High permittivity from defective carbon-coated Cu nanocapsules

Carbon-coated Cu [Cu(C)] nanocapsules were prepared by a DC arc discharge method in a methane (CH4) atmosphere, and characterized by x-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning differential thermal analysis (SDTA), transmission electron microscopy (TEM) and Raman spectroscopy. The results show that the as-made product consists of carbon-coated Cu nanocapsules and giant onion-like fullerenes (GOLFs) in the diameter range of 20-50 nm. The graphite outer shells effectively protect the Cu cores from environmental oxidation, and have a greater defect density in comparison with bulk graphite and carbon nanotubes (CNTs). Its relatively complex permittivity (epsilon(r) = epsilon' + i epsilon '') is also measured at 2-18 GHz. The values of epsilon' and epsilon '' reach 14.5 and 4.1, respectively, exhibiting excellent electromagnetic wave loss ability.