Diamond crystallization in a CO 2 -rich alkaline carbonate melt with a nitrogen additive

Experimental and Theoretical Evidence for Surface-Induced Carbon and Nitrogen Fractionation during Diamond Crystallization at High Temperatures and High Pressures

“…Sodium oxalate decomposes at experimental conditions producing sodium carbonate fluid (CO 2 -containing Na 2 CO 3 melt) with about 4.5 wt % excess of carbon. This excess of carbon in the carbonate fluid prevents diamond seeds from dissolution, a phenomenon often seen in metal-carbon systems and leads to the seeds being overgrown by synthetic diamond material with maximum thickness of 120 µm Diamond crystals recovered from the ampoules were inspected for growth morphology as described in [42], then cut in a parallel [110] direction, polished and examined using a Philips XL30CP scanning electron microscope (Philips, Germany) with attached CL detector at the Edinburgh University, thereby revealing internal structure within the samples.…”

Shift of CO2-I absorption bands in diamond: A pressure or compositional effect? A FTIR mapping study

“…Our detailed FTIR mapping and profiling show that although some amount of structural hydrogen and nitrogen is definitely present in all parts of the studied samples as manifested by the 3107 cm -1 peak, the CO2-absorption bands indeed become weaker with increased concentration of common A and B defects. Interestingly, diamond synthesis in CO2-rich alkaline systems always produces N-rich crystals (Khokhryakov et al, 2016. Incorporation of nitrogen in diamond is clearly a complex function of N speciation and abundance in the growth medium, which, in turn, depend on its composition and fO2.…”