Synthesis and microwave absorption property of nanostructured Ketjen black/Fe ₃ O ₄ core/shell particles

Nanostructured Ketjen black/Fe 3 O 4 core/shell particles have been prepared through a simple one‐step hydrothermal method. The microstructure analysis shows that the as‐synthesized composite particles display a typical core/shell structure: the Ketjen black is playing as the core, while a large number of Fe 3 O 4 nanoparticles are uniformly attaching to the surface of the Ketjen black and forming the shell. The investigation of the magnetic properties of the nanostructured Ketjen black/Fe 3 O 4 core/shell materials reveals that the as‐synthesized composite is a typical soft ferromagnetism material. The 40 wt% Ketjen black/Fe 3 O 4 ‐paraffin composites exhibit an excellent reflection loss value of −64.21 dB at a thickness of 2.00 mm, and the broadest effective bandwidth of 4.17 GHz at a thickness of 1.50 mm. This work provides a brand‐new type of magnetic carbon nanoparticles, defined as Ketjen black/Fe 3 O 4 core/shell particles, which are an excellent candidate for high‐performance electromagnetic wave absorber materials.