Abstract:

Taking synthetic graphite as the carbon source, boron as the additive, and NiMnCo alloy as the metal solvent, the morphology changes of metastable regrown graphite crystals are studied by temperature gradient method under high pressure and high temperature (HPHT)-diamond-stale pressure and temperature (5.4 GPa, 1550 K). It is found that the morphology of the regrown graphite is obvious different compared with the used synthetic graphite. The synthetic graphite shows an irregular squama-like morphology, but the regrown graphite shows a more-regular morphology. If no boron is present in the system, sheet-like regrown graphite crystals, most with regular hexagonal morphology, stand vertically in the metal solvent, with {0001} facet parallel to the direction of axial temperature gradient. When boron additive is present, regrown graphite crystals, with half-sphere-like or wafer-like morphology, grow in spiral mode, with {0001} face perpendicular to the direction of axial temperature gradient.

Key words: material experiments, regrown graphite, temperature gradient method, synthetic graphite, high pressure and high temperature