Jiangyin Youtejia Air Treatment Equipment Co., Ltd.

Huh, what's this? It looks like frozen smoke.

This isn’t smoke—it’s a solid, specifically the world’s lightest solid: aerogel.

What is an aerogel? First, let’s get to know “gel.”

A polymer solution or sol of a certain concentration, under appropriate conditions, gradually increases in viscosity until it eventually loses its fluidity, transforming the entire system into an elastic semi-solid with a uniform appearance and a stable, defined shape. This elastic semi-solid is known as a gel.

Jelly is one of the earliest gels recognized by scientists—it forms when water or other liquids fill its structure. There are also gels that are made up of gases, known as "aerogels."

In 1931, American scientist Samuel Stephens Kistler prepared this new material and named it "aerogel," or "air gel." The combination of "aero" (meaning "air") and "gel" vividly captures the material's unique characteristic: a gel-like substance filled with gas.

Aerogels have a key feature that sets them apart from conventional porous materials: their skeletal structure exists at the nanoscale. As a result, when visible light passes through, it experiences minimal scattering, giving the material a mesmerizing appearance—almost as if "frozen smoke" has been captured in time.

Aerogels are incredibly lightweight—indeed, they’re the lightest solids in the world. Currently, the lightest aerogel available is an "all-carbon aerogel," with a density of just 0.16 mg/cm³ (after accounting for air density), making it only 1/6 as dense as air itself. When this material is placed gently on a flower, the delicate stamen remains virtually unchanged, barely even deformed.

The preparation of aerogels involves two main steps: 1. Fabricating a wet gel; 2. Drying the wet gel using a specialized technique. The most traditional method for preparing wet gels is the sol-gel process. In this method, compounds containing highly reactive chemical components are dispersed in a solvent, where hydrolysis reactions generate active monomers. These monomers then polymerize to form a sol, which eventually evolves into a gel with a well-defined spatial structure. At this stage, the resulting gel closely resembles the jelly we commonly consume. To further transform this jelly-like gel into an aerogel, it must undergo an additional drying process. Typically, under normal conditions, the evaporation of liquid within the gel due to surface tension can cause the fragile gel skeleton to collapse. However, this issue can be effectively addressed by employing freeze-drying technology. First, the wet gel is rapidly frozen at low temperatures, and then it is placed under vacuum for drying. Since the freezing process has already converted the liquid inside the gel into solid form, subsequent sublimation under vacuum allows the frozen material to escape directly from the gel’s porous structure—without passing through the liquid phase. This unique approach prevents the collapse of the gel’s delicate framework, ultimately yielding the highly desired aerogel.

“What are the uses of aerogel?” No doubt, everyone has this question. And the answers will vary widely—“It boasts extremely low thermal conductivity, making it an excellent insulation material,” or “It can be used as an electrode,” and so on.

Overall, the performance of aerogels is primarily attributed to two key factors: one is their structural properties—simply put, characteristics derived from their porous nature, such as exceptional thermal insulation. For instance, when a flower is heated directly over an aerogel using a flame, the flower remains virtually undamaged. Additionally, certain aerogels exhibit remarkable adsorption capabilities, exemplified by materials like "carbon sponges."

Another aspect of its performance stems from the fact that the components forming the aerogel skeleton are at the nanoscale. Nanoscale particles inherently possess certain unique properties, which tend to be enhanced when they exist in the form of aerogels. For instance, the electrode material for lithium batteries—manganese dioxide (MnO2—exhibits significantly improved discharge performance in lithium batteries when it is structured as an aerogel.

As a material that emerged in the early 20th century, aerogel doesn’t technically qualify as a "newly discovered 'new material.'" Nevertheless, its exceptional properties across the board have drawn widespread attention, and its practical applications still require ongoing research and exploration.