Chromium nitride

Darker odorless solid

Fixed

5.9 g · cm -3

1500 ° C (decomposition to Cr and N2)

Insoluble in water

Mixture of CrN and Cr 2 N

Risk

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Chromium (III) - inorganic nitride is a chemical compound of the elements chromium and nitrogen. It is characterized by very high hardness and extreme corrosion resistance, resulting in a number of technical applications such as passivation and coating of chromium materials or coating of cutting tools.

Occurrence

Chromium ( III ) nitride occurs naturally as a mineral Carlsbergit and has been demonstrated in several iron meteorites.

Production and representation

Chromium ( III ) nitride is usually produced in the form of very thin coatings, rarer than ceramic body or as a powder.

A production of the elements is possible at temperatures above 800 ° C, the workpiece or the chromium powder is heated in this process under pure nitrogen atmosphere for several hours to the necessary temperature. This is done according to the following equation:

Also possible is the preparation by the reaction of chromium ( III) chloride with ammonia.

Properties

Chromium (III) is a nitride Einlagerungsnitrid with metallic properties. An ionic formulation within the meaning of Cr3 and N3 - is misleading, while an assignment of appropriate oxidation numbers is correct.

It is in the form of a black, a magnetic powder which is insoluble in acids and alkalis. It has a crystal structure of the sodium chloride type (a = 415 pm ). At higher temperatures, chromium ( III ) nitride ( γ - Chromnitridphase ) decomposes increasingly and goes into Chromheminitrid Cr2N ( β - Chromnitridphase, CAS: 12053-27-9 ) above. It is formed depends on the temperature and the nitrogen pressure is between these two phases, a balance between, for example, at 1100 ° C and a nitrogen pressure of 1.7 Torr. Chromheminitrid has a hexagonal crystal structure corresponding to that of iron nitride Fe2N and has the space group P63/mmc.