Fabrication and electromagnetic properties of soft-core functional particles by way of electroless Ni–Fe–P alloy plating on helical microorganism cells

In order to fabricate lightweight heteromorphic filler particles with excellent electromagnetic properties, Spirulina platensis were used as templates to produce helical soft-core functional particles by way of electroless plating of Ni–Fe–P alloy. The morphologies and ingredients of the coated Spirulina cells were analyzed with scanning electron microscopy and energy dispersive spectrometer respectively. The coating structures were characterized by employing the X-ray diffraction. The electromagnetic parameters (complex permittivity and complex permeability) of samples containing the coated Spirulina cells before and after heat treatment were measured by a vector network analyzer. The results showed that the Spirulina cells were deposited with Ni–Fe–P coating by electroless plating and kept their initial helical shape perfectly after plating. The effects of the content of P and the mass ratio of Ni:Fe in the particle surface coating on the surface qualities and electromagnetic properties of the coated Spirulina cells were also studied in detail, which showed that lower P content and suitable Ni:Fe ratio is more preferable for better coating quality and electromagnetic properties of the as-prepared particles. And heat treatment can further improve the electromagnetic properties of the coated Spirulina cells, since heat treatment can bring phase transformation of the coating and reduce structural imperfections.