Cellulose Nanofiber/Carbon Nanotube@Polypyrrole-Silver Nanowires Composite Films with a Multilayer Double Conductive Structure for High-Efficiency Electromagnetic Interference Shielding and Infrared Stealth

Fiber-based conductive films show great potential for use in electromagnetic interference shielding (EMI). However, it remains a challenge to meet the multifunctional requirements of ultrathin materials, such as simultaneous infrared stealth and outdoor stability. Here, this work prepared multilayer composite membranes composed of cellulose nanofiber layer (CNF), CNF/carbon nanotube@polypyrrole layer, and CNF/silver nanowire (AgNWs) layer in different sequences by a simple step-by-step vacuum filtration strategy and named them F, P, and A, respectively. Compared with the uniformly mixed film, the three-layer films have excellent shielding effectiveness (SE), attributed to the double gradient conductive network structure and loss of interfacial polarization. The P–F–A film, in particular, has a unique blank sandwich layer that makes the reflection and scattering paths of electromagnetic waves longer. As a result, the EMI SE of the P–F–A film is 69.8 dB, which is higher than those of F–P–A (64.06 dB) and F–A–P (63.8 dB). In addition, this work constructed a superhydrophobic surface by using 1H,1H,2H,2H-perfluorodecanethiol (PFDT) as the composite membranes. Because of the extremely low infrared emissivity of AgNWs, F–P–A and P–F–A films have excellent infrared stealth capabilities, and their performances are not affected by bending and abrasion, which can meet the requirements of multifunctions and adapt to complex environments. Overall, the composite films designed in this study have broad application prospects in flexible electronics wearable products, radar stealth, aerospace, and other fields.