Evaluation of microwave and magnetic properties of substituted SrFe12O19 and substituted SrFe12O19/multi-walled carbon nanotubes nanocomposites

SrFe12−xCrx/2Alx/2O19 (x = 0–2.5) nanoparticles and ferrite/multi-walled carbon nanotubes (MWCNTs) nanocomposites were synthesized by a sol–gel method. The XRD patterns show a relatively weak peak around 26° which is corresponding to the graphite (002) lattice plane of the MWCNTs. The peak of Fourier transform infrared spectroscopy (FTIR) at 1729 cm−1 can be assigned to Cdouble bond; length as m-dashO bond of carboxylic groups, indicating the presence of poly(acrylic acid) (PAA) chains in PAA–carbon nanotubes. Field emission scanning electron microscopy (FE-SEM) micrographs demonstrate that strontium ferrite nanoparticles are strung along the MWCNTs. Transmission electron microscopy (TEM) was employed to study the structure of MWCNTs. Vibrating sample magnetometer (VSM) measurements show that with an increase in x content, the values of saturation of magnetization of SrFe12−xCrx/2Alx/2O19 nanoparticles reduce, while coercivity increases. Results of reflection loss indicate that with adding Cr–Al cations and MWCNTs to strontium ferrite; it is possible to cover a wideband of electromagnetic waves in the frequency range of 50–74 and 12–18 GHz. In addition, it can be seen that the strontium ferrite nanoparticles and nanocomposites display a great potential application as wideband electromagnetic wave absorbers.