Nickel nitride, decomposition

Ni3C decomposition is included in this class on the basis of Doremieux s conclusion [669] that the slow step is the combination of carbon atoms on reactant surfaces. The reaction (543—613 K) obeyed first-order [eqn. (15)] kinetics. The rate was not significantly different in nitrogen and, unlike the hydrides and nitrides, the mobile lattice constituent was not volatilized but deposited as amorphous carbon. The mechanism suggested is that carbon diffuses from within the structure to a surface where combination occurs. When carbon concentration within the crystal has been decreased sufficiently, nuclei of nickel metal are formed and thereafter reaction proceeds through boundary displacement. 

Li3(BN2) have already demonstrated the decomposition of (BN2) ions into boron nitride. The remaining nitride can lead to the formation of a binary metal nitride or reduce the transition metal ion under the formation of N2. Both mechanisms have been obtained experimentally, depending on the stability of the metal nitride. For instance niobium pentachloride forms NbN, titanium trichloride forms TiN, and nickel dichloride forms Ni, plus BN and nitrogen, respectively, in reactions with Li3(BN)2 (at 300-600°C) [24]. 

The reaction of copper metal with ammonia [42] between 540 and 570 K gave copper nitride, CujN. A reactant containing a high proportion of CujN (92%) was more stable than that containing more copper metal (70% CujN). Decomposition occurred at 700 K and above in nitrogen. Reaction (- NHj) commenced at about 380 K in Hj and above 650 K in NH,. Nickel metal reacted with ammonia to give NijN at 623 K and the main decomposition occurred at 723 K. NijN was stable only... 

There are good NH3 decomposition catalysts such as ICI-47-1 (10 weight % nickel on alirmina) Haldor Topsoe DNK-2R (triply promoted iron-cobalt) SUD-Chemie 27-2 (nickel oxide on alirmina) various supported nitrided catalysts (e.g. molybdenum nitride and nickel molybdenum nitride on - a alumina) and ruthenium modified nickel oxide on alumina. 

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