Synthesis of diamond in cast iron

Influence of mechanical and thermal treatments on microstructural transformations in cast irons and properties of synthesized diamond crystals

“…Chagelishvili, N. S. Turmanidze et al, 1979Turmanidze et al, -1983; V. S. Kravtsov, L. G. Gan kevich, 1986; A. R. Patel, K. A. Cherian, 1984) [28] and the ex perimental results obtained in our works [29,30] originated the studies on the possibility of growing single crystals on polycrys talline diamonds generated by explosion. These studies cov ered the influence of the initial solid medium on diamond out put [31], various thermal cycling conditions of cast iron after shock wave (SW) treatment [32], plastic strains followed by SW treatment [33], SW treatment followed by plastic strains [34,35]. The physical properties of diamond crystals with the nu clei synthesized in a highpressure chamber by the HPHT method and then grown under atmospheric pressure with pass ing a weak electric current through a technological mixture of a catalyst metal with graphite were studied in [36].…”

“…The studies [31][32][33][34][35] gave some examples of the methods used for synthesis of metastable single crystals on polycrystal line explosion diamonds. The characteristic features of these methods are subsequent treatments; the primary treatment includes exposure to shock waves and plastic deformation whereas the secondary treatment does thermal cycling, plastic deformation, and passing a weak electric current.…”

“…SW treatment activates the cast iron matrix by introducing a large number of crystal structure de fects and contributes to increasing the carbon diffusion rate in the matrix when passing the SW front up to 10 -2 -10 -3 cm 2 /s, whereas subsequent forging and thermal cycling intensify dif fusion only to 10 -5 -10 -6 cm 2 /s. These results were obtained by penetration depth evaluation for carbon from cast iron into a steel holder taking into account treatment duration [29][30][31][32][33][34][35]. Metalphysical studies of the contact "cast iron -steel" have revealed the largest diffusion changes when using austenitic cast iron 2 with foliated graphite.…”

“…The diamond crystals may grow both in kinetic and diffu sion modes. In the studies [29][30][31][32][33][34][35] the correlations governing the crystal growth rates for various modes were evaluated for the given conditions of steadystate growth and when diffusion fluxes to different growth centers do not cross each other. A comparison of the diamond and graphite crystal growth rates in the system "graphite -solid carbon solution in irondiamond" showed that the preferred diamond crystals growth (a) with respect to graphite growth (β) during the decomposi tion of a supersaturated solid carbon solution in a metal is pos sible only in the kinetic mode under the condition…”

Compound physical and mechanical effects stimulating metastable diamond formation

“…Small diamonds first discovered in Neogene sandy deposits [17], and lonsda leite crystals found in placers [18], do not yet have a scientifi cally substantiated mechanism of formation. Diamonds in the graphite shales of Liberia [19], the wellknown deposits of Kumdykul (North Kazakhstan) [20] and Haggerty (West Af rica) are crustal formations of diamond in association with graphite within deep fault zones, which may indicate in favor of metastable growth. During magmatic, metasomatic, meta morphic and hydrothermal processes, the formation of miner als is actively involved in the fluid phase, which contains main ly such volatile components as hydrogen, oxygen and carbon.…”