Composite dispersed materials Agglomeration

Microstructures of CLs vary depending on applicable solvenf, particle sizes of primary carbon powders, ionomer cluster size, temperafure, wetting properties of carbon materials, and composition of the CL ink. These factors determine the complex interactions between Pt/carbon particles, ionomer molecules, and solvent molecules, which control the catalyst layer formation process. The choice of a dispersion medium determines whefher fhe ionomer is to be found in solubilized, colloidal, or precipitated forms. This influences fhe microsfrucfure and fhe pore size disfribution of the CL. i It is vital to understand the conditions under which the ionomer is able to penetrate into primary pores inside agglomerates. Another challenge is to characterize the structure of the ionomer phase in the secondary void spaces between agglomerates and obtain the effective proton conductivity of the layer. 

Other polymer materials which can be prepared include latexes, or particle agglomerates, by dispersed phase polymerisation. These can be either hydrophilic or hydrophobic in nature, or may have core-shell morphologies. They can be employed as support materials for a number of catalyst systems. Polymerisation of both phases of the emulsions produces composite materials, which have found use as selective membranes for the separation of mixtures of liquids with similar physical properties. 

Nanophase materials feature a three-dimensional structure and a domain size of less than 100 nm. They are usually produced by compaction of a nanoscale powder and are characterized by a large number of grain boundary interfaces in which the local atomic arrangements are different from those of the crystal lattice [11.2]. Nanocomposites, in contrast, consist of nanoparticles that are dispersed in a continuous matrix, creating a compositional heterogeneity of the final structure. The matrix is usually either ceramic or polymeric. Only the manufacturing of ceramic nanocomposites applies the principles of agglomeration (Section 6.7). 

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