Effect of different coating methods on magnetic and microwave behavior of nano-Fe3O4 coated carbon fibers

Radar absorbing materials, i.e. magnetite (nano-Fe3O4) coated carbon fibers (MCCFs) were fabricated by electro-deposition (ED) and electrophoretic deposition (EPD) techniques. The structure, morphology, magnetic and microwave absorption properties of prepared samples were investigated and the two coating methods (i.e. ED and EPD) were compared. In order to prepare the MCCFs samples, in ED technique, a multi-step cathodic method employed to deposit magnetite on the surface of activated carbon fibers (CFs) through the reduction of Fe (III) -Triethanolamine complex in an aqueous alkaline solution at 60-80 oC and regard to EPD technique, by deposition of nano-Fe3O4 particles distributed stably in a suspension, a uniform and compact Fe3O4 thin-film was fabricated on the activated CFs surface. Our results indicated that, a more homogenous and denser magnetite coating and consequently, improved EM absorption properties could be achieved by EPD and multi-step ED methods on CFs comparing to single step method at ambient and 80 oC, respectively. Considering the magnetic hysteresis loop of MCCFs coated at 60 oC, it seems that the exchange bias effect occurred in this sample. Also, the strongest RL of MCCFs was recognized to be −11 dB at 10.37 and 11.4 GHz for a layer of 1.7 mm in thickness, which coated by EPD, so EPD was introduced as a suitable method for production of MCCFs due to its low cost, easy productivity and time efficiency as same as the high absorption properties of resulted MCCFs in comparison with the ED method.