Effect of electroless plating temperature on the electromagnetic properties and microwave absorption performance of Ni@ MWCNTs composites with core‐shell Ni microspheres

The rational design of magnetic‐dielectric composites with tunable electromagnetic parameters is crucial for achieving lightweight and broadband microwave absorption. Among these, Ni‐based composites are particularly attractive due to their ferromagnetic response, moderate electrical conductivity, and good chemical stability. While the electroless plating temperature plays an important role in determining the shell structure of Ni microspheres, its influence on the dielectric behaviour and microwave absorption performance of their hybrids has not been thoroughly studied. In this work, Ni core‐shell microspheres with temperature‐dependent Ni deposition characteristics are synthesized via electroless plating on polystyrene templates at controlled temperatures and subsequently hybridized with multi‐walled carbon nanotubes (MWCNTs) to construct Ni@MWCNTs composites with coupled magnetic and conductive components. Microstructural characterization shows that Ni microspheres prepared at 40°C have a relatively uniform and dense shell (~0.285 μm), providing a favourable structural configuration for interaction with the MWCNTs. This electromagnetic response is associated with synergistic loss mechanisms, including multiple polarization relaxations and hopping conduction loss, as well as improved impedance matching and moderate magnetic loss. Consequently, the Ni‐2@MWCNTs composite delivers a minimum reflection loss of −33.2 dB and an effective absorption bandwidth of 3.9 GHz at only 1.8 mm thickness, covering the upper X‐band and lower Ku‐band. CST simulations confirm a substantial radar cross‐section reduction of −26.8 dBsm. These results demonstrate that electroless plating temperature provides an effective means of regulating Ni deposition characteristics and tailoring the electromagnetic response and microwave absorption performance of Ni@MWCNTs composites.