• Garcia-Moreno, F.: chapter 23: Metallic Foams. In: Dotchi Exerowa ... [Ed.] : Foam films and foams: fundamental and applicationsBoca Raton: CRC Press, 2018. - ISBN 978-1-4665-8772-4, p. 445-464

Solid foams are light weight cellular materials inspired by nature. Wood, bones or sea sponges are some well known exemplars. In fact, solid metallic foam structures are the conserved image of the corresponding liquid metallic foam. Scientific attempts to improve foam quality have to concentrate on the foam physics, that is, bubble formation, foam nucleation, growth, stability, development, and gas diffusion in the liquid state where the foam structure evolves [1–13]. The engineering and industrial approach is to scale up the processes and provide reliable conditions for serial productions at acceptable quality and cost levels [14–17]. Depending on the production method, the foam structure is more or less homogeneous and comprises different characteristic features that determine its properties, and therefore, the fields of application [18]. Some applications based on foamed materials such as polymeric foams, porous concreate or food foams are quite popular in society. Several applications of ceramic foams are also well known in industry [19], but metal foams and their applications are still quite unfamiliar. The reason is they are still not wide spread, although they have a very high potential and a large number of applications already exist on the market. Several reviews about the applications of metallic foams are available in the literature [18,20,21], but in the past years, new applications and application fields have emerged. These applications depend strongly on the foam type and properties, that is, on the manufacturing process. There is a large number of manufacturing processes divided into two main families: the melt and the powder metallurgical route. All these production methods are extensively described in literature [18,22]. There are further manufacturing methods which are not directly connected with foaming in the strict sense of the word, but lead to a foam similar structure, like foam replication or casting, coating of polymeric foam, place holder methods, and so on. This is especially the case for open cell metal foams, which should be called metal sponges more precisely speaking, which can obviously not be foamed directly as the gas will leak [23]. On the other hand, these products possess a foam-like structure, therefore, we will consider them for applications. In contrast, other kinds of cellular or porous materials like lattices, fibers, honey combs, and so on, will not be taken into account. A large number of companies made a bet for the future and started producing and commercializing metallic foams in the past two decades, although several closed, stopped the production field or concentrated on their core business, especially during the worldwide economic crisis starting in 2007. Their major problem was caused not by the quality or properties of their products, but mainly by two factors: a lack of effective marketing for the small metallic foam market and the price, that is, their benefit margin.