Microwave absorption of Mn 0.5 Zn 0.5 Fe 2 O 4 nanoparticles integrated in multi-walled carbon nanotubes

Nanoparticles of Mn 0.5 Zn 0.5 Fe 2 O 4 are prepared by the simple co-precipitation method. To get smaller nanoparticles having different sizes, as dried powdered sample is annealed for 5 h at 200 and 400 °C. The two annealed samples with low average sizes are encapsulated in multi-walled carbon nanotubes (MWCNTs). Desired crystallographic phase formation is confirmed by recording and analysing X-ray diffraction (XRD) patterns. Other structural and microstructure information is derived using the Rietveld analysis of the observed XRD patterns. The average crystallite sizes of all samples lie in the range of 6–10 nm. Hexagonal phase of MWCNTs is found in both the encapsulated samples. Crystallographic phase formation and integration of the nanoparticles in MWCNTs are further confirmed by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. Elemental analysis confirms the desired atomic percentages of Mn, Zn and Fe in the samples. Microwave (MW) absorption capability of the encapsulated nanoparticles is ensured by recording the reflection loss (RL) profile in the X (8–12 GHz) and K u (12–18 GHz) bands of frequency. A maximum RL of ~ − 20.3 dB is achieved at a matching frequency of 15.45 GHz for ~ 10 nm nanoparticles in the MWCNT matrix with a layer thickness of 1 mm. This high value of RL with bandwidth corresponding to RL less than − 10 dB of 4.32 GHz suggests that Mn 0.5 Zn 0.5 Fe 2 O 4 nanoparticles in the MWCNT matrix could be a significant MW-absorbing material.