Synergistic enhancement of microwave absorption in CNT-NZF CI/epoxy and carbon black/epoxy nanocomposites through dual phase structuring

Idza Riati, Ibrahim and Rodziah, Nazlan and Siti Nor Ain, Rusly and Fadzidah, Mohd Idris and Khamirul Amin, Matori and Ismayadi, Ismail and Ghazaleh, Bahmanrokh and Muhammad Misbah, Muhammad Zulkimi and Nor Hapishah, Abdullah and Muhammad Syazwan, Mustaffa and Arlina, Ali (2025) Synergistic enhancement of microwave absorption in CNT-NZF CI/epoxy and carbon black/epoxy nanocomposites through dual phase structuring. Ceramics International, 51 (30). pp. 64619-64629. ISSN 0272-8842

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Abstract

An efficient microwave absorber is essential for reducing electromagnetic interference in modern technologies. Here we highlight a magnetic-catalyst-assisted route to carbon nanotubes (CNTs): CNTs were grown by CVD using Ni–Zn ferrite/carbonyl iron (NZF/CI) as magnetic catalysts, embedding magnetic nanophases within the CNT network. This magnetic–dielectric coupling increases magnetic loss (μ″) through natural-resonance and eddy-current pathways. When combined with a graded double-layer structure which CNT/epoxy (matching/front) and carbon black (CB)/epoxy (absorbing/back), synergistically optimizing impedance matching and in-layer attenuation across the X- and Ku-bands. Single-layer CNT/epoxy and double-layer CNT/epoxy–CB/epoxy nanocomposites were fabricated and characterized by Raman spectroscopy, field emission scanning electron microscopy (FESEM), and a PNA network analyzer over the X- and Ku-band frequency ranges. Results revealed that the optimized double-layer structure, comprising a 1 mm CNT as a matching layer and a 1 mm carbon black as an absorbing layer, achieved a −10 dB absorption bandwidth of 2.58 GHz and over 99.99 % absorption at 11.14 GHz. Microstructural analysis shows nanosized CB (∼41 nm) uniformly distributed, providing abundant interfacial sites and micro-capacitive contacts that elevate ε″, while entangled CNTs (outer diameter ∼61 nm; spiral/twisted/net-like) promote multiple internal reflections and efficient dissipation. The close contact between CNTs and NZF/CI further strengthens magnetic loss and stabilizes impedance matching. These results demonstrate a cost-effective, magnetic–dielectric double-layer strategy for high-performance and thin microwave absorbers.

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