Fabrication and purification of carbon nano onions

Carbon nano onions (CNOs) with diameters of 70–100 nm were fabricated by chemical vapor deposition at 800 °C, using methane as carbon source and high-temperature steam treated 316 stainless steel mesh as catalyst. The CNOs were isolated from the substrate by HNO3 refluxing, calcination in air at 500 °C and magnetic separation. The morphology, microstructures and magnetic properties of the CNOs were characterized by SEM, TEM, XRD, Raman spectroscopy, FT-IR spectroscopy and vibration sample magnetometer tests. Results showed that the surface-attached catalyst particles and amorphous carbon can be effectively removed from raw CNOs through HNO3-refluxing and calcination. Magnetic separation can selectively remove the CNOs encapsulating a [Ni, Fe] magnetic catalyst from the CNOs that are hollow. arbon Materials 2014, 29(5): 398–403]