The most investigated inorganic aerogels are made of silica using a typical Sol-Gel process or carbon obtained by carbonizing organic aerogels under inert atmosphere.
Pristine aerogels are too brittle for many applications. This can be circumvented by tuning the synthesis, for example by changing and mixing different precursors. This allows the introduction of different (e.g. organic) groups into the aerogel network, which changes the flexibility or hydrophobicity along other properties. Different metals can also be added, which increases high temp stability while maintaining the porous structure, resulting in high-performance insulating aerogels.
Carbon aerogels can be tuned by changing the properties of the organic precursor aerogel. This can enhance the flexibility, allowing the material to host for example sulfur and be used in lithium-sulfur batteries. Additionally, carbon aerogels have a very high electrical conductivity, excellent for electrodes, and can be used for hydrogen storage due to the high total surface area, or even radiation absorption.
Images: semitransparect silica aerogel (top left), carbon aerogel (top right), transparent (bottom left) and Marshmallow (bottom right) flexible silica aerogels.