Thermodynamic Aspect in Synthesis of AlN Powders by Carbothermal Reduction and Nitridation Process

摘要

A thermodynamical calculation shows that AlN powders were synthesized in the process bythe overall reaction Al2O3(s)+3C(s)+N2(g)=2AlN(s)+3CO(g) and its minimum reaction tem-perature T0=1852 K, if all reactants and products were in standard states. ln the practicalexperiments, AlN phase appeared obviously at only 1300℃, the major reasons are related to thepartial pressure of its gaseous product pco and the mixed free energy. The synthesis temperaturecould be lowered by either increasing N2 flow rate or elevating N2 pressure. On the other hand，as the temperature decreases, the equilibrium constant Km also reduces, and the reducing ratestrongly depends on the temperature： the lower the temperature, the higher the rate.