Uniform Fe3O4 coating on flower-like ZnO nanostructures by atomic layer deposition for electromagnetic wave absorption

Abstract

An elegant atomic layer deposition (ALD) method has been employed for controllable preparation of a uniform Fe₃O₄-coated ZnO (ZnO@Fe₃O₄) core–shell flower-like nanostructure. The Fe₃O₄ coating thickness of the ZnO@Fe₃O₄ nanostructure can be tuned by varying the cycle number of ALD Fe₂O₃. When serving as additives for microwave absorption, the ZnO@Fe₃O₄–paraffin composites exhibit a higher absorption capacity than the ZnO–paraffin composites. For ZnO@500-Fe₃O₄, the effective absorption bandwidth below −10 dB can reach 5.2 GHz and the RL values below −20 dB also cover a wide frequency range of 11.6–14.2 GHz when the coating thickness is 2.3 mm, suggesting its potential application in the treatment of the electromagnetic pollution problem. On the basis of experimental observations, a mechanism has been proposed to understand the enhanced microwave absorption properties of the ZnO@Fe₃O₄ composites.