Graphitization and microstructure transformation of nanodiamond to onion-like carbon

Onion-like carbons were synthesized by annealing diamond nanoparticles at 1100–1400 °C. The diamond nanoparticles begin to graphitize in the range of 1100–1200 °C and all the particles transform into onion-like carbons at 1400 °C. The transformation temperature changes with the nanoparticle size. The onion-like carbons exhibit similarity to the original nanoparticles in shape.