X-ray spectroscopy studies of the electronic structure and band-structure calculations of cubic TaCxN1-x carbonitrides

The electronic structure of almost stoichiometric cubic (NaCl structure) tantalum carbonitrides TaCxN₁₋x synthesized under high pressure-high temperature conditions (7-10 GPa and 2100-2400°C) was studied employing X-ray photoelectron spectroscopy (XPS), Xray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS). The XPS valence-band and core-level spectra, the XES Ta Lβ ₅, C Kα and N Kα bands (reflecting energy distributions of mainly the Ta 5d-, C 2p- and N 2p-like states, respectively), as well as the XAS Ta LIII edges (unoccupied Ta d-like states) were derived and compared on a common energy scale for the compounds TaC₀.₉₈, TaC₀.₅₂N₀.₄₉ and TaN₀.₉₇ obtained under the mentioned high pressure-high temperature conditions. To investigate the influence of substitution of carbon atoms by nitrogen in the cubic TaCxN₁₋x system, the cluster self-consistent calculations of the electron density of states for cubic TaC, TaC₀.₅N₀.₅ and TaN compounds were carried out with the FEFF8 code. In the present work a rather good agreement of the experimental and theoretical results for the electronic structure of the TaCxN₁₋x system under consideration was obtained

Characterization of Ti-B-C-N Nanocomposite Coatings

Nanocomposite Ti-B-N-C coatings were deposited by magnetron sputtering of TiN and B4C targets in the argon-nitrogen atmosphere at different nitrogen flow rates (FN2). The structure, chemical bonding and mechanical properties were investigated. The results of the investigations of the nanocomposite, TiN and BCN coatings show that the Ti-B-C-N coatings consist of the TiNC nanocrystals (3.4 – 6.5 nm) embedded into the amorphous matrix that consists of amorphous boron nitrogen (a-BN) and amorphous carbon (a-C). The coatings contain a small admixture of titanium oxides that are aggregated at the grain boundaries. The coatings deposited at high nitrogen flow rates were textured. An introduction of nitrogen prompts the formation of the nanocrystallites of the TiN-TiC solid solutions and the a-BN amorphous tissue, which, in turn, causes the improvement of the mechanical properties of the Ti-B-C-N coatings. The best samples ex-hibited nanohardnes above 39 GPa. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3505

X-ray emission and photoelectron spectroscopy studies of interaction of nanocrystalline TiN and TiB₂ after highpressure sintering

A few samples of nanocrystalline TiN–TiB₂ ceramics were synthesized by high-pressure (3.0 GPa) and high-temperature (t = 1300–1500°C) sintering a mixture of TiN and TiB₂ nanopowders (80 wt.% TiN and 20 wt.% TiB₂) and the microhardness of the samples was determined. Peculiarities of the chemical bonding of the TiN–TiB₂ ceramics possessing the highest microhardness among the samples under consideration, mainly 29.65 ± 0.90 GPa, were studied in the present work using the X-ray emission and photoelectron spectroscopy methods. The X-ray emission spectra reflecting the energy distribution of the valence electronic states of the constituents (the N Kα (N 2p-like states), B Kα (В 2p-like states), Ti Lα (valence Ti s,d-like states) and Ti Kβ₅ (Ti 4p-like states) bands) were measured for the mentioned ceramics and for the initial mixture of TiN and TiB₂ nanopowders. For the above substances the X-ray photoelectron core-level binding energies were evaluated as well. It has been established that, when synthesizing the nanocrystalline TiN–TiB₂ ceramics from the initial mixture of TiN and TiB₂ nanopowders, the half-widths of the X-ray emission Ti Lα and Ti Kβ₅ bands decrease by (0.5–0.6) ± 0.2 eV