Synthesis of aluminum nitride by a modified carbothermal reduction and nitridation method using basic dicarboxylate Al(III) complexes Al(OH)(Cn+2H2nO4)•xH2O (n=3, 6, 8)

Aluminum nitride (AIN) particles and whiskers were synthesized by using basic dicarboxylate Pl(III) complexes AI(OH)(Cn+2H2nO4). xH(2)O (n = 3, 6, 8) as a precursor. AIN was obtained by calcining the glutarate complex (n = 3, AG) without further additions of carbon source under flowing nitrogen in the temperature range 1200-1500 degreesC and then burning out the residual carbon. In contrast, for suberate (n = 6, ASu) and sebacate (n = 8, ASe) complexes additional carbon was required for their complete conversion to AIN. The process of conversion of AG to AlN was investigated by Al-27 magic-angle spinning (MAS) nuclear magnetic resonance, infrared spectroscopy, and X-ray diffraction. The complex began to decompose at ca. 400 degreesC and then turned into gamma -alumina at temperature above 600 degreesC. Finally, the gamma -alumina was converted to AIN without gamma-alpha alumina phase transformation. The morphology of AIN powders was very similar to that of the precursor, indicating that conversion of alumina to AIN during the carbothermal reduction and nitridation does not proceed through gaseous intermediates but through solid-state Al-oxynitride compounds. The AIN powders obtained consisted of ultrafine particles or mixtures of particles and whiskers. (C) 2000 Elsevier Science Ltd. All rights reserved.