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Characteristics and main applications of aerogel

wallpapers Industry 2020-07-28
Aerogel is a solid material form, the smallest dense solid in the world. The density is 3 kilograms per cubic meter. The most common aerogel is silicon aerogel. This aerogel is translucent and light blue in weight, so people also call it "solid smoke." The new aerogel was developed by Dr. Stephen Jones, a materials scientist at the "Jet Propulsion Laboratory" under NASA. Its main component is silica like glass, but because 99.8% of it is air, its density is only one-thousandth of glass.

Aerogel looks "weak and windy," but it is very durable. It can withstand a pressure several thousand times its mass, and will only melt when the temperature reaches 1200 degrees Celsius. Its thermal conductivity and refractive index are also very low, and its insulating ability is 39 times stronger than the best glass fiber. Because of these characteristics, aerogel has become an irreplaceable material in space exploration. Both the Russian Mir space station and the US Mars Pathfinder probe use it for thermal insulation.
1. As a thermal insulation material

The slender nano network structure of silica aerogel effectively limits the propagation of local thermal excitation. Its solid-state thermal conductivity is 2-3 orders of magnitude lower than that of the corresponding glassy materials. Nano-pores suppress the contribution of gas molecules to heat conduction. The refractive index of silicon aerogel is close to 1, and the ratio of the annihilation coefficient to infrared and visible light is more than 100. It can effectively transmit sunlight and prevent infrared heat radiation at ambient temperature, making it an ideal transparent thermal insulation material. It has been applied in solar energy utilization and building energy saving. Using doping, the radiant heat conduction of silicon aerogel can be further reduced. The thermal conductivity of carbon-doped aerogel can be as low as 0.013w/m·K at room temperature and pressure, solid material with the lowest thermal conductivity. It is expected to replace polyurethane foam as a new type of refrigerator insulation material. Incorporating titanium dioxide can make silicon aerogel become a new type of high-temperature thermal insulation material. The thermal conductivity at 800K is only 0.03w/m·K, and it will be further developed as a new material for military products.

Due to its low sound velocity, silicon aerogel is also an ideal acoustic delay or high-temperature sound insulation material. The material has a broad acoustic impedance variable range (103-107 kg/m2·s) and is an excellent acoustic resistance coupling material for ultrasonic detectors. For example, the collective acoustic resistance turns Zp=1. 5×l07 kg/ Piezoelectric ceramics of m2·s are used as ultrasonic generators and sensors, while the acoustic resistance of air is only 400 kg/m2·s. Silicon aerogel with a 1/4 wavelength thickness is used as the acoustic resistance coupling material between piezoelectric ceramics and air. It can improve the transmission efficiency of sound waves and reduce the signal-to-noise ratio in device applications. Preliminary experimental results show that silica aerogel with a density of about 300 kg/m3 as a coupling material can increase the sound intensity by 30 dB. If a silica aerogel with a density gradient is used, a higher sound intensity gain is expected.

In the environmental protection and chemical industry. Nano-structured aerogel can also be used as a new type of gas filtration. The difference from other materials is that the article has uniform pore size distribution and high porosity. It is a high-efficiency gas filtration material. Because the content is unusually large than the table product. Aerogels also have broad application prospects as new catalysts or catalyst carriers.

2. In terms of energy storage devices

After the sintering process processes the organic aerogel, carbon aerogel is obtained. This conductive porous material is a new type of carbon material developed after fibrous activated carbon. It has a large specific surface area (600-1000 m2). /g) and high conductivity (10-25 s/cm). Moreover, the density has a wide range (0.05-1.0 g/cm3). If the micropores are filled with appropriate electrolytes, a new type of rechargeable battery can be made. It has excellent characteristics such as large storage capacity, small internal resistance, lightweight, strong charge, and discharge capacity, and repeated use. Preliminary experimental results show that the charge capacity of carbon aerogel is 3×104/kg2, the power density is seven kW/kg, and the repeated charge and discharge performance is good.

In the research of quantum size effect of materials. Due to the formation of quantum dot structure in the nano network of silicon aerogel, the results of chemical vapor infiltration method doping Si and solution method doping C60 show that the dopant exists in the form of nanocrystalline particles, and strong visible light emission is observed. It provides strong evidence for the quantum confinement effect of porous silicon to emit light. Using the structure of silicon aerogel and the nonlinear optical effect of C60, new laser protective glasses can be further developed. The doping method is also an effective means to form nanocomposite phase materials.

Also, silica aerogel is a material with an adjustable refractive index. Using aerogel media of different densities as Cherenkov threshold detectors can determine the mass and energy of high-energy particles. Because high-speed particles can easily penetrate porous materials and gradually slow down to achieve a "soft landing," if a transparent aerogel is used to capture high-speed particles in space, the blocked and captured particles can be observed naked eye or a microscope.

As a new type of nanoporous material, in addition to silicon aerogel, other units, binary or multiple oxide aerogels, organic aerogels, and carbon aerogels have been developed. As a unique material preparation method, related processes have been widely used in developing other new materials, such as the preparation of porous silicon with extremely high porosity, metal-aerogel hybrid materials for the development of high-performance catalysts, high-temperature superconducting materials, Ultrafine ceramic powder, etc.

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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