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 °C. 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.