Facile surface coating of Ni–Co–P alloy particles on hollow glass microspheres for enhanced wave absorbing.

The surface coating of magnetic nanoparticles onto hollow glass microspheres (HGMs) is of vital importance as light-weighted powders with wave-absorbing properties. In this study, HGMs were successfully coated by Co/Ni nanoparticles through a four-stepped strategy of NaF + HCl roughening, NaOH washing, PdCl₂ activation, and electroless plating, successively. The soft roughening of SiO₂ with NaF and the post-washing of Na₂SF₆ byproducts with NaOH were validated to ensure the integrity of the as-coated HGMs. The Ni–Co–P alloy coatings were measured to be lower than 1 μm in thickness with nanoparticles of 100–200 nm in diameter. The reflection loss of HGMs coated by 30 wt% Ni/Co not only retained the peak of the Co coating (− 4.5 dB) but also reached about − 6.7 dB at 16.4 GHz, much higher than that of HGMs coated by Ni and Co. The overall trend of input and output impedance ratio of the sample coated by Ni/Co does not change significantly compared with HGMs coated by Co, but the impedance matching has been optimized compared with Ni-plated powders. The novel light material with a uniform and complete coating prepared in this paper provides a new idea for the modification of HGMs for multi-functional applications. [ABSTRACT FROM AUTHOR]