Study of special burr defects in high‑nitrogen diamonds synthesized with NiMnCo catalysts

Abstract

Macroscopic and microscopic defect control in diamonds is a key research area in both diamond synthesis and its applications. High‑nitrogen diamonds have received significant attention in both research and industry owing to their unique properties, which result from nitrogen impurities. Therefore, the preparation of high-quality high‑nitrogen diamonds has emerged as a focal point of interest in recent years. This study thoroughly analyzed the causes of local burrs in high‑nitrogen diamonds synthesized with the NiMnCo catalyst and introduced corresponding strategies to address this issue. Optical microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction results reveal that on the one hand, the burr is caused by the complex effect of the interaction of hard phase particles (such as MnO) and fluid-rich growth media with carbon and metal catalyst melt. On the other hand, during cooling, the hard phase (such as MnO) generated in the metal catalyst melt rich in highly saturated C–N–H–O fluid precipitates out. The destruction of diamond surface morphology. Raman spectroscopy and X-ray photoelectron spectroscopy results indicate that the use of the FeNi catalyst in diamond synthesis prevents burr formation and effectively reduces residual stress. Additionally, increasing synthesis pressure and applying hydrogen doping can further reduce burrs and residual stress in the diamond.