Liquid metal modified hexagonal boron nitride flakes for efficient electromagnetic wave absorption and thermal management

The rapid advancement of lightweight and high-power electronic devices has brought about increasingly aggravated issues of electromagnetic wave (EMW) interference and heat accumulation, which severely threaten the stability and service life of the devices. To address these challenges, we propose a simple and scalable mechanochemical strategy to activate hexagonal boron nitride flakes (BNFs) using liquid metal (LM), enduing BNFs outstanding EMW absorption and high thermally conductive capabilities. This facile modification approach avoids multi-step reactions, large solvent consumption, and high energy input, while simultaneously introducing abundant interfacial polarization centers, and electron and heat transfer pathways, thus optimizing EMW absorption and thermally conductive performances of BNFs. Consequently, the optimized BNF@LM composites exhibit remarkable EMW absorption with a minimum reflection loss of -48.4 dB and an effective absorption bandwidth of 5.76 GHz. Besides, coupling the BNF@LM composites with aramid nanofibers (ANFs) can impart the ANF based films with good thermal conductivity and flexibility, making them suitable for flexible electronics. Typically, the BNF@LM/ANF films can reach a thermal conductivity of 0.54 W m^-1 K^-1 measured by hot wire method, nearly 5 times higher than that of ANF film (0.10 W m^-1 K^-1). Moreover, the BNF@LM/ANF films can effectively attenuate incident EMW and exhibit remarkable flame retardancy, endowing them with strong adaptability to extreme environments.