The hottest nano fiber thermal insulation material

2022-08-23
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Nanofiber thermal insulation materials: promising in the aerospace field

aerospace vehicles need to withstand long-term aerodynamic heating during flight, and the substrate surface will produce high temperature. In order to ensure the safety of the main structure and internal instruments and equipment of the aircraft, efficient thermal insulation materials must be used to prevent the external heat flow from diffusing to the interior. At the same time, light and efficient thermal insulation protection system is of great significance to reduce the load of aircraft and extend the flight distance. Nanofiber material has the advantages of small pore size and high porosity. It is an ideal lightweight and efficient heat insulation material. This paper mainly introduces the latest research progress of two-dimensional nanofiber film and three-dimensional nanofiber aerogel thermal insulation materials

two dimensional nanofiber film thermal insulation material

materials with small thickness but excellent thermal insulation performance are required in narrow spaces such as missile battery thermal insulation sleeve and engine. Two dimensional nanofiber film materials have controllable stacking thickness (generally less than 100) due to small fiber diameter μ m) The advantages of high porosity can be used for heat insulation in narrow spaces. According to the composition, the thermal insulation materials of nanofiber membrane can be divided into polymer nanofiber membrane, carbon nanofiber membrane and ceramic nanofiber membrane

polymer nanofibers, such as polyvinylidene fluoride (PVDF) nanofiber membrane, have higher porosity and zigzag pore channels, so that the transmission path of air molecules in the material becomes longer, and heat is lost in the transmission process, which can reduce the thermal conductivity of the material. In order to further reduce the thermal conductivity of the material, some scholars coated SiO2 nanoparticles on the surface of PVDF nanofibers through impregnation modification technology to further reduce the pore diameter of the fiber membrane and reduce thermal convection. However, the structure of this material is easy to be destroyed in high temperature environment, which is difficult to meet the application needs

carbon nanofibers have the advantages of large specific surface area, high porosity, good chemical stability and high specific strength. They have broad application prospects in the fields of electronics, energy, aerospace and so on. With the increase of graphitization degree, the high temperature resistance of carbon nanofiber membrane materials will gradually improve, but its thermal insulation performance will also decline significantly, so it is difficult to meet the needs of simultaneous improvement of high temperature resistance and thermal insulation performance

ceramic materials have the advantages of high temperature resistance, corrosion resistance and good insulation. They are widely used in high temperature insulation, sound absorption, catalysis and other fields. However, most of the existing ceramic nanofibers have defects such as brittleness, poor mechanical properties and bending resistance, which limit their practical use. In order to overcome this shortcoming, some scholars prepared SiO2 nanofiber films with amorphous structure and good flexibility by adjusting the properties of spinning solution and process parameters. At the same time, SiO2 aerogel gel nanoparticles can be introduced between fibers through impregnation modification to construct SiO2 Nanoparticles/nanofiber composites and improve the thermal insulation performance of SiO2 nanofiber films

three-dimensional nanofiber aerogel thermal insulation material

although two-dimensional nanofiber has good thermal insulation performance, it is difficult to achieve effective increase in thickness (> 1 cm), which seriously limits its application in high-power engine thermal insulation, bulkhead fire insulation and other fields. Compared with two-dimensional nanofiber film, three-dimensional nanofiber aerogel gel material has the advantages of controllable size, high porosity and high degree of pore tortuosity, so it has the advantages of heat insulation, heat preservation and sound absorption The oil tank has broad application prospects in fields such as mixing water or dirt. At present, the common nanofiber aerogel gel thermal insulation materials mainly include polymer nanofiber aerogel and ceramic nanofiber gel

ceramic nanofiber aerogel

ceramic aerogel material has excellent high temperature resistance, corrosion resistance and heat insulation properties, and is one of the main materials for thermal protection of aerospace vehicles. At present, the aerogel gel thermal insulation material used is mainly SiO2 nanoparticle aerogel reinforced by ceramic fibers. Due to the weak interaction between nanoparticles and ceramic fibers, the nanoparticles are easy to fall off during the use of the material, which greatly reduces the structural stability and thermal insulation performance of the material. In order to solve the above problems, some scholars used flexible ceramic nanofibers as building elements, and used the original three-dimensional fiber network reconstruction method to construct ultra light and super elastic ceramic nanofiber aerogel materials

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schematic diagram of the preparation process of ceramic nanofiber aerogel

the aerogel material has a honeycomb like pore structure, and the fibers in each pore are intertwined and bonded to form a stable fiber complex, giving the aerogel gel good structural stability. It can still rebound rapidly under large deformation (80% strain) compression, and its plastic deformation is only 12% after 500 compression cycles, which is better than the existing ceramic aerogel gel materials. At the same time, the material can still recover after being compressed by 50% under the flame of alcohol lamp (about 600 ℃) and butane blowtorch (about 1100 ℃), showing excellent high-temperature compression resilience

compressed photos of ceramic nanofiber aerogel under alcohol lamp

compressed photos of ceramic nanofiber aerogel under butane blowtorch flame

has high precision and powerful data processing ability; Photos of different materials of petals after 10 minutes on a 350 ℃ hot stage

polymer nanofiber aerogel

aiming at the problems of poor mechanical properties and brittleness of existing aerogel gel materials. Some scholars used cellulose nanocrystals with high elastic modulus, high strength and low density as building blocks, and prepared cellulose nanocrystalline aerogel with good transparency and mechanical properties through gel and supercritical drying. It can be bent to 180 without damage. At the same time, it can still recover after compression under large deformation (80%) and the maximum stress is greater than 200 kPa. In addition, cellulose nanocrystals also exhibit excellent thermal insulation properties

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