In-situ growth of carbon nanotubes for the modification of wood-derived biomass porous carbon to achieve efficient Low/Mid-Frequency electromagnetic wave absorption.

Ideal wave-absorbing materials are required to possess the characteristics such as being "broad, lightweight, thin, and strong." Biomass-derived materials for absorbing electromagnetic waves (EMWs) are widely explored due to their low cost, lightweight, environmentally friendly, high specific surface area, and porous structure. In this study, wood was used as the raw material, and N-doped carbon nanotubes were grown in situ in porous carbon derived from wood, loaded with magnetic metal Co nanoparticles through chemical vapor deposition. The Fir@Co@CNT composite material exhibited a three-dimensional conductive electromagnetic network structure and excellent impedance matching, thereby demonstrating excellent wave absorption performance. By controlling the introduction of carbon nanotubes, the roles of polarization loss and conduction loss in the Fir@Co@CNT composite material were precisely regulated. The Fir@Co@CNT 1:5 composite material achieved a minimum reflection loss (RL) of -43.03 dB in the low-frequency region and a maximum effective absorption bandwidth (EAB) of 4.3 GHz (1.5 mm). Meanwhile, the Fir@Co@CNT 1:10 composite material achieved a RL of -52 dB with a thickness of only 2.3 mm, along with an EAB of 4.2 GHz (1.6 mm). Both materials collectively cover the entire C-band, X-band, and Ku-band in terms of EAB. This work introduces a method for regulating polarization loss and conduction loss, showcasing the potential of biomass carbon materials as low-frequency EMW absorption materials for the first time. It also provides a new direction for the development and application of environmentally friendly, lightweight, high-performance wave-absorbing materials.