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Onion-like carbon synthesis by annealing nanodiamond at lower temperature and vacuum

The onion-like carbon (OLC) was synthesised by annealing the nanodiamond fabricated by detonation for 1 h at the temperature of 1150°C in the low vacuum of 2 Pa. The OLC particles were characterised using a high-resolution transmission electron microscope (HRTEM) for observing its microstructure, an X-ray diffractometer (XRD) for determining its crystal structure and component, and a Raman spectrometer for confirming its content. The results showed that the OLC particles exhibited similar shape to that of the original nanodiamond particles. The average size of the OLC was found to be approximately 5 nm. The transformation mechanism of the OLC from the nanodiamond by annealing at lower temperature and lower vacuum was also discussed.