Organic capping-restricted calcination strategy to prepare iron-based nanocomposites and aerogel films for infrared stealth

Integrating multifunctional nanomaterials with phase change material (PCM) provides great potential in the fields of thermal management, energy storage, infrared stealth and thermal camouflage. Herein, shuttle-shaped β-FeOOH nanoparticles were firstly prepared and coated with one layer of poly(pyrrole) (PPy) as the photothermal agent. The β-FeOOH@PPy nanocomposites can easily thermally transfer into Fe 3 O 4 @PPy at a low calcination temperature of 300 °C while maintaining their shuttle-like morphology. The obtained Fe 3 O 4 @PPy exhibited a wide-spectral strong absorption over the UV-Vis-NIR region, excellent photothermal conversion effect, and magnetic properties. To fabricate the composite film, the β-FeOOH@PPy nanocomposites were dispersed into the matrix of polyimide (PI) precursor, and then freeze-dried to acquire hybrid aerogel. During the thermal treatment at 300 °C, both the thermal imidization of polymer backbone into PI and crystal transformation of β-FeOOH into Fe 3 O 4 took place at the same time, resulting in PI/Fe hybrid aerogel. By vacuum impregnation of polyethylene glycol (PEG) as the PCM into the aerogel framework, a flexible PI/Fe/PEG composite film was obtained, which possessed strong wide-spectral absorption, magnetic property, and thermal regulation capacity. Taking advantages of the thermal energy absorption capacity of PEG and the reduced radiation via the wide NIR absorption of Fe-based nanocomposites, the PI/Fe/PEG composite film could achieve superior performance in infrared stealth and thermal camouflage.