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Date：2022-08-16
What is the role of the aerogel sheet?
Aerogels are three-dimensional continuous porous materials composed of nanopores and nanoskeletons. Its unique structure enables it to have many properties unmatched by conventional materials, the most notable of which is its extremely low thermal conductivity, so aerogel insulation sheet: what is the role of aerogel sheet?
1. In the study of fractal structure. As a structurally controllable nanoporous material, the apparent density of silica aerogels clearly depends on the standard size. In a certain scale range, its density tends to be scale-invariant, that is, the density decreases with the increase of scale, and has a self-similar structure. The structural fractal structural dynamics study of aerogels also shows that there are three excitation regions with significantly different dispersion relations at different scales, corresponding to the excitation of phonon, fractal and particle modes, respectively. By changing the preparation conditions of the aerogel, the association length can be changed by two orders of magnitude. Therefore, silica aerogel becomes a good material to study the fractal structure and its dynamic behavior.
2. In the research of "863" high-tech and strong laser. Porous materials have important application value. For example, the use of porous target materials below the critical density can improve the beam quality of X-ray lasers excited by electron collisions, saving driving energy. Using the porous target of the new microsphere node structure can realize the rapid cooling of the three-dimensional adiabatic expansion of the plasma, improve the gain coefficient of the X-ray laser generated by the electron recombination mechanism, and use ultra-low density materials to absorb nuclear fuel, which can form a high-speed laser inertial confinement fusion fusion. Gain frozen target. Aerogels have slender nanoporous network structures, huge specific surface areas, and controllable mesoscopic structures, making them good candidates for developing novel low-density targets.
3. As a thermal insulation material. The elongated nano-network structure of silica aerogel effectively confines the propagation of localized thermal excitations, and its solid-state thermal conductivity is 2–3 orders of magnitude lower than the corresponding glassy materials. Nanopores inhibit the contribution of gas molecules to heat conduction. The refractive index of silica aerogel is close to L, and the ratio of the extinction coefficients of infrared and visible light is greater than 100. It can effectively transmit sunlight and prevent infrared thermal radiation at ambient temperature. It is an ideal transparent thermal insulation material and has been used in solar energy utilization and building energy conservation. The radiative heat conduction of the silica aerogel can be further reduced by doping. At room temperature and pressure, the thermal conductivity of doped carbon aerogels can be as low as 0.013 W/mk. It is a solid material with the lowest thermal conductivity at present, and is expected to replace polyurethane foam as a new type of refrigerator insulation material. The addition of titanium dioxide can make silicon aerogel a new type of high-temperature thermal insulation material. The thermal conductivity at 800K is only 0.03 W/mk. As a new material for military products, it will be further developed.
