Microstructures induced microwave resonance peak shift of Co/Al2O3 nanocomposites prepared by ball milling

► The Co/Al2O3 nanocomposites were prepared by ball milling. ► The microstructures of the Co/Al2O3 nanocomposites were characterized. ► The microwave absorption properties of the Co/Al2O3 nanocomposites were measured. ► The microwave resonance peak shift induced by interfaces was found. ► The Co/Al2O3-paraffin wax mixture shows good microwave absorption in a broad range.