Ag₃PO₄ nanoparticle-decorated Ni/C nanocapsules with tunable electromagnetic absorption properties

Core/shell-structured nickel/carbon (Ni/C) nanocapsules with Ag₃PO₄ nanoparticle decoration (Ag₃PO₄@Ni/C) are prepared by an arc-discharge process and an ion-exchange process. The Ag₃PO₄@Ni/C nanocapsules show a clear decoration of Ag₃PO₄ nanoparticles of 4-20 nm diameter on the C shell of the Ni/C nanocapsules of ∼60 nm diameter. The amount of Ag₃PO₄ nanoparticles that can be decorated on the Ni/C nanocapsules depends on the volume of Na₂HPO₄ reactant used in the ion-exchange process. The Ag₃PO₄@Ni/C nanocapsules demonstrate interestingly high and tunable electromagnetic absorption properties with different amounts of Ag₃PO₄ nanoparticle decoration in the paraffin-bonded composites over the 2-18 GHz microwave range. The nanocapsules prepared with 100 ml Na₂HPO₄ exhibit much enhanced dielectric and magnetic losses for an improved electromagnetic impedance match. These result in a large reflection loss (RL) of -31.4 dB at 12.3 GHz for a small absorber thickness of 2.6 mm in conjunction with a very wide effective absorption bandwidth (for RL<-10 dB) of 14 GHz (4-18 GHz) at a wide absorber thickness range of 1.4-5.0 mm.