Effect of CH₆N₄O Additive on Ib-Type Diamond from Ni-Based Alloy under HPHT Conditions

Natural diamond inclusions comprise elements such as carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), which can be assumed to exist in the natural diamond growth environment. Therefore, the artificial construction of the C-H-O-N system plays an important role in exploring the growth mechanism of natural diamonds. Herein, diamond crystals were successfully synthesized in the NiMnCo-C system by adding carbohydrazide (CH₆N₄O) as the organic additive at 1280 to 1320 °C and 5.4 GPa-6.0 GPa. The crystals were characterized using various analytical tools. Optical microscopy (OM) showed that the additive caused new extended defects similar to different dislocations. These filiform defects mainly appeared inside the top {111} face of the synthesized diamond and were always perpendicular to the {111} face. Raman spectroscopy and X-ray diffraction (XRD) analysis indicated that the synthesized diamond had high-quality sp³ structures. The Fourier transform infrared spectroscopy (FTIR) spectra showed that under a constant doping concentration, the N content inside the diamond increased with increasing synthesis temperature and constant pressure but decreased with increasing synthesis pressure and constant temperature. X-ray photoelectron (XPS) spectroscopy confirmed that N, O, and H successfully entered the diamond lattice.