The characteristics of diamonds crystallized using Fe-C-H at high pressure and temperature

Diamond crystallization in an Fe–C system with C10H10Fe additive(collectively called the Fe-C-H system) has been studied at 5.0–6.0GPa and temperatures ranging from 1400 to 1700°C. Both spontaneous diamond nucleation and growth were studied. The results showed that the stable form of diamond growth is octahedral in Fe-C-H systems, which is similar to pure Fe-C systems. However, the diamond morphologies changed from high quality octahedral to aggregated octahedral as the amount of C10H10Fe increased, accompanied by a deterioration of the surfaces. The FTIR results indicated that hydrogen-doped diamonds with less than 1ppm nitrogen are easily synthesized in this system. The crystallization of diamonds in the Fe-C-H system was not only affected by the pressure and temperature conditions, but also by the amount of C10H10Fe additive. This was attributed to changes in the pure Fe catalyst caused by the elemental hydrogen produced by the decomposition of C10H10Fe. •Diamond crystallized using Fe-C-H has been studied under HPHT.•The diamonds synthesized from Fe-C-H system show different morphologies colors, and sizes.•The FTIR results indicated that hydrogen doped diamonds with rarely nitrogen are synthesized in our systems.