Polymer foams have low density, good heat insulation, good sound insulation effects, high specific strength, and high corrosion resistance, and are widely used in civil and industrial applications. In this paper, the classification of polymer foams, principles of the foaming process, types of blowing agents, and raw materials of polymer foams are reviewed. The research progress of various foaming methods and the current problems and possible solutions are discussed in detail.

https://www.mdpi.com/2073-4360/11/6/953/pdf

Recent Trends of Foaming in Polymer Processing: A Review.

Waste environmental sources of metakaolin and corn cob ash for preparation and characterisation of green ceramic hollow fibre membrane (h-MCa) for oil-water separation

In contrast to the wetting phenomenon of pure substance phase, we here concentrate on the wetting behavior of immiscible fluids with two components via numerical simulations. We investigate the energetic contribution, the wall energy and the surface excess energy, to the wetting behavior of liquid solutions varying with temperature. This investigation is in accordance with Cahn's wetting transition theory, where the surface composition plays a vital role. By analyzing the energetic contributions, we reveal two different physical mechanisms of complete wetting: (i) surface tension driven complete wetting, where the wetting microstructure is achieved via the outward spreading of the triple junction, and (ii) diffusion induced complete wetting, where the wetting film is achieved through a direct deposition of the solute on the substrate. The former one is consistent with the classic theory of Young's law, and the latter one is an alternative mechanism. To indicate the broad multiplicity of the microstructural arrangements, we take porous structures to exemplarily elucidate the formation of alternative perfect wetting structures. Differing from the wetting on a flat substrate, we show that the surface composition varying with temperature leads to a distinct wetting phenomenon in porous structures. The present findings provide an alternative interpretation for complete wetting and are expected to be exploited for designing more effectively and efficiently superhydrophilic structures.

Wetting transition and phase separation on flat substrates and in porous structures.

Phase-field study on the growth of magnesium silicide occasioned by reactive diffusion on the surface of Si-foams

Microscale Janus particles have versatile potential applications in many physical and biomedical fields, such as microsensor, micromotor, and drug delivery. Here, we present a phase-field approach of multicomponent and multiphase to investigate the Janus droplet formation via thermally induced phase separation. The crucial kinetics for the formation of Janus droplets consisting of two polymer species and a solvent component via an interplay of both diffusion and convection is considered in the Cahn–Hilliard–Navier–Stokes equation. The simulation results of the phase-field model show that unequal interfacial tensions between the two polymer species and the solvent result in asymmetric phase separation in the formation process of Janus droplets. This asymmetric phase separation plays a vital role in the establishment of the so-called core–shell structure that has been observed in previous experiments. By varying the droplet size, the surface tension, and the molecular interaction between the polymer species, several novel droplet morphologies are predicted in the development process of Janus droplets. Moreover, we stress that the hydrodynamics should be reckoned as a non-negligible mechanism that not only accelerates the Janus droplet evolution but also has great impacts on the coarsening and coalescence of the Janus droplets.

https://doi.org/10.1021/acs.langmuir.2c00308

Janus Droplet Formation via Thermally Induced Phase Separation: A Numerical Model with Diffusion and Convection

The present work explores the growing behavior of the intermetallic layer in the Mg-Si system. Following achievements have been obtained in our investigation: (i) A complete wetting concept is proposed for the lateral spreading of the intermetallic layer. (ii) In contrast to the stoichiometric property for the intermetallic phase in the phase diagram, the authors show that concentration gradients are able to be established in the kinetic process. (iii) Contrary to the reported growth behavior, d ∝ t0.25–0.5 in other intermetallics, the authors find a transition from d ∝ t to d ∝ t with an increase of the temperature, where d is the thickness of the intermetallic layer and t is the time.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adem.201700063

Numerical and Experimental Investigations on the Growth of the Intermetallic Mg2Si Phase in Mg Infiltrated Si‐Foams

Open-pore cellular Si structures are manufactured by investment casting and, subsequently, infiltrated with molten Mg(-Sn), representing the initial state for a formation of the intermetallic compound Mg2Si1–xSnx. The processing parameters which govern the evolution of microstructure after the infiltration process are studied in the alloy systems Mg-Si and Mg-Si-Sn. The resulting microstructures are analyzed using SEM and EDS. It is found that an initial diffusion layer is already formed after infiltration. Its thickness can slightly be increased by raising the infiltration temperature of the Mg(-Sn) melt. A variation in mold temperature does not show a noticeable impact. The comparison of the diffusion layer formed in the systems Mg-Si and Mg-Si-Sn showed that a lower Sn content resulted in thicker layers.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/adem.201700023

Johann Heimann

Papers

Phase-field study on the growth of magnesium silicide occasioned by reactive diffusion on the surface of Si-foams

Numerical and Experimental Investigations on the Growth of the Intermetallic Mg2Si Phase in Mg Infiltrated Si‐Foams

Infiltration of Cellular Silicon by Molten Magnesium Alloys

Processing of open-pore silicon foams using graphite composite as space holder

Investigation of a Template-Based Process Chain for Investment Casting of Open-Cell Metal Foams