Enhanced microwave absorption properties of wheat straw composites by multi-walled carbon nanotube (MWCNT) incorporation in X-band and Ku-band

Wheat straw, an abundant but underutilized agricultural residue, offers promise as a sustainable raw material for the development of eco-friendly microwave absorbers. In this study, wheat straw-based composites were fabricated and systematically investigated for their dielectric characteristics using the transmission line method. To enhance microwave absorption efficiency, multi-walled carbon nanotubes (MWCNTs) were incorporated at 2%, 4% and 6% loading levels, leading to significant improvements in both dielectric permittivity and loss. The electromagnetic absorption characteristics of all samples were evaluated through a combination of experimental methods and numerical simulations in CST Microwave Studio, using the measured dielectric parameters for model accuracy. The results demonstrate that MWCNT-modified wheat straw composites exhibit markedly higher absorption efficiency and broader effective bandwidth compared to unmodified counterparts with almost covering 95% of both X- and Ku-bands giving a minimum Reflection loss (RL) of −22.081 dB and −75.061 dB, respectively. These findings highlight the potential of MWCNT-enriched wheat straw composites as high-performance, environmentally sustainable microwave absorbers suitable for advanced electromagnetic interference (EMI) shielding applications in both X-band and Ku-band.