Aerogel is a synthetic porous ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas. The result is a solid with extremely low density and low thermal conductivity. Aerogel is a superhydrophobic solid.
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water When a surface is covered by aerogel powder that surface becomes extremely difficult to wet or get dirty.
Aerogels made with aluminium oxide are known as alumina aerogels. Alumina aerogels are being considered by NASA for capturing hypervelocity particles.