Aerogel, also known as dry gel. When most of the solvent is removed from the gel, the liquid content in the gel is much less than the solid content, or the medium filled in the spatial network structure of the gel is gas, and the appearance is solid, this is called dry gel, also known as aero gel. Air gel composite melamine sponge air gel blanket has the characteristics of softness, easy cutting, small density, fire resistance, flame retardancy, green environmental protection, etc. It can replace the traditional flexible insulation materials with poor environmental protection and insulation performance, such as glass fiber products, asbestos insulation blanket, silicate fiber products, etc.
Aerogels have ultra light, low density, nano micropores, and are characterized by ultra-fine honeycomb pore size and porous structure, which are connected by interconnected polymer chains. The pore diameter is generally less than 100 nm, and the size of aerogel particles is generally less than 20 nm. It can be made of inorganic materials (such as silica, alumina, etc.), organic materials (such as polyimide, carbon, etc.), or mixed materials (such as gel glass, etc.).
There are generally three heat insulation principles of aerogel:
1. Infinite occlusion effect:
The pores of gel are nano pores and the gel itself has a very low density. The pores in the aerogel tend to be "infinite", and each pore wall has the function of a heat shield, thus producing a nearly "infinite number of heat shields" effect to minimize the heat radiation.
2. No convection effect:
When the pore diameter of aerogel nano materials is less than 70nm, the air molecules in the pores lose the ability of free flow and are in a near vacuum state, unable to conduct thermal convection.
3. Infinite Loose Path Effect:
The density of gel is extremely low, the specific surface is large, and the volume skeleton is loose. Aerogel has an infinite number of nano pores. Heat is transmitted along the pore wall in the solid material of gel, and an infinite number of pore walls constitute an "infinite loose path" effect, which reduces the ability of solid heat conduction to the lowest limit.
Compared with other traditional thermal insulation materials, aerogel products have the lowest thermal conductivity and obvious advantages in thermal insulation effect. The thermal conductivity of aerogel materials changes little with temperature. The thermal conductivity of traditional thermal insulation materials changes greatly with temperature, and the thermal insulation effect will become worse.
Aerogel is a solid material form, which is one of the smallest density solids in the world. Generally, the common aerogel is silicon aerogel gel, and carbon aerogel gel also exists. At present, the lightest silica aerogel gel is only 3 mg per cubic centimeter, three times heavier than air, so it is also called "frozen smoke" or "blue smoke".
Characteristics of aerogel:
1. The porosity is very high, up to 99.8%;
2. Nano scale pores (20-100nm) and three-dimensional nano skeleton particles (2-5nm);
3. High specific surface area, up to 1000m2/g;
4. Low density, can be as low as 0.003g/cm3;
5. The unique structure of aerogel determines its extremely low thermal conductivity, which can be as low as 0.013W/(m · K) at room temperature;
6. Low strength, high brittleness, due to its large specific surface area and porosity, low density, resulting in low strength.