Chokoleti cha petroleum chopangidwa ndi grafited chimapangidwa ndi chokoleti cha petroleum chopangidwa ndi calcium. Njira yayikulu ndi graphitiztion mu uvuni wa graphitization. Chokoleti cha petroleum chopangidwa ndi grafited ndi chinthu chabwino kwambiri chopangidwa ndi recarburizer chomwe chili ndi nayitrogeni yochepa.
