Effect of Annealing on Microwave-absorption Properties of Fe/Al2O3 Nanocomposite Prepared by Ball-milling

Abstract

An Fe/Al2O3 nanocomposite was prepared by high energy ball milling method, and which then annealed at 700C for 0.5 h in Ar atmosphere. The effect of annealing on the microstructure, magnetism and microwaveabsorption properties of Fe/Al2O3 nanocomposite has been investigated. It follows that the annealing resulted in increasing grain size, decreasing lattice defects and releasing the residual microstrain; meanwhile, decreasing the intensity of photoluminescence peaks of Al2O3 significantly, therewith the peaks at 398 nm and 484 nm exhibit a blue shift. An optimal reflection loss of -11.4 dB at 15.5 GHz was measured for a 7.7 mm thick layer of as-milled composite powder mixture with paraffin. However, the annealing treatment could remarkably enhance the dielectric loss, magnetic loss and microwave absorption performance of the composite, leading to an optimal reflection loss of -35.5 dB at 17 GHz for a layer thickness of 6.4 mm for the annealed composite.