The possibility of stabilizing the theoretically predicted β-C3N4 phase by high-energy ball milling is investigated. Charges of graphitic carbon were milled with and without . 11. minor alloying additions under different atmospheric media, namely gas and/or liquid phases of nitrogen, air, or ammonia. Milling was performed at either of two energy levels for periods of up to 48 h. The β-C_3N_4 phase was found to exist as small crystallites in a matrix of primarily amorphous carbon at volume fractions estimated between 5 and 10 at.. High-resolution electron diffraction and x-ray diffraction indicate that the crystalline nature of the C_3N_4 phase corresponds with a hexagonal lattice with a = 6.46 A and c/a = 0.374. which are within 2 of the theoretically calcullated lattice parameter values. Analysis of electron energy-loss spectroscopy (EELS), x-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectra verify the presence of chemically bonded carbon and nitrogen with chemical states reflecting combined sp~2 and sp~2 hybridization. Chemical analysis confirms nitrogen enrichment at levels consistent with the C_3N_4 stoichiometry and the estimated degree of stabilization. The possible mechanism(s) responsible for the stabilization of the β-C_3N_4 phase are briefly discussed.
展开▼
