Abstract
To obtain new high-temperature resistant composites that can meet the requirements of aircraft development for thermal insulation and mechanical properties, SiBCO aerogel composites were prepared by sol-gel, supercritical drying and high-temperature pyrolysis with trimethyl borate (TMB) or phenylboronic acid (PBA) as the boron source and mullite fiber as reinforcement. The structure and composition of the SiBCO aerogel and its composites were characterized with SEM, FT-IR, ICP and nitrogen adsorption tests. The specific surface area of the SiBCO aerogel is 293.22 m2/g, and the pore size is concentrated in the range of 10–150 nm. The mechanical properties, the thermal insulation properties and the temperature resistance were also studied. Due to the introduction of boron, the temperature resistance of SiBCO aerogel composites is improved greatly, and the service temperature of composites reached 1773 K. When n (TMB)/n (TEOS) = 1/1, the temperature resistance of the composites is the best. After heating in air at 1773 K for 30 min, the shrinkage of SiBCO aerogel composites is only 2.45%, and the thermal conductivity of the composites is 0.138 W/(m·K) at 1773 K. In addition, the type and amount of catalyst also have certain effects on the mechanical properties and temperature resistance of the composites.
Highlights
Aerogel is considered to be the solid material with the lowest thermal conductivity [1,2,3], among which SiO2 aerogel is studied most comprehensively and has been applied in military, aeronautic and civil uses due to its thermal conductivity that can be as low as 0.013 W/(m·K) [4,5,6,7]
According to the preparation methods of SiBCO materials reported in papers combined with the previous studies of SiCO aerogel thermal insulation composites by our research group [27,28], SiBCO aerogels and their composites reinforced by mullite fiber are prepared in this paper using the composites with n (TMB):n (TEOS), DMDES and trimethyl borate (TMB)
The SiBCO aerogel and its composites were synthesized through the sol‐gel method, while the hydrolysis and the can be carried out simultaneously during the preparation
Summary
Aerogel is considered to be the solid material with the lowest thermal conductivity [1,2,3], among which SiO2 aerogel is studied most comprehensively and has been applied in military, aeronautic and civil uses due to its thermal conductivity that can be as low as 0.013 W/(m·K) [4,5,6,7]. Relevant studies show that SiBCO ceramics and SiBCO high-temperature resistant glass prepared by the introduction of boron in the SiCO material system show better high-temperature thermal stability [20,21,22,23]. Studies of SiBCO materials mostly focused on porous ceramics and high-temperature resistant glass, and there is no relevant literature about SiBCO aerogels. According to the preparation methods of SiBCO materials reported in papers combined with the previous studies of SiCO aerogel thermal insulation composites by our research group [27,28], SiBCO aerogels and their composites reinforced by mullite fiber are prepared in this paper using TEOS, DMDES and trimethyl borate (TMB). The effects of raw materials and their amount on the microstructure, composition and properties of the SiBCO aerogel composites were investigated
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