Surfactant-assisted solvothermal synthesis of Ba(CoTi)_xFe _12-2xO₁₉ nanoparticles and enhancement in microwave absorption properties of polyaniline

Barium ferrite (BaFe₁₂O₁₉) nanoparticles have been successfully synthesized from solvothermal route with the assistance of surfactant P123 (EO₂₀PO₇₀EO₂₀), which has been proven to be a better method for barium-ferrite synthesis as compared to conventional hydrothermal technique, and the resultant product shows high-purity crystalline phase, small particle size, excellent magnetic properties, and characteristic of single magnetic domains. A series of Co-Ti-doped barium-ferrite nanoparticles [Ba(CoTi)_xFe_12-2xO ₁₉, 0.25 ? x ? 1.0] were also prepared by this method, indicating that this route is versatile for barium-ferrite nanoparticles with different chemical compositions. With increasing heteroatoms content, saturation magnetization and coercivity drastically decreased because of the selective substitution of Fe³⁺ sites by Co²⁺ and Ti⁴⁺ in the magnetoplumbite structure. By supplying these inorganic nanoparticles as nucleation sites, polyaniline/ferrite composites were prepared through in situ polymerization technique. Compared with pure polyaniline, these composites exhibited essentially enhanced reflection loss properties because of the synergetic behavior between organic and inorganic materials, and proper heteroatom substitution can even improve the reflection loss. More importantly, well reflection loss over a wide frequency range can be simply achieved by manipulating the absorber thickness, suggesting these composites may be used as lightweight and highly effective microwave absorbers.