Iron nitrides

Iron has five nitrides observed at ambient conditions: Fe2N, Fe3N4, Fe4N, Fe7N3 and Fe16N2. They are crystalline, metallic solids. Group 7 and group 8 transition metals form nitrides that decompose at relatively low temperatures—iron nitride, Fe2N, decomposes with loss of molecular nitrogen at around 400 °C and formation of lower-nitrogen content iron nitrides. They are insoluble in water. At high pressure, stability and formation of new nitrogen-rich nitrides (N/Fe ratio at least one) were suggested and later discovered. These include the FeN, FeN2 and FeN4 solids which become thermodynamically stable above 17.7 GPa, 72 GPa and 106 GPa, respectively. ==Health hazards==

When heated to decomposition or exposed to humidity, iron nitride may emit toxic fumes of ammonia. It is considered a moderate explosion hazard. Inhalation of iron nitride dust or powder may cause irritation to the respiratory system and possibly acute iron poisoning or pneumoconiosis. ==Research applications==

Colloidal solution of magnetic iron nitride nanoparticles is a way to create ferrofluids. Iron nitrides also make the strongest naturally magnetic material. ==References==