEG) blended nanofiber membranes with various PEG-PPG-PEG concentrations by electrospinning. Changes in the morphological and chemical properties, surface wettability, and thermal stability of the PLA/PEG-PPG-PEG composite nanofiber membranes were confirmed using field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, contact angle testing, and thermogravimetric analysis. As the PEG-PPG-PEG content of the nanofiber membranes increased, their hydrophilicity increased. Water stability, membrane porosity, and water transport rate tests were also conducted to observe the behavior of the hydrophilic PLA nanocomposite membranes in aqueous media. Finally, we applied the PLA-based membranes as fog collectors. As the PEG-PPG-PEG content of the nanofiber membranes increased, their ability to collect fog increased by over 40% compared with that collected by a pure PLA membrane. The prepared membranes not only improve the ability of fog collectors to harvest water but also broaden the use of PLA-based membranes in multiple applications, including tissue engineering, drug delivery, scaffolds, and pharmaceuticals.
