Synthesis of novel rambutan-like graphene@aluminum composite spheres and non-destructive terahertz characterization.

Graphene reinforced Al (graphene@Al) spheres were synthesized using microwave plasma chemical vapor deposition technique in which H, CH, and Ar were used as the reduced gas, carbon source, and plasma enhancement gas, respectively. The obtained graphene@Al spheres presented a rambutan-like structure and had a graphene shell wrapped on the sphere surface, which was proved by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The thickness of the graphene shell on the Al sphere is difficult to be characterized by conventional techniques. However, it was successfully measured with a sophisticated terahertz (THz) time-domain spectroscopic technique. To the best of our knowledge, neither have graphene@Al spheres been synthesized before nor has a THz-based technique been exploited to characterize the thickness of a shell structure. Therefore, the present work sheds useful insights on both the rational synthesis and non-destructive characterization of graphene reinforced functional structures.