Microwave Absorption Properties of Fe/Fe16N2 Nanoparticles Prepared from Iron Oxide

Fe/Fe
16
N
2
nanoparticles were synthesized from Fe
3
O
4
nanoparticles by hydrogen reduction and subsequent low-temperature nitridation. XRD analysis revealed that the Fe
3
O
4
phase was fully transformed into the
$\alpha$
-Fe phase after hydrogen reduction at 400°C. The Fe
16
N
2
phase was observed after ammonia nitridation of the Fe nanoparticles at temperatures ranging from 140°C to 160°C. The weight fraction of Fe
16
N
2
increased with increasing nitridation temperature, leading to enhanced coercivity. Evaluation of the electromagnetic properties of resin composites of the samples revealed a resonance frequency of 6.9 GHz for the reduced Fe nanoparticles, which shifted to 9.5 GHz after nitridation owing to the large anisotropic field of the Fe
16
N
2
crystal structure. The obtained results suggest that resin composites containing Fe
16
N
2
nanoparticles are promising microwave absorption materials for 5G applications.