Citric Acid-Assisted Combustion-Carbothermal Synthesis of Well-Distributed Highly Sinterable AlN Nanopowders

Aluminum nitride (AlN) nanopowders were synthesized by carbothermal reduction of a citric acid‐assisted combustion synthesis precursor derived from aluminum nitrate, glucose, citric acid, and urea mixed solution. Effects of citric acid on the size and morphology of precursors as well as synthesized AlN powders were studied in detail. The results indicated that the precursor synthesized from citric acid (0.02 M), was comprised of paper‐thin flaky particles with high specific surface area (14.6 m2/g). Moreover, the precursor, synthesized from citric acid (0.02 M), had exhibited the completion of the nitridation at 1400°C for 2 h. On the contrary, the nitridation reactions for the precursors, synthesized from citric acid (0 and 0.04 M), were incomplete under the same conditions. The decarburized as well as nondecarburized AlN powders from citric acid (0.02 M), synthesized at 1400°C, maintained its appearance similar to that of the original precursor. In addition, the decarburized AlN powders were found to be free of any hard agglomeration, and exhibited the well distributed and high sinterability spherical particles of 60–100 nm. The relative density of the sintered AlN pellet, calcined at 1800°C for 2 h with pressureless and additive free sintering, was found to be 99.05% of its theoretical density.