Graphene Oxide Paper as a Lightweight, Thin, and Controllable Microwave Absorber for Millimeter-Wave Applications

The production and verification of microwave absorbers are a subject of high priority. These are due to the fast development of telecommunication technologies and the need to reduce electromagnetic pollution. Such materials are implementable in multiple industries, including military, medical, and laboratory equipment. One should remember that the desired material should exhibit a high total shielding effectiveness SE _{T} and controllable performance properties. In this work, an ultrathin graphene oxide paper is fabricated and verified as a wide-range, controllable microwave absorber. Stepwise (100 ^\circ C - 200 ^\circC - 300 ^\circC) thermally reduced G-Flake graphene oxide paper of 4.95 μm thickness revealed the conductivity of 1.86 S/cm. A mild level of reduction was proven with combustion elemental analysis, resulting in a 22.4 oxygen percentage (50.9 % before the reduction). Raman spectroscopy suggested the limitation of Stone-Wales defects after heat treatment. Microwave absorption was measured in the W-band frequency region, and the SE_{T}/t parameter reached 606 dB/mm for a c.a. 5-μm-thick individual reduced paper sheet. The controlled increase in conductivity resulted in conduction losses, and the occurrence of pores enabled scattering, while the absorption remained the primary shielding mechanism.