Introduction

Once a scientist accidentally discovered a material similar to "air", which has almost no weight but is exceptionally strong, like an incredible "magical material".

Magic aerogel

In 1931, American scientist Samuel Stephens Kistler prepared this new material, named "aerogel", aerogel. "Aero"+"gel" describe the characteristics of this new material, that is, a gel filled with gas.

Next, let's take a look at this magical 'magic material'.

What is aerogel?

Aerogel is a solid material with microporous structure. It looks like a cloud or a cloud of smoke, but it is actually composed of countless tiny pores. Aerogel is often called "solid smoke" because its appearance is very similar to smoke. The density of aerogel is very low, usually only several times to tens of times of that of ordinary solid materials, so it looks like a fluffy and light cloud or smoke, as if it can disperse and disappear at any time. Moreover, due to their microporous structure, many aerogels are highly transparent, which makes them look more light, hazy and soft, just like smoke floating out of the container. Therefore, people are used to comparing aerogel to "solid smoke".

Aerogel has extremely low density and is the lightest solid in the world. At present, the lightest aerogel is a "all carbon aerogel" with a density of only 0.16mg/cm3 (air density removed), which is only 1/6 of the air density. Place this material on the flower, and the soft stamen will hardly deform.

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How is aerogel prepared?

The invention of aerogel can be traced back to 1931. Professor Samuel Kistler and his colleague Charles learned bet that whether gel (such as jelly) can remove liquid from jelly without destroying the three-dimensional rigid structure?

A common gel in life jelly

We know that jelly is actually a combination of liquid and solid, with the main component being liquid, but the liquid needs to be embedded in a three-dimensional solid structure. Therefore, we can think that a gel like jelly has a skeleton with nano sized pores. This skeleton makes the gel rigid, and the skeleton only accounts for 1% of the weight of the gel.

We know that if only the liquid is evaporated, the solid structure of the gel will shrink, because when the liquid molecules are removed, they will attract each other and pull the rigid structure, so that the gel will be destroyed from the inside. Therefore, the preparation of aerogel needs to ensure the integrity of the solid framework, and this process requires special drying methods: for example, the liquid is converted into the "supercritical fluid" state of semi liquid and semi gas. Under the "supercritical fluid" state, there will be no difference between the liquid and gas, and the molecules will no longer attract each other, which can ensure that the solid framework will not be damaged.

Taking graphene aerogels as an example, the process of preparing aerogels is as follows:

Process flow chart of graphene aerogel preparation

Preparation method of aerogel

Aerogel material has low thermal conductivity:

Aerogel materials often have excellent thermal insulation performance, with the lowest thermal conductivity of 0.013w/mk, which is lower than that of dry air, meaning that it is a better thermal insulator than air. Its thermal insulation performance mainly comes from its structure, and the low thermal conductivity of aerogel materials is mainly due to three reasons:

Thermal insulation test of aerogel

Application of aerogel

Based on the in-depth study of the characteristics of aerogel itself, scientists have further applied it to daily life and even military industry.

1. Aerogel can be used as heat insulation board for external walls of buildings, which plays a role in heat preservation. The use of aerogel thermal insulation materials will not increase the thickness of the external wall of the building, but also can save building materials and reduce construction costs.

Aerial gel nucleic acid detection sampling chamber

2. Graphene aerogel is a kind of high-strength oxidized aerogel with the characteristics of high elasticity, strong adsorption, low density and large specific surface area. According to research, graphene aerogel can adsorb many substances, such as formaldehyde, acetone, dyes and other organic pollutants.

Adsorption experiment of aerogel

3. The graphene aerogel is made into a thin layer, which can make cold proof clothes from the perspective of heat insulation; Improving its impact resistance can make it a bulletproof vest.

Display of cold proof clothes made of aerogel

4. 

is the solid material with the best thermal insulation performance at present. In the civil field, the thermal insulation of glass, walls, refrigerators and pipes is very effective; Especially in aviation, aerospace, and military, this good insulation material is increasingly being used.

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Display of thermal insulation effect of aerogel