Transformation mechanism from carbon nanotubes to n-diamond

摘要

Nanocrystal n-diamond particles were synthesized after a pyrogenation of carbon nanotubes and colloidal Fe(OH)_3 at atmospheric pressure. The product was investigated with x-ray diffraction, transmission electron microscopy, thermal gravimetric analysis, and differential thermal analysis. The results indicate that the n-diamond can be synthesized with the carbon nanotubes as carbon source. The formation mechanism of the n-diamond is suggested in this paper. With the increase of temperature and hence the carbon diffusion in iron, the phase sequence is from Fe(OH)_3 into Fe_2O_3, a-Fe, 7-Fe, and then liquid iron. When carbon in the liquid iron is saturated, graphite separated out of the liquid iron. With the decrease of temperature, the carbon in 7-Fe is separated out, and the n-diamond nuclei form and grow.