Remarkable microwave absorption performance of graphene at a very low loading ratio

Abstract The microwave absorption properties of silicone rubber containing various graphene products acquired from different sources were studied. The complex permittivity, permeability, and return loss (RL) of the composites in the range of 3–18 GHz were characterized using contactless free-space measurement geometry. The large differences in the permittivity and RL for all samples indicated that the quality of graphene significantly affected the microwave absorption of the composite. Among the graphene samples, our homemade Staudenmaier reduced graphene oxide (RGO) offered a significantly improved RL at very low loading of 1 wt%, its minimum RL reached −37.8 dB at 12.3 GHz with a thickness of 2.5 mm. To identify the key factor that caused the difference in the microwave characteristics, the material properties of the graphene samples, including surface morphology, specific surface area, and C/O ratio, were analyzed and compared. The comparison revealed that the specific surface area, which is an indicator of the degree of exfoliation, is the most critical property that affects the microwave absorption performance of graphene-filled composites. Our results indicated that a well-dispersed, highly exfoliated RGO is capable of providing excellent microwave absorption at very low loading, which is favorable for cost reduction in future applications.