ALUMINUM NITRIDE
Tuesday, October 14th, 2008Formula: AlN; MW 40.99
Uses
Aluminum nitride is used in manufacturing of steel and in semiconductors.
Physical Properties
White crystalline solid, hexagonal; odor of ammonia in moist air; sublimes at 2000°C; melts in N2 atmosphere over 2200°C; density 3.26 g/cm3 ; decomposes in water, alkalies and acids
Thermochemical Properties
ΔH°ƒ(s) –76.0 kcal/mol
ΔG°ƒ(s) –68.6 kcal/mol
S° 4.82 cal/degree mol
Cρ 7.20 cal/degree mol
Preparation
Aluminum nitride may be prepared in the laboratory by heating powdered aluminum metal with nitrogen.
Commercially, it is made by heating an aluminous mineral, such as, bauxite with coal in a stream of nitrogen.
Chemical Reactions
The nitride reacts with water forming aluminum hydroxide and ammonia.
AlN + 3H2O ——›Al(OH)3 + NH3
The compound decomposes in alkalies and acids forming products of complex stoichiometry.
Analysis
Elemental composition: Al 65.82%, N 34.18%, the metal is determined by wet analysis or AA spectroscopy. NH3 liberated on hydrolysis may be determined by titration or colorimetry (see under Ammonia).
