Three-dimensional Nanotube Networks and a New Horizon of Applications

Carbon nanotubes (CNTs) are considered one-dimensional systems that possess fascinating electronic, chemical and mechanical properties. They exhibit metallic or semiconducting behavior depending on the nanotube diameter and chirality, and they are ultrarobust and lightweight. Moreover, their surface can be chemically activated thus being able to establish different types of bonds between the carbon nanotube surface and a large number of chemical species; for instance, they could be introduced into a polymeric matrix improving its mechanical or electronic properties. In addition, CNTs are able to host different species in their hollow core, such as ferromagnetic clusters, molecules, and gases. Nowadays, synthesis techniques have achieved control of the length and diameter of CNTs, which constitutes a step forward toward applications. In this chapter, we address the issue of using CNTs as fundamental building blocks for constructing three-dimensional (3D) networks. Here, we present a review of the experimental and theoretical investigations on the formation of 3D networks using CNTs as the main component. In addition, the latest advances on the synthesis and characterization of different carbon nanostructures involving CNTs such as branches, junctions and foams are discussed.