Boride

Name:
Boride
Detailed information:
An interstitial compound of boron and another metal (transition, alkaline-earth, or rare-earth). Such compounds are not stoichiometric, the boron atoms being linked together in zigzag chains, two-dimensional nets, or three-dimensional structures throughout the crystal.

Properties:

Color varies from gray (transition-metal) to black (alkaline-earth) to blue (rare-earth). Highly refractory, with mp from 2000 to 3000C; Mohs hardness from 8 to 10; thermally and electrically conductive. High chemical stability. Does not react with hydrochloric or hydrofluoric acids but is attacked by hot alkali hydroxides.

Derivation:

(1) Sintering mixtures of metal powder and boron at 2000C; (2) reduction of mixture of the metal oxide and boric oxide with aluminum, silicon, or carbon; (3) fused-salt electrolysis; (4) vapor-phase deposition.

Use:

High-temperature service such as rocket nozzles, turbines, etc.