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 ℃,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 ℃ 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.