Polyaniline Assisted Uniform Dispersion for Magnetic Ultrafine Barium Ferrite Nanorods Reinforced Epoxy Metacomposites with Tailorable Negative Permittivity

In this paper, a special dielectric property with tailorable negative permittivity is attained in the polyaniline assisted magnetic ultrafine barium ferrite (BaFe₁₂O₁₉) nanorods reinforced epoxy metacomposites. The ultrafine BaFe₁₂O₁₉ nanorods have been prepared through a citrate assisted sol-gel method and a self-propagating combustion combined with high temperature annealing. A thin polyaniline (PANI) layer is introduced on the surface of BaFe₁₂O₁₉ nanorods by in situ polymerization method under the sonication combined with the mechanical stirring in order to improve the dispersion quality and interfacial compatibility between BaFe₁₂O₁₉ and epoxy matrix. The enhanced tensile strength with maximum value of 90.7 MPa for the cured epoxy nanocomposites filled with 10 wt % loading of PANI modified BaFe₁₂O₁₉ (s-BaFe₁₂O₁₉) nanorods was obtained in the tensile tests compared with that of the cured pure epoxy (75.2 MPa) and cured epoxy nanocomposites filled with the same loading of bare BaFe₁₂O₁₉ (u-BaFe₁₂O₁₉) nanorods (74.4 MPa). In the cured s-BaFe₁₂O₁₉/epoxy nanocomposites, the uniform BaFe₁₂O₁₉ distribution has been observed by scanning electron microscope (SEM), which contributes to the improved tensile strength. A negative real permittivity is achieved in both of u-BaFe₁₂O₁₉ and s-BaFe₁₂O₁₉/epoxy nanocomposites at the low frequency range (∼10³ Hz). After further increasing frequency, the real permittivity was changed from negative to positive. The permittivity has no u-BaFe₁₂O₁₉ loading dependency for the u-BaFe₁₂O₁₉/epoxy nanocomposites. However, it is decreased with increasing s-BaFe₁₂O₁₉ loadings in the s-BaFe₁₂O₁₉/epoxy nanocomposites, which exhibits the component rather than structure controlled epoxy metacomposites.