The effect of an iron powder catalyst clad with a Fe2O3 layer on the nucleation of diamonds

In this paper, we have researched the effect of a Fe2O3 clad layer covering iron catalyst particles on the nucleation of a diamond under high pressure and high temperature (HPHT). The Fe2O3 layer is deoxidized by graphite to form Fe3O4 and FeO at 5.7 GPa and 1600 °C. At the same time the iron melts and is exuded through the Fe2O3 layer, and then contacts with graphite, to cause the nucleation and growth of a diamond. Compared with a pure iron catalyst, the Fe2O3 clad layer distinctly restrains the nucleation of the diamond. Furthermore, the thicker the clad layer becomes, the more obvious this effect is. The Mössbauer spectrum, X-ray diffraction (XRD) and a scanning electronic microscope (SEM) were used to characterize and analyze the experimental samples.