Titanium Carbide Surface Research Articles

Behaviour of selenium in GaAs

We have performed ab initio simulation of oxygen atom adsorption on TiC(0 0 1) laser-reconstructed surface. Relaxed atomic structures of the O/TixCy(0 0 1) surface observed upon thermal impact have been studied. DFT calculations of their thermodynamic, electronic, and elastic properties have been carried out. For the first time we have established the bond length and adsorption energy for various reconstructions of the O/TixCy(0 0 1) surface atomic structure. We have examined the effects of the oxygen adatom upon the band and electron spectra of the O/TiC(0 0 1) surface in its various reconstructions. For the first time we have established a correlation between the energy level of flat bands (−5.4 eV and −5.8 eV) responsible for the doublet of singular peaks of partial densities of oxygen 2p electrons, and the adsorption energy of oxygen atom in non-stoichiometric O/TiCy(0 0 1) systems. Effective charges of titanium and carbon atoms surrounding the oxygen adatom in various reconstructions have been identified. We have established charge transfer from titanium atom to oxygen and carbon atoms determined by the reconstruction of local atomic and electron structures which correlate with atomic electronegativity values and chemisorption processes. Potential mechanisms for laser nanostructuring of titanium carbide surface have been suggested.

Selective exchange of cation sites in zeolites observed by electron spin resonance on Mn 2+ - I: Linde X. T.I. Barry and L.A. Lay

We have performed ab initio simulation of oxygen atom adsorption on TiC(0 0 1) laser-reconstructed surface. Relaxed atomic structures of the O/TixCy(0 0 1) surface observed upon thermal impact have been studied. DFT calculations of their thermodynamic, electronic, and elastic properties have been carried out. For the first time we have established the bond length and adsorption energy for various reconstructions of the O/TixCy(0 0 1) surface atomic structure. We have examined the effects of the oxygen adatom upon the band and electron spectra of the O/TiC(0 0 1) surface in its various reconstructions. For the first time we have established a correlation between the energy level of flat bands (−5.4 eV and −5.8 eV) responsible for the doublet of singular peaks of partial densities of oxygen 2p electrons, and the adsorption energy of oxygen atom in non-stoichiometric O/TiCy(0 0 1) systems. Effective charges of titanium and carbon atoms surrounding the oxygen adatom in various reconstructions have been identified. We have established charge transfer from titanium atom to oxygen and carbon atoms determined by the reconstruction of local atomic and electron structures which correlate with atomic electronegativity values and chemisorption processes. Potential mechanisms for laser nanostructuring of titanium carbide surface have been suggested.

Bulk plastic flow and the frictional properties of titanium carbide at high temperature

In this study it has been shown that dislocations are mobile in titanium carbide crystals at 20°C and that, although bulk stresses are relieved by cleavage, the asperities are likely to be deformed in a plastic manner during sliding. Consequently, when the temperature is increased—thus allowing extensive bulk plastic flow and reducing the hardness by a factor of five—the magnitude of the coefficient of friction is not significantly influenced. An epitaxial titanium oxide film is formed on the surface of titanium carbide at temperatures above 1200°C and in a vacuum of 10 −4 mm Hg. This effectively lubricates the surfaces and prevents the increase in friction usually observed with other transition metal compounds above 0.48 Tm. The magnitude of friction above this temperature for tungsten carbide specimens, where a surface film is not formed, is dependent on both the temperature and time of contact. It is suggested that this is due to growth and strengthening of the contact area by volume diffusion.