In-situ self-assembly from physical fields for recyclable wave-transparent heat-conducting composites

In the field of communication, it seems counterintuitive that materials with high water absorption have high microwave transmittance (MWT) and thermal conductivity (λ). However, utilizing the fluid field generated by water absorption is expected to actively draw particles into the material, thereby facilitating the in situ formation of functional networks. Herein, coupling the fluid field from water absorption and the suction field from vacuum-assisted filtration, functional particles undergo situ self-assembly within the ramie lumen to form a nacre-like brick-and-mortar microstructure. This microstructure enables ramie fiber-reinforced composites with water-absorbing properties to have high MWT and λ. On one hand, by significantly reducing the dipole moment perpendicular to its plane to weaken polarizability, the composite achieves an impressive MWT of 98.5 %. On the other hand, by increasing multi-directional phonon transmission coefficients, both in-plane λ and through-plane λ reach high values of 1.2928 W/mK and 2.0812 W/mK, respectively. Importantly, the waste composite can be fully converted into functional particles, thereby achieving closed-loop recycling. This study provides a novel insight for developing recyclable wave-transparent heat-conducting composites based on absorbent materials.