Nitrides are nitrogen compounds with less electronegative elements, for example, with metals ( AlN ; TiN x ; Na 3 N ; Ca 3 N 2 ; Zn 3 N 2 ; etc.) and with a number of non-metals ( NH 3 , BN , Si 3 N 4 ).
Compounds of nitrogen with metals are most often refractory and stable at high temperatures, for example, elbor . Nitride coatings give products hardness, corrosion resistance; find application in energy, space technology.
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Depending on the type of chemical bond between the atoms, nitrides are divided into ionic, covalent and metal-like (ion-covalent-metal). Nitrogen atoms in nitrides can accept electrons of a less electronegative element, while forming a stable electronic configuration s 2 p 6 or give an electron to a partner with the formation of a stable configuration sp 3 ). In the first case, nitrides are characterized by the presence of an ionic bond; in the second, the chemical bond is typically metallic. In both cases, there is also a certain proportion of the covalent component. In nitrogen compounds with boron and silicon, the covalent nature of the chemical bond predominates.
The ionic bond is observed in metal nitrides of groups I and II of the periodic system. The composition of these nitrides corresponds to the usual valence ratios. These nitrides undergo hydrolysis with the release of ammonia, have high electrical resistance, they have semiconductor properties).
Covalent nitrides are boron, silicon, aluminum, gallium, indium nitrides. Covalent nitrides are dielectrics and semiconductors with a wide forbidden zone.
Transition metals form nitrides with a predominant metal bond. These substances have significant hardness and brittleness, high electrical conductivity, high melting points, and high enthalpy of formation.
Getting
Ion-type nitrides are obtained by the interaction of metals with nitrogen at temperatures of 700β1200 Β° C. Other nitrides can be obtained by reacting the metal with nitrogen or ammonia, or by reducing oxides, metal chlorides with carbon in the presence of nitrogen or ammonia at high temperatures. Nitrides are also formed in plasma in arc, high-frequency and microwave plasmatrons. In the latter case, nitrides are formed as ultrafine powders with a particle size of 10-100 nm.
Chemical Properties
Ion-type nitrides are readily decomposed by water and acids, exhibiting basic properties:
- {\ displaystyle {\ mathsf {Li_ {3} N + 3H_ {2} O \ rightarrow 3LiOH + NH_ {3} \ uparrow}}}
Heating of nitrides of elements of groups V, VI and VIII leads to their decomposition with the release of nitrogen, lower nitrides and solid solutions of nitrogen in metals. Nitrides of boron, silicon, aluminum, indium, gallium, and transition metals of group IV do not decompose upon heating in vacuum.
Oxidation of nitrides with oxygen leads to the formation of metal and nitrogen oxides. The interaction of nitrides with carbon leads to carbides and carbonitrides.
Application
Refractory nitrides are used as refractory and heat-resistant materials, hard - in the production of carbide and abrasive tools, as wear-resistant, heat-resistant and heat-resistant materials.
See also
- Nitrates
- Nitrite