Flame synthesis of carbon nanotubes and few-layer graphene on metal-oxide spinel powders

Multi-walled and single-walled carbon nanotubes (CNTs) and few-layer graphene (FLG) are grown directly on spinel powders using flame synthesis. CNT and FLG growth occurs via the decomposition of flame-generated carbon precursors (e.g., CO, C2H2, and CH4) over nanoparticles (i.e., Ni, Co, Fe, and Cu) reduced from the solid oxide. The growth of CNTs is investigated on NiAl2O4, CoAl2O4, and ZnFe2O4, using counterflow diffusion flame and multiple inverse-diffusion flames (m-IDFs), while the growth of FLG is investigated on CuFe2O4 using m-IDFs. As shown by analytical electron microscopy techniques, Raman spectroscopy, and X-ray diffraction, substrate temperature and spinel composition play critical roles in the growth of both CNTs and FLG.