Diamond crystallization in the Ni-Mn-C system was studied at 4.5 GPa, 1250 ± 50 °C, for 180 seconds with 0 -5 wt.% Mg compositions. It has been found that when the Mg content of the system increases from 0 to 4 wt.% Mg, the degree of conversion of graphite to diamond decreases from about 100 to 5% (Tab. 1). Depending on the solubility of the system and the conversion of graphite to diamond with Mg additive, the crystallization of the diamond occurs along with the magnesium carbide formation. The typical cubic diamond growth from the Mg-C system is converted into the cube-octahedron by the addition of 1 wt.% Mg and then to the octahedron morphology having a Mg content of 2 wt.% Mg and more than 2 wt.% Mg originate cube octahedron diamonds [1] (Figure 1). XDR results (Fig. 2), reveal the presence of the metallic perovskite crystalline structure (MgCNi3) that has a superconducting property [2]. The FT-IR identified the presence of MgNi2, MgOH and MgC for the bands 471, 1085 and 2313 cm-1 [1,3], respectively, confirming their participation in the synthesis of diamonds during crystal growth (Fig. 3).
References:
[1] Y. Palyanov, I. Kupriyanov, Y. Borzdov, D. Nechaev, Y. Bataleva, HPHT Diamond Crystallization in the Mg-Si-C System: Effect of Mg/Si Composition, Crystals. 7 (2017) 119
[2] Z.F. Wei, X.L. Chen, G.C. Che, F.M. Wang, W.C. Li, M. He, Debye temperature of the MgCNi3 superconductor, Chinese Phys. Lett. 19 (2002) 249–251.
[3] C. Hua, X. Yan, J. Wei, J. Guo, J. Liu, L. Chen, L. Hei, C. Li, Intrinsic stress evolution during different growth stages of diamond film, Diam. Relat. Mater. 73 (2017) 62–66.