Effect of magnetic fillers and their orientation on the electrodynamic properties of BaFe12-xGaxO19(x=0.1-1.2)-epoxy composites with carbon nanotubes within GHz range

Epoxy composites filled with 30 wt.%-, 60 wt.%- of BaFe12-xGaxO19(x = 0.1-1.2) and with 1 wt.% of multiwall carbon nanotubes were prepared and the filler was aligned via magnetic field action at composites polymerization. The orientation of magnetic filler (BaFe12-xGaxO19) in composites was evidenced by scanning electron microscopy and X-ray diffraction methods: the peak intensity of the (008) crystalline plane increases noticeably in composites which were cured under the action of a magnetic field, while (hkl)-peaks decrease. Frequency dependencies (in the range 26-37.5 GHz) of transmission index and of standing wave ratio have been used to study the effect of fillers content, type and their orientation on the electrodynamic properties of the prepared composites. The investigated materials demonstrate maximum effect of alignment of magnetic filler when its content is lower. Namely, six times increase of reflection/absorption indexes ratioR/Aat 29 GHz for 30 wt.% BaFe11.4Ga0.6O19-L285 was achieved due to the magnetic field action.