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Beryllium nitride

Beryllium nitride, Be<sub>3</sub>N<sub>2</sub>, is a nitride of beryllium. It can be prepared from the elements at high temperature (1100–1500&nbsp;°C); unlike beryllium azide or BeN<sub>6</sub>, it decomposes in vacuum into beryllium and nitrogen. It is readily hydrolysed forming beryllium hydroxide and ammonia. It has two polymorphic forms cubic α-Be<sub>3</sub>N<sub>2</sub> with a defect anti-fluorite structure, and hexagonal β-Be<sub>3</sub>N<sub>2</sub>. It reacts with silicon nitride, Si<sub>3</sub>N<sub>4</sub> in a stream of ammonia at 1800–1900&nbsp;°C to form BeSiN<sub>2</sub>.

Preparation

Beryllium nitride is prepared by heating beryllium metal powder with dry nitrogen in an oxygen-free atmosphere in temperatures between 700 and 1400&nbsp;°C.

3Be + N<sub>2 </sub> → Be<sub>3</sub>N<sub>2</sub>

Uses

It is used in refractory ceramics as well as in nuclear reactors.

It is used to produce radioactive carbon-14 for tracer applications by the + n → + p reaction. It is favoured due to its stability, high nitrogen content (50%), and the very low capture cross section of beryllium for neutrons.

Reactions

Beryllium nitride reacts with mineral acids producing ammonia and the corresponding salts of the acids:

Be<sub>3</sub>N<sub>2</sub> + 6 HCl → 3 BeCl<sub>2</sub> + 2 NH<sub>3</sub>

In strong alkali solutions, a beryllate forms, with evolution of ammonia:

Be<sub>3</sub>N<sub>2</sub> + 6 NaOH → 3 Na<sub>2</sub>BeO<sub>2</sub> + 2 NH<sub>3</sub>

Both the acid and alkali reactions are brisk and vigorous. Reaction with water, however, is very slow:

Be<sub>3</sub>N<sub>2</sub> + 6 H<sub>2</sub>O → 3 Be(OH)<sub>2</sub> + 2 NH<sub>3</sub>

Reactions with oxidizing agents are likely to be violent. It is oxidized when heated at 600&nbsp;°C in air.

References