| In recent years, helical carbon nanofibers as a kind of advanced materials hadbeen studied widely, because of their excellent physical and chemical properties. Theycould be applied broadly to the structure strengthen materials, electromagneticwave,absorbing and wave-shielding materials, and so on. To further improve theelectromagnetic properties and enhance the interface bonding strength with metal orceramic matrix, Ni-Co-B, Ni-Fe-B and Ni-Fe-Co-B coatings were deposited ontohelical carbon nanofibers via electroless plating in the experiment.The experiment could be divided into two parts, as follow:Firstly, the three kinds of alloy-coatings that consisted of Ni-Co-B, Ni-Fe-B andNi-Fe-Co-B are prepared on iron samples by electroless plating, which used alkali bathcomposed of metallic salt, reducing agents and complexing agent. The main saltincluded NiSO4·6H2O, CoSO4·7H2O, Fe(NH4)2·(SO4)2·6H2O, the complexing agentincluded KNaC4H4O6·2H2O, Na3C6H5O7·2H2O, the reducing agents were(CH3)2NH·BH3. The effects of the concentration of metallic salt ratio, theconcentration of reducing agents and bath pH on deposition rate and coatingcomposition were studied, as a result of which the optimum formula and platingconditions were found. The deposition rate of electroless plating was measured by themethod of increased mass.Secondly, Ni-Co-B, Ni-Fe-B, Ni-Fe-Co-B alloy coatings were deposited on the sensitized and activated helical carbon nanofibers under the optimized conditions. Themorphology of the coatings, the magnetic properties of the Ni-Co-B coatings, and theelectromagnetic wave absorbing property of Ni-Co-B coated carbon nanofibers/epoxyresin matrix composites were researched.The morphology, composition, crystal structure and magnetic properties of thecoatings were analyzed by scanning electron microscopy (SEM), energy dispersiveX-ray spectrometer (EDX), X-ray diffraction (XRD) and vibration magnetometer(VSM), respectively. The electromagnetic wave absorbing property of Ni-Co-B coatedcarbon nanofibers/epoxy resin matrix composites was measured by far-field radercross section (RCS) reflectance measurement system.The results showed that continuous and uniform alloy coatings could be depositedon the helical carbon nanofibers. The effect of the coating composition varied by thedifferent concentration of metallic salts ratio on the magnetic properties of coatedcarbon nanofibers were researched. The optimization magnetic properties Hc and Br ofthe coated Ni-Co-B helical carbon nanofibers were 43.7 kA·m-1, 9.2Am2·kg-1,respectively. The electromagnetic wave absorption peak appeared in the frequencyregion of 8～18GHz by far-field rader cross section (RCS) reflectance measurementsystem. The absorbing peak frequency was 11.8GHz. The percentage of RCSreflection loss was 99%. The carbon nanofibers coated Ni-Co-B/epoxy resin matrixcomposites exhibited fine electromagnetic, wave-absorbing property in the frequencyregion of 11～14GHz.
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