CO-DEPOSITION OF IRON AND NICKEL ON NANOGRAPHITE FOR MICROWAVE ABSORPTION THROUGH FLUIDIZED BED ELECTROLYSIS

Abstract

Conventional radar absorbent materials (RAM) such as iron ball (carbonyl iron) and carbon black prove less effective against modern homing devices specially those which operate at low frequency microwaves. Hybrid nanoparticles based on ferrite are found to be more suitable for such applications. Iron (Fe) coated carbon nanoparticles can also be successfully used for conducting, sensing and electromagnetic shielding or radar absorbent applications. Among the carbon nanoparticles, nanographite has its potential for such applications because of its conductivity, nanomagnetism and layered structure. Therefore, nanographite coated with Fe , nickel (Ni) or chromium is an attractive choice for microwave absorbing material. In the present study, Fe coating has been carried out on acid functionalized nanographite by a simple and novel fluidized bed electroplating process. The acid functionalization helps to adhere the coating on the nanographite surface. The electroplating of Fe–Ni alloys is recognized as an anomalous co-deposition and is characterized by a preferential deposition of the less noble metal Fe , even when the concentration of Ni in the bath was higher than that of Fe . The efficiency of the electrolytic coating of powdered material is strongly affected by the applied current density, the rotation speed, the average size of the particles and the density of the electrolyte-powder suspension. The nanoparticles were further dispersed in polyurethane matrix and cast into nanocomposite films. The microwave absorption property observed in the frequency range 300 MHz to 1.5 GHz shows that a very thin coating of Fe–Ni helps to absorb the microwave quite efficiently. Fe–Ni coated functionalized nanographite synthesized by this method is thus an effective microwave absorbent material and can find potential use in several defence applications as specialty coatings for fighter aircrafts/radomes and other coated textiles used for aerial surveillance etc.