Bio-derived graphitic carbon microspheres: A green approach for high-frequency microwave absorption

Abstract

Bio-derived carbon materials have emerged as a sustainable alternative to non-renewable petroleum-based carbon sources, thanks to their reproducibility and environmental benefits. There is a strong demand for developing and efficiently utilizing carbon-based microwave absorbing materials (MAMs) that are lightweight, require low filler loading, and offer broadband absorption for electromagnetic wave (EM) applications. In this context, we successfully synthesized uniform carbon microspheres from the natural precursor turpentine oil using the chemical vapor deposition (CVD) technique at various temperatures. The sample prepared at 1000 °C (GC-1000) exhibited a uniform carbon microsphere morphology, as confirmed by XRD and Raman spectroscopy, and demonstrated extremely good microwave absorption properties. With a low filler loading of just 5 wt%, the GC-1000 sample achieved a minimum reflection loss (RL) of −39.77 dB at 10.21 GHz and an effective absorption bandwidth of 2.51 GHz at a matching thickness of only 2.8 mm. Additionally, this sample showed a total shielding effectiveness (SE_T) of −44.74 dB, surpassing the threshold required for commercial applications. The graphitic phase formation, confirmed by XRD and Raman analysis, acts as a conductive trap for electromagnetic radiation, and the high surface area of the uniform carbon microspheres facilitates multiple internal reflections, enhancing overall microwave absorption performance in the X-band region. Our lightweight, durable, bioderived carbon microspheres, synthesized through a cost-effective and scalable process, show significant potential for EM wave absorption in military and electromagnetic compatibility (EMC) devices.