INHIBITING EFFECT OF METAL-SUPPORT REACTION ON CARBONIZATION OF NI/SIO2 FILMS

The effect of a metal-support reaction occurring during high-temperature treatment in hydrogen, on the deposition of carbon from acetylene on Ni/SiO2 thin films was studied by transmission electron microscopy and electron diffraction. It was found that increasing the temperature of the hydrogen treatment from 770 K to 970 K resulted in minor changes in morphology of the Ni deposit, which drastically altered its reaction behavior. The formation of Ni3C carbide was hindered, and a new FCC NiCx phase with a lattice parameter of 0.362 nm occurred during reaction at 520 K. At 800 K, the total amount of deposited carbon was greatly reduced, and its morphology changed from filamentous into encapsulating, shell-like. Growth of an alpha-Ni(Si) solid solution during hydrogen treatment at 970 K is proposed to account for the observed effects.