Manufacture and Properties of Boron Nitride

Boron nitride (BN) exists in a hexagonal modification with a graphite-like crystal structure and a cubic high temperature/high pressure modification with a diamondlike structure. 

The most widely used industrial process for the manufacture of hexagonal boron(III) nitride is the reaction of boron(III) oxide with ammonia at 800 to 1200°C in a calcium phosphate matrix  

Boron(III) nitride cry.stalli/.es in a hexagonal and a cubic modification 

Hexagonal boron(lll) nitride is produced by reacting boron(Ill) oxide with ammonia (1) or nitrogen and carbon (2) 

After the reaction the matrix is dissolved in cold hydrochloric acid and unreacted boron(III) oxide washed out with hot alcohol. A raw product with 80 to 90% purity is thereby obtained. Postreaction in nitrogen at 1800°C or in ammonia at above 1200°C increases the BN-content still further. 

---