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

Ni1-xCox alloy nanoparticles (x = 0.2,0.5,0.75), 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.