Synergistic Electromagnetic Wave Absorbing Properties of NiFe2O4/MWCNT Composites Synthesized via Microwave-Assisted Combustion Method in Ku-band

Abstract

This study investigates the synthesis, microstructural characteristics, magnetic properties, and electromagnetic wave absorption performance of nickel ferrite (NiFe₂O₄) composites reinforced with multi-walled carbon nanotubes (MWCNTs) synthesized via the microwave-assisted combustion (MAC) method. Through X-ray diffraction (XRD) analysis, the desired structure of NiFe₂O₄ and the successful integration of MWCNTs with NiFe₂O₄ were confirmed. Field emission scanning electron microscopy (FESEM) analysis revealed the entanglement of MWCNTs and their significant impact on hindering grain growth, resulting in a finer grain structure. The average grain size reduction from 1.317 µm for pure NiFe₂O₄ to 0.436 µm for NiFe₂O₄/2wt%MWCNT demonstrated the effectiveness of MWCNTs as grain boundary migration obstacles. Magnetic property analyses showed a nuanced interplay between MWCNT concentration and composite behaviour, with the saturation magnetization (M_s) exhibiting substantial enhancement in the NiFe₂O₄/2wt%MWCNT composite, indicative of effective alignment of magnetic moments. However, a subsequent decrease in M_s at higher MWCNT concentrations (4wt% and 6wt%) suggested potential dilution effects and disruptions in magnetic interactions within the composite. Electromagnetic wave absorption investigations revealed NiFe₂O₄/4wt%MWCNT as a highly efficient absorber in the Ku-band, with superior impedance matching and a high attenuation constant. The reflection loss (RL) reached a maximum of -17.58 dB at 12.78 GHz, signifying absorption of more than 99% of the incident EM wave in the microwave range. The favourable impedance matching and high attenuation constant contributed to the superior performance of NiFe₂O₄/4wt%MWCNT compared to pure NiFe₂O₄ and MWCNT. These findings suggest the potential of NiFe₂O₄/MWCNT composites for applications in telecommunications, aerospace, and electronics, with opportunities for further optimization and investigation into long-term stability and durability under varying environmental conditions.