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The secret of aerogel: How was this ultra-light material born?
In the broad field of materials science, aerogels are known for their lightweight and excellent insulating properties. The process of making this substance originated from an accidental discovery in the 1920s, and today it is widely used in aerospace, building insulation and environmental protection. So, what exactly is aerogel and how was it born?
Aerogel is a synthetic porous ultra-light material formed by replacing the liquid component in the gel with gas. It is characterized by extremely low density and excellent thermal insulation properties.
History
The history of aerogels can be traced back to 1931, when American chemist Samuel Stephens Kister created the first aerogels due to a bet with Charles Learn. This breakthrough achievement marks the beginning of a new era in materials science.
Properties of aerogels
Despite the name "aerogels," these materials are actually solid and have hard and dry properties. Aerogels have excellent compressive strength, mainly due to their unique tree-like microstructure. Therefore, the load-bearing capacity of aerogels is amazing.
The structure of aerogel is made up of spherical particles of different sizes tightly bound together, forming a three-dimensional porous network structure, almost similar to a fractal chain.
The porosity of airgel also leads to its excellent thermal insulation properties. Aerogels can virtually eliminate conductive and convective heat transfer, providing excellent support for a variety of applications for this type of material. The microstructure of aerogel effectively inhibits gas flow, making it an excellent thermal insulator.
Production process
The production of aerogels usually goes through three main steps: gelation, network refinement and drying. Gelation refers to the formation of a gel-like substance under specific conditions, and subsequent network improvement is to strengthen the structure of the gel-like substance, and finally the liquid is removed through supercritical drying or freeze-drying.
Supercritical drying vs. freeze drying
Supercritical drying is a relatively mature technology in the production of aerogels. The core of this technology is to pressurize a liquid material to its supercritical point and then convert it into a gas by reducing the pressure, thereby reducing the presence of liquid and ultimately forming a stable aerogel structure.
During the supercritical drying process, the resulting liquid-gas phase change can effectively avoid the collapse of the internal structure caused by liquid evaporation.
In contrast, freeze-drying converts the liquid part of the aerogel into ice, and then sublimates the ice into water vapor. This process can better maintain the network structure of the aerogel. Although freeze-drying technology is slightly insufficient in controlling the structure, its operation is relatively simple.
Application scope
Due to its unique properties, aerogel is widely used in a variety of fields. In aerospace, for example, researchers are using aerogels as thermal barrier materials. In the construction industry, the superior thermal insulation properties of aerogel also make it an ideal thermal insulation material. In addition, in the process of environmental protection, aerogels are also used in water purification and air filtration.
The successful emergence of aerogels has opened up unlimited possibilities for the development of materials science and changed our understanding of materials.
With continuous research, aerogels will bring innovation to more industries in the future, and their excellent performance has also attracted widespread attention. In the process of exploring aerogels, we can't help but wonder, what areas will this extremely light material change in the future that we have not yet imagined?
