SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS OF ALN IN A GRAPHITE CRUCIBLE IN AIR BY MECHANICAL ACTIVATION

Powders of Al and C were mixed in a molar ratio of AI:C = 3:1 and were then ground in a planetary ball mill. When the thus mechanically acti vated mixtures were transferred into a graphite crucible and exposed t o air, they spontaneously ignited and self-propagating high-temperatur e synthesis took place in two successive steps. The products were slic ed along the depth direction and examined by X-ray diffraction. Depend ing on the depth of the crucible, aluminium nitride, aluminium carbide , aluminium oxynitride, aluminium oxycarbide and alpha alumina were de tected. From measurements of the lattice constant, it was found that a luminium nitride with a 97% purity could be obtained at the bottom of the graphite crucible.