Graphene/Carbon Nanotube Aerogels

An aerogel is an open-celled, mesoporous, and solid foam composed of a network of interconnected nanostructures with porosity of over 50%. The term mesoporous or mesoporous material is commonly defined as a material that contains pores ranging from 2 to 50 nm in diameter. The term aerogel does not refer to a specific substance, but rather to a network structure, which a substance can take on. Aerogels can be made of a wide variety of substances, including silica, most of the transition metal oxides, lanthanide and actinide metal oxides, several main group metal oxides, organic polymers, semiconductor nanostructures, metals, and carbon-based nanomaterials (carbon powder, CNTs, and graphene). Aerogels are well known for their extremely low densities (often ranging from 0.00016 to ~0.5 g/cm3) and have 95%–99% air (or other gases) in their volume (El-Nahhal & El-Ashgar 2007, Du et al. 2013). They are even considered as the lowest-density solid materials that have ever been made (Sun et al. 2012). Because of their extraordinary low densities and the length-scale effects from the nanostructure features, aerogels can exhibit several advanced properties over the nonaerogel forms made of the same substances such as larger surface area and catalytic activity. But the aerogel structure may also have reduced mechanical strength (Fricke & Emmerling 1998, Du et al. 2013). 25