Microwave Absorbing Properties of Composite Agriculture Waste and CNT

Abstract

ABSTRACT In recent years, the exponential growth of wireless communication systems, radar technologies, and compact electronic devices has resulted in excessive electromagnetic (EM) wave emissions, causing severe electromagnetic interference (EMI) and electromagnetic pollution. This not only reduces the performance and reliability of sensitive electronic equipment but also poses potential risks to human health. Conventional chemical-based microwave absorber materials (MAMs) have been employed to mitigate this issue, but their use is constrained due to high production costs, bulkiness, brittleness, and environmental concerns. Therefore, there is a strong motivation to develop lightweight, cost-effective, and eco-friendly alternatives by utilizing agricultural waste-derived materials. This research explores the potential of dried banana leaves (DBL) and sugarcane bagasse (SG), which are rich in carbon content and abundantly available, as sustainable microwave absorbers. The dielectric and magnetic properties of these biowaste materials are first investigated within the X-band frequency range (8.2-2.4 GHz). However, due to their inherently low conductivity and limited absorption bandwidth, agricultural wastes alone cannot meet the requirements of high-performance MAMs. To overcome this limitation, multi-walled carbon nanotubes (MWCNTs), known for their high electrical conductivity, large aspect ratio, and excellent dielectric properties, are incorporated into DBL and SG matrices. These CNT-based composites enhance microwave absorption through mechanisms such as conduction loss, interfacial polarization, multiple scattering, and improved impedance matching. Composite samples of DBL-MWCNT and SG-MWCNT are fabricated by optimizing filler concentration and thickness, followed by evaluation of their dielectric response, reflection loss (RL), and absorption bandwidth. Experimental studies reveal that the addition of even a small amount of MWCNTs substantially improves absorption efficiency, with optimized composites achieving strong attenuation of incident EM waves. Structural and morphological analyses further support the enhanced absorption mechanisms. To ensure reliability under practical conditions, the thermal stability of these composites is also examined. Temperature-dependent studies of DBL and DBL-MWCNT absorbers demonstrate that MWCNT incorporation not only increases absorption efficiency but also stabilizes performance across varying thermal environments. Furthermore, the findings establish that agriculture waste-MWCNTs composites exhibit high absorption efficiency, broadband characteristics, reduced thickness, lightweight structure, and eco-friendly nature, which makes them promising candidates for applications in electromagnetic interference (EMI) shielding, stealth technology, aerospace, and wireless communication devices. The study concludes that utilizing agricultural residues such as DBL and SG, in combination with MWCNTs, provides a sustainable and cost-effective pathway to replace conventional chemical-based absorbers. These results validate the potential of hybrid agricultural waste-CNT composites as next-generation microwave absorber materials and highlight their significance in addressing both technological demands and environmental challenges.