Tunable Twin Matching Frequency (fm1/fm2) Behavior of Ni1?xZnxFe2O4/NBR Composites over 2–12.4?GHz: A Strategic Material System for Stealth Applications

摘要

The gel to carbonate precipitate route has been used for the synthesis of Ni1?xZnxFe2O4 (x?=?0, 0.25, 0.5 and 0.75) bulk inverse spinel ferrite powder samples. The optimal zinc (50%) substitution has shown the maximum saturation magnetic moment and resulted into the maximum magnetic loss tangent (tanδm??1.2 over the entire 2–10?GHz frequency range with an optimum value ~?1.75 at 6?GHz. Ni0.5Zn0.5Fe2O4- Acrylo-Nitrile Butadiene Rubber (NBR) composite samples are prepared at different weight percentage (wt%) of ferrite loading fractions in rubber for microwave absorption evaluation. The 80?wt% loaded Ni0.5Zn0.5Fe2O4/NBR composite (FMAR80) sample has shown two reflection loss (RL) peaks at 5 and 10?GHz. Interestingly, a single peak at 10?GHz for 3.25?mm thickness, can be scaled down to 5?GHz by increasing the thickness up to 4.6?mm. The onset of such twin matching frequencies in FMAR80 composite sample is attributed to the spin resonance relaxation at ~5?GHz (fm1) and destructive interference at λm/4 matched thickness near ~10?GHz (fm2) in these composite systems. These studies suggest the potential of tuning the twin frequencies in Ni0.5Zn0.5Fe2O4/NBR composite samples for possible microwave absorption applications.