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Research progress on the mechanism of aerogel explosion-proof performance

wallpapers Tech 2020-07-28
In modern warfare, anti-terrorism operations, and even in the industrial production process of petroleum, chemical industry, and pharmaceuticals, the direct losses caused by the explosion of explosives, hazardous chemicals, and other materials are becoming more and more shocking, and how to use protective materials to effectively slow down the destructive power of the explosion shock wave is also attracted Attention of more researchers.
Due to the viscous dissipation of the aerogel matrix's porous material, the shock wave will attenuate and diffuse in the porous material. In the high-speed impact process caused by the explosion, the gas in the aerogel is challenging to escape instantly, and violent collisions occur between gas molecules and between gas molecules and the pore wall. Since the free path of air molecules is 70nm, the average pore diameter of aerogel is only about 20nm, the distance between the pore wall of aerogel and the air molecules in the pore is much smaller than the average free path of air molecules, and the high specific surface area increases the aerogel The probability of collision between the pore wall of the matrix and the air molecules is correspondingly reduced. In the high-speed compression process caused by shock waves, the clash between air molecules and the pore wall of the aerogel matrix is ​​more severe than the high-speed collision between air molecules. The flow resistance caused by the gas's accident with the pore wall and the collision resistance between the air molecules in the pore will cause the pressure in the orifice to increase accordingly. The faster the material deforms, the more difficult it is for gas molecules to escape. The higher the pressure inside the pores, the more shock wave energy the aerogel matrix consumes. Since the stress in all directions inside the pores is approximately equal, the gas in the aerogel converts the axial compressive stress into weight in all directions. That is the stress state in the aerogel changes, thus playing an excellent protective role.

Due to the viscous dissipation of the aerogel material, the shock wave will attenuate and diffuse in the aerogel matrix. The degree of shock wave attenuation inside the content is affected by the microstructure of the material. Usually, the attenuation degree is smaller when propagating in a denser solid. Influenced by the structural characteristics of aerogel, shock wave attenuation is more evident in aerogel. Because the size of the pores and colloidal particles in the aerogel is on the order of nanometers, the porosity of the aerogel is generally 80%-99.8%. The typical pore size is in the range of 50 nm. The specific surface area can be as high as 1000 m2.g-1. The colloidal gel particles are cross-linked and cause the shock wave to propagate in the aerogel without appearing in the local area inside the aerogel, which is similar to the small attenuation faster propagation speed commonly seen in dense solids. Therefore, the attenuation effect of the shock wave in aerogel is more prominent.

When the shock wave generated by the explosion enters the aerogel colloidal particle structure, the colloidal particle structure of the aerogel material breaks down during the shock wave propagation process. Because the size of the colloidal particle structure of the aerogel is at the nanometer level, The particle structure has low strength, and it is difficult to carry and transfer muscular stress under a load of the shock wave, which leads to fracture and damage, which also leads to visible attenuation of a shock wave in aerogel. Therefore, the nano-size effect of aerogel particles is an essential reason for the apparent attenuation of shock waves in aerogels. The chasing and unloading effect of the rear unloading wave when the shock wave propagates in the porous material is also an essential reason for the attenuation of the shock wave in the porous material. The slower the propagation speed of the shock wave in the porous material, the more obvious the unloading effect of the rear unloading wave is. The better the attenuation effect of the shock wave in the porous material. Together, the above factors lead to the appearance of the low propagation speed of the mechanical wave in the aerogel.

Trunnano is one of the world's largest aerogel manufacturers, mainly producing silica aerogels. If necessary, please contact Dr. Leo, email: brad@ihpa.net.

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Tag: aerogel   Trunnano