Cobalt nitride

The Preparation and the Crystal Structures of Cobalt Nitride, CoaN, of... 

Cobalt Nitrides. The following Co-N compds are described in the literature Co3N2,... 

Co4N2, Co3N, Co2N and CoN. Of these only the cobaltous nitride, Co3N2, mw 204.84,... 

Cobalt Nitride, Co2N or Co4N2, has been prepared by heating cobalt in ammonia vapour to a little below 500° C., the most favourable temperature being 470° C. The metal slowly combines with the nitrogen, some 10-33 per cent, of the gas being absorbed.2... 

Cobalt nitride is a dull grey powder, readily soluble in hydrochloric and sulphuric aci.ds, yielding cobaltous salts, the nitrogen being liberated as ammonia. At 600° C. it evolves nitrogen, so that the formation of cobalt nitride can only proceed within very narrow limits of temperature. It is completely decomposed when heated in hydrogen or steam in the latter case the reaction proceeds slowly. 

As a large part of NH, is always retained by the nitride, the resulting compd, Co,N2 zNH may be called "ammonium cobaltous nitride". A similar compd, AlN>zNH called "ammonium aluminum nitride" was prepd by pouring a soln of NH Br in liq NH, into a soln of Na K ammonoaluminate. The amt of NH, retained by these complexes varies within certain limits depending on the temp and pressure. Attempts to prepare a similar complex from stannous nitride, Sn,N, were unsuccessful Ref F.W.Bergstrom, JPhysChem 32,433-40 (1928)... 

Co(SCN), + 2KNH, - 2KSCN + Co(NH,), it was suggested by Bergstrom(Ref), that actually reaction proceeds further and cobaltous nitride and ammonia are formed ... 

Solid State Reactions.—There are three reports of kinetic and mechanistic studies on substitution in the solid state which may have some interest or relevance to cobalt(m) complex substitution mechanisms in solution. [Co(NH3)6](N3)3 decomposes to give cobalt nitride. The initial step, as in several solution mechanisms cited above, seems to be azide to cobalt electron transfer there is no evidence for nitrene intermediates. Decomposition of [Co(NH3)e]Cl3, which gives cobalt(ii) amongst the products, does not proceed via formation of [CoCl(NH3)5]Cl2, but for some nitrites, e.g. cis- and /ra j-[Coen2(NH3)2](N02)3, nitrite does enter the first co-ordination sphere of the cobalt in the course of reaction. Lastly, the mechanism of thermal and of photochemical decomposition of [Co(NH3)s(OH2)]X3 is said to be similar to the mechanism of reaction in solution, despite the ultimate formation of tetrahedral cobalt(ii) complexes in the solid state reactions. ... 

Azuma M, Kashihara M, Nakato Y, Tsubomura H (1988) Reduction of oxygen to water on cobalt-nitride thin fihn electrodes prepared by the reactive RF sputtering technique. J Electroanal Chem 250 73-82... 

P-BN tools work satisfactorily in hardened steel up to contact temperatures of 1000°C, since there is no chemical reaction between boron nitride and iron. This, however, also depends on the binding phase of the polycrystalline materials and can lead to adhesive wear [24, 25]. In hard steel, the main wear mechanism on the tool is abrasion by hard alloy carbide particles [26]. In the case of Co-based super alloy (Vitallium), the results on hard-BN tool wear are somewhat incongruous [27, 28], while Inconel 718 can be machined under proper selection of the cutting conditions [29]. Apparently, austenitic steels containing a high percentage of Co are difficult to cut by hard-BN tools, due to the formation of cobalt nitrides which leads to high tool wear [8]. 

Today s most stable Me-N-C catalysts are the Me-PANI-C catalysts of Zelenay s group [11]. In order to obtain the nitrogen precursor, aniline is impregnated on a carbon support and then an oxidative polymerization is initiated in the presence of iron chlorine and/or cobalt nitride (both in various concentrations). As oxidant, either hydrogen peroxide or ammonium peroxydisulfate can be used [38]. In order to obtain the final catalysts, two heat treatment steps are performed, both at the same temperature and both followed by an acid leaching. Best results were obtained for catalysts prepared at 900 °C [29]. These catalysts were stable for 4 weeks of FC run under potentiostatic conditions (0.4 V) and even showed increasing currents... 

Nitrogen interacts weakly with most of the Group Vlll/Ib metals. Dissociative adsorption is only possible on iron, ruthenium, and on metals toward the left of the Periodic Table. This behavior correlates well with the enthalpy of metal nitride formation which is positive for copper, nickel, and cobalt nitrides, but negative for... 

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