Preparation and Investigation of Structural, Magnetic, and Microwave Absorption Properties of a SrAl1.3Fe10.7O19/Multiwalled Carbon Nanotube Nanocomposite in X and Ku-Band Frequencies

Abstract

A magnetic composite of SrAl1.3Fe10.7O19 nanoparticles (NPs) and multiwalled carbon nanotubes (MWCNTs) was prepared using a modified Sol-gel method. The MWCNTs were functionalized using a mixture of sulfuric and nitric acids and then coated with SrAl1.3Fe10.7O19 NPs in the presence of poly(methyl methacrylate) (PMMA) in an argon atmosphere furnace. The crystalline structure was studied by X-ray diffraction (XRD) confirming the single phase and hexagonal structure (M-type ferrite) of the SrAl1.3Fe10.7O19 NPs. The magnetic properties of the as-prepared composites investigated by a vibrating sample magnetometer (VSM) revealed that the metallic magnetic NPs have greater magnetization compared to the SrAl1.3Fe10.7O19/MWCNT nanocomposite and exhibit acceptable magnetic behavior at room temperature. The maximum reflection loss of the sample having a coating thickness of 3.10 mm diameter and 30 weight percentage (wt%) of SrAl1.3Fe10.7O19/MWCNT was -44.08 dB at 9.56 GHz, possessing a bandwidth of 2.21 GHz with a microwave absorption up to 10 dB for the X-band. The comparison of the reflection loss in both the X and Ku-band frequencies of the individual components, i.e., silicone rubber, functionalized MWCNT, and SrAl1.3Fe10.7O19/silicone rubber, revealed that the synergistic effect of the components in the nanocomposite originate from a better impedance match. By reducing the thickness to 1.00 mm, the RL was reduced to -14.85 dB at 17.75 GHz possessing a bandwidth of 1.12 GHz (with a microwave absorption up to 10 dB) for the Ku-band. The microwave absorption of the sample was then studied in an anechoic chamber, and a similar result was obtained.