Ⅰ. Is Aerogel a Solid or a Gas?
Aerogel is a solid material derived from a gel. The liquid component of the gel is replaced by air, making it dry and porous. In fact, over 90% of its volume is vacuum, making it the lightest solid material in the world. Its density is 1,000 times less than that of glass, making it also the world's lowest-density solid material. Its tightly distributed particle size is particularly suitable for thermal insulation applications because aerogel has extremely low thermal conductivity, high shear resistance, and strong hydrophobicity.

Ⅱ. Advantages of Aerogel
Aerogel has three advantages: light weight, strong insulation, and high bearing capacity. First, with a density approximately one-thousandth that of glass, it's no exaggeration to call it the world's lightest material. Second, aerogel blocks nearly all pathways of heat transfer, achieving insulation that is unmatched by other materials. Finally, it can withstand pressures thousands of times its own mass. These advantages have led to its widespread use in various industries. For example, in the aerospace and defense industries, aerogels can be used as thermal insulation materials for aircraft cabins, as well as for nuclear reactors in nuclear submarines and steam-powered missile destroyers, and as highly efficient thermal insulation materials for complex high-temperature steam boiler systems.
III. Disadvantages of Aerogels
Aerogels are expensive to produce. Furthermore, the material's inherently high porosity results in inherently low strength and toughness, making ordinary aerogels easily crushable. Furthermore, because the spatial network structure of aerogels is filled with gas, their structure is unstable. These shortcomings are bottlenecks that hinder their widespread application.