Ambient Pressure Dried Polyimide/Silica Aerogels for Efficient Radar Stealth at High Temperature

Abstract

A facile and scalable magnetic polyimide-based silica composite aerogel with excellent mechanical and radar stealth performance at high temperature is successfully fabricated via free-foaming of polyimide, impregnating GN/Fe₃O₄ and silica sol, followed by ambient pressure drying process. The free-foamed polyimide foam is employed to support the loading of silica aerogel. As silica sol precursor, hydrolysis and polymerization of methyltrimethoxysilane significantly reinforces the interfacial interaction between polyimide skeleton, GN/Fe₃O₄ and silica aerogel through the hydrogen bonding effect. Meanwhile, the existence of methyl groups in methyltrimethoxysilane effectively preserve the structural integrity of aerogel during ambient pressure drying process. As a result, the formation of polyimide-based silica composite aerogel with strong interfacial interaction brings an excellent thermal insulation and stability, and outstanding mechanical properties. The effective loading of GN and Fe₃O₄ can promote the optimization of impedance matching and the formation of multiple loss mechanisms, endowing it with an efficient radar stealth performance at 300 oC. Such excellent comprehensive performance makes it possible to become a promising candidate for high-temperature radar stealth materials in application scenarios of engine areas on tank and/or warplane.

Keywords: Polyimide, Foam, Silica, Aerogel, Radar stealth