Foam Materials Made from Carbon Nanotubes

Abstract

Introduction 1.1 What is CNT foam?Foam is a macroporous material and comes in many forms, such as polystyrene shock absorbers, dish-washing sponges, and foam board insulation.This chapter describes a technique to prepare foam materials from carbon nanotubes (CNTs).The use of a CNTmade foam as a kitchen sponge may not be a good idea, however.We of course expect the nano-carbons to have a specific functionality on the prepared bulk material.A challenge would be to place a function derived from nanomaterials on a bulk structuralized material.It would be highly useful to make up a material with a specific function that is attained only by nano-and micro-structuralization.A major feature of a foam material is that it has a function derived from its microstructures (macropores).The present chapter discusses a preparation strategy to produce a material with controlled microstructures from CNTs.Fig. 1.Foam materials made from carbon nanotubes.Samples in grey and white (pictured bottom left) were prepared by mixing titanium nano-powders.www.intechopen.comCarbon Nanotubes -From Research to Applications 314 1.2 How is it made?Recent studies explain how to make from CNTs highly porous foam materials, which are composite materials made from polymers and CNTs.CNT foams can be prepared using several methods, as illustrated in Fig. 2. One is a bottom-up method using phase separations induced by thermal phase transition, polymerization reaction, solubility shift, and so on.When a phase separation is induced in a CNT suspension, a phase that cannot include dispersed materials (such as CNTs) generates a counter phase in which the dispersed materials are concentrated (concentrated phase).Frequent phase separation produces a microstructure in the resultant solution after the pure phases are removed by posttreatment.As shown in Fig. 2A, this phase separation route is mainly realized by a gasliquid phase separation process (foaming) and solid-liquid phase separation process (freezing).CNT foam preparation using a poly(vinyl alcohol) foaming process was first reported by Shaffer and Windle (1999).Subsequent researchers found that foaming processes with polystyrene, polyurethane, poly(methyl methacrylate), and so on showed potential in preparing CNT foam with controlled pore structures (Shen et al.,