Wetting of TiC and TiN by metals

Abstract

A number of important issues raised by brazing technologies and recent wetting experiments with liquid metals on TiC and TiN are analyzed at the microscopic level, using first-principles density-functional computational experiments. The large variations of the wetting angles for Cu and Ag on TiC and TiN from experiment to experiment are connected of the relative contributions of different local atomic coordinations at the interface. The key factors in the structure dependence of Ag/Ti͑C,N͒ interface energetics are identified, such as the varying number of the metal-C͑N͒ bonds and the strength of metal-Ti bonding. Interface adhesion is shown to be improved by C͑N͒ vacancies, in agreement with observed better wettability of hypostoichiometric carbides. Based on Al/Ti͑C,N͒͑001͒ and Ti/Ti͑C,N͒͑001͒ simulations, the effects of Ti and Al interface segregation in the metal melt are estimated. The metal-C͑N͒ bonding across the Cu,Ag,Au/Ti͑C,N͒͑001͒ interfaces is similar to the metal-enhanced covalent bonding previously reported for Co/Ti͑C,N͒͑001͒ and Co/WC͑001͒. The systematics of the calculated work of separation correlates well with the noticeable variations of the charge-density values at the interface metal-C͑N͒ bonds.

First-principles study of adhesion atCu/SiO2interfaces

“…The adhesion energy in the OO-terminated case turns out to be much larger than those in the O-and Si-terminated cases, and comparable to values previously computed for other metal-dielectric interfaces, such as Co/TiC (Ref. 21) and Nb/Al 2 O 3 (Ref. 22).…”

“…A first principles treatment would therefore be most appropriate for examining the nature of local bonding at an ideal interface between the two systems, and indeed this approach has proved insightful in the past for studying adhesion between metal films and insulating substrates. [21][22][23][24] Previous first-principles work on the α−quartz surface 20 observed significant changes in bonding near the surface; to our knowledge, however, the effects of metallic overlayers on SiO 2 surface geometries and electronic properties have yet to be examined from first principles.…”

Trends in atomic adsorption on titanium carbide and nitride

“…Our calculated values are: E cleav = 9.81 (11.74) J/m 2 for the unrelaxed TiN (TiC) surface and E cleav = 9.17 (11.43) J/m 2 after relaxation of only the Ti-terminated side of the TiN (TiC) slab. These values should be compared with those for the nonpolar (001) surface, 2.76 (3.46) J/m 2 for TiN (TiC) [13]. Thus, for both TiX's, the polar (111) surface has a much lower stability than the (001) surface.…”

Enhance diamond coating adhesion by oriented interlayer microcracking

“…The ͑110͒ and ͑100͒ surface have only one configuration, which is terminated stoichiometrically by Ti and C. The calculated surface energies were listed in Table I and compared with experimental results and other DFT calculations. [22][23][24] As shown in Table I, among all the three TiC surfaces, the ͑100͒ surface has the lowest surface energy ͑1.68 J m −2 ͒.…”