A NEW SYNTHESIS PROCESS FOR ALUMINUM NITRIDE

Thermodynamic considerations show that, even at room temperature, pure aluminium can react with nitrogen to form the aluminium nitride AlN. However, pure aluminium does not exist : it is always surrounded by an alumina shell that protects the metal from further reactions. Further more, in the hypothesis where one has been able to make aluminium reac t with nitrogen, an aluminium nitride shell will protect as well the m etal core from further oxidation. Prompted by the Lanxide process allo wing to form Al/Al2O3 CoMPosites, we have mixed aluminium powders with lithium salts, and easily synthesized pure aluminium nitride by heati ng the mixed powders in nitrogen at temperatures ranging from 800 to 1 200-degrees-C. Starting from aluminium powders with a specific area r anging from 0.3 to 4 M2/g, we have been able to produce aluminium nitr ide with specific are ranging from 1 to 20 m2/g. Mixed with Y2O3-CaO a nd sintered at 1 720-degrees-C in N2, we obtained AlN ceramics owning 92 % density and 160 W/m.K thermal conductivity.