Co2W hexaferrite nanoparticles-carbon nanotube microwave absorbing nanocomposite

Co2W-type hexaferrite nanoparticles with composition of SrCo2−x(MnZnCa)x/3Fe16O27(x = 0-0.5) were synthesized by a co-precipitation method. The synthesized nanoparticles were decorated on the outer surface of multi-walled carbon nanotubes by chemical method. X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry, magnetic susceptometer and vector network analyzer were utilized to characterize the structural, magnetic, and reflection loss properties of the nanocomposites. The structural results showed a perfect diffusion of Mn, Zn and Ca ions into the crystal structure of Co2W hexaferrite without forming any secondary phases. The SEM images provide clear information about the size of nanoparticles (50-85 nm) through these samples. The hysteresis loops showed hard magnetic property with enhanced coercivity which reflects that the synthesized particles have almost high magnetic anisotropic field, well suitable for absorbing materials. The coercivity (Hc) increased from 1450 Oe at x = 0.0, to 1650 Oe at x = 0.3, and then decreases to 1320 Oe at x = 0.5. High reduction in the coercivity was detected consistent with the large particle sizes for these samples. Ferrite nanoparticles were decorated on the surface of carbon nanotubes in almost constant distance. The interacting mode was confirmed between magnetic nanoparticles by means of plotting real and imaginary parts of magnetic susceptibility versus temperature at various frequencies. Based on reflectivity measurement, the sample with x = 0.3 showed a maximum reflection loss of −37 dB at the frequency of 9.4 GHz. This sample revealed the best performance with low reflectivity and high absorption broadband (4 GHz) at X-band frequency range.