Solids are normally stronger but heavier than gases because their atoms are bound together more tightly. Writing in Advanced Materials, however, Sun et al.1 describe how they have used two carbon-based nanomaterials — graphene and carbon nanotubes — to make a strong carbon aerogel that is lighter than air, is super-elastic and has a variety of useful properties. Aerogels are highly porous solid foams that have an interconnected network of thin, solid walls. They have an extremely low density and a high specific surface area — the total surface area per unit mass. But they tend to suffer from poor strength and low elasticity: pressing them firmly can cause a catastrophic breakdown of the network. The first aerogel to be reported2 was prepared from a silica gel by supercritical drying, in which the liquid component of the gel is dried off in a controlled manner. This silica aerogel is transparent and has the lowest thermal conductivity of any known solid, making it suitable as a thermal insulating material.
展开▼
