Sustainable Microwave Absorbing Material based on Macadamia Nutshell Derived Porous Carbon

Increasingly severe electromagnetic pollution problem boosts the demand for light weight microwave absorbing materials with high absorption capacity over wide frequency range. Biomass-derived porous carbon has been regarded as one of the promising candidates for microwave attenuation as the biomaterials are vastly available and renewable. Here, macadamia nutshell derived porous carbon (MPC) was fabricated by activated carbonization. Evidenced by the morphological results, the resulted MPC demonstrates three-dimensional frameworks with tubular skeletons. Owing to such hierarchical structures, the resulted composite MPC-filled paraffin composites exhibit a minimum reflection loss of [Formula: see text]44.14[Formula: see text]dB and effective absorption bandwidth of 3.84[Formula: see text]GHz. Moreover, the resulted MPC can be explored as a practical absorber in a frequency range of 3.68–18.00[Formula: see text]GHz via tuning of the thickness. The analysis of microwave attenuation mechanism indicates that such outstanding microwave absorption capacity is attributed to hierarchical structure tuned impedance matching conditions and multiple attenuation mechanisms. All results in this work open the avenue for the development of nutshell derived sustainable microwave absorber with high absorption capacity as well as broad effective absorption bandwidth, boosting the utilizing of biomass resources.