Thermodynamic Analysis of the Formation of a Nanostructural Polycrystalline Material Based on Nanodiamonds Modified With Non-Diamond Carbon (Part 2)

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The paper presents the results of thermodynamic analysis showing that the use of nanodiamonds with a thin graphite-like coating formed by surface graphitization of nanodiamonds makes it possible to increase the thermodynamic stimulus for the formation of a diamond structure under conditions of high pressures and temperatures. For a thin carbon film with a disordered structure (amorphous carbon, soot), the pressure of transition into diamond will exceed the equilibrium pressure due to the lower surface energy of amorphous carbon compared to the surface energy of graphite. In this case, a decrease in the thickness of the non-diamond carbon film on the surface of a diamond particle leads to an increase in the pressure of the graphite–diamond phase transition. The proposed approach provides the possibility of reducing the synthesis parameters of nanostructured polycrystalline diamond materials without additional use of phase transformation catalysts.