Ultra-light h-BCN architectures derived from new organic monomer with tunable electromagnetic wave absorption

Hexagonal BCN (h-BCN) has been identified as a promising class of electromagnetic wave (EMW) absorption material for critical Mach number aerocraft due to its exceptional thermal and chemical stabilities as well as adjustable dielectric property. Herein, we report a facile precursor synthesis-pyrolysis method to obtain ultra-light h-BCN bulk ceramics and microtubes (MTs) using commercially available BCl₃, ethylenediamine and aniline as the monomers. The h-BCN bulk with a density of 15 mg/cm³ can be in situ synthesized derived from the precursor located in a tube furnace, while h-BCN MTs are simultaneously obtained on the downstream graphite sheets by controlling the pyrolysis temperature at the wide range of 800–1200 °C. For the h-BCN bulk ceramics, the minimum reflection loss (RL) can be tailored by controlling the N dopants, ranging from −52.7 dB at 5.44 GHz (the band width below −10 dB is achieved in a wide frequency range from 2.8 to 18 GHz) to −20.6 dB at 14.8 GHz (the band width below −10 dB is narrowed from 13.4 to 18 GHz). The excellent and frequency-controllable microwave absorption properties are due to the combination of tunable complex permittivity and lattice polarization resulting from B and N dopants in carbon networks.