Functionally Graded Tunable Microwave Absorber with Graphene-Augmented Alumina Nanofibers

Area of Science:

• Materials Science
• Nanotechnology
• Electromagnetics

Background:

• Graphene exhibits promising radiation absorption properties at gigahertz and terahertz frequencies.
• Advanced materials are needed for efficient microwave absorption in the X-band spectrum.

Purpose of the Study:

• To investigate the X-band absorption efficiency of graphene-augmented γ-Al2O3 nanofibers in an α-Al2O3 matrix.
• To design and fabricate a functionally graded multilayer structure for maximized microwave absorption.

Main Methods:

• Composites with varying graphene/γ-Al2O3 filler concentrations (1-25 wt%) were prepared and tested.
• Dielectric data was used to construct a functionally graded multilayer absorber.
• Shielding effectiveness (SE) and reflection coefficient were measured to evaluate absorption efficiency.

Main Results:

• Composites with 15 and 25 wt% graphene fillers achieved SE of 38 and 45 dB, respectively.
• Near the electrical percolation threshold (~1 wt%), an SE of 10 dB was observed.
• The fabricated multilayer absorber demonstrated 99.99% absorption efficiency at ~9.6 GHz and >90% absorption across the full X-band.

Conclusions:

• Graphene-augmented alumina composites show significant potential as microwave absorbers.
• Functionally graded multilayer designs can optimize absorption efficiency for specific frequency bands.
• The developed materials are suitable for both broad-band and frequency-specific microwave absorption applications.