Synthesis and characterization of multilayer core–shell structure hollow spheres with low density, favorable magnetic and conductive properties

Multilayer core–shell structure hollow spheres were synthesized on the basis of hollow glass sphere (HGS) along with magnetic layer and conducting layer. The deposition of ferrite compound was conducted via chemical co-precipitation method onto HGS surface using ammonium acetate stabilizing precursor solution which performed as chemical plating process. The ratio of ammonium acetate: metal ion appeared to be critical when forming ferroferric oxide compounds. Sequentially, in situ chemical oxidative polymerization in H2O/C2H5OH/5-sulfosalicylic acid/pyrrole/FeCl3 system consequently obtained multilayer HGS@Ferrite@Polypyrrole composites. 5-Sulfosalicylic acid-FeCl3 constitutes a doping-initiating chelate which was found to provide good compactness and uniformity resulting in good conductivity. Qualitative characterization proved the core–shell structure and encapsulation effect. Doping amount and organic/inorganic ratio was quantitatively calculated. The HGS@Ferrite@PPy composite has remarkable excellent properties. The magnetization reaches 20.61 emu/g as soft magnetic materials, with a hysteresis loop presenting superparamagnetic whose coercivity and remnant magnetization hitting zero. The conductivity was as high as 16.5 S/cm much higher than other composites with similar structure. The cavity effect, magnetic loss and conducting loss combined provide this kind of material good electromagnetic wave absorption effect under low addition amount.