Effect of Boron Contained in the Catalyst on Thermal Stability of Boron-Doped Diamond Single Crystals

The synthesizing diamond experiment was carried out at cubic hinge press apparatus with iron-based catalyst made by powder metallurgy, in which hexahedral nitride boron (h-BN) was doped with different proportions. Microstructures and morphologies of the diamond single crystals were observed under stereological microscope, and the boron concentration was investigated by electron probe microanalysis (EPMA) and wave distribution spectrum (WDS). It is shown that boron element exists on the (111) crystal surface of diamond, and the concentration of boron changes with boron content in the catalyst. Static compressive strength was also measured. Furthermore, impact toughness measurement, different thermal analysis (DTA), and thermal gravity (TG) analysis were performed to probe into the thermal stability of different boron-doped diamond in atmosphere. The results demonstrate that boron content in the catalyst plays a very important role in mechanical performance and thermal stability of boron-doped diamond, which possess optimum values with increase of the boron concentration.