Shock-compression of C-N precursors for possible synthesis of β-C₃N₄

We report on the possible synthesis of the theoretically predicted β-phase of carbon nitride (C₃N₄) by shock compression of sodium dicyanamide mixed with sodium azide and carbon tetra-iodide. Shock-compression experiments were performed on starting precursor blended with ∼95 wt.% Cu powder, statically pressed in steel capsules. The capsules were impacted under conditions of constant shock amplitude, but varying shock-pulse duration. TEM analysis of the recovered shock-compressed residue showed crystallites of a cubic C-N compound dispersed in an amorphous matrix, with overall yield of the crystalline phase being a function of the shock-pulse duration. Parallel-detection electron energy loss spectroscopy of the nitrogen-containing crystallites revealed diamond-like sp³ bonding. Infra-red spectroscopy indicated absorption lines in regions calculated to be appropriate for β-C₃N₄.