**Vapor state processing**:

g.Vapor deposition onto polymeric foams

### **Ionic solution state processing**:

h.Electrodeposition onto polymeric foams

Despite the wide range of fabrication methods that these four groups generate, there are actually only two different strategies for generating porosity [17]:

**5**

(**Figure 3**).

in the chapter.

*preform*

interconnected porous structure.

*Open-Pore Foams Modified by Incorporation of New Phases: Multiphase Foams for Thermal…*

the physical principles. Self-formation includes the d method.

Predesign includes a, b, c, e, f, g, h, i, and j methods.

(801°C) and then removed by dissolution in aqueous solutions [13].

**3.2 Manufacturing techniques of multiphase open-pore foams**

• Self-formation: porosity is formed through a process of evolution according to

• Predesign: the structure is created with the use of molds that determine the porous cavities. By means of this strategy, closed-pore (or not interconnected) and open-pore (or interconnected) foams can be manufactured, depending on whether the mold forms part of the final material or is removed, respectively.

Among the manufacturing techniques, the infiltration of martyr preforms, also known as the replication (predesign) method, allows the best control over the material. This method was traditionally used to produce open-pore metal foams and recently adapted to produce carbon/graphite foams [18]. The replication method consists of the infiltration with molten metal or any other liquid precursors of a porous template preform that is later removed by dissolution or controlled reaction to leave a foam material with a porous structure that replicates the original preform. This method allows perfect control of size, shape, and size distribution of pores. Depending on the matrix material and the desired final porous architecture, different raw materials have been used as templates. Nevertheless, the most widespread martyr material is sodium chloride in particulate form, which can be conveniently packaged and infiltrated with liquid metals at temperatures below its melting point

The multiphase open-pore foam materials developed so far are still scarce and can be manufactured by various methods, which are reviewed in **Table 1** and later

*3.2.1 Composite foams/foams with guest phases with preload of new phases in the* 

*3.2.2 Composite foams with preload of new phases in the liquid precursor*

Loading of new phases is achieved by one of the following two strategies: (i) loading particles (inclusions) are packed together with larger martyr particles forming a porous bimodal preform, or (ii) loading particles are covered by a martyr material and packed forming a porous monomodal preform. Preforms are infiltrated and the martyr material is leached away. As a result, composite foams or foams with guest phases are obtained. They show homogeneous dispersion of new phases in a continuous matrix. **Figure 2** represents the aforementioned material structures. In particular cases, loading powders are packed combined with larger martyr particles and sintered. The martyr particles are later removed to obtain an

Loading of new phases is achieved by the dispersion of particles into the liquid precursor. The preform is leached away after its infiltration with the liquid precursor, and the final material shows a homogeneous dispersion of new phases in a continuous matrix. Material consolidation can also be obtained (instead of by infiltration) by electrochemical (co)-deposition of a metal and/or the new phases on a leachable preform or a preexistent porous material (the liquid precursor is an electrolyte that contains metal ions and dispersed particles of the new phases)

*DOI: http://dx.doi.org/10.5772/intechopen.88977*

*Open-Pore Foams Modified by Incorporation of New Phases: Multiphase Foams for Thermal… DOI: http://dx.doi.org/10.5772/intechopen.88977*


Among the manufacturing techniques, the infiltration of martyr preforms, also known as the replication (predesign) method, allows the best control over the material. This method was traditionally used to produce open-pore metal foams and recently adapted to produce carbon/graphite foams [18]. The replication method consists of the infiltration with molten metal or any other liquid precursors of a porous template preform that is later removed by dissolution or controlled reaction to leave a foam material with a porous structure that replicates the original preform. This method allows perfect control of size, shape, and size distribution of pores. Depending on the matrix material and the desired final porous architecture, different raw materials have been used as templates. Nevertheless, the most widespread martyr material is sodium chloride in particulate form, which can be conveniently packaged and infiltrated with liquid metals at temperatures below its melting point (801°C) and then removed by dissolution in aqueous solutions [13].

### **3.2 Manufacturing techniques of multiphase open-pore foams**

The multiphase open-pore foam materials developed so far are still scarce and can be manufactured by various methods, which are reviewed in **Table 1** and later in the chapter.
