[en] Nitrogen was implanted into the chemical vapor deposition (CVD) diamond films, and the electron field-emission properties of the nitrogenated diamond films were investigated. Raman and x-ray photoelectron spectroscopy (XPS) measurement revealed that nitrogen-implantation damaged the structure of diamond film and promoted the formations of sp² C-C and sp² C-N bonding. By increasing the implantation dose, the threshold field of the emission of the diamond film could be lowered from 18 V/μm to 4V/μm. The enhancement of field emission for nitrogen-implanted CVD diamond films was attributed to the increase of the fraction of sp² C bonds and the formation of defect bands within the bulk diamond band gap induced by nitrogen-implantation, which could alter the work function and elevate the Fermi level. Consequently, the energy barrier on diamond surface for electron tunneling was reduced. (authors)

[en] Ultra-hard ceramic coatings with microhardness of 2535 Hv have been synthesized on the Al alloy substrate by microarc oxidation (MAO) technique. The effects of anodic current density (j _a) and the ratio of cathodic to anodic current density (j _c/j _a) on the mechanical and corrosion resistance properties of MAO coatings have been studied by microhardness and pitting corrosion tests, respectively. In addition, the phase composition and microstructure of the coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the coatings prepared at high anodic current density consist mainly of α-Al₂O₃, while those fabricated at low anodic current density are almost composed of γ-Al₂O₃. Microhardness test shows that the coatings have high microhardness, and the highest one is found in the coating formed at j _a = 15 A/dm² and j _c/j _a = 0.7. Pitting corrosion test shows that the structure of coatings is strongly influenced by the varying j _c/j _a