Synthesis Process And Structure Of The Catalyst And Metal Coated Diamond Single Crystal And High Temperature And High Pressure Thermodynamics,

Time, temperature and pressure play important roles in phase transformation of synthetic diamond single crystal. However, there are few reports about the diamond growth at different time, temperature and pressure. In view of this, the compositions, morphologies and microstructures of the film and the molten solvent formed by iron-based and nickel-based alloys were systematically investigated using metallographic microscope, transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), Raman spectrum (Raman) and high resolution transmission electron microscope (HRTEM) methods at different time, temperature and pressure. In this paper the relative optimum technological parameters of synthesized diamond by iron-based and nickel-based accelerants were discussed, meanwhile the synthetic mechanism of high-quality diamond single crystals under HPHT were analyzed. On the basis of the results obtained by the methods mentioned -above, combining with thermodynamic calculation at HPHT, carbon resource that transformed into diamond single crystal was affirmed, at the same time the "V" range of diamond crystallization was redefined from the point of view of thermodynamics under HPHT.The metallographic analysis of the different cell assemblies adopted different technological parameters showed that diamond single crystal started to nucleate when ultimate pressure (P₃) was lasted one to two minutes, and the relative optimum technological parameters of synthesized diamond by iron -based and nickel-based catalysts were about t=12min, T=1623K, P₃=5.3GPa and t=13min, T=1643K, P₃=5.5GPa.The comparison between the molten solvent and the metallic film by iron-based and nickel-based catalysts showed that the metallographic microstructures of the molten solvent and the metallic film (iron-based catalyst) were made up of lathy original cementite and eutectic structure, the metallographic micro -structures of the molten solvent (nickel-based catalyst) made up of globular and dendritic γ solid solution and globular and lathy recrystallization graphite, but...