Iron nitrides are inorganic chemical compounds of iron from the group of nitrides . With diiron nitride Fe 2 N, triiron nitride Fe 3 N (more precisely Fe 3 N 1 + x ), tetrairon nitride Fe 4 N and nitrogen martensite α´´-Fe 16 N 2 as well as FeN several iron nitrides are known.
Extraction and presentation
Iron nitrides can be obtained by reacting iron with ammonia at 350 to 550 ° C. The resulting product corresponds in its composition to the formula Fe 2 N and represents the orthorhombic γ´-modification, which has a very narrow homogeneity range.
However, with similar production, the occurrence of a hexagonal ε-phase with a lower nitrogen content, roughly equivalent to Fe 3 N, is often observed. When heated in vacuo at around 500 ° C., the product initially changes to the ε phase and then to Fe 4 N , releasing nitrogen .
Iron nitrides are gray to black powders with a metallic character. ζ-Fe 2 N (CAS number: 12023-20-0) has a density of 6.35 gcm −3 and has an orthorhombic crystal structure with the space group Pbcn (space group no. 60) (a = 444 pm, b = 554 pm, c = 484 pm). The ε-modification Fe 3 N (CAS number: 12053-51-7) has a density of 7.36 g · cm −3 and has a hexagonal crystal structure with the space group P 6 3 22 (No. 182) (a = 270 pm, c = 437 pm). Fe 4 N (CAS number: 12023-64-0) has a density of 6.57 g cm −3 and has a crystal structure with a cubic closest packing of the iron atoms and the space group P 4 3 m (No. 215) (a = 379.5 pm).
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