A new carbon nitride synthesized by shock compression of organic precursors

A series of shock recovery experiments up to ∼50 GPa were carried out on three nitrogen-rich materials of a C–N–O amorphous precursor, dicyandiamide and melamine. The powder X-ray diffractions (XRD) of recovered samples show that carbon nitride phases are formed. They are β-C3N4 and a new crystalline phase. The new phase is indexed as a monoclinic cell with a=0.981 nm, b=0.723 nm, c=0.561 nm, β=95.2° and Vcell=0.3966 nm3. Melamine was very stable and did not decompose up to ∼37 GPa. This new phase is considered to form during the adiabatic release process with an extremely high quenching rate (∼109 K/s) and shock compression may provide a novel synthesis route for various C–N phases from appropriate organic materials.