Controllable synthesis, characterization and microwave absorption properties of magnetic Ni1−xCoxP alloy nanoparticles attached on carbon nanotubes

Ni 1− x Co x alloy nanoparticles ( x = 0.25, 0.50, 0.75), with diameters in the range 8–18 nm were uniformly attached on the surface of multi-walled carbon nanotubes (MWNTs) by electroless plating, and were characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray diffraction analysis, vibrating sample magnetometry and vector network analysis. Magnetization measurement indicates that both coercivities and saturation magnetizations decreased linearly with increasing Ni concentration in Ni–Co–P deposits. The complex permittivities of MWNT–olefin matrix composites also decreased linearly with increasing Ni concentration while the complex permeabilities increased slightly, which were measured in the range 2–18 GHz. The microwave absorbing properties enhanced with increasing Co concentration and a maximum reflection loss of −26.84 dB was obtained at a frequency of 7.75 GHz when the matching thickness was 2.5 mm and x = 0.75.