Preparation of hexagonal BN
The nitridation or ammonolysis of boron trioxide produces hexagonal boron nitride. H-BN parts can be made by hot-pressing with subsequent machining; the machining cost is low due to the mechanical hardness similar to graphite. The parts are made from boron nitride powders, using boron oxide as a sintering agent. Thin boron nitride films can be obtained by chemical vapor deposition from boron trichloride and nitrogen precursors. Industrial production is based on two reactions: melted boric acid w