Title

Mechanism of Different Types Synthetic Diamond Formation

Mechanism of Different Types Synthetic Diamond Formation

Authorship

POLIAKOV, VLADIMIR

POLIAKOV, VLADIMIR

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DOI

10.5151/2594-5327-C00211-3306-3317

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Abstract

There are general regularities in the formation of single crystal (SD) and carbonado type synthesized polycrystalline diamond (CSPD). It is found that the diamond nuclei are formed under high pressure (P) and temperature (T) by the fluctuational or martensitic transition of the graphite crystallites that are contained in initial carbon material (for example, graphite) in the presence of the molten metal or alloy. This mechanism for SD is associated with the solution of the graphite crystallites into the molten metal followed by above-mentioned diamond nucleus formation. The growth of SD takes relatively long time by diffusion process. The basic difference between CSPD formation and SD one is that the initial porous polycrystalline graphite under high P and T far from the line of equilibrium G->D is impregnated with metal melt with high rate (few seconds) in the absence of visible dissolution of graphite into the latter. The impregnation of graphite bulk with metal melt at the overall high P is accompanied by very fast solid phase transformation of graphite lattice to diamond one, going in parallel or in consecutive order (martensite transition). This results in a diamond polycrystalline composite with inclusions of metallic phase on the grain boundaries.

There are general regularities in the formation of single crystal (SD) and carbonado type synthesized polycrystalline diamond (CSPD). It is found that the diamond nuclei are formed under high pressure (P) and temperature (T) by the fluctuational or martensitic transition of the graphite crystallites that are contained in initial carbon material (for example, graphite) in the presence of the molten metal or alloy. This mechanism for SD is associated with the solution of the graphite crystallites into the molten metal followed by above-mentioned diamond nucleus formation. The growth of SD takes relatively long time by diffusion process. The basic difference between CSPD formation and SD one is that the initial porous polycrystalline graphite under high P and T far from the line of equilibrium G->D is impregnated with metal melt with high rate (few seconds) in the absence of visible dissolution of graphite into the latter. The impregnation of graphite bulk with metal melt at the overall high P is accompanied by very fast solid phase transformation of graphite lattice to diamond one, going in parallel or in consecutive order (martensite transition). This results in a diamond polycrystalline composite with inclusions of metallic phase on the grain boundaries.

Keywords

single crystal, polycrystalline diamond, mechanism of synthesis

single crystal, polycrystalline diamond, mechanism of synthesis