Transformation of Onion-Like Carbon from Nanodiamond by Annealing

摘要

Onion-like carbon (OLC) was synthesized by annealing nanodiamond in low vacuum (1 Pa) at the temperatures from 500 to 11400℃. The high-resolution transmission electron microscope images, X-ray diffraction patterns and Raman spectra showed that, when the annealing temperatures were lower than 900℃, there was no OLC fabricated. The amorphous carbon and the nanodiamond coexisted. The graphitization started from the surfaces of the nanodiamond particles. When the annealing temperatures were higher than 900℃, the OLC was fabricated. At 900℃, OLC began appearing and the size of the OLC particles was smaller than 5 nm. At the annealing temperature of 1400℃ all the nanodiamond particles were transformed into OLC. The OLC particles exhibited similarity to the original nanodiamond particles in shape. Based on these results, a mechanism for the OLC synthesis by the method of annealing in vacuum was provided.