Mass-Spectrometric Investigation of the High-Temperature Reaction between Nickel and Chlorine

Abstract

The volatile products of the reaction between a molecular beam of room-temperature chlorine and a polycrystalline nickel surface have been identified; their formation rates have been measured by a mass-spectrometric technique at surface temperatures between 1000° and 1600°K and beam fluxes equivalent to pressures of 10—7 to 10—5 mm Hg. The surface coverage is estimated to be less than 0.1% under these conditions. NiCl and NiCl2 are formed on the nickel surface; the former is observed above 1450°, the latter below 1100°; and both are found at intermediate temperatures. About 70% of the incident chlorine is consumed by the interaction with nickel over the pressure and temperature ranges covered. The removal of chlorine and the production of NiCl and NiCl2 are first order in chlorine pressure. A mechanism which accounts satisfactorily for the results involves dissociative adsorption of chlorine to form two NiCl's on the surface; these either evaporate, or disproportionate to form NiCl2 which evaporates.