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<p>The design of the cost-effective, eco-friendly and sustainable microwave absorbers is still difficult due to material’s properties limitation. This work bridges this gap by developing a microwave absorber using sugarcane bagasse (SB), an agriculture waste (environmentally friendly) mixed with metal-free multi-walled carbon nanotubes (MWCNTs). Five samples (SB, SBCNT-1, SBCNT-2, SBCNT-3, and SBCNT-5) of 4&#xa0;mm thickness are prepared with varying MWCNT loadings (0–5&#xa0;wt%) and tested for the X-band (8.2–12.4&#xa0;GHz). Dielectric properties are analyzed via the coaxial transmission line technique, while reflection loss (RLmin) is measured using a free-space system. The dielectric constant and loss factor of the samples are improved by 32% and 84% by increasing the loading percentage of MWCNTs from (0 to 5&#xa0;wt %) into SB. Pure SB exhibited a 1.84&#xa0;GHz absorption bandwidth with RLmin =  − 14.64&#xa0;dB at 11.8&#xa0;GHz. Adding 1&#xa0;wt.% MWCNTs (SBCNT-1) improved RLmin to − 19.91&#xa0;dB at 10.92&#xa0;GHz (99.99% absorption) and effective absorption bandwidth to 2.45&#xa0;GHz. Higher MWCNT loadings further increased bandwidth: SBCNT-2 (3.3&#xa0;GHz, 78% X-band coverage) and SBCNT-3 (3.9&#xa0;GHz, 92% coverage), representing a&#xa0;112% improvement&#xa0;over SB. However, SBCNT-5 showed reduced bandwidth (2.7&#xa0;GHz), attributed to surpassing the percolation threshold, where excessive conductivity promotes reflection. The tunable dielectric properties and scalable fabrication highlight these composites as sustainable alternatives to conventional absorbers, balancing performance, cost, and environmental benefits.</p> Graphical abstract <p></p>

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Metal-free MWCNT and sugarcane bagasse composites: sustainable solutions for enhanced X-band microwave absorption

  • 期刊论文

  • 发表日期：

    2025年6月13日

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  • Hitender Gupta,
  • Rajesh Khanna,
  • Mayank Kumar Rai

摘要

The design of the cost-effective, eco-friendly and sustainable microwave absorbers is still difficult due to material’s properties limitation. This work bridges this gap by developing a microwave absorber using sugarcane bagasse (SB), an agriculture waste (environmentally friendly) mixed with metal-free multi-walled carbon nanotubes (MWCNTs). Five samples (SB, SBCNT-1, SBCNT-2, SBCNT-3, and SBCNT-5) of 4 mm thickness are prepared with varying MWCNT loadings (0–5 wt%) and tested for the X-band (8.2–12.4 GHz). Dielectric properties are analyzed via the coaxial transmission line technique, while reflection loss (RLmin) is measured using a free-space system. The dielectric constant and loss factor of the samples are improved by 32% and 84% by increasing the loading percentage of MWCNTs from (0 to 5 wt %) into SB. Pure SB exhibited a 1.84 GHz absorption bandwidth with RLmin =  − 14.64 dB at 11.8 GHz. Adding 1 wt.% MWCNTs (SBCNT-1) improved RLmin to − 19.91 dB at 10.92 GHz (99.99% absorption) and effective absorption bandwidth to 2.45 GHz. Higher MWCNT loadings further increased bandwidth: SBCNT-2 (3.3 GHz, 78% X-band coverage) and SBCNT-3 (3.9 GHz, 92% coverage), representing a 112% improvement over SB. However, SBCNT-5 showed reduced bandwidth (2.7 GHz), attributed to surpassing the percolation threshold, where excessive conductivity promotes reflection. The tunable dielectric properties and scalable fabrication highlight these composites as sustainable alternatives to conventional absorbers, balancing performance, cost, and environmental benefits.

Graphical abstract